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MD 1769 CONCERNING SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY FOR MUCH OF SD INTO SOUTHEAST ND
Mesoscale Discussion 1769 NWS Storm Prediction Center Norman OK 1231 PM CDT Sat Aug 17 2019 Areas affected...much of SD into southeast ND Concerning...Severe potential...Severe Thunderstorm Watch likely Valid 171731Z - 171930Z Probability of Watch Issuance...80 percent SUMMARY...Severe thunderstorms are expected to increase across South Dakota into southeast North Dakota through the afternoon. Large hail and damaging wind gusts will be possible with these storms. DISCUSSION...An isolated supercell has developed early this afternoon near SPF in the Black Hills in moist, upslope flow regime and 1.5 inch hail was recently reported. Surface temperatures across far western SD to the south of a cold front have only warmed into the low 70s, resulting in weak instability. However, further east into central SD, temperatures are rapidly warming into the 80s with surface dewpoints in the mid to upper 60s. With additional heating, instability should continue to increase with MLCAPE values approaching 2000 J/kg in the next few hours. EML should also rapidly erode as forcing for ascent continues to increase, both along the southeastward-advancing cold front and as midlevel shortwave impulse brushes the area. As a result, a gradual increase in thunderstorms development along/ahead of the front is expected over the next few hours across western into central SD and southeast ND. Effective shear around 40+ kt and steep midlevel lapse rates will support rotating updrafts and supercell structures capable of producing large hail initially. However, convection may quickly become more linear or clustered, which could limit a larger/greater hail threat. Steep low level lapse rates and a well-mixed sub-cloud layer will support strong downdrafts and damaging winds are possible. With time, convection may congeal into one or more surging lines either along the cold front or through storms mergers/outflow interactions, further increasing severe/damaging wind potential. Given the expected increase in storm coverage/intensity over the next 1-3 hours, a severe thunderstorm watch will likely be needed in the next hour or two. ..Leitman/Grams.. 08/17/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGF...FSD...ABR...BIS...UNR... LAT...LON 45880070 46679871 46969809 46929757 46769712 46189707 45319749 44419819 43869891 43479981 43240228 43390378 43650407 44120420 44410409 44760367 45880070 Read more

MD 1768 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF THE NORTHEAST
Mesoscale Discussion 1768 NWS Storm Prediction Center Norman OK 1227 PM CDT Sat Aug 17 2019 Areas affected...Portions of the Northeast Concerning...Severe potential...Watch possible Valid 171727Z - 171930Z Probability of Watch Issuance...40 percent SUMMARY...Thunderstorms are expected to continue increasing in coverage and intensity into early evening. The strongest storms will be capable of scattered wind damage and isolated large hail. A WW is possible. DISCUSSION...Latest regional radar imagery and lightning data shows thunderstorms gradually increasing in intensity/coverage over portions of northeast Ohio, northwest Pennsylvania, and northern New York in association with a shortwave impulse over southern Ontario. The kinematic environment across the area is characterized by at least modest deep-layer shear, with effective bulk shear of 30-40 knots -- greatest across northern portions of MCD area. While cloud cover and relatively warm mid-level temperatures will impede strong destabilization over the area, at least filtered sunshine should allow MLCAPE values to rise to near 1000-1500 J/kg by this afternoon -- especially over portions of central Pennsylvania/New York where visible satellite imagery shows greater cloud breaks. The combination of these ingredients should allow for at least periodic storm intensification with scattered wind damage and isolated large hail in the strongest storms/updrafts. A Severe Thunderstorm Watch is possible over parts of this area in the next few hours. ..Elliott/Grams.. 08/17/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BTV...OKX...ALY...PHI...BGM...BUF...CTP...PBZ... CLE... LAT...LON 43147732 43407651 44017533 44167417 43827337 42327392 40907470 39997523 39927597 40067645 40527676 41287689 41477790 41447881 41447973 41488051 41568088 42237989 43147732 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Sat Aug 17 2019 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST OKLAHOMA...SOUTHEAST KANSAS...AND SOUTHWEST MISSOURI... ...SUMMARY... Scattered thunderstorms capable of severe gusts and large hail are possible over northeastern Oklahoma, southeast Kansas, and western Missouri mainly Sunday afternoon into the early evening. ...Synopsis... An upper trough initially over the eastern Dakotas will rapidly move through the Upper Midwest during the day before reaching the Ontario/Quebec border by daybreak Monday. A cold front will extend from the Upper Midwest southwest into central KS with the northern portion of the front moving east into the central Great Lakes during the day while the trailing portion of the boundary decelerates over KS. South and east of the boundary, a reservoir of lower-middle 70s F dewpoints will encompass much of the area from the eastern half of OK and AR northeast into the southern Great Lakes in areas void of convective outflow. ...MO/KS/OK vicinity... One or more thunderstorm clusters will likely be ongoing Sunday morning from eastern KS eastward into IA/IL aided by a weakening southwesterly LLJ extending from the southern High Plains to southern Lake MI. Convective outflow and cloud debris will retard surface heating over the lower MO Valley and across parts of IL during the morning into the early afternoon. Strong heating is forecast over eastern OK into southeast KS where a very unstable airmass is forecast (3000-4500 J/kg MLCAPE). Strong westerly flow increasing from 30kt at 500mb to 60kt at 200mb atop low-level southerlies will yield a wind profile supportive of organized storms. Large hail and severe gusts are the primary hazards with this activity. Storm coverage is expected to become increasingly isolated with southwest extent along the I-44 corridor from northeast OK into southwest OK. ...Mid MS Valley into the southern Great Lakes... Storms are forecast to be ongoing across parts of IA, IL, and WI related to warm advection with a southwesterly low-level jet. Some of this activity could produce strong wind gusts, but is expected to weaken during the day. Recent model data indicates the possibility for a convective line to develop or rejuvenate along preexisting outflow from earlier storms moving into the southwest Great Lakes. Boundary layer destabilization will lead to potential for intensifying storms with a risk for strong to locally severe gusts capable of wind damage. If a corridor can be identified in later outlooks, an upgrade to slight risk is possible across the southern Great Lakes (i.e., Michiana and northwest OH) for this scenario. Storms are expected to weaken by early evening coincident with the loss of heating. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Smith.. 