Aggregator

...NEW TROPICAL DEPRESSION FORMS SOUTHWEST OF MEXICO... As of 9:00 AM MDT Thu Sep 12 the center of Thirteen-E was located near 15.9, -111.1 with movement WNW at 13 mph. The minimum central pressure was 1006 mb with maximum sustained winds of about 35 mph.

Issued at 1500 UTC THU SEP 12 2019 000 WTPZ23 KNHC 121450 TCMEP3 TROPICAL DEPRESSION THIRTEEN-E FORECAST/ADVISORY NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132019 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1500 UTC THU SEP 12 2019 THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT. TROPICAL DEPRESSION CENTER LOCATED NEAR 15.9N 111.1W AT 12/1500Z POSITION ACCURATE WITHIN 30 NM PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 11 KT ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 15.9N 111.1W AT 12/1500Z AT 12/1200Z CENTER WAS LOCATED NEAR 15.7N 110.6W FORECAST VALID 13/0000Z 16.3N 112.8W MAX WIND 35 KT...GUSTS 45 KT. 34 KT... 20NE 0SE 0SW 20NW. FORECAST VALID 13/1200Z 16.5N 114.8W MAX WIND 40 KT...GUSTS 50 KT. 34 KT... 40NE 20SE 0SW 40NW. FORECAST VALID 14/0000Z 16.7N 116.7W MAX WIND 50 KT...GUSTS 60 KT. 50 KT... 20NE 0SE 0SW 20NW. 34 KT... 60NE 30SE 30SW 60NW. FORECAST VALID 14/1200Z 17.0N 118.4W MAX WIND 60 KT...GUSTS 75 KT. 50 KT... 30NE 20SE 10SW 30NW. 34 KT... 70NE 40SE 40SW 70NW. FORECAST VALID 15/1200Z 17.9N 122.0W MAX WIND 75 KT...GUSTS 90 KT. 50 KT... 30NE 30SE 20SW 30NW. 34 KT... 70NE 50SE 50SW 70NW. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 100 NM ON DAY 4 AND 150 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 16/1200Z 18.8N 124.8W MAX WIND 65 KT...GUSTS 80 KT. OUTLOOK VALID 17/1200Z 19.5N 126.0W MAX WIND 50 KT...GUSTS 60 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 15.9N 111.1W NEXT ADVISORY AT 12/2100Z $$ FORECASTER CHENARD/BLAKE

