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April 2nd - April 5th Severe Weather


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DVN..still doesn't seem too bullish

TO THE SOUTH...TEMPERATURES WERE

IN THE 60S TO AROUND 70 BEHIND THE WARM FRONT...BUT THE LOW LEVEL

MOISTURE RETURN WAS LAGGING WELL TO THE SOUTH. AN AXIS OF SURFACE

DEWPOINTS IN THE MID 50S TO MID 60S REACHED FROM TX TO E CENTRAL KS.

ALOFT...MOISTURE AT 850 MB WAS LACKING AS WELL. AT 00Z...THE 850 MB

MOISTURE RETURN WAS LIMITED TO E TX INTO SE OK AND WRN AR. A STRONG

LOW LEVEL JET WAS INDICTED BY VAD WIND PROFILERS AND THE PROFILER

NETWORK WITH 925 TO 850 SW WINDS FROM 60 TO NEARLY 80 KTS FROM W TX

INTO WRN IA.

POOR MOISTURE INITIALIZATION BY THE AMERICAN MODELS WAS AGAIN AN

ISSUE WITH THE 00Z RUN...WITH THE WRF/NAM CLOSEST TO REALITY WITH

SURFACE AND 850 MB DEWPOINTS. BASED ON CURRENT TRENDS...THE VERY

STRONG LOW LEVEL JET HAS NOT LIKELY TAPPED INTO THE GULF MOISTURE

RETURN SO FAR TONIGHT AND THUS MOISTURE RETURN AND ASSOCIATED

NOCTURNAL THUNDERSTORM DEVELOPMENT WILL NOT LIKELY BE AN ISSUE EARLY

THIS MORNING. RECENT FOG CHANNEL ON SATELLITE IMAGERY SHOWS LOW

CLOUDS DEVELOPING IN THE AREA OF STRONGEST ELEVATED MOISTURE RETURN

OVER EASTERN OK AND AR...WHICH IS PROGGED TO SURGE NORTHEAST INTO

THE FORECAST AREA BY MIDDAY. THIS WAS BEST DEPICTED BY A BLEND OF

THE NAM AND ECMWF AND HAVE GENERALLY FOLLOWED THESE SOLUTIONS TODAY

AND TONIGHT. HOWEVER...HAVE KEPT THE PRIMARY SURFACE LOW TRENDED

CLOSER TO THE MORE CONSISTENT ECMWF AND GFS NORTHERLY TRACK ACROSS

NORTHERN IA INTO LAKE MI BY MIDNIGHT. RECENT STRONG PRESSURE FALLS

OVER EASTERN SD INDICATE THIS LOW IS ALREADY ON THE MOVE EASTWARD.

BASED ON A SLIGHTLY SLOWER...DRIER SOLUTION...WILL COUNT ON MORNING

SUNSHINE AND THE SURFACE WARM FRONT TO LIFT NORTHWARD THROUGH THE

FORECAST AREA THIS MORNING ALLOWING TEMPERATURES TO RISE WELL INTO

THE 60S AND 70S WITH SCATTERED TO BROKEN STRATOCU LATE MORNING INTO

AFTERNOON. CURRENT BATCH OF SHOWERS ALONG THE HIGHWAY 20 CORRIDOR

MAY AFFECT THE NORTHEAST EARLY...THEN A STRONG CAP OF WARM AIR ALOFT

WILL LIKELY LIMIT THE NEXT ROUND OF CONVECTION TO ALONG THE

APPROACHING COLD FRONT THAT REACHES THE WESTERN CWA AROUND

21Z...THEN PUSHES THROUGH DURING THE EVENING. WITH WARM SECTOR

AIRMASS LIKELY SEEING SURFACE DEWPOINTS IN THE 50S TO LOWER

60S...CAPES IN THE 1000 TO 1500 J/KG...AND DEEP SHEAR...SEVERE

STORMS ARE LIKELY AND THE SLIGHT RISK SPC HAS OVER MUCH OF THE

FORECAST AREA IS REASONABLE AS THE FRONT PASSES THROUGH JUST AFTER

PEAK HEATING.

