Aggregator

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Fri Aug 23 2019 Valid 231300Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTH CAROLINA AND VIRGINIA...AS WELL AS THE CENTRAL HIGH PLAINS... ...SUMMARY... Organized severe thunderstorms appear most probable today over portions of North Carolina and Virginia, as well as the central High Plains. ...Synopsis... The upper-air pattern over the CONUS this period will be dominated by a fairly high-amplitude northern stream across roughly the northern half, along with several slow-moving shortwaves and related MCVs from the central/southern Plains to the Tidewater region of the Atlantic Coast. A synoptic cyclone over eastern QC will devolve into an open-wave trough, extending southwestward over the lower Great Lakes and interior Mid-Atlantic region. This will contribute to the eastward ejection of a subtle, convectively enhanced vorticity lobe, now apparent in moisture-channel imagery over the Appalachians between southern WV and northeastern GA. This perturbation should move east-northeastward across VA and northern NC today, then offshore from the Delmarva Peninsula by 00Z. Upstream, high-amplitude ridging will shift eastward from the upper Mississippi Valley across the upper Great Lakes. The trailing region of large-scale height falls will be populated by several slowly eastward- to northeastward-moving MCVs and small shortwave troughs over the central/southern Plains. A substantial shortwave trough is located from a closed 500-mb low over southwestern MT southward across UT to northern AZ. This trough will move eastward to central/eastern portions of WY and CO through the period. At the surface, 11Z analysis depicted a cold front from offshore New England across DE, northern VA, central WV, southern IL and central MO, becoming quasistationary northeastward across east-central/ north-central NE and southwestern ND, to a low over northeastern MT north of GDV. As a surface anticyclone over Lake Superior shifts eastward, the front will move southeastward/southward over VA/NC/KY, reaching SC, TN, and northern AR by 12Z. The western segment of the front will move little over NE while shifting northeastward slowly across the Dakotas as a warm front. ...NC/VA... Scattered thunderstorms are expected to develop along/ahead of the front from midday through afternoon, mainly over western and northern VA. This activity should expand and intensify while encountering a favorably moist and destabilizing air mass across central/southern VA, the southern Delmarva and northeastern NC. A few severe gusts will be possible, along with more-widespread damaging wind approaching severe limits. Isolated large hail also may occur, especially over northern portions of the outlook in association with colder air aloft and less-messy convective modes. This area will reside under the southern rim of the stronger midlevel winds aloft, related to the eastern Canadian synoptic trough and the ejecting southern Appalachians shortwave trough, the latter also providing support through subtle DCVA/ascent in midlevels. The associated mass responses should encourage enhanced convergence in the frontal/prefrontal air mass, amidst weak ambient MLCINH. Favorable buoyancy will occur despite modest mid/upper- level lapse rates, thanks to 1. Rich boundary-layer moisture (70s F surface dew points and PW of 1.75 to 2.25 inches being common), and 2. Areas of intermittent (but cumulatively favorable) diabatic surface heating in the warm sector. Peak preconvective MLCAPE should vary from around 500-1000 J/kg in the northern and western parts of the outlook to around 1500-2000 J/kg over northeastern NC. 25-35-kt flow is forecast in much of the 700-400-mb layer, with marginally supercell-favorable effective shear in northern areas. However, deep shear will diminish markedly with southward extent. Upper-level winds will be weaker over most of the area, however, contributing to potential for messy convective modes after early semi-discrete phases. One or more bowing segments may evolve within a band of mostly multicellular thunderstorms across VA and