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Thu Sep 12 2019 Valid 121300Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID/UPPER MISSISSIPPI VALLEY...SOUTHWESTWARD TO THE SOUTH-CENTRAL PLAINS... ...SUMMARY... Scattered strong-severe thunderstorms are expected across portions of the mid/upper Mississippi Valley, southwestward to the south-central Plains. ...Synopsis... The most pertinent mid/upper-level feature for this outlook will be a well-defined synoptic trough -- initially evident in moisture- channel imagery from a newly redeveloped 500-mb low over southeastern MT south-southwestward over the Four Corners area. The cyclone is forecast to deepen and pivot eastward across the Dakotas, reaching northern MN by the end of the period, when the trough should extend south-southwestward to central/southern KS. The associated surface low was analyzed at 11Z near SUX, with cold front southwestward across eastern NE, west-central KS and northeastern NM. A warm front -- reinforced by antecedent precip to its north -- was analyzed from the low through an area of outflow over northern IA, to northwestern IL, becoming quasistationary eastward over Lake Erie, north-central PA, northern NJ, and south of Long Island. By 00Z, the synoptic low should be occluding over northwestern MN, with a triple point farther southeast over southeastern MN. The warm front should extend from there over northwestern IL, becoming quasistationary from there across north-central IN, then a slow-moving cold front over parts of PA and NJ. The western cold front should reach central IA, eastern KS, western OK, and east-central NM by 00Z. By 12Z, this cold front should extend from a triple point near or over southern Lake Michigan across southwestern IL, southwestern MO, southwestern OK, and the TX South Plains region. ...Southern MN, IA and vicinity... An ongoing swath of precip and embedded thunderstorms, over the northern IA/southern MN area, will continue east-northeastward at through the remainder of the morning with continued gradual weakening expected. This constitutes the remnants of the MCS from the Siouxland area discussed in the previous outlook, and appears to have a gradual rather than sudden increase in stabilizing effects on the boundary layer with westward extent toward the surface low/ front. As such, some trimming has been performed on the 5% and 15% severe areas, but additional stabilization may be minimal from roughly the current position of this convective plume eastward. Scattered thunderstorms are expected to develop in a generally north/south corridor over the western parts of the outlook area from midday through mid afternoon, shifting eastward and increasing in coverage with time. The relatively undisturbed warm sector and prospective inflow layer will contain very favorable theta-e as moisture transport, evapotranspiration and gradual/muted diabatic heating (under broken cloud cover) all occur, with dew points commonly upper 60s to low 70s F. The most favorable low-level and deep shear for supercells will exist in and just south of the warm-frontal zone, east and southeast of the surface low, where isallobaric forcing will keep near-surface winds relatively backed. This will lead to a relative maximum in storm-relative surface winds and low-level hodograph size, with the warm front also representing a relative corridor of boundary-layer vorticity and low LCL along the north rim of most favorable moisture and buoyancy. Given these factors, any relatively sustained/ discrete convection that can persist in this environment will have the greatest potential to become supercellular, with tornadoes and large hail as well as localized severe gusts. Otherwise, the threat will transition more toward wind with southward extent through IA. The band of convection should proceed eastward across the Mississippi River this evening, maintaining some severe threat, particularly near the warm front where storm-relative winds/ helicity, lift and vorticity will remain relatively maximized. ...MO to southern High Plains... Widely scattered to scattered thunderstorms should develop near the front this afternoon and persist into evening, offering the threat of damaging to severe gusts. A narrow prefrontal corridor of peak preconvective MLCAPE 1500-2500 J/kg should develop mid/late afternoon, related to diurnal surface heating/destabilization, modest but adequate mid/upper-level lapse rates, a deep troposphere, and rich low-level moisture. This, and minimal MLCINH, will encourage convection in the frontal convergence zone that should peak late afternoon into early evening. Mid/upper-level winds and related deep shear should remain strongest behind the front, with deep-layer mean flow having a large component parallel to the boundary. As a result, only short-lived discrete/ semi-discrete convective character is expected with multicellular mode, ultimately developing a band of convection. This band should be more dense from about central/west-central OK northeastward across MO. It also generally should be shorter-lived with southwestward extent, leading to a tapering outlook geometry. These factors account for the greater unconditional severe potential from about central OK northeastward, relative to the more brief/isolated nature of the threat across the southern High Plains region. With substantial upper support and the strongest LLJ each remaining roughly north of I-70, expected nocturnal cooling of the warm-sector boundary layer, and the front's being shallower in slope than across the IA/MN area, the convective/severe threat should wane late this evening through the overnight hours. ...Mid-Atlantic/Tidewater... Isolated to widely scattered thunderstorms should form this afternoon along the front, and a surface trough extending southwestward across the region near the western rim of the outlook area. Damaging gusts are expected from the most intense cells, with isolated severe (50+ kt) downdrafts possible. Deep-layer flow/shear will be weak, limiting overall organization of the severe threat, However, strong surface heating amidst favorable low-level moisture (surface dew points commonly upper 60s to low 70s F) will offset modest midlevel lapse rates enough to support MLCAPE in the 1000- 1500 J/kg range over norther parts of the area, where greater low-level lift is expected near the boundaries, to 2000-3000 J/kg across portions of southeastern VA and the Carolinas, amidst weaker low-level forcing. Water-loaded downdrafts and shallow but well- mixed boundary layers should contribute to the potential for strong/isolated severe convective gusts. ..Edwards/Dial.. 