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Severe Weather Threat in Dixie Alley/OV Feb 27 - Mar 1


Fred Gossage

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14z RUC showing CAPE values near 2500 j/kg in OK this evening..

I wouldn't be shocked if he see a high risk in later outlooks.

I think in ther 16:30z update

1) probs increased over KS/OK

2) hatched wind ADDED over the MS valley/AR

any updates tOo high would be in the 20z outlook,,still think best shot of that over MS river valley/AR

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This is becoming a pretty complicated setup, with 3 rounds of severe possible. Seems like this type of event has high bust potential. I seem to remember a few previous situations where either a) nothing happened, or B the system overperformed significantly. I guess it's just a wait-and-see scenario at this point. But I don't like the shrinking MDT zone on the last Day 1 update. Seems smaller than previous Day 2 outlook.

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15z RUC and 14z HRRR are focusing development this afternoon along and south of the warm front in SE KS. Latest mesoanalysis has LI's down to -7 and a SBCAPE of 500-1000 in that area with steep mid-level lapse rates, around 200 helicity and 40 kts of effective bulk shear.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1030 AM CST SUN FEB 27 2011

VALID 271630Z - 281200Z

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

AR NEWD TO THE LOWER OH VALLEY...

..THERE IS A SLGT RISK OF SVR TSTMS FROM SRN KS

NRN AND ERN

OK...AND NE TX NEWD INTO THE OH VALLEY...

..MID SOUTH/LOWER OH VALLEY THIS AFTERNOON THROUGH TONIGHT

THE AXIS OF RICHEST LOW-LEVEL MOISTURE EXTENDS NEWD FROM SE TX TO NW

MS AND ERN AR...ALONG THE LLJ AXIS. CONTINUED NWD/NEWD EXPANSION OF

THE WARM SECTOR AND SOME SURFACE HEATING IN CLOUD BREAKS WILL RESULT

IN SUFFICIENT DESTABILIZATION /MLCAPE OF 1000-1500 J PER KG/ FOR

SEVERE STORMS IN THE WARM SECTOR BY MID-LATE AFTERNOON. VERTICAL

SHEAR PROFILES WILL BE FAVORABLE FOR SUPERCELLS WITH EFFECTIVE BULK

SHEAR IN EXCESS OF 50 KT AND EFFECTIVE SRH AOA 300 M2/S2.

THE PRIMARY CONCERNS THIS AREA DURING THE AFTERNOON WILL BE A FOCUS

FOR STORM INITIATION...THE INFLUENCE OF CLOUDS ON SURFACE

HEATING...AND EWD EXPANSION OF THE ELEVATED MIXED LAYER/CAP.

ASSUMING A FEW STORMS CAN FORM THIS AFTERNOON FROM NE AR INTO WRN

TN...THE ENVIRONMENT WILL BE FAVORABLE FOR TORNADIC SUPERCELLS...AND

THE POTENTIAL FOR A STRONG TORNADO OR TWO. OTHERWISE...AN INCREASE

IN THUNDERSTORMS IS EXPECTED OVERNIGHT IN ADVANCE OF THE EJECTING

MIDLEVEL TROUGH AND ALONG THE LLJ CORRIDOR...ALONG/IN ADVANCE OF THE

COLD FRONT MOVING EWD FROM OK ACROSS AR. THE PRE-FRONTAL CONVECTION

MAY CONTAIN SUPERCELLS WITH A CONTINUED TORNADO RISK OVERNIGHT INTO

THE LOWER OH VALLEY...WHILE A MORE LINEAR CONVECTIVE MODE IS

EXPECTED TO EVOLVE ALONG THE COLD FRONT BY 09-12Z. DAMAGING WINDS

WILL BE THE MAIN THREAT WITH THE FRONTAL CONVECTIVE BAND...THOUGH

QLCS TORNADOES WILL ALSO BE POSSIBLE.

..KS/OK BORDER THIS EVENING INTO NRN MO/IL OVERNIGHT

THE INITIAL LEE CYCLONE IN SE CO WILL DEVELOP EWD ALONG THE KS/OK

BORDER THIS EVENING INTO EARLY TONIGHT IN RESPONSE TO THE MIDLEVEL

SHORTWAVE TROUGH THAT WILL EJECT ENEWD OVER THE SRN HIGH PLAINS.

SLY FLOW INDUCED BY THE LEE CYCLONE HAS RESULTED IN AN INCREASE IN

LOW-LEVEL MOISTURE IN THE WARM SECTOR INTO OK...WITH BOUNDARY LAYER

DEWPOINTS EXPECTED TO HOLD IN THE LOW 60S THROUGH THE AFTERNOON.