into northeastern SC late this afternoon into early evening before activity weakens and/or moves offshore. ...Central High Plains... Scattered thunderstorms should develop this afternoon over well-heated higher terrain, near that part of the I-25 corridor between CPR-RTN. This activity is forecast to move eastward to northeastward across the adjoining High Plains into a favorable moist, diabatically destabilized air mass, offering damaging gusts and sporadic hail. A tornado cannot be ruled out as well, this threat depending strongly on mesobeta- to storm-scale processes that remain rather uncertain/unfocused in predictability terms as this time. Mid/upper-level support is forecast to be atypically strong for this time of year, with large-scale ascent from the shortwave perturbations and strongly difluent upper flow. Steep midlevel lapse rates and moist/warm advection in low levels will contribute to destabilization as well, west of a well-defined moist axis that parallels the frontal zone from central/eastern KS to the western Dakotas. Surface dew points 50s to low 60s F should become common across the central High Plains, and at least near and east of the axis of the outlook area. These factors will contribute to peak MLCAPE values ranging from around 1500 J/kg over parts of eastern WY to the 2000-3000 J/kg range over much of the NE Panhandle, and parts of eastern CO and western KS. Given the strong veering with height expected in the low/middle- level wind profiles, low-level bulk shear and hodographs will be favorable for supercells and hail, though mid/upper winds will be modest amidst the aforementioned difluence. Effective-shear magnitudes 25-40 kt should be common. Modal uncertainties include timing of the transition from discrete to clustered with respect to storms moving from higher-elevation genesis areas into greater moisture. Still, at least a few cold-pool-driven arcs or bands of convection should develop to contribute to the wind potential, while moving into well-mixed subcloud/inflow layers. ..Edwards/Gleason.. 08/23/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Fri Aug 23 2019 Valid 231300Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTH CAROLINA AND VIRGINIA...AS WELL AS THE CENTRAL HIGH PLAINS... ...SUMMARY... Organized severe thunderstorms appear most probable today over portions of North Carolina and Virginia, as well as the central High Plains. ...Synopsis... The upper-air pattern over the CONUS this period will be dominated by a fairly high-amplitude northern stream across roughly the northern half, along with several slow-moving shortwaves and related MCVs from the central/southern Plains to the Tidewater region of the Atlantic Coast. A synoptic cyclone over eastern QC will devolve into an open-wave trough, extending southwestward over the lower Great Lakes and interior Mid-Atlantic region. This will contribute to the eastward ejection of a subtle, convectively enhanced vorticity lobe, now apparent in moisture-channel imagery over the Appalachians between southern WV and northeastern GA. This perturbation should move east-northeastward across VA and northern NC today, then offshore from the Delmarva Peninsula by 00Z. Upstream, high-amplitude ridging will shift eastward from the upper Mississippi Valley across the upper Great Lakes. The trailing region of large-scale height falls will be populated by several slowly eastward- to northeastward-moving MCVs and small shortwave troughs over the central/southern Plains. A substantial shortwave trough is located from a closed 500-mb low over southwestern MT southward across UT to northern AZ. This trough will move eastward to central/eastern portions of WY and CO through the period. At the surface, 11Z analysis depicted a cold front from offshore New England across DE, northern VA, central WV, southern IL and central MO, becoming quasistationary northeastward across east-central/ north-central NE and southwestern ND, to a low over northeastern MT north of GDV. As a surface anticyclone over Lake Superior shifts eastward, the front will move southeastward/southward over VA/NC/KY, reaching