09/12/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Thu Sep 12 2019 Valid 121300Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID/UPPER MISSISSIPPI VALLEY...SOUTHWESTWARD TO THE SOUTH-CENTRAL PLAINS... ...SUMMARY... Scattered strong-severe thunderstorms are expected across portions of the mid/upper Mississippi Valley, southwestward to the south-central Plains. ...Synopsis... The most pertinent mid/upper-level feature for this outlook will be a well-defined synoptic trough -- initially evident in moisture- channel imagery from a newly redeveloped 500-mb low over southeastern MT south-southwestward over the Four Corners area. The cyclone is forecast to deepen and pivot eastward across the Dakotas, reaching northern MN by the end of the period, when the trough should extend south-southwestward to central/southern KS. The associated surface low was analyzed at 11Z near SUX, with cold front southwestward across eastern NE, west-central KS and northeastern NM. A warm front -- reinforced by antecedent precip to its north -- was analyzed from the low through an area of outflow over northern IA, to northwestern IL, becoming quasistationary eastward over Lake Erie, north-central PA, northern NJ, and south of Long Island. By 00Z, the synoptic low should be occluding over northwestern MN, with a triple point farther southeast over southeastern MN. The warm front should extend from there over northwestern IL, becoming quasistationary from there across north-central IN, then a slow-moving cold front over parts of PA and NJ. The western cold front should reach central IA, eastern KS, western OK, and east-central NM by 00Z. By 12Z, this cold front should extend from a triple point near or over southern Lake Michigan across southwestern IL, southwestern MO, southwestern OK, and the TX South Plains region. ...Southern MN, IA and vicinity... An ongoing swath of precip and embedded thunderstorms, over the northern IA/southern MN area, will continue east-northeastward at through the remainder of the morning with continued gradual weakening expected. This constitutes the remnants of the MCS from the Siouxland area discussed in the previous outlook, and appears to have a gradual rather than sudden increase in stabilizing effects on the boundary layer with westward extent toward the surface low/ front. As such, some trimming has been performed on the 5% and 15% severe areas, but additional stabilization may be minimal from roughly the current position of this convective plume eastward. Scattered thunderstorms are expected to develop in a generally north/south corridor over the western parts of the outlook area from midday through mid afternoon, shifting eastward and increasing in coverage with time. The relatively undisturbed warm sector and prospective inflow layer will contain very favorable theta-e as moisture transport, evapotranspiration and gradual/muted diabatic heating (under broken cloud cover) all occur, with dew points commonly upper 60s to low 70s F. The most favorable low-level and deep shear for supercells will exist in and just south of the warm-frontal zone, east and southeast of the surface low, where isallobaric forcing will keep near-surface winds relatively backed. This will lead to a relative maximum in storm-relative surface winds and low-level hodograph size, with the warm front also representing a relative corridor of boundary-layer vorticity and low LCL along the north rim of most favorable moisture and buoyancy. Given these factors, any relatively sustained/ discrete convection that can persist in this environment will have the greatest potential to become supercellular, with tornadoes and large hail as well as localized severe gusts. Otherwise, the threat will transition more toward wind with southward extent through IA. The band of convection should proceed eastward across the Mississippi River this evening, maintaining some severe threat, particularly near the warm front where storm-relative winds/ helicity, lift and vorticity will remain relatively maximized. ...MO to southern High Plains... Widely scattered to scattered thunderstorms should develop near the front this afternoon and persist into evening, offering the threat of damaging to severe gusts. A narrow prefrontal corridor of peak preconvective MLCAPE 1500-2500 J/kg should develop mid/late afternoon, related to diurnal surface heating/destabilization, modest but adequate mid/upper-level lapse rates, a deep troposphere, and rich low-level moisture. This, and minimal MLCINH, will encourage convection in the frontal convergence zone that should peak late afternoon into early evening. Mid/upper-level winds and related deep shear should remain strongest behind the front, with deep-layer mean flow having a large component parallel to the boundary. As a result, only short-lived discrete/ semi-discrete convective character is expected with multicellular mode, ultimately developing a band of convection. This band should be more dense from about central/west-central OK northeastward across MO. It also generally should be shorter-lived with southwestward extent, leading to a tapering outlook geometry. These factors account for the greater unconditional severe potential from about central OK northeastward, relative to the more brief/isolated nature of the threat across the southern High Plains region. With substantial upper support and the strongest LLJ each remaining roughly north of I-70, expected nocturnal cooling of the warm-sector boundary layer, and the front's being shallower in slope than across the IA/MN area, the convective/severe threat should wane late this evening through the overnight hours. ...Mid-Atlantic/Tidewater... Isolated to widely scattered thunderstorms should form this afternoon along the front, and a surface trough extending southwestward across the region near the western rim of the outlook area. Damaging gusts are expected from the most intense cells, with isolated severe (50+ kt) downdrafts possible. Deep-layer flow/shear will be weak, limiting overall organization of the severe threat, However, strong surface heating amidst favorable low-level moisture (surface dew points commonly upper 60s to low 70s F) will offset modest midlevel lapse rates enough to support MLCAPE in the 1000- 1500 J/kg range over norther parts of the area, where greater low-level lift is expected near the boundaries, to 2000-3000 J/kg across portions of southeastern VA and the Carolinas, amidst weaker low-level forcing. Water-loaded downdrafts and shallow but well- mixed boundary layers should contribute to the potential for strong/isolated severe convective gusts. ..Edwards/Dial.. 