SURFACE HEATING WILL BE INHIBITED BY LOW STRATUS AND A SEPARATE BELT

OF MID-HIGH CLOUDS NOW OVERSPREADING THE ERN TX PANHANDLE/NW TX AND

WRN OK. HOWEVER...CLEARING FROM THE W IS EXPECTED OVER THE DRYLINE

AND TRIPLE POINT BY ABOUT 21Z...AND THIS SURFACE HEATING WILL

CORRESPOND WITH INCREASING LOW-LEVEL ASCENT AND LOCAL WEAKENING OF

CONVECTIVE INHIBITION. THUS...AT LEAST ISOLATED THUNDERSTORM

DEVELOPMENT IS EXPECTED IN THE 22-00Z TIME FRAME NEAR THE TRIPLE

POINT INVOF THE KS/OK BORDER...W OF I-35.

A COMBINATION OF 7-8 C/KM MIDLEVEL LAPSE RATES ABOVE BOUNDARY LAYER

DEWPOINTS OF 58-62 F...AND AFTERNOON SURFACE TEMPERATURES IN THE LOW

70S...WILL SUPPORT MLCAPE NEAR 1500 J/KG. EFFECTIVE BULK SHEAR OF

50-70 KT WILL FAVOR SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL...AND

A COUPLE OF TORNADOES WILL BE POSSIBLE BEFORE STORMS CROSS INTO THE

COOL AIR N OF THE WARM FRONT. OTHERWISE... ELEVATED THUNDERSTORMS

WILL EXPAND NEWD ACROSS SRN AND ERN KS INTO MO AND IL OVERNIGHT IN

ADVANCE OF THE SURFACE LOW...WITH A CONTINUED RISK FOR LARGE HAIL.

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Missouri kicks it off with a SVR T-Storm warning

BULLETIN - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE ST LOUIS MO

1037 AM CST SUN FEB 27 2011

THE NATIONAL WEATHER SERVICE IN ST LOUIS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

EAST CENTRAL AUDRAIN COUNTY IN CENTRAL MISSOURI...

PIKE COUNTY IN NORTHEAST MISSOURI...

* UNTIL 1100 AM CST

* AT 1035 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND

DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR

VANDALIA...AND MOVING EAST AT 50 MPH.

* LOCATIONS IMPACTED INCLUDE...

BOWLING GREEN...LOUISIANA...NEW HARTFORD...CURRYVILLE...

CLARKSVILLE...ASHLEY...ST. CLEMENT...CYRENE AND EDGEWOOD.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

SEVERE THUNDERSTORMS PRODUCE DAMAGING WIND IN EXCESS OF 60 MILES PER

HOUR...DESTRUCTIVE HAIL...DEADLY LIGHTNING...AND VERY HEAVY RAIN. FOR

YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF YOUR

HOME OR BUSINESS. HEAVY RAINS FLOOD ROADS QUICKLY SO DO NOT DRIVE

INTO AREAS WHERE WATER COVERS THE ROAD.

TO REPORT SEVERE WEATHER...CONTACT YOUR NEAREST LAW ENFORCEMENT

AGENCY. THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE

IN ST LOUIS.

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Missouri kicks it off with a SVR T-Storm warning

BULLETIN - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE ST LOUIS MO

1037 AM CST SUN FEB 27 2011

THE NATIONAL WEATHER SERVICE IN ST LOUIS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

EAST CENTRAL AUDRAIN COUNTY IN CENTRAL MISSOURI...

PIKE COUNTY IN NORTHEAST MISSOURI...

* UNTIL 1100 AM CST

* AT 1035 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND

DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR

VANDALIA...AND MOVING EAST AT 50 MPH.

* LOCATIONS IMPACTED INCLUDE...

BOWLING GREEN...LOUISIANA...NEW HARTFORD...CURRYVILLE...

CLARKSVILLE...ASHLEY...ST. CLEMENT...CYRENE AND EDGEWOOD.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

SEVERE THUNDERSTORMS PRODUCE DAMAGING WIND IN EXCESS OF 60 MILES PER

HOUR...DESTRUCTIVE HAIL...DEADLY LIGHTNING...AND VERY HEAVY RAIN. FOR

YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF YOUR

HOME OR BUSINESS. HEAVY RAINS FLOOD ROADS QUICKLY SO DO NOT DRIVE

INTO AREAS WHERE WATER COVERS THE ROAD.