SC, TN, and northern AR by 12Z. The western segment of the front will move little over NE while shifting northeastward slowly across the Dakotas as a warm front. ...NC/VA... Scattered thunderstorms are expected to develop along/ahead of the front from midday through afternoon, mainly over western and northern VA. This activity should expand and intensify while encountering a favorably moist and destabilizing air mass across central/southern VA, the southern Delmarva and northeastern NC. A few severe gusts will be possible, along with more-widespread damaging wind approaching severe limits. Isolated large hail also may occur, especially over northern portions of the outlook in association with colder air aloft and less-messy convective modes. This area will reside under the southern rim of the stronger midlevel winds aloft, related to the eastern Canadian synoptic trough and the ejecting southern Appalachians shortwave trough, the latter also providing support through subtle DCVA/ascent in midlevels. The associated mass responses should encourage enhanced convergence in the frontal/prefrontal air mass, amidst weak ambient MLCINH. Favorable buoyancy will occur despite modest mid/upper- level lapse rates, thanks to 1. Rich boundary-layer moisture (70s F surface dew points and PW of 1.75 to 2.25 inches being common), and 2. Areas of intermittent (but cumulatively favorable) diabatic surface heating in the warm sector. Peak preconvective MLCAPE should vary from around 500-1000 J/kg in the northern and western parts of the outlook to around 1500-2000 J/kg over northeastern NC. 25-35-kt flow is forecast in much of the 700-400-mb layer, with marginally supercell-favorable effective shear in northern areas. However, deep shear will diminish markedly with southward extent. Upper-level winds will be weaker over most of the area, however, contributing to potential for messy convective modes after early semi-discrete phases. One or more bowing segments may evolve within a band of mostly multicellular thunderstorms across VA and into northeastern SC late this afternoon into early evening before activity weakens and/or moves offshore. ...Central High Plains... Scattered thunderstorms should develop this afternoon over well-heated higher terrain, near that part of the I-25 corridor between CPR-RTN. This activity is forecast to move eastward to northeastward across the adjoining High Plains into a favorable moist, diabatically destabilized air mass, offering damaging gusts and sporadic hail. A tornado cannot be ruled out as well, this threat depending strongly on mesobeta- to storm-scale processes that remain rather uncertain/unfocused in predictability terms as this time. Mid/upper-level support is forecast to be atypically strong for this time of year, with large-scale ascent from the shortwave perturbations and strongly difluent upper flow. Steep midlevel lapse rates and moist/warm advection in low levels will contribute to destabilization as well, west of a well-defined moist axis that parallels the frontal zone from central/eastern KS to the western Dakotas. Surface dew points 50s to low 60s F should become common across the central High Plains, and at least near and east of the axis of the outlook area. These factors will contribute to peak MLCAPE values ranging from around 1500 J/kg over parts of eastern WY to the 2000-3000 J/kg range over much of the NE Panhandle, and parts of eastern CO and western KS. Given the strong veering with height expected in the low/middle- level wind profiles, low-level bulk shear and hodographs will be favorable for supercells and hail, though mid/upper winds will be modest amidst the aforementioned difluence. Effective-shear magnitudes 25-40 kt should be common. Modal uncertainties include timing of the transition from discrete to clustered with respect to storms moving from higher-elevation genesis areas into greater moisture. Still, at least a few cold-pool-driven arcs or bands of convection should develop to contribute to the wind potential, while moving into well-mixed subcloud/inflow layers. ..Edwards/Gleason.. 08/23/2019 Read more