09/12/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Thu Sep 12 2019 Valid 121300Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID/UPPER MISSISSIPPI VALLEY...SOUTHWESTWARD TO THE SOUTH-CENTRAL PLAINS... ...SUMMARY... Scattered strong-severe thunderstorms are expected across portions of the mid/upper Mississippi Valley, southwestward to the south-central Plains. ...Synopsis... The most pertinent mid/upper-level feature for this outlook will be a well-defined synoptic trough -- initially evident in moisture- channel imagery from a newly redeveloped 500-mb low over southeastern MT south-southwestward over the Four Corners area. The cyclone is forecast to deepen and pivot eastward across the Dakotas, reaching northern MN by the end of the period, when the trough should extend south-southwestward to central/southern KS. The associated surface low was analyzed at 11Z near SUX, with cold front southwestward across eastern NE, west-central KS and northeastern NM. A warm front -- reinforced by antecedent precip to its north -- was analyzed from the low through an area of outflow over northern IA, to northwestern IL, becoming quasistationary eastward over Lake Erie, north-central PA, northern NJ, and south of Long Island. By 00Z, the synoptic low should be occluding over northwestern MN, with a triple point farther southeast over southeastern MN. The warm front should extend from there over northwestern IL, becoming quasistationary from there across north-central IN, then a slow-moving cold front over parts of PA and NJ. The western cold front should reach central IA, eastern KS, western OK, and east-central NM by 00Z. By 12Z, this cold front should extend from a triple point near or over southern Lake Michigan across southwestern IL, southwestern MO, southwestern OK, and the TX South Plains region. ...Southern MN, IA and vicinity... An ongoing swath of precip and embedded thunderstorms, over the northern IA/southern MN area, will continue east-northeastward at through the remainder of the morning with continued gradual weakening expected. This constitutes the remnants of the MCS from the Siouxland area discussed in the previous outlook, and appears to have a gradual rather than sudden increase in stabilizing effects on the boundary layer with westward extent toward the surface low/ front. As such, some trimming has been performed on the 5% and 15% severe areas, but additional stabilization may be minimal from roughly the current position of this convective plume eastward. Scattered thunderstorms are expected to develop in a generally north/south corridor over the western parts of the outlook area from midday through mid afternoon, shifting eastward and increasing in coverage with time. The relatively undisturbed warm sector and prospective inflow layer will contain very favorable theta-e as moisture transport, evapotranspiration and gradual/muted diabatic heating (under broken cloud cover) all occur, with dew points commonly upper 60s to low 70s F. The most favorable low-level and deep shear for supercells will exist in and just south of the warm-frontal zone, east and southeast of the surface low, where isallobaric forcing will keep near-surface winds relatively backed. This will lead to a relative maximum in storm-relative surface winds and low-level hodograph size, with the warm front also representing a relative corridor of boundary-layer vorticity and low LCL along the north rim of most favorable moisture and buoyancy. Given these factors, any relatively sustained/ discrete convection that can persist in this environment will have the greatest potential to become supercellular, with tornadoes and large hail as well as localized severe gusts. Otherwise, the threat will transition more toward wind with southward extent through IA. The band of convection should proceed eastward across the Mississippi River this evening, maintaining some severe threat, particularly near the warm front where storm-relative winds/ helicity, lift and vorticity will remain relatively maximized. ...MO to southern High Plains... Widely scattered to scattered thunderstorms should develop near the front this afternoon and persist into evening, offering the threat of damaging to severe gusts. A narrow prefrontal corridor of peak preconvective MLCAPE 1500-2500 J/kg should develop mid/late afternoon, related to diurnal surface heating/destabilization, modest but adequate mid/upper-level lapse rates, a deep troposphere, and rich low-level moisture. This, and minimal MLCINH, will encourage convection in the frontal convergence zone that should peak late afternoon into early evening. Mid/upper-level winds and related deep shear should remain strongest behind the front, with deep-layer mean flow having a large component parallel to the boundary. As a result, only short-lived discrete/ semi-discrete convective character is expected with multicellular mode, ultimately developing a band of convection. This band should be more dense from about central/west-central OK northeastward across MO. It also generally should be shorter-lived with southwestward extent, leading to a tapering outlook geometry. These factors account for the greater unconditional severe potential from about central OK northeastward, relative to the more brief/isolated nature of the threat across the southern High Plains region. With substantial upper support and the strongest LLJ each remaining roughly north of I-70, expected nocturnal cooling of the warm-sector boundary layer, and the front's being shallower in slope than across the IA/MN area, the convective/severe threat should wane late this evening through the overnight hours. ...Mid-Atlantic/Tidewater... Isolated to widely scattered thunderstorms should form this afternoon along the front, and a surface trough extending southwestward across the region near the western rim of the outlook area. Damaging gusts are expected from the most intense cells, with isolated severe (50+ kt) downdrafts possible. Deep-layer flow/shear will be weak, limiting overall organization of the severe threat, However, strong surface heating amidst favorable low-level moisture (surface dew points commonly upper 60s to low 70s F) will offset modest midlevel lapse rates enough to support MLCAPE in the 1000- 1500 J/kg range over norther parts of the area, where greater low-level lift is expected near the boundaries, to 2000-3000 J/kg across portions of southeastern VA and the Carolinas, amidst weaker low-level forcing. Water-loaded downdrafts and shallow but well- mixed boundary layers should contribute to the potential for strong/isolated severe convective gusts. ..Edwards/Dial.. 09/12/2019 Read more