08/17/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Sat Aug 17 2019 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST OKLAHOMA...SOUTHEAST KANSAS...AND SOUTHWEST MISSOURI... ...SUMMARY... Scattered thunderstorms capable of severe gusts and large hail are possible over northeastern Oklahoma, southeast Kansas, and western Missouri mainly Sunday afternoon into the early evening. ...Synopsis... An upper trough initially over the eastern Dakotas will rapidly move through the Upper Midwest during the day before reaching the Ontario/Quebec border by daybreak Monday. A cold front will extend from the Upper Midwest southwest into central KS with the northern portion of the front moving east into the central Great Lakes during the day while the trailing portion of the boundary decelerates over KS. South and east of the boundary, a reservoir of lower-middle 70s F dewpoints will encompass much of the area from the eastern half of OK and AR northeast into the southern Great Lakes in areas void of convective outflow. ...MO/KS/OK vicinity... One or more thunderstorm clusters will likely be ongoing Sunday morning from eastern KS eastward into IA/IL aided by a weakening southwesterly LLJ extending from the southern High Plains to southern Lake MI. Convective outflow and cloud debris will retard surface heating over the lower MO Valley and across parts of IL during the morning into the early afternoon. Strong heating is forecast over eastern OK into southeast KS where a very unstable airmass is forecast (3000-4500 J/kg MLCAPE). Strong westerly flow increasing from 30kt at 500mb to 60kt at 200mb atop low-level southerlies will yield a wind profile supportive of organized storms. Large hail and severe gusts are the primary hazards with this activity. Storm coverage is expected to become increasingly isolated with southwest extent along the I-44 corridor from northeast OK into southwest OK. ...Mid MS Valley into the southern Great Lakes... Storms are forecast to be ongoing across parts of IA, IL, and WI related to warm advection with a southwesterly low-level jet. Some of this activity could produce strong wind gusts, but is expected to weaken during the day. Recent model data indicates the possibility for a convective line to develop or rejuvenate along preexisting outflow from earlier storms moving into the southwest Great Lakes. Boundary layer destabilization will lead to potential for intensifying storms with a risk for strong to locally severe gusts capable of wind damage. If a corridor can be identified in later outlooks, an upgrade to slight risk is possible across the southern Great Lakes (i.e., Michiana and northwest OH) for this scenario. Storms are expected to weaken by early evening coincident with the loss of heating. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Smith.. 08/17/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Sat Aug 17 2019 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST OKLAHOMA...SOUTHEAST KANSAS...AND SOUTHWEST MISSOURI... ...SUMMARY... Scattered thunderstorms capable of severe gusts and large hail are possible over northeastern Oklahoma, southeast Kansas, and western Missouri mainly Sunday afternoon into the early evening. ...Synopsis... An upper trough initially over the eastern Dakotas will rapidly move through the Upper Midwest during the day before reaching the Ontario/Quebec border by daybreak Monday. A cold front will extend from the Upper Midwest southwest into central KS with the northern portion of the front moving east into the central Great Lakes during the day while the trailing portion of the boundary decelerates over KS. South and east of the boundary, a reservoir of lower-middle 70s F dewpoints will encompass much of the area from the eastern half of OK and AR northeast into the southern Great Lakes in areas void of convective outflow. ...MO/KS/OK vicinity... One or more thunderstorm clusters will likely be ongoing Sunday morning from eastern KS eastward into IA/IL aided by a weakening southwesterly LLJ extending from the southern High Plains to southern Lake MI. Convective outflow and cloud debris will retard surface heating over the lower MO Valley and across parts of IL during the morning into the early afternoon. Strong heating is forecast over eastern OK into southeast KS where a very unstable airmass is forecast (3000-4500 J/kg MLCAPE). Strong westerly flow increasing from 30kt at 500mb to 60kt at 200mb atop low-level southerlies will yield a wind profile supportive of organized storms. Large hail and severe gusts are the primary hazards with this activity. Storm coverage is expected to become increasingly isolated with southwest extent along the I-44 corridor from northeast OK into southwest OK. ...Mid MS Valley into the southern Great Lakes... Storms are forecast to be ongoing across parts of IA, IL, and WI related to warm advection with a southwesterly low-level jet. Some of this activity could produce strong wind gusts, but is expected to weaken during the day. Recent model data indicates the possibility for a convective line to develop or rejuvenate along preexisting outflow from earlier storms moving into the southwest Great Lakes. Boundary layer destabilization will lead to potential for intensifying storms with a risk for strong to locally severe gusts capable of wind damage. If a corridor can be identified in later outlooks, an upgrade to slight risk is possible across the southern Great Lakes (i.e., Michiana and northwest OH) for this scenario. Storms are expected to weaken by early evening coincident with the loss of heating. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Smith.. 08/17/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Sat Aug 17 2019 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST OKLAHOMA...SOUTHEAST KANSAS...AND SOUTHWEST MISSOURI... ...SUMMARY... Scattered thunderstorms capable of severe gusts and large hail are possible over northeastern Oklahoma, southeast Kansas, and western Missouri mainly Sunday afternoon into the early evening. ...Synopsis... An upper trough initially over the eastern Dakotas will rapidly move through the Upper Midwest during the day before reaching the Ontario/Quebec border by daybreak Monday. A cold front will extend from the Upper Midwest southwest into central KS with the northern portion of the front moving east into the central Great Lakes during the day while the trailing portion of the boundary decelerates over KS. South and east of the boundary, a reservoir of lower-middle 70s F dewpoints will encompass much of the area from the eastern half of OK and AR northeast into the southern Great Lakes in areas void of convective outflow. ...MO/KS/OK vicinity... One or more thunderstorm clusters will likely be ongoing Sunday morning from eastern KS eastward into IA/IL aided by a weakening southwesterly LLJ extending from the southern High Plains to southern Lake MI. Convective outflow and cloud debris will retard surface heating over the lower MO Valley and across parts of IL during the morning into the early afternoon. Strong heating is forecast over eastern OK into southeast KS where a very unstable airmass is forecast (3000-4500 J/kg MLCAPE). Strong westerly flow increasing from 30kt at 500mb to 60kt at 200mb atop low-level southerlies will yield a wind profile supportive of organized storms. Large hail and severe gusts are the primary hazards with this activity. Storm coverage is expected to become increasingly isolated with southwest extent along the I-44 corridor from northeast OK into southwest OK. ...Mid MS Valley into the southern Great Lakes... Storms are forecast to be ongoing across parts of IA, IL, and WI related to warm advection with a southwesterly low-level jet. Some of this activity could produce strong wind gusts, but is expected to weaken during the day. Recent model data indicates the possibility for a convective line to develop or rejuvenate along preexisting outflow from earlier storms moving into the southwest Great Lakes. Boundary layer destabilization will lead to potential for intensifying storms with a risk for strong to locally severe gusts capable of wind damage. If a corridor can be identified in later outlooks, an upgrade to slight risk is possible across the southern Great Lakes (i.e., Michiana and northwest OH) for this scenario. Storms are expected to weaken by early evening coincident with the loss of heating. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Smith.. 08/17/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Sat Aug 17 2019 Valid 171700Z - 181200Z Some minor adjustments have been made to the Elevated area, but the overall forecast reasoning remains unchanged. Locally critical conditions will be possible within the Elevated area, but confidence in meeting critical criteria remains too low for any upgrade. See the previous discussion below for more details. No changes have been made to the isolated dry-thunderstorm area. A few strikes were noted earlier this morning from northeast UT and northwest CO, and some redevelopment of mainly dry thunderstorms appears possible across the same region this afternoon. Some threat of lightning ignitions will continue this afternoon across the Caprock and Rolling Plains of TX on the periphery of heavier rain cores. See the previous discussion below for more details. ..Dean.. 08/17/2019 .PREV DISCUSSION... /ISSUED 0139 AM CDT Sat Aug 17 2019/ ...Synopsis... An upper-level shortwave trough will move over the northern Rockies and northern Plains with zonal upper-level flow across much of the CONUS. The dry slot will move over portions of the Intermountain West with stronger 700-500 mb flow stretching from southern Idaho into the central/northern High Plains. With daytime heating, stronger winds will likely mix to the surface resulting in elevated to locally critical conditions from the Snake River Plain through the Great Divide Basin and across portions of western/northern Colorado. Westerly winds of 15-20 mph and RH values of 10-20% are likely to develop this afternoon/evening across the area. Additionally, locally elevated conditions are possible in northern Arizona where multiple large fires are active, which produced smoke plumes seen on visible satellite imagery on Friday. Isolated dry thunderstorms are likely to develop across northwest Colorado, far northeast Utah, and far southern Wyoming this afternoon/evening. High LCLs (around 3 km), a dry sub-cloud layer, and storm motions of 30-35 knots will limit wetting rains and increase chances for lightning ignitions. There is some concern that the Cu field will not become vertically developed enough for thunderstorms due to the limited amount of moisture (forecast precipitable water values of 0.4-0.55") and instability present. Isolated dry thunderstorms may also be possible across the Caprock and Texas Rolling Plains this afternoon and evening. While wetting rains are likely, lightning ignitions on the periphery of storms have occurred recently per LUB. Given the high LCLs and forecast DCAPE of 1500+ J/kg, strong outflow winds are also possible. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Sat Aug 17 2019 Valid 171700Z - 181200Z Some minor adjustments have been made to the Elevated area, but the overall forecast reasoning remains unchanged. Locally critical conditions will be possible within the Elevated area, but confidence in meeting critical criteria remains too low for any upgrade. See the previous discussion below for more details. No changes have been made to the isolated dry-thunderstorm area. A few strikes were noted earlier this morning from northeast UT and northwest CO, and some redevelopment of mainly dry thunderstorms appears possible across the same region this afternoon. Some threat of lightning ignitions will continue this afternoon across the Caprock and Rolling Plains of TX on the periphery of heavier rain cores. See the previous discussion below for more details. ..Dean.. 08/17/2019 .PREV DISCUSSION... /ISSUED 0139 AM CDT Sat Aug 17 2019/ ...Synopsis... An upper-level shortwave trough will move over the northern Rockies and northern Plains with zonal upper-level flow across much of the CONUS. The dry slot will move over portions of the Intermountain West with stronger 700-500 mb flow stretching from southern Idaho into the central/northern High Plains. With daytime heating, stronger winds will likely mix to the surface resulting in elevated to locally critical conditions from the Snake River Plain through the Great Divide Basin and across portions of western/northern Colorado. Westerly winds of 15-20 mph and RH values of 10-20% are likely to develop this afternoon/evening across the area. Additionally, locally elevated conditions are possible in northern Arizona where multiple large fires are active, which produced smoke plumes seen on visible satellite imagery on Friday. Isolated dry thunderstorms are likely to develop across northwest Colorado, far northeast Utah, and far southern Wyoming this afternoon/evening. High LCLs (around 3 km), a dry sub-cloud layer, and storm motions of 30-35 knots will limit wetting rains and increase chances for lightning ignitions. There is some concern that the Cu field will not become vertically developed enough for thunderstorms due to the limited amount of moisture (forecast precipitable water values of 0.4-0.55") and instability present. Isolated dry thunderstorms may also be possible across the Caprock and Texas Rolling Plains this afternoon and evening. While wetting rains are likely, lightning ignitions on the periphery of storms have occurred recently per LUB. Given the high LCLs and forecast DCAPE of 1500+ J/kg, strong outflow winds are also possible. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Sat Aug 17 2019 Valid 171700Z - 181200Z Some minor adjustments have been made to the Elevated area, but the overall forecast reasoning remains unchanged. Locally critical conditions will be possible within the Elevated area, but confidence in meeting critical criteria remains too low for any upgrade. See the previous discussion below for more details. No changes have been made to the isolated dry-thunderstorm area. A few strikes were noted earlier this morning from northeast UT and northwest CO, and some redevelopment of mainly dry thunderstorms appears possible across the same region this afternoon. Some threat of lightning ignitions will continue this afternoon across the Caprock and Rolling Plains of TX on the periphery of heavier rain cores. See the previous discussion below for more details. ..Dean.. 08/17/2019 .PREV DISCUSSION... /ISSUED 0139 AM CDT Sat Aug 17 2019/ ...Synopsis... An upper-level shortwave trough will move over the northern Rockies and northern Plains with zonal upper-level flow across much of the CONUS. The dry slot will move