000
ABPZ20 KNHC 231137
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Fri Aug 23 2019

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

The National Hurricane Center is issuing advisories on Tropical
Storm Ivo, located several hundred miles southwest of the southern
tip of the Baja California peninsula.

A surface trough located about 1000 miles east-southeast of the Big
Island of Hawaii is producing disorganized cloudiness and showers.
Although this disturbance is not currently showing any signs of
development, environmental conditions could become a little more
conducive for some development in the central Pacific basin well to
the east of the Hawaiian Islands in a few days as the system moves
slowly northwestward.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...30 percent.

$$
Forecaster Latto/Beven

5-Day Uncertainty Track last updated Fri, 23 Aug 2019 08:44:28 GMT


Wind Speed Probabilities last updated Fri, 23 Aug 2019 09:31:08 GMT

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Aug 23 2019 Valid 261200Z - 311200Z ...DISCUSSION... Current medium-range guidance is in good agreement that a cold front will push through the TX Panhandle, much of OK, and the Ozark Plateau on D4/Monday. Given the strong buoyancy and modest vertical shear expected ahead of the front, some severe potential exists. However, despite consensus within the 00Z model suite, forecast confidence is still low owing to the potential for antecedent precipitation and variance in frontal timing noted in previous model runs. After D4/Monday, model solutions diverge with little run-to-run or model-to-model consistency noted. This leads to low forecast confidence, although the persistent moisture across the central and southeastern CONUS suggests severe thunderstorms remain possible. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Aug 23 2019 Valid 261200Z - 311200Z ...DISCUSSION... Current medium-range guidance is in good agreement that a cold front will push through the TX Panhandle, much of OK, and the Ozark Plateau on D4/Monday. Given the strong buoyancy and modest vertical shear expected ahead of the front, some severe potential exists. However, despite consensus within the 00Z model suite, forecast confidence is still low owing to the potential for antecedent precipitation and variance in frontal timing noted in previous model runs. After D4/Monday, model solutions diverge with little run-to-run or model-to-model consistency noted. This leads to low forecast confidence, although the persistent moisture across the central and southeastern CONUS suggests severe thunderstorms remain possible. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Aug 23 2019 Valid 261200Z - 311200Z ...DISCUSSION... Current medium-range guidance is in good agreement that a cold front will push through the TX Panhandle, much of OK, and the Ozark Plateau on D4/Monday. Given the strong buoyancy and modest vertical shear expected ahead of the front, some severe potential exists. However, despite consensus within the 00Z model suite, forecast confidence is still low owing to the potential for antecedent precipitation and variance in frontal timing noted in previous model runs. After D4/Monday, model solutions diverge with little run-to-run or model-to-model consistency noted. This leads to low forecast confidence, although the persistent moisture across the central and southeastern CONUS suggests severe thunderstorms remain possible. Read more

Issued at 300 AM MDT Fri Aug 23 2019 000 WTPZ45 KNHC 230842 TCDEP5 Tropical Storm Ivo Discussion Number 8 NWS National Hurricane Center Miami FL EP102019 300 AM MDT Fri Aug 23 2019 Unexpectedly, stronger than anticipated northeasterly shear affected Ivo during the past 12 hours or so, and the low-level center became detached from the main area of deep convection. The center can be clearly seen on microwave and conventional imagery, and it is located very near Clarion Island, Mexico. An automatic Mexican Navy weather station at that location reported that the surface pressure has been falling and has measured gusts to 39 kt. This information is very valuable to diagnose the structure of the cyclone. Despite the deterioration of the cloud pattern, a recent ASCAT pass measured a peak wind of 50 kt associated with Ivo, but this value was confined to a small area in the southeast quadrant. On this basis, the initial intensity has been adjusted downward to 50 kt, which is also a value close to the Dvorak estimates, or perhaps a tad higher. The cyclone is expected to be over warm waters for about a day or so, and given its vigorous circulation, Ivo could maintain the same intensity for the next 12 hours. After that time, Ivo should begin to weaken over cooler waters. Unanimously, all the models weaken the cyclone and so does the NHC forecast, and by 72 hours or sooner, Ivo should have degenerated into a remnant low. The center is moving toward the north-northwest or 330 degrees at 9 kt. The cyclone managed to find a weakness in the ridge, and since the steering pattern is not expected to change, this general motion is anticipated to continue until dissipation in 4 days. The NHC forecast is on the left edge of the guidance envelope and is basically on top of the multi-model consensus TVCE. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 17.9N 114.5W 50 KT 60 MPH 12H 23/1800Z 19.0N 115.2W 50 KT 60 MPH 24H 24/0600Z 20.5N 116.1W 45 KT 50 MPH 36H 24/1800Z 22.0N 116.8W 40 KT 45 MPH 48H 25/0600Z 24.0N 117.5W 30 KT 35 MPH 72H 26/0600Z 27.5N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/0600Z...DISSIPATED $$ Forecaster Avila