LOT sounds sort of indifferent

IT APPEARS THAT A HEALTHY AMOUNT OF

WARM MOIST AIR WILL MOVE ACROSS THE ACROSS THE AREA TOMORROW

AFTERNOON AND EVENING...LEADING TO AROUND 1200-1500 J/KG OF CAPE.

OF MORE CONCERN IS IS THE KINEMATIC FIELD. THE LATEST GUIDANCE

INDICATES UPWARDS OF 40 KT OF 0-1 KM BULK SHEAR AND HODOGRAPHS

ADVERTISE SOME GOOD LOW LEVEL DIRECTIONAL VEERING AHEAD OF THE

FRONT. WITH THIS IN MIND...I THINK THERE WILL BE A TORNADIC

THREAT...IN ADDITION TO THE WIND AND HAIL THREAT...ACROSS PORTIONS

OF THE AREA...ESPECIALLY EARLY ON FOR THOSE STORMS THAT CAN BECOME

ROOTED IN THE BOUNDARY LAYER. AS THE STORMS PROGRESS EASTWARD

TOWARDS NORTHEASTERN ILLINOIS AND NW INDIANA SHEAR VECTORS AND

INCREASING ASCENT ALONG THE FRONT SHOULD LEAD TO UPSCALE GROWTH.

THERE IS SOME UNCERTAINTY TO THE DURATION OF THE SEVERE THREAT

AFTER 06 UTC AS SOUNDINGS INDICATE LESS FAVORABLE THERMODYNAMIC

PROFILES.

ILX barley mentions anything

SLIGHT RISK OVER ALMOST ENTIRE CWA FOR

THREAT IN THE OVERNIGHT HOURS. STORMS COULD BE QUITE DIVERSE BY

THE TIME THEY REACH CENTRAL/NW IL...AND ALONG WITH THE THREAT OF

LG HAIL AND DAMAGING WINDS...THE LLVL SHEAR IS SUBSTANTIAL ENOUGH

TO SUPPORT A THREAT FOR ROTATING STORMS/ISLD TORNADOES AS WELL

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new RUC goes nuts with moisture return and instability this afternoon with 3500-4500 CAPE from IA SW along the dryline at 22z

this is overdone but this may be the faster/best moisture return I have ever seen, as of 11z they look on par with the 00z models...maybe even a tad ahead of the NAM..by 12z 60+ dewpoints will likely be over much of eastern KS

80kt LLJ wind barb on the SPC meso page at this time

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Hmm GFS 06z run going much higher for Southern Lower MI with MU CAPE over night, values of 1000 to 1600 J/KG, that could certainly up the hail potential significantly and help sustain anything that moves in from the Southwest

I will certainly be watching this afternoon for development in MO and IL and for me tonight. I keep thinking LaSalle county Illinois down to Galesburg as a prime area of interest this evening.

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no change on 12z outlook

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT OVER

PARTS OF ERN KS AND WRN INTO NRN MO...

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE UPPER

GREAT LAKES TO SOUTHERN PLAINS...

..SYNOPSIS

ELONGATED VORTICITY LOBE NOW OVER THE NRN INTERMOUNTAIN REGION WILL

PROGRESS EWD THROUGH THE NRN PLAINS INTO UPPER MS VALLEY BY MONDAY

MORNING. A MORE INTENSE VORTICITY MAXIMUM DIGGING SEWD THROUGH THE

GREAT BASIN WILL CONCURRENTLY TRANSLATE SEWD...REACHING THE SRN HIGH

PLAINS BY 04/12Z. THESE TWO SEPARATE IMPULSES WILL REMAIN

PHASED...COMPRISING A LARGE-SCALE TROUGH WHICH WILL UNDERGO

CONSIDERABLE DEEPENING/AMPLIFICATION WHILE MOVING INTO THE CNTRL

CONUS.