000
ABPZ20 KNHC 121153
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Thu Sep 12 2019

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

Showers and thunderstorms have become more concentrated and better
organized this morning around an area of low pressure located about
500 miles south of the southern tip of the Baja California
peninsula, and a tropical depression appears to be forming. If this
trend continues, advisories will be initiated later this morning or
afternoon while the system moves west-northwestward at about 10 mph.
For additional information on this system, please refer to High Seas
Forecasts issued by the National Weather Service.
* Formation chance through 48 hours...high...near 100 percent.
* Formation chance through 5 days...high...near 100 percent.

A tropical wave located about 1500 miles southwest of the southern
tip of the Baja California peninsula continues to produce
disorganized showers and thunderstorms. Some slow development of
this disturbance is possible during the next few days while the
system moves slowly westward at 5 to 10 mph.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...low...30 percent.

An area of low pressure is expected to form west of the coast of
Central America over the weekend. Development of this system is
possible early next week while it moves westward well south of the
southern coast of Mexico.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...30 percent.

&&
High Seas Forecasts issued by the National Weather Service can be
found under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on
the web at ocean.weather.gov/shtml/NFDHSFEPI.php

$$
Forecaster Latto

000
ABNT20 KNHC 121148
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Thu Sep 12 2019

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Satellite images indicate that the area of disturbed weather over
the central and southeastern Bahamas is gradually becoming better
organized while surface pressures are falling in the area.
Conditions are becoming favorable for a tropical depression or a
tropical storm to form within the next day or so as the system moves
toward the northwest through the northwestern Bahamas and toward
the Florida Peninsula at 5 to 10 mph. If this development trend
continues Potential Tropical Cyclone advisories will likely be
initiated later today. This disturbance will bring heavy rainfall
and gusty winds across portions of the Bahamas through Friday,
especially in portions of the northwestern Bahamas affected by
Hurricane Dorian. An Air Force Reserve reconnaissance aircraft is
scheduled to investigate the system this afternoon, if necessary.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...80 percent.