over portions of the Intermountain West with stronger 700-500 mb flow stretching from southern Idaho into the central/northern High Plains. With daytime heating, stronger winds will likely mix to the surface resulting in elevated to locally critical conditions from the Snake River Plain through the Great Divide Basin and across portions of western/northern Colorado. Westerly winds of 15-20 mph and RH values of 10-20% are likely to develop this afternoon/evening across the area. Additionally, locally elevated conditions are possible in northern Arizona where multiple large fires are active, which produced smoke plumes seen on visible satellite imagery on Friday. Isolated dry thunderstorms are likely to develop across northwest Colorado, far northeast Utah, and far southern Wyoming this afternoon/evening. High LCLs (around 3 km), a dry sub-cloud layer, and storm motions of 30-35 knots will limit wetting rains and increase chances for lightning ignitions. There is some concern that the Cu field will not become vertically developed enough for thunderstorms due to the limited amount of moisture (forecast precipitable water values of 0.4-0.55") and instability present. Isolated dry thunderstorms may also be possible across the Caprock and Texas Rolling Plains this afternoon and evening. While wetting rains are likely, lightning ignitions on the periphery of storms have occurred recently per LUB. Given the high LCLs and forecast DCAPE of 1500+ J/kg, strong outflow winds are also possible. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Sat Aug 17 2019 Valid 171700Z - 181200Z Some minor adjustments have been made to the Elevated area, but the overall forecast reasoning remains unchanged. Locally critical conditions will be possible within the Elevated area, but confidence in meeting critical criteria remains too low for any upgrade. See the previous discussion below for more details. No changes have been made to the isolated dry-thunderstorm area. A few strikes were noted earlier this morning from northeast UT and northwest CO, and some redevelopment of mainly dry thunderstorms appears possible across the same region this afternoon. Some threat of lightning ignitions will continue this afternoon across the Caprock and Rolling Plains of TX on the periphery of heavier rain cores. See the previous discussion below for more details. ..Dean.. 08/17/2019 .PREV DISCUSSION... /ISSUED 0139 AM CDT Sat Aug 17 2019/ ...Synopsis... An upper-level shortwave trough will move over the northern Rockies and northern Plains with zonal upper-level flow across much of the CONUS. The dry slot will move over portions of the Intermountain West with stronger 700-500 mb flow stretching from southern Idaho into the central/northern High Plains. With daytime heating, stronger winds will likely mix to the surface resulting in elevated to locally critical conditions from the Snake River Plain through the Great Divide Basin and across portions of western/northern Colorado. Westerly winds of 15-20 mph and RH values of 10-20% are likely to develop this afternoon/evening across the area. Additionally, locally elevated conditions are possible in northern Arizona where multiple large fires are active, which produced smoke plumes seen on visible satellite imagery on Friday. Isolated dry thunderstorms are likely to develop across northwest Colorado, far northeast Utah, and far southern Wyoming this afternoon/evening. High LCLs (around 3 km), a dry sub-cloud layer, and storm motions of 30-35 knots will limit wetting rains and increase chances for lightning ignitions. There is some concern that the Cu field will not become vertically developed enough for thunderstorms due to the limited amount of moisture (forecast precipitable water values of 0.4-0.55") and instability present. Isolated dry thunderstorms may also be possible across the Caprock and Texas Rolling Plains this afternoon and evening. While wetting rains are likely, lightning ignitions on the periphery of storms have occurred recently per LUB. Given the high LCLs and forecast DCAPE of 1500+ J/kg, strong outflow winds are also possible. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No Mesoscale Discussions are in effect as of Sat Aug 17 16:45:02 UTC 2019.

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 17 2019 Valid 171630Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST SD...NORTHWEST IA...SOUTHWEST MN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE NORTHEAST... ...SUMMARY... Scattered severe thunderstorms with damaging winds and large hail as the primary threats are expected across a large portion of the northern to central Great Plains into the Midwest, generally during the late afternoon into tonight. Damaging winds are also possible into early evening in parts of the Northeast States. ...Northern Great Plains/Upper Midwest... A broad positive-tilt shortwave trough will advance east across the southern Prairie Provinces and MT to ND through tonight. A surface front well in advance of this wave extends from the Red River Valley southwest towards the Black Hills and should remain quasi-stationary before accelerating south/east tonight. The bulk of stronger mid-level west-southwesterlies accompanying the wave will remain confined to the cool side of the front, while a separate belt of enhanced westerlies is confined south across NE. In addition, the northern periphery of steeper mid-level lapse rates from an elevated mixed-layer will probably only overlap the SD portion of the front. Low to mid 60s F surface dew points are expected along the front and should support moderate buoyancy with MLCAPE around 1500-2500 J/kg. Owing to a lack of stronger capping, at least scattered thunderstorms will develop in the late afternoon. A few transient supercells should develop initially, but hodographs do not appear particularly elongated or enlarged given modest low-level winds and weakness aloft in the split flow regime. Given the frontal forcing and predominance of outflow consolidation, broader clusters fusing into one or more lines are expected with eastern extent tonight. Some risk for damaging winds will probably continue across southern MN and northern IA along the northern extent of the larger buoyancy plume. ...Central Great Plains... High-based convection that develops off the Front Range this afternoon should impinge on the recovering moist sector near the CO/KS/NE border towards early evening. On the southern periphery of a belt of enhanced mid-level westerlies centered from southern WY across NE amid a very steep lapse rate environment, a swath of severe wind gusts will be possible into north-central KS tonight. ...Mid-MS Valley to IN vicinity... An MCV is centered near the MO/IA/IL border area and should drift east. Several CAMs indicate redevelopment of scattered storms ahead of this feature. This will be highly dependent on more robust destabilization occurring in the wake of a leading MCS in IN. At least a conditional threat for damaging winds and severe hail exists, mainly during the evening. Warm-advection storms overnight may also pose an isolated severe risk. ...Northeast... A low-amplitude shortwave impulse over southern Ontario should slowly move across the Saint Lawrence Valley. Scattered convection is ongoing in association with this wave and will likely persist through the afternoon as further surface-based destabilization occurs downstream. Weak low-level winds and modest mid-level lapse rates will be limiting factors. Most of the stronger speed shear should be confined to the upper portion of the buoyancy profile. Setup should foster a risk of isolated marginally severe hail and scattered damaging winds. ..Grams.. 