Issued at 0900 UTC FRI AUG 23 2019 000 FOPZ15 KNHC 230841 PWSEP5 TROPICAL STORM IVO WIND SPEED PROBABILITIES NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102019 0900 UTC FRI AUG 23 2019 AT 0900Z THE CENTER OF TROPICAL STORM IVO WAS LOCATED NEAR LATITUDE 17.9 NORTH...LONGITUDE 114.5 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 50 KTS...60 MPH...95 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) PACIFIC DAYLIGHT TIME (PDT)...SUBTRACT 7 HOURS FROM Z TIME HAWAIIAN STANDARD TIME (HST)...SUBTRACT 10 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 06Z FRI AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 06Z FRI 18Z FRI 06Z SAT 18Z SAT 06Z SUN 06Z MON 06Z TUE PERIODS TO TO TO TO TO TO TO 18Z FRI 06Z SAT 18Z SAT 06Z SUN 06Z MON 06Z TUE 06Z WED FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT IS GUADALUPE 34 X X( X) X( X) X( X) 3( 3) X( 3) X( 3) ISLA CLARION 34 98 1(99) X(99) X(99) X(99) X(99) X(99) ISLA CLARION 50 19 2(21) X(21) X(21) X(21) X(21) X(21) ISLA CLARION 64 1 X( 1) X( 1) X( 1) X( 1) X( 1) X( 1) 20N 115W 34 26 41(67) 1(68) X(68) X(68) X(68) X(68) 20N 115W 50 X 10(10) X(10) X(10) X(10) X(10) X(10) 25N 115W 34 X X( X) 1( 1) 1( 2) 1( 3) X( 3) X( 3) 25N 120W 34 X X( X) 1( 1) 1( 2) 6( 8) X( 8) X( 8) $$ FORECASTER AVILA

Issued at 300 AM MDT Fri Aug 23 2019 281 WTPZ35 KNHC 230841 TCPEP5 BULLETIN Tropical Storm Ivo Advisory Number 8 NWS National Hurricane Center Miami FL EP102019 300 AM MDT Fri Aug 23 2019 ...A WEAKER IVO APPROACHING CLARION ISLAND MEXICO... SUMMARY OF 300 AM MDT...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...17.9N 114.5W ABOUT 455 MI...735 KM SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H PRESENT MOVEMENT...NNW OR 330 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 300 AM MDT (0900 UTC), the center of Tropical Storm Ivo was located near latitude 17.9 North, longitude 114.5 West. Ivo is moving toward the north-northwest near 10 mph (17 km/h), and this general motion is expected to continue for the next 2 to 3 days. Maximum sustained winds are near 60 mph (95 km/h) with higher gusts. Little change in intensity is expected today, but Ivo should begin to weaken on Saturday. Tropical-storm-force winds extend outward up to 115 miles (185 km) from the center. A Mexican Navy automatic station at Clarion Island recently reported a wind to 45 mph (72 km/h). The estimated minimum central pressure is 996 mb (29.42 inches). HAZARDS AFFECTING LAND ---------------------- None NEXT ADVISORY ------------- Next complete advisory at 900 AM MDT. $$ Forecaster Avila

...A WEAKER IVO APPROACHING CLARION ISLAND MEXICO... As of 3:00 AM MDT Fri Aug 23 the center of Ivo was located near 17.9, -114.5 with movement NNW at 10 mph. The minimum central pressure was 996 mb with maximum sustained winds of about 60 mph.

MD 1837 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTH-CENTRAL NE INTO NORTH-CENTRAL KS
Mesoscale Discussion 1837 NWS Storm Prediction Center Norman OK 0338 AM CDT Fri Aug 23 2019 Areas affected...Portions of south-central NE into north-central KS Concerning...Severe potential...Watch unlikely Valid 230838Z - 231045Z Probability of Watch Issuance...5 percent SUMMARY...A long-lived supercell thunderstorm may continue to produce severe wind gusts and large hail through the early morning hours. This threat is expected to remain too isolated to justify watch issuance. DISCUSSION...A measured severe wind gust to 66 kt (76 mph) was recorded at 0759Z at Hastings NE (KSI) with a supercell thunderstorm moving slowly southward across south-central NE. This storm may be related to an MCV from convection yesterday across the central Plains, and it is located along a moisture/instability gradient evident on latest 850 mb and MUCAPE mesoanalysis fields. The VWP from KUEX has shown only a modest increase in a 15-20 kt south-southeasterly low-level jet over the past couple of hours, with mid-level westerly flow increasing to only about 30-35 kt. Regardless, this is apparently sufficient to support a persistent supercell, as observed by KUEX radar imagery. Given the ongoing storm organization and modestly steepened mid-level lapse rates across this region, isolated large hail may occur with this supercell in addition to severe wind gusts. It is uncertain how long this storm will persist, but it is moving slowly southward into a region with a relative minimum in convective inhibition owing to upper 60s to low 70s surface dewpoints. A severe risk may continue for the next couple of hours into part of north-central KS, but watch issuance is not currently expected given the very isolated nature of the threat. ..Gleason/Edwards.. 08/23/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TOP...GID... LAT...LON 40689863 40679819 40179778 39669763 39529814 39609863 40349878 40689863 Read more