A tropical wave located several hundred miles west of the Cabo
Verde Islands is producing disorganized showers and thunderstorms.
Conditions appear conducive for development, and a tropical
depression could form early next week while the system moves
westward over the tropical Atlantic.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...40 percent.

$$
Forecaster Avila

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0256 AM CDT Thu Sep 12 2019 Valid 151200Z - 201200Z ...DISCUSSION... ...Sunday/Day 4 to Tuesday/Day 6... The medium-range models develop an upper-level ridge across the Mississippi Valley from Sunday to Tuesday. Low-level moisture is forecast to increase across the north-central U.S. during that time. However, capping associated with the upper-level ridge will keep convective development isolated. Uncertainty regarding the spatial distribution of instability and any resulting severe threat is substantial early in the week. ....Wednesday/Day 7 to Thursday/Day 8... For Wednesday and Thursday, the models move an upper-level trough across the Rockies and establish southwest flow in the central and northern Plains. This pattern should result in a potential for thunderstorm development in parts of the northern Plains on Wednesday and upper Mississippi Valley on Thursday. Moderate instability and deep-layer shear would be strong enough for a severe threat during that time. However, uncertainty remains considerable concerning the timing of the upper-level trough and exact distribution of instability each afternoon. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0256 AM CDT Thu Sep 12 2019 Valid 151200Z - 201200Z ...DISCUSSION... ...Sunday/Day 4 to Tuesday/Day 6... The medium-range models develop an upper-level ridge across the Mississippi Valley from Sunday to Tuesday. Low-level moisture is forecast to increase across the north-central U.S. during that time. However, capping associated with the upper-level ridge will keep convective development isolated. Uncertainty regarding the spatial distribution of instability and any resulting severe threat is substantial early in the week. ....Wednesday/Day 7 to Thursday/Day 8... For Wednesday and Thursday, the models move an upper-level trough across the Rockies and establish southwest flow in the central and northern Plains. This pattern should result in a potential for thunderstorm development in parts of the northern Plains on Wednesday and upper Mississippi Valley on Thursday. Moderate instability and deep-layer shear would be strong enough for a severe threat during that time. However, uncertainty remains considerable concerning the timing of the upper-level trough and exact distribution of instability each afternoon. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0256 AM CDT Thu Sep 12 2019 Valid 151200Z - 201200Z ...DISCUSSION... ...Sunday/Day 4 to Tuesday/Day 6... The medium-range models develop an upper-level ridge across the Mississippi Valley from Sunday to Tuesday. Low-level moisture is forecast to increase across the north-central U.S. during that time. However, capping associated with the upper-level ridge will keep convective development isolated. Uncertainty regarding the spatial distribution of instability and any resulting severe threat is substantial early in the week. ....Wednesday/Day 7 to Thursday/Day 8... For Wednesday and Thursday, the models move an upper-level trough across the Rockies and establish southwest flow in the central and northern Plains. This pattern should result in a potential for thunderstorm development in parts of the northern Plains on Wednesday and upper Mississippi Valley on Thursday. Moderate instability and deep-layer shear would be strong enough for a severe threat during that time. However, uncertainty remains considerable concerning the timing of the upper-level trough and exact distribution of instability each afternoon. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Thu Sep 12 2019 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms associated with marginally severe wind gusts and hail will be possible on Saturday across parts of the Upper Midwest. ...Upper Midwest... A shortwave trough is forecast to move eastward across the western Great Lakes on Saturday as a cold front advances quickly eastward through the Dakotas. Ahead of the front, a corridor of maximized low-level moisture is forecast to setup from the mid Missouri Valley northward into the eastern part of the northern Plains. Although moderate instability is forecast to develop along the moist corridor, a capping inversion should limit thunderstorm development during the afternoon. The cap should weaken enough in the early to mid evening to allow for scattered thunderstorm development from far northeast Nebraska into Iowa and southern Minnesota. With moderate deep-layer shear across much of the region, cells could become strong enough to produce marginally severe wind gusts and hail. The shortwave trough is forecast to move eastward away from the region during the evening. Subsidence in the wake of this feature should keep any convection from becoming organized during the evening and early overnight period. ..Broyles.. 