08/17/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 17 2019 Valid 171630Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST SD...NORTHWEST IA...SOUTHWEST MN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE NORTHEAST... ...SUMMARY... Scattered severe thunderstorms with damaging winds and large hail as the primary threats are expected across a large portion of the northern to central Great Plains into the Midwest, generally during the late afternoon into tonight. Damaging winds are also possible into early evening in parts of the Northeast States. ...Northern Great Plains/Upper Midwest... A broad positive-tilt shortwave trough will advance east across the southern Prairie Provinces and MT to ND through tonight. A surface front well in advance of this wave extends from the Red River Valley southwest towards the Black Hills and should remain quasi-stationary before accelerating south/east tonight. The bulk of stronger mid-level west-southwesterlies accompanying the wave will remain confined to the cool side of the front, while a separate belt of enhanced westerlies is confined south across NE. In addition, the northern periphery of steeper mid-level lapse rates from an elevated mixed-layer will probably only overlap the SD portion of the front. Low to mid 60s F surface dew points are expected along the front and should support moderate buoyancy with MLCAPE around 1500-2500 J/kg. Owing to a lack of stronger capping, at least scattered thunderstorms will develop in the late afternoon. A few transient supercells should develop initially, but hodographs do not appear particularly elongated or enlarged given modest low-level winds and weakness aloft in the split flow regime. Given the frontal forcing and predominance of outflow consolidation, broader clusters fusing into one or more lines are expected with eastern extent tonight. Some risk for damaging winds will probably continue across southern MN and northern IA along the northern extent of the larger buoyancy plume. ...Central Great Plains... High-based convection that develops off the Front Range this afternoon should impinge on the recovering moist sector near the CO/KS/NE border towards early evening. On the southern periphery of a belt of enhanced mid-level westerlies centered from southern WY across NE amid a very steep lapse rate environment, a swath of severe wind gusts will be possible into north-central KS tonight. ...Mid-MS Valley to IN vicinity... An MCV is centered near the MO/IA/IL border area and should drift east. Several CAMs indicate redevelopment of scattered storms ahead of this feature. This will be highly dependent on more robust destabilization occurring in the wake of a leading MCS in IN. At least a conditional threat for damaging winds and severe hail exists, mainly during the evening. Warm-advection storms overnight may also pose an isolated severe risk. ...Northeast... A low-amplitude shortwave impulse over southern Ontario should slowly move across the Saint Lawrence Valley. Scattered convection is ongoing in association with this wave and will likely persist through the afternoon as further surface-based destabilization occurs downstream. Weak low-level winds and modest mid-level lapse rates will be limiting factors. Most of the stronger speed shear should be confined to the upper portion of the buoyancy profile. Setup should foster a risk of isolated marginally severe hail and scattered damaging winds. ..Grams.. 08/17/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 17 2019 Valid 171630Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST SD...NORTHWEST IA...SOUTHWEST MN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE NORTHEAST... ...SUMMARY... Scattered severe thunderstorms with damaging winds and large hail as the primary threats are expected across a large portion of the northern to central Great Plains into the Midwest, generally during the late afternoon into tonight. Damaging winds are also possible into early evening in parts of the Northeast States. ...Northern Great Plains/Upper Midwest... A broad positive-tilt shortwave trough will advance east across the southern Prairie Provinces and MT to ND through tonight. A surface front well in advance of this wave extends from the Red River Valley southwest towards the Black Hills and should remain quasi-stationary before accelerating south/east tonight. The bulk of stronger mid-level west-southwesterlies accompanying the wave will remain confined to the cool side of the front, while a separate belt of enhanced westerlies is confined south across NE. In addition, the northern periphery of steeper mid-level lapse rates from an elevated mixed-layer will probably only overlap the SD portion of the front. Low to mid 60s F surface dew points are expected along the front and should support moderate buoyancy with MLCAPE around 1500-2500 J/kg. Owing to a lack of stronger capping, at least scattered thunderstorms will develop in the late afternoon. A few transient supercells should develop initially, but hodographs do not appear particularly elongated or enlarged given modest low-level winds and weakness aloft in the split flow regime. Given the frontal forcing and predominance of outflow consolidation, broader clusters fusing into one or more lines are expected with eastern extent tonight. Some risk for damaging winds will probably continue across southern MN and northern IA along the northern extent of the larger buoyancy plume. ...Central Great Plains... High-based convection that develops off the Front Range this afternoon should impinge on the recovering moist sector near the CO/KS/NE border towards early evening. On the southern periphery of a belt of enhanced mid-level westerlies centered from southern WY across NE amid a very steep lapse rate environment, a swath of severe wind gusts will be possible into north-central KS tonight. ...Mid-MS Valley to IN vicinity... An MCV is centered near the MO/IA/IL border area and should drift east. Several CAMs indicate redevelopment of scattered storms ahead of this feature. This will be highly dependent on more robust destabilization occurring in the wake of a leading MCS in IN. At least a conditional threat for damaging winds and severe hail exists, mainly during the evening. Warm-advection storms overnight may also pose an isolated severe risk. ...Northeast... A low-amplitude shortwave impulse over southern Ontario should slowly move across the Saint Lawrence Valley. Scattered convection is ongoing in association with this wave and will likely persist through the afternoon as further surface-based destabilization occurs downstream. Weak low-level winds and modest mid-level lapse rates will be limiting factors. Most of the stronger speed shear should be confined to the upper portion of the buoyancy profile. Setup should foster a risk of isolated marginally severe hail and scattered damaging winds. ..Grams.. 