Issued at 0900 UTC FRI AUG 23 2019 135 WTPZ25 KNHC 230837 TCMEP5 TROPICAL STORM IVO FORECAST/ADVISORY NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102019 0900 UTC FRI AUG 23 2019 THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT. TROPICAL STORM CENTER LOCATED NEAR 17.9N 114.5W AT 23/0900Z POSITION ACCURATE WITHIN 25 NM PRESENT MOVEMENT TOWARD THE NORTH-NORTHWEST OR 330 DEGREES AT 9 KT ESTIMATED MINIMUM CENTRAL PRESSURE 996 MB MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT. 50 KT....... 0NE 40SE 0SW 0NW. 34 KT....... 50NE 100SE 80SW 30NW. 12 FT SEAS..150NE 180SE 120SW 90NW. 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 17.9N 114.5W AT 23/0900Z AT 23/0600Z CENTER WAS LOCATED NEAR 17.5N 114.3W FORECAST VALID 23/1800Z 19.0N 115.2W MAX WIND 50 KT...GUSTS 60 KT. 50 KT... 0NE 40SE 0SW 0NW. 34 KT... 50NE 100SE 80SW 30NW. FORECAST VALID 24/0600Z 20.5N 116.1W MAX WIND 45 KT...GUSTS 55 KT. 34 KT... 70NE 80SE 40SW 40NW. FORECAST VALID 24/1800Z 22.0N 116.8W MAX WIND 40 KT...GUSTS 50 KT. 34 KT... 50NE 60SE 20SW 20NW. FORECAST VALID 25/0600Z 24.0N 117.5W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 26/0600Z 27.5N 119.0W...POST-TROP/REMNT LOW MAX WIND 25 KT...GUSTS 35 KT. 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 27/0600Z...DISSIPATED REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 17.9N 114.5W NEXT ADVISORY AT 23/1500Z $$ FORECASTER AVILA