AT THE SURFACE...INITIAL SURFACE LOW OVER SERN SD/NERN NEB WILL

DEEPEN SLIGHTLY WHILE DEVELOPING ENEWD TO NERN IA/SWRN WI BY

04/00Z...AND NRN OR CNTRL LOWER MI BY THE END OF THE D1 PERIOD.

ASSOCIATED WARM FRONTOGENESIS IS FORECAST TO OCCUR OVER PORTIONS OF

ERN IA INTO IL/IND WITH THIS INTENSIFYING BOUNDARY GRADUALLY LIFTING

NWD THROUGH PORTIONS OF THE UPPER GREAT LAKES.

MEANWHILE...TRAILING COLD FRONT WILL ADVANCE SEWD FROM THE NRN INTO

CNTRL PLAINS...AND BY LATE AFTERNOON...WILL LIKELY EXTEND FROM THE

ABOVE-MENTIONED SURFACE LOW SWWD THROUGH NRN MO TO A SECONDARY

SURFACE LOW DEVELOPING OVER CNTRL KS. A DRYLINE WILL LINK WITH COLD

FRONT AT SECONDARY CYCLONE...EXTENDING SSWWD AND LIKELY MIXING TO

NEAR THE U.S. 81 CORRIDOR OF CNTRL OK/NWRN TX BY 03/21Z. THE COLD

FRONT WILL PROGRESSIVELY OVERTAKE THE DRYLINE AS IT SURGES SEWD INTO

THE SRN PLAINS AND OZARK PLATEAU REGION TONIGHT.

..UPPER MIDWEST INTO SRN PLAINS

SATELLITE-DERIVED PW IMAGERY AND SURFACE OBSERVATIONS INDICATE THE

RAPID NWD ADVECTION OF AN INCREASINGLY MOIST AIR MASS THROUGH THE

SRN AND CNTRL PLAINS INTO THE MID/LOWER MO VALLEY...A PROCESS THAT

IS BEING ENHANCED BY A 50-60+ KT SWLY LLJ. BY LATE AFTERNOON...

EXPECT A SWATH OF LOWER 60S BOUNDARY LAYER DEWPOINTS TO EXTEND FROM

E OF THE DRYLINE IN TX/OK THROUGH ERN KS...WRN/NRN MO TO VICINITY OF

RETREATING WARM FRONT OVER ERN IA/WRN IL. THIS MOISTURE RETURN WILL

OCCUR BENEATH AN EML /AS SAMPLED BY 12Z PLAINS SOUNDINGS/

CHARACTERIZED BY MIDLEVEL LAPSE RATES OF 8-9 C/KM. THESE LAPSE

RATES COUPLED WITH THE INCREASING MOISTURE CONTENT AND DAYTIME

HEATING ARE EXPECTED TO YIELD A MODERATELY TO STRONGLY UNSTABLE WARM

SECTOR BY AFTERNOON. MLCAPE VALUES SHOULD RANGE FROM 1000-1500 J/KG

NEAR LEAD SURFACE LOW AND WARM FRONT OVER THE MIDWEST...TO AS HIGH

AS 2000-3000+ J/KG AHEAD OF COLD FRONT WITHIN THE MODERATE RISK

AREA.

ASIDE FROM CLUSTERS OF ELEVATED STORMS WHICH ARE EXPECTED TO FORM

AND POSE A MARGINAL HAIL THREAT ACROSS PORTIONS OF THE UPPER

MIDWEST/UPPER GREAT LAKES TODAY...A STRONG CAP AT THE BASE OF THE

EML WILL LIKELY DELAY SURFACE-BASED STORM DEVELOPMENT UNTIL LATE

THIS AFTERNOON OR EVENING. A CONSENSUS OF CONVECTION-ALLOWING AND

MESOSCALE MODEL GUIDANCE INDICATES THAT INITIAL STORM DEVELOPMENT IN

THE WARM SECTOR WILL OCCUR BETWEEN 03/21Z-04/00Z ALONG SEGMENT OF

COLD FRONT OVER NRN MO INTO NERN KS.