08/17/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 17 2019 Valid 171630Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST SD...NORTHWEST IA...SOUTHWEST MN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE NORTHEAST... ...SUMMARY... Scattered severe thunderstorms with damaging winds and large hail as the primary threats are expected across a large portion of the northern to central Great Plains into the Midwest, generally during the late afternoon into tonight. Damaging winds are also possible into early evening in parts of the Northeast States. ...Northern Great Plains/Upper Midwest... A broad positive-tilt shortwave trough will advance east across the southern Prairie Provinces and MT to ND through tonight. A surface front well in advance of this wave extends from the Red River Valley southwest towards the Black Hills and should remain quasi-stationary before accelerating south/east tonight. The bulk of stronger mid-level west-southwesterlies accompanying the wave will remain confined to the cool side of the front, while a separate belt of enhanced westerlies is confined south across NE. In addition, the northern periphery of steeper mid-level lapse rates from an elevated mixed-layer will probably only overlap the SD portion of the front. Low to mid 60s F surface dew points are expected along the front and should support moderate buoyancy with MLCAPE around 1500-2500 J/kg. Owing to a lack of stronger capping, at least scattered thunderstorms will develop in the late afternoon. A few transient supercells should develop initially, but hodographs do not appear particularly elongated or enlarged given modest low-level winds and weakness aloft in the split flow regime. Given the frontal forcing and predominance of outflow consolidation, broader clusters fusing into one or more lines are expected with eastern extent tonight. Some risk for damaging winds will probably continue across southern MN and northern IA along the northern extent of the larger buoyancy plume. ...Central Great Plains... High-based convection that develops off the Front Range this afternoon should impinge on the recovering moist sector near the CO/KS/NE border towards early evening. On the southern periphery of a belt of enhanced mid-level westerlies centered from southern WY across NE amid a very steep lapse rate environment, a swath of severe wind gusts will be possible into north-central KS tonight. ...Mid-MS Valley to IN vicinity... An MCV is centered near the MO/IA/IL border area and should drift east. Several CAMs indicate redevelopment of scattered storms ahead of this feature. This will be highly dependent on more robust destabilization occurring in the wake of a leading MCS in IN. At least a conditional threat for damaging winds and severe hail exists, mainly during the evening. Warm-advection storms overnight may also pose an isolated severe risk. ...Northeast... A low-amplitude shortwave impulse over southern Ontario should slowly move across the Saint Lawrence Valley. Scattered convection is ongoing in association with this wave and will likely persist through the afternoon as further surface-based destabilization occurs downstream. Weak low-level winds and modest mid-level lapse rates will be limiting factors. Most of the stronger speed shear should be confined to the upper portion of the buoyancy profile. Setup should foster a risk of isolated marginally severe hail and scattered damaging winds. ..Grams.. 08/17/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Sat Aug 17 2019 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTH-CENTRAL PLAINS REGION... ...SUMMARY... The greatest threat for severe storms appears to be over parts of the northern and central Plains into the upper Midwest late this afternoon into tonight. ...Synopsis... In mid/upper levels, a highly amplified and blocky pattern inhabits North America's neighborhood in the Northern Hemisphere. A large, complex cyclone will remain anchored over the north-central Pacific, with sharp ridging to its north through east, from the Bering Sea to waters west of both CA and Baja. Broadly cyclonic mean flow will persist over much of Canada and the northern half of the CONUS, much of it accompanied by seasonally cold mid/upper-level temperatures. The most influential shortwave feature appears to be the trough now moving eastward out of the northern Rockies region, and forecast to amplify as it crosses MT and the Dakotas through the period. By 12Z, this perturbation should reach southeastern MB, eastern ND and central/eastern SD. Meanwhile, convectively generated/enhanced vorticity maxima from prior activity will aid convective potential on the mesoscale across portions of the marginal-risk area from IN-NY. At the surface, the 11Z analysis showed a surface low over extreme northern Lower MI with cold front southwestward across northern IL, becoming quasistationary and somewhat diffused by convective activity over southern IA and southern NE. Baroclinicity was stronger on an outflow arc extending from eastern MO across the eastern KS/OK border region to west-central KS. The latter boundary should weaken from west to east through the day, with some northeastward retreat possible, while the frontal zone to its north moves little. Meanwhile, a better-defined cold front was drawn from southern MB across east-central ND and northwestern SD, to a low over northeastern WY. This front should move eastward/southeastward across the remainder of the northern Plains through the period. By 12Z the cold front should reach eastern MN, western/central IA, southeastern NE, and northeastern CO. ...North-central Plains, upper Midwest... Scattered thunderstorms should develop over western parts of the north-central Plains this afternoon, predominantly along the cold front and over higher terrain in and near the Black Hills and Bighorns, offering the potential for severe hail/gusts. Supercells are possible relatively early in the convective cycle. Then the potential exists for some of the western SD/frontal activity to evolve upscale toward a more wind-dominant severe risk, perhaps aided by additional convective development to its east. Being fairly well-removed from the ongoing extensive clouds/precip in the eastern KS/MO region, areas of strong heating are expected in the prefrontal warm sector. This, combined with 60s F surface dew points and steep low/middle-level lapse rates, should render areas of 2000-3500 J/kg late-afternoon/preconvective MLCAPE in central/ eastern SD and much of NE, decreasing westward toward the higher terrain as moisture diminishes (but still should be sufficient to support convection). Vertical shear should strengthen through the afternoon and evening in the warm sector, with 40-55-kt effective- shear magnitudes supporting supercell potential before upscale growth occurs. The threat accordingly should transition from hail to wind with time into the overnight period. ...IA, eastern NE, portions of KS, northern MO... Additional scattered to numerous thunderstorms may form farther south tonight over parts of the eastern NE/IA/northern MO area in a zone of strong low-level warm advection and moisture transport, with severe/significant hail potential. This regime is a good deal more uncertain in how it may develop and evolve, including how much influence may persist from High Plains activity persisting into the region vs. in situ development with the warm-advection/LLJ corridor. The extensive area of antecedent convection over KS/MO -- and related airmass effects on timing/extent of recovery farther north this afternoon and evening -- yield the bulk of uncertainty in this forecast. The severe that occurred late over KS/MO during the past overnight period required 12-18 hours of postconvective recovery following extensive convection to the south. Loosely similarly, a delayed onset of convective/severe potential into the evening/overnight hours is probable across the outlook area again this day-1 period. Two main differences will be: 1. Somewhat weaker but still adequate low-level moisture/theta-e, and 2. Stronger but still peripheral mid/upper-level influences southeast of the pronounced shortwave trough, in terms of synoptic-scale lift via warm advection and weak DCVA/cooling, and strengthening gradient winds aloft for favorable deep shear. At this time, uncertainty remains too large to increase or areally refine the unconditional severe probabilities. ..Edwards/Marsh.. 