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Fri Aug 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND SOUTHERN PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Sunday across portions of the northern and southern Plains. ...Synopsis... Medium-range guidance is in good agreement that a strong shortwave trough embedded within the enhanced westerlies moves from the northern Rockies through the northern Plains on Sunday. This results in a deepening of the cyclonic flow across the north-central CONUS. This pattern evolution will also push a cold front eastward/ southeastward through much of northern Plains. Elsewhere, warm and moist conditions will persist across much of southern Plains and Southeast while weakening high pressure across much of the eastern CONUS will allow for some moisture return into the OH Valley. ...Southern Plains... Air mass across the region will be warm, very moist, and strongly buoyant. Strengthening northwesterly flow aloft will also contribute to moderate vertical shear. Overall environment would support severe potential as long as forcing exists for storm initiation. Current guidance suggests a MCS will be moving out of KS early in the period, with a resulting severe threat anticipated downstream. Low (i.e. 5%) severe probabilities will be introduced with this forecast. More model consistency is needed before issuing higher probabilities. ...Northern Plains... Ample low-level moisture (i.e. dewpoints in the mid to upper 60s) will be in place over the region ahead of the approaching cold front. Even so, relatively warm low to mid-level temperatures will likely limit destabilization, particularly across southern portions of the region where less large-scale forcing for ascent (from the approaching shortwave trough) is expected. The environment supports a severe threat where deep updrafts persists but uncertainty regarding coverage currently precludes higher than 5% probability. ..Mosier.. 08/23/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Fri Aug 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND SOUTHERN PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Sunday across portions of the northern and southern Plains. ...Synopsis... Medium-range guidance is in good agreement that a strong shortwave trough embedded within the enhanced westerlies moves from the northern Rockies through the northern Plains on Sunday. This results in a deepening of the cyclonic flow across the north-central CONUS. This pattern evolution will also push a cold front eastward/ southeastward through much of northern Plains. Elsewhere, warm and moist conditions will persist across much of southern Plains and Southeast while weakening high pressure across much of the eastern CONUS will allow for some moisture return into the OH Valley. ...Southern Plains... Air mass across the region will be warm, very moist, and strongly buoyant. Strengthening northwesterly flow aloft will also contribute to moderate vertical shear. Overall environment would support severe potential as long as forcing exists for storm initiation. Current guidance suggests a MCS will be moving out of KS early in the period, with a resulting severe threat anticipated downstream. Low (i.e. 5%) severe probabilities will be introduced with this forecast. More model consistency is needed before issuing higher probabilities. ...Northern Plains... Ample low-level moisture (i.e. dewpoints in the mid to upper 60s) will be in place over the region ahead of the approaching cold front. Even so, relatively warm low to mid-level temperatures will likely limit destabilization, particularly across southern portions of the region where less large-scale forcing for ascent (from the approaching shortwave trough) is expected. The environment supports a severe threat where deep updrafts persists but uncertainty regarding coverage currently precludes higher than 5% probability. ..Mosier.. 08/23/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Fri Aug 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND SOUTHERN PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Sunday across portions of the northern and southern Plains. ...Synopsis... Medium-range guidance is in good agreement that a strong shortwave trough embedded within the enhanced westerlies moves from the northern Rockies through the northern Plains on Sunday. This results in a deepening of the cyclonic flow across the north-central CONUS. This pattern evolution will also push a cold front eastward/ southeastward through much of northern Plains. Elsewhere, warm and moist conditions will persist across much of southern Plains and Southeast while weakening high pressure across much of the eastern CONUS will allow for some moisture return into the OH Valley. ...Southern Plains... Air mass across the region will be warm, very moist, and strongly buoyant. Strengthening northwesterly flow aloft will also contribute to moderate vertical shear. Overall environment would support severe potential as long as forcing exists for storm initiation. Current guidance suggests a MCS will be moving out of KS early in the period, with a resulting severe threat anticipated downstream. Low (i.e. 5%) severe probabilities will be introduced with this forecast. More model consistency is needed before issuing higher probabilities. ...Northern Plains... Ample low-level moisture (i.e. dewpoints in the mid to upper 60s) will be in place over the region ahead of the approaching cold front. Even so, relatively warm low to mid-level temperatures will likely limit destabilization, particularly across southern portions of the region where less large-scale forcing for ascent (from the approaching shortwave trough) is expected. The environment supports a severe threat where deep updrafts persists but uncertainty regarding coverage currently precludes higher than 5% probability. ..Mosier.. 08/23/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SNAKE RIVER VALLEY INTO SOUTHERN WYOMING... ...Synopsis... On D2/Saturday, a strong mid-level jet will overspread the Pacific Northwest with the nose of the jet impinging upon the northern Great Basin/central Rockies. Critical fire weather will be most likely for portions of the Snake River Valley and southern Wyoming. In these locations, terrain-enhanced downslope flow will promote 20-25 mph winds with 10-15% afternoon RH. Upper and potentially mid-level clouds will again be a factor in stunting afternoon heating/boundary-layer mixing, which will likely limit the spatial extent of the critical fire weather threat. Surrounding portions of the northern Great Basin and central Rockies will see elevated fire weather conditions, with similar afternoon RH but winds generally in the 15-20 mph range. ..Wendt.. 08/23/2019 ...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 0156 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SNAKE RIVER VALLEY INTO SOUTHERN WYOMING... ...Synopsis... On D2/Saturday, a strong mid-level jet will overspread the Pacific Northwest with the nose of the jet impinging upon the northern Great Basin/central Rockies. Critical fire weather will be most likely for portions of the Snake River Valley and southern Wyoming. In these locations, terrain-enhanced downslope flow will promote 20-25 mph winds with 10-15% afternoon RH. Upper and potentially mid-level clouds will again be a factor in stunting afternoon heating/boundary-layer mixing, which will likely limit the spatial extent of the critical fire weather threat. Surrounding portions of the northern Great Basin and central Rockies will see elevated fire weather conditions, with similar afternoon RH but winds generally in the 15-20 mph range. ..Wendt.. 08/23/2019 ...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 0156 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SNAKE RIVER VALLEY INTO SOUTHERN WYOMING... ...Synopsis... On D2/Saturday, a strong mid-level jet will overspread the Pacific Northwest with the nose of the jet impinging upon the northern Great Basin/central Rockies. Critical fire weather will be most likely for portions of the Snake River Valley and southern Wyoming. In these locations, terrain-enhanced downslope flow will promote 20-25 mph winds with 10-15% afternoon RH. Upper and potentially mid-level clouds will again be a factor in stunting afternoon heating/boundary-layer mixing, which will likely limit the spatial extent of the critical fire weather threat. Surrounding portions of the northern Great Basin and central Rockies will see elevated fire weather conditions, with similar afternoon RH but winds generally in the 15-20 mph range. ..Wendt.. 08/23/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE PLAINS.... ...SUMMARY... Isolated severe storms are possible over parts of the central and northern southern Plains on Saturday. A severe storm or two is also possible across the northern Plains. ...Synopsis... A shortwave trough is expected to move southeastward from the central High Plains across the central Plains and into the Ozark Plateau on Saturday. Interaction between this shortwave and the moist air mass across the central Plains is expected to result in thunderstorm development. Farther northwest, mean cyclonic flow aloft will progress eastward across western Canada and the northwestern/north-central CONUS. Consequently, enhanced mid-level westerly flow will extend from the Pacific Northwest into the central Rockies by the end of the period (12Z Sunday). A shortwave trough will move quickly eastward within this enhanced flow aloft along the US/Canada border. An associated surface low is expected to move eastward across Saskatchewan and Manitoba, with an attendant cold front moving across eastern MT and into the western Dakotas. Expansive surface high centered over eastern Ontario/western Quebec will keep much of the northeast CONUS free of thunderstorms while warm and moist conditions will persist across the Southeast. ...Central/Southern Plains... Thunderstorms will likely be ongoing from central NE southward into the eastern TX Panhandle/western OK early Saturday morning. Strength and coverage of these storms will have an impact on air mass recovery and destabilization later during the afternoon. Additionally, outflow from these storms could provide a boundary for potential convective initiation. These mesoscale features introduce uncertainty into the forecast. Current expectation is for the air mass to destabilize by the late afternoon with isolated storms developing along the lee trough extending from northeast NM into eastern MT. Higher storm coverage is possible during the evening as a strengthening low-level jet promotes additional thunderstorm development across KS. The environment is characterized by favorable low-level moisture, steep mid-level lapse rates, and strengthening northwesterly flow aloft with enough vertical shear and buoyancy to support severe storms. Uncertainty regarding antecedent storms precludes higher probabilities with this outlook, but an upgrade may be needed in a subsequent outlook if mesoscale details become more clear. ...Northern Plains... Elevated storms will likely be ongoing at the beginning of the period. Modest instability and shear support a marginal hail threat. Recent model guidance has trended towards less low-level moisture during the afternoon and evening across the northern Plains. As a result, convective inhibition remains in place across much of the area, limiting surface-based storm initiation. Best location for surface-based initiation currently appears to be across north-central/northeast ND. Isolated storms are also possible late Saturday night/early Sunday morning along the approaching cold front. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Mosier.. 08/23/2019 Read more