09/12/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Thu Sep 12 2019 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms associated with marginally severe wind gusts and hail will be possible on Saturday across parts of the Upper Midwest. ...Upper Midwest... A shortwave trough is forecast to move eastward across the western Great Lakes on Saturday as a cold front advances quickly eastward through the Dakotas. Ahead of the front, a corridor of maximized low-level moisture is forecast to setup from the mid Missouri Valley northward into the eastern part of the northern Plains. Although moderate instability is forecast to develop along the moist corridor, a capping inversion should limit thunderstorm development during the afternoon. The cap should weaken enough in the early to mid evening to allow for scattered thunderstorm development from far northeast Nebraska into Iowa and southern Minnesota. With moderate deep-layer shear across much of the region, cells could become strong enough to produce marginally severe wind gusts and hail. The shortwave trough is forecast to move eastward away from the region during the evening. Subsidence in the wake of this feature should keep any convection from becoming organized during the evening and early overnight period. ..Broyles.. 09/12/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Thu Sep 12 2019 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms associated with marginally severe wind gusts and hail will be possible on Saturday across parts of the Upper Midwest. ...Upper Midwest... A shortwave trough is forecast to move eastward across the western Great Lakes on Saturday as a cold front advances quickly eastward through the Dakotas. Ahead of the front, a corridor of maximized low-level moisture is forecast to setup from the mid Missouri Valley northward into the eastern part of the northern Plains. Although moderate instability is forecast to develop along the moist corridor, a capping inversion should limit thunderstorm development during the afternoon. The cap should weaken enough in the early to mid evening to allow for scattered thunderstorm development from far northeast Nebraska into Iowa and southern Minnesota. With moderate deep-layer shear across much of the region, cells could become strong enough to produce marginally severe wind gusts and hail. The shortwave trough is forecast to move eastward away from the region during the evening. Subsidence in the wake of this feature should keep any convection from becoming organized during the evening and early overnight period. ..Broyles.. 09/12/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 AM CDT Thu Sep 12 2019 Valid 131200Z - 141200Z ...Synopsis... The next in a series of mid-level shortwave troughs will eject into the northern Plains, with zonal flow aloft dominating the western CONUS on Day 2/Friday. Surface high pressure across the Great Basin, and an inverted surface trough off of the California Coast, will again be fortified, with a modest pressure gradient (though weaker than Day 1) established across southern California. Offshore flow will again promote dry, breezy conditions to parts of the southern California coastal areas. ...Southern Coastal California... Offshore flow will likely be ongoing at the start of Day 2, with 15-25 mph northeasterly sustained surface winds and 15-25% RH expected, from the Santa Ynez to San Gabriel Mountains. Fuels across the areas remain at least marginally receptive to fire spread, with the greatest potential of elevated-conditions/receptive-fuels overlap expected in the higher terrain. Relaxation of the pressure gradient will result in calmer winds during the day, with some increase in offshore flow again at night (towards the end of the period) with re-tightening of the gradient and poor RH recoveries likely. ..Squitieri.. 09/12/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 AM CDT Thu Sep 12 2019 Valid 131200Z - 141200Z ...Synopsis... The next in a series of mid-level shortwave troughs will eject into the northern Plains, with zonal flow aloft dominating the western CONUS on Day 2/Friday. Surface high pressure across the Great Basin, and an inverted surface trough off of the California Coast, will again be fortified, with a modest pressure gradient (though weaker than Day 1) established across southern California. Offshore flow will again promote dry, breezy conditions to parts of the southern California coastal areas. ...Southern Coastal California... Offshore flow will likely be ongoing at the start of Day 2, with 15-25 mph northeasterly sustained surface winds and 15-25% RH expected, from the Santa Ynez to San Gabriel Mountains. Fuels across the areas remain at least marginally receptive to fire spread, with the greatest potential of elevated-conditions/receptive-fuels overlap expected in the higher terrain. Relaxation of the pressure gradient will result in calmer winds during the day, with some increase in offshore flow again at night (towards the end of the period) with re-tightening of the gradient and poor RH recoveries likely. ..Squitieri.. 09/12/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 AM CDT Thu Sep 12 2019 Valid 131200Z - 141200Z ...Synopsis... The next in a series of mid-level shortwave troughs will eject into the northern Plains, with zonal flow aloft dominating the western CONUS on Day 2/Friday. Surface high pressure across the Great Basin, and an inverted surface trough off of the California Coast, will again be fortified, with a modest pressure gradient (though weaker than Day 1) established across southern California. Offshore flow will again promote dry, breezy conditions to parts of the southern California coastal areas. ...Southern Coastal California... Offshore flow will likely be ongoing at the start of Day 2, with 15-25 mph northeasterly sustained surface winds and 15-25% RH expected, from the Santa Ynez to San Gabriel Mountains. Fuels across the areas remain at least marginally receptive to fire spread, with the greatest potential of elevated-conditions/receptive-fuels overlap expected in the higher terrain. Relaxation of the pressure gradient will result in calmer winds during the day, with some increase in offshore flow again at night (towards the end of the period) with re-tightening of the gradient and poor RH recoveries likely. ..Squitieri.. 09/12/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0647 Status Updates
STATUS REPORT ON WW 647 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 W YKN TO 5 ESE MHE TO 20 NNE FSD. ..DIAL..09/12/19 ATTN...WFO...OAX...FSD...ABR...UNR... STATUS REPORT FOR WS 647 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS NEC003-011-027-043-051-107-119-139-141-120740- NE . NEBRASKA COUNTIES INCLUDED ARE ANTELOPE BOONE CEDAR DAKOTA DIXON KNOX MADISON PIERCE PLATTE SDC009-027-061-067-083-087-099-125-127-135-120740- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BON HOMME CLAY HANSON HUTCHINSON LINCOLN MCCOOK MINNEHAHA TURNER UNION YANKTON THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 647 SEVERE TSTM NE SD 120100Z - 120800Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 647 NWS Storm Prediction Center Norman OK 800 PM CDT Wed Sep 11 2019 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of northeastern Nebraska parts of central and eastern South Dakota * Effective this Wednesday night and Thursday morning from 800 PM until 300 AM CDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Thunderstorms are forecast to continue increasing in coverage this evening, across the South Dakota vicinity, with isolated severe storms gradually evolving within the larger area of convection. Large hail is expected to be the primary severe risk, though locally damaging winds -- and possibly a tornado -- will also be a possibility this evening. The severe thunderstorm watch area is approximately along and 60 statute miles north and south of a line from 55 miles southwest of Pierre SD to 15 miles north northeast of Sioux Falls SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 645...WW 646... AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 600. Mean storm motion vector 24035. ...Goss Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0121 AM CDT Thu Sep 12 2019 Valid 121200Z - 131200Z ...Synopsis... A mid-level shortwave trough will eject into the Plains states, with a second mid-level shortwave impinging on the Pacific Northwest. At the surface, a large-scale high will dominate the west-southwestern CONUS, with an inverted surface trough fortified off of the California Coast, inducing a modest pressure gradient across central into southern California. Offshore breezy, dry flow will promote marginally favorable conditions for wildfire spread across the southern Coastal Range. ...Southern Coastal California... With the aforementioned pressure gradient in place, offshore flow will likely be present at the start of the period across the Santa Ynez to San Gabriel Mountains, with 15+ mph sustained northeasterly winds and 15-25% RH expected. Through the late morning to late afternoon hours, some diffusion of the larger-scale pressure gradient is expected, with subsiding winds likely. After dark, into the early morning hours (at the end of the period), tightening of the pressure gradient is expected, with a return of offshore flow exceeding 15 mph and 15-25% RH, from the Santa Ynez to Laguna Mountain Ranges. ..Squitieri.. 09/12/2019 ...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 0121 AM CDT Thu Sep 12 2019 Valid 121200Z - 131200Z ...Synopsis... A mid-level shortwave trough will eject into the Plains states, with a second mid-level shortwave impinging on the Pacific Northwest. At the surface, a large-scale high will dominate the west-southwestern CONUS, with an inverted surface trough fortified off of the California Coast, inducing a modest pressure gradient across central into southern California. Offshore breezy, dry flow will promote marginally favorable conditions for wildfire spread across the southern Coastal Range. ...Southern Coastal California... With the aforementioned pressure gradient in place, offshore flow will likely be present at the start of the period across the Santa Ynez to San Gabriel Mountains, with 15+ mph sustained northeasterly winds and 15-25% RH expected. Through the late morning to late afternoon hours, some diffusion of the larger-scale pressure gradient is expected, with subsiding winds likely. After dark, into the early morning hours (at the end of the period), tightening of the pressure gradient is expected, with a return of offshore flow exceeding 15 mph and 15-25% RH, from the Santa Ynez to Laguna Mountain Ranges. ..Squitieri.. 09/12/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more