THE POSITIVELY-TILTED CONFIGURATION OF THE LARGE-SCALE TROUGH WILL

RESULT IN VEERED LOW-LEVEL WINDS...EXCEPT INVOF SURFACE CYCLONES

WHERE ISALLOBARIC FORCING MAY ENHANCE SOME BACKING OF THE LOCAL FLOW

FIELD. NONETHELESS...FORECAST HODOGRAPHS SHOW 40-50 KT OF DEEP

WSWLY SHEAR WHICH WILL BE SUPPORTIVE OF SUPERCELLS WITHIN THE FIRST

ONE TO TWO HOURS OF STORM INITIATION. LARGE HAIL /SOME POTENTIALLY

DESTRUCTIVE/ WILL BE THE PRIMARY HAZARD WITH THE INITIAL STORM

DEVELOPMENT.

TONIGHT...THE COMBINATION OF SURGING COLD FRONT AND LARGELY PARALLEL

ORIENTATION OF DEEP-LAYER SHEAR VECTORS TO THE FRONT SHOULD FOSTER

THE UPSCALE GROWTH OF TSTMS TO LINE SEGMENTS OR A CONTINUOUS BAND

FROM VICINITY OF LEAD SURFACE LOW AND WARM FRONT OVER SRN WI/NRN IL

SWWD THROUGH THE MID MS VALLEY INTO OZARK PLATEAU. THE GREATEST

THREAT FOR TORNADOES WILL EXIST WITH ANY EMBEDDED SUPERCELL AND/OR

BOWING STRUCTURES THAT CAN EVOLVE NEAR THE SURFACE LOW TRACK FROM

NERN MO INTO NRN IL WHERE NEAR-GROUND SHEAR WILL BE ENHANCED.

OTHERWISE...DAMAGING WIND GUSTS AND SOME HAIL WILL BE THE PRIMARY

HAZARDS WITH QLCS INTO MONDAY MORNING.

..MEAD/SMITH.. 04/03/2011

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Look y'all. I saw several comments about individual NWS offices being unimpressed in the discussions. My experience is that most of the time the met on duty has everything to do with these curt discos. They seem to put the less experienced forecasters on duty right before a severe event. My guess is so the main guys can sleep. So don't let curt or unimpressive sounding local discos throw you off. I follow SPC almost exclusively for severe.

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Look y'all. I saw several comments about individual NWS offices being unimpressed in the discussions. My experience is that most of the time the met on duty has everything to do with these curt discos. They seem to put the less experienced forecasters on duty right before a severe event. My guess is so the main guys can sleep. So don't let curt or unimpressive sounding local discos throw you off. I follow SPC almost exclusively for severe.

That isn't really the case, during the event they may put their strongest radar operators on the warning desk and leave the forecast to others, but the schedule typically isn't changed on days prior to events.

I think what we're seeing is a conditional severe weather risk. If they go they have a chance to produce a good deal of severe weather, but these AFDs are highlighting potential failure modes of the events. All of which are legitimate concerns. For instance, the moisture return will be impressive, but can it make it in time for the forcing is a big question. Dewpoints are currently in the upper 20s over the northern end of the 10% tornado probability contour.

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LaCrosse takes the honor for the first svr report of the day...for hail

BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE LA CROSSE WI

826 AM CDT SUN APR 3 2011

THE NATIONAL WEATHER SERVICE IN LA CROSSE HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

MONROE COUNTY IN WEST CENTRAL WISCONSIN...

* UNTIL 900 AM CDT

* AT 820 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM LOCATED NEAR I 90 EXIT 25...OR NEAR SPARTA...

MOVING EAST AT 45 MPH. THIS STORM CAN PRODUCE QUARTER SIZE HAIL AND

DAMAGING WINDS IN EXCESS OF 60 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...

FORT MC COY AND JACKSON PASS AROUND 835 AM...

TUNNEL CITY AND RIDGEVILLE AROUND 840 AM...

TOMAH AND I 90 EXIT 43 AROUND 845 AM...

OAKDALE AND I 90 AND I 94 INTERCHANGE AROUND 850 AM...

SHENNINGTON AND MILL BLUFF STATE PARK AROUND 855 AM...

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