TO REPORT SEVERE WEATHER...CONTACT YOUR NEAREST LAW ENFORCEMENT

AGENCY. THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE

IN ST LOUIS.

See, you look at the mesoanalysis on the SPC page and you see it showing almost zero CAPE for that area. But evidently there is plenty of instability.

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SLGT extended further west to the triple point with stronger wording. I like :thumbsup:

I'm just north of Ardmore on I-35 heading north.

Yeah that area might be pretty good today to chase. I am also thinking the triple point where the 10% hatched area for strong tornadoes would be ok. I dont chase but I would probably stay around where your at or eastern OK /western AR.

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coupled with insane amounts of 0-1km SRH..

15z HRRR continues to suggest triple point initiation in the 22-00z timeframe...

Pretty hard to believe this will all come together properly when one considers climo for this region, but the potential can't be ignored. If storms do initiate, they likely won't have a ton of time in the warm sector. With parameters like that, they may not need it, though.

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15z HRRR continues to suggest triple point initiation in the 22-00z timeframe...

Pretty hard to believe this will all come together properly when one considers climo for this region, but the potential can't be ignored. If storms do initiate, they likely won't have a ton of time in the warm sector. With parameters like that, they may not need it, though.

Ya the potential is huge at the triple if something goes, if that amount of instability is realized...wow. that area should be clearing out nicely in the next few hours.

are you going to be on SN?

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Any storm that goes up in the warm sector in OK will have the potential to produce a violent tornado. It is just that simple. The fact that the mesoscale high-res models are pointing toward initiation is extremely disturbing.

I agree with you 100% on that one. I am not good with reading maps but from what I can tell those parameters look scary.

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From SPC Severe Weather Outlook:

THE MOST SIGNIFICANT THREAT FOR TORNADOES SHOULD BEGIN LATER THIS AFTERNOON ACROSS THE NORTHEAST ARKANSAS AND WESTERN TENNESSEE AREA...AND THEN CONTINUE OVERNIGHT WHILE SPREADING NORTHEASTWARD ACROSS SOUTHEAST MISSOURI...SOUTHERN ILLINOIS...WESTERN KENTUCKY...AND EXTREME SOUTHWEST INDIANA. A COUPLE OF STRONG TORNADOES WILL BE POSSIBLE IN THIS AREA...ALONG WITH DAMAGING WINDS AND LARGE HAIL. A FEW SEVERE STORMS ARE ALSO EXPECTED BY LATE AFTERNOON/EVENING FROM NORTHERN OKLAHOMA INTO SOUTHEAST KANSAS...WHERE A FEW TORNADOES AND LARGE HAIL WILL BE THE MAIN THREATS. STATE AND LOCAL EMERGENCY MANAGERS ARE MONITORING THIS POTENTIALLY VERY DANGEROUS SITUATION. THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE WEATHER SAFETY RULES AND TO LISTEN TO RADIO...TELEVISION...AND NOAA WEATHER RADIO FOR POSSIBLE WATCHES...WARNINGS...AND STATEMENTS LATER TODAY.

Could we see a PDS watch out of this?

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Norman 11 AM update:

REGARDING SEVERE THUNDERSTORM CHANCES...THE LATEST MESOSCALE AND
SHORT TERM MODELS /INCLUDING THE LATEST LOCAL WRF RUN/ DO NOT
INITIATE STORMS ALONG THE DRYLINE IN THE OUN CWA THIS AFTERNOON OR
EVENING. THOUGH THE CAP MAY WIN OUT...WE WILL STILL MENTION A
CHANCE OF STORMS THIS AFTERNOON/EVENING. THE NORTHEASTERN CORNER
OF OUR CWA...WHERE TEMPERATURES ALOFT ARE FORECAST TO BE
COMPARATIVELY COOLER THAN LOCATIONS FARTHER SOUTH...WOULD PROBABLY
STAND THE BEST CHANCE OF SEEING THUNDERSTORMS.

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From SPC Severe Weather Outlook:

THE MOST SIGNIFICANT THREAT FOR TORNADOES SHOULD BEGIN LATER THIS AFTERNOON ACROSS THE NORTHEAST ARKANSAS AND WESTERN TENNESSEE AREA...AND THEN CONTINUE OVERNIGHT WHILE SPREADING NORTHEASTWARD ACROSS SOUTHEAST MISSOURI...SOUTHERN ILLINOIS...WESTERN KENTUCKY...AND EXTREME SOUTHWEST INDIANA. A COUPLE OF STRONG TORNADOES WILL BE POSSIBLE IN THIS AREA