08/17/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Sat Aug 17 2019 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTH-CENTRAL PLAINS REGION... ...SUMMARY... The greatest threat for severe storms appears to be over parts of the northern and central Plains into the upper Midwest late this afternoon into tonight. ...Synopsis... In mid/upper levels, a highly amplified and blocky pattern inhabits North America's neighborhood in the Northern Hemisphere. A large, complex cyclone will remain anchored over the north-central Pacific, with sharp ridging to its north through east, from the Bering Sea to waters west of both CA and Baja. Broadly cyclonic mean flow will persist over much of Canada and the northern half of the CONUS, much of it accompanied by seasonally cold mid/upper-level temperatures. The most influential shortwave feature appears to be the trough now moving eastward out of the northern Rockies region, and forecast to amplify as it crosses MT and the Dakotas through the period. By 12Z, this perturbation should reach southeastern MB, eastern ND and central/eastern SD. Meanwhile, convectively generated/enhanced vorticity maxima from prior activity will aid convective potential on the mesoscale across portions of the marginal-risk area from IN-NY. At the surface, the 11Z analysis showed a surface low over extreme northern Lower MI with cold front southwestward across northern IL, becoming quasistationary and somewhat diffused by convective activity over southern IA and southern NE. Baroclinicity was stronger on an outflow arc extending from eastern MO across the eastern KS/OK border region to west-central KS. The latter boundary should weaken from west to east through the day, with some northeastward retreat possible, while the frontal zone to its north moves little. Meanwhile, a better-defined cold front was drawn from southern MB across east-central ND and northwestern SD, to a low over northeastern WY. This front should move eastward/southeastward across the remainder of the northern Plains through the period. By 12Z the cold front should reach eastern MN, western/central IA, southeastern NE, and northeastern CO. ...North-central Plains, upper Midwest... Scattered thunderstorms should develop over western parts of the north-central Plains this afternoon, predominantly along the cold front and over higher terrain in and near the Black Hills and Bighorns, offering the potential for severe hail/gusts. Supercells are possible relatively early in the convective cycle. Then the potential exists for some of the western SD/frontal activity to evolve upscale toward a more wind-dominant severe risk, perhaps aided by additional convective development to its east. Being fairly well-removed from the ongoing extensive clouds/precip in the eastern KS/MO region, areas of strong heating are expected in the prefrontal warm sector. This, combined with 60s F surface dew points and steep low/middle-level lapse rates, should render areas of 2000-3500 J/kg late-afternoon/preconvective MLCAPE in central/ eastern SD and much of NE, decreasing westward toward the higher terrain as moisture diminishes (but still should be sufficient to support convection). Vertical shear should strengthen through the afternoon and evening in the warm sector, with 40-55-kt effective- shear magnitudes supporting supercell potential before upscale growth occurs. The threat accordingly should transition from hail to wind with time into the overnight period. ...IA, eastern NE, portions of KS, northern MO... Additional scattered to numerous thunderstorms may form farther south tonight over parts of the eastern NE/IA/northern MO area in a zone of strong low-level warm advection and moisture transport, with severe/significant hail potential. This regime is a good deal more uncertain in how it may develop and evolve, including how much influence may persist from High Plains activity persisting into the region vs. in situ development with the warm-advection/LLJ corridor. The extensive area of antecedent convection over KS/MO -- and related airmass effects on timing/extent of recovery farther north this afternoon and evening -- yield the bulk of uncertainty in this forecast. The severe that occurred late over KS/MO during the past overnight period required 12-18 hours of postconvective recovery following extensive convection to the south. Loosely similarly, a delayed onset of convective/severe potential into the evening/overnight hours is probable across the outlook area again this day-1 period. Two main differences will be: 1. Somewhat weaker but still adequate low-level moisture/theta-e, and 2. Stronger but still peripheral mid/upper-level influences southeast of the pronounced shortwave trough, in terms of synoptic-scale lift via warm advection and weak DCVA/cooling, and strengthening gradient winds aloft for favorable deep shear. At this time, uncertainty remains too large to increase or areally refine the unconditional severe probabilities. ..Edwards/Marsh.. 08/17/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Sat Aug 17 2019 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTH-CENTRAL PLAINS REGION... ...SUMMARY... The greatest threat for severe storms appears to be over parts of the northern and central Plains into the upper Midwest late this afternoon into tonight. ...Synopsis... In mid/upper levels, a highly amplified and blocky pattern inhabits North America's neighborhood in the Northern Hemisphere. A large, complex cyclone will remain anchored over the north-central Pacific, with sharp ridging to its north through east, from the Bering Sea to waters west of both CA and Baja. Broadly cyclonic mean flow will persist over much of Canada and the northern half of the CONUS, much of it accompanied by seasonally cold mid/upper-level temperatures. The most influential shortwave feature appears to be the trough now moving eastward out of the northern Rockies region, and forecast to amplify as it crosses MT and the Dakotas through the period. By 12Z, this perturbation should reach southeastern MB, eastern ND and central/eastern SD. Meanwhile, convectively generated/enhanced vorticity maxima from prior activity will aid convective potential on the mesoscale across portions of the marginal-risk area from IN-NY. At the surface, the 11Z analysis showed a surface low over extreme northern Lower MI with cold front southwestward across northern IL, becoming quasistationary and somewhat diffused by convective activity over southern IA and southern NE. Baroclinicity was stronger on an outflow arc extending from eastern MO across the eastern KS/OK border region to west-central KS. The latter boundary should weaken from west to east through the day, with some northeastward retreat possible, while the frontal zone to its north moves little. Meanwhile, a better-defined cold front was drawn from southern MB across east-central ND and northwestern SD, to a low over northeastern WY. This front should move eastward/southeastward across the remainder of the northern Plains through the period. By 12Z the cold front should reach eastern MN, western/central IA, southeastern NE, and northeastern CO. ...North-central Plains, upper Midwest... Scattered thunderstorms should develop over western parts of the north-central Plains this afternoon, predominantly along the cold front and over higher terrain in and near the Black Hills and Bighorns, offering the potential for severe hail/gusts. Supercells are possible relatively early in the convective cycle. Then the potential exists for some of the western SD/frontal activity to evolve upscale toward a more wind-dominant severe risk, perhaps aided by additional convective development to its east. Being fairly well-removed from the ongoing extensive clouds/precip in the eastern KS/MO region, areas of strong heating are expected in the prefrontal warm sector. This, combined with 60s F surface dew points and steep low/middle-level lapse rates, should render areas of 2000-3500 J/kg late-afternoon/preconvective MLCAPE in central/ eastern SD and much of NE, decreasing westward toward the higher terrain as moisture diminishes (but still should be sufficient to support convection). Vertical shear should strengthen through the afternoon and evening in the warm sector, with 40-55-kt effective- shear magnitudes supporting supercell potential before upscale growth occurs. The threat accordingly should transition from hail to wind with time into the overnight period. ...IA, eastern NE, portions of KS, northern MO... Additional scattered to numerous thunderstorms may form farther south tonight over parts of the eastern NE/IA/northern MO area in a zone of strong low-level warm advection and moisture transport, with severe/significant hail potential. This regime is a good deal more uncertain in how it may develop and evolve, including how much influence may persist from High Plains activity persisting into the region vs. in situ development with the warm-advection/LLJ corridor. The extensive area of antecedent convection over KS/MO -- and related airmass effects on timing/extent of recovery farther north this afternoon and evening -- yield the bulk of uncertainty in this forecast. The severe that occurred late over KS/MO during the past overnight period required 12-18 hours of postconvective recovery following extensive convection to the south. Loosely similarly, a delayed onset of convective/severe potential into the evening/overnight hours is probable across the outlook area again this day-1 period. Two main differences will be: 1. Somewhat weaker but still adequate low-level moisture/theta-e, and 2. Stronger but still peripheral mid/upper-level influences southeast of the pronounced shortwave trough, in terms of synoptic-scale lift via warm advection and weak DCVA/cooling, and strengthening gradient winds aloft for favorable deep shear. At this time, uncertainty remains too large to increase or areally refine the unconditional severe probabilities. ..Edwards/Marsh.. 08/17/2019 Read more

MD 1767 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL AND NORTHERN ILLINOIS AND WESTERN INDIANA
Mesoscale Discussion 1767 NWS Storm Prediction Center Norman OK 0800 AM CDT Sat Aug 17 2019 Areas affected...central and northern Illinois and western Indiana Concerning...Severe potential...Watch unlikely Valid 171300Z - 171500Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorms will continue to move out of Missouri and into central Illinois this morning. Additional thunderstorms will be possible across northern Illinois as well. Hail and gusty winds may be possible with the strongest cores. The area will be monitored for potential watch, but current indications are that the threat should remain sufficiently isolated to not warrant one. DISCUSSION...Long-lived cluster of thunderstorms continues to move east from northern Missouri into central Iowa. Most-unstable CAPE along and ahead of this cluster is around 1000-1500 J/kg; however, deep-layer shear is generally less than 25 knots. Thus, although a severe hail or strong thunderstorm wind gust will be possible with the strongest cores, the threat should remain sufficiently isolated/episodic that a watch is not currently anticipated for this activity. To the north, across northern Illinois, additional thunderstorms may develop within a belt of stronger midlevel flow, likely in response to ageostrophic forcing from the mesoscale convective system to the southwest. The result will be thunderstorms developing in an objectively analyzed environment of most-unstable CAPE around 1000-1500 J/kg and deep-layer shear of 40-50 knots. Although this would normally suggest a threat for organized severe thunderstorms, considerable uncertainty remains regarding convective coverage and longevity. As such, area will continue to be monitored for potential watch, but expectations are that the threat will remain too isolated in nature to warrant watch issuance. ..Marsh/Edwards.. 08/17/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IWX...IND...LOT...ILX...LSX...DVN... LAT...LON 39948994 41609062 42338945 41488669 39198715 38529025 39948994 Read more

000
ABPZ20 KNHC 171147
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat Aug 17 2019

For the eastern North Pacific...east of 140 degrees west longitude:

An area of low pressure located a couple of hundred miles south of
the coast of Guatemala is producing some disorganized showers and
thunderstorms. Environmental conditions are expected to be
conducive for development, and a tropical depression is likely to
form early next week while the low moves west-northwestward at about
10 mph parallel to the coast of Mexico. Regardless of development,
moisture associated with the low is forecast to produce heavy
rainfall and possible flash flooding across portions of Central
America and southeastern Mexico during the next few days.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...high...80 percent.

Shower and thunderstorm activity has increased in association with
a tropical wave located about 850 miles south-southwest of the
southern tip of the Baja California peninsula. Some slow
development of this system is possible over the next several days
while it moves westward to west-northwestward at 5 to 10 mph.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

Another tropical wave located about 1300 miles west-southwest of
the southern tip of the Baja California peninsula continues to
produce disorganized showers and thunderstorms. Gradual development
of this system is possible during the next couple of days while it
moves slowly westward at about 5 mph across the southwestern portion
of the eastern Pacific.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...low...20 percent.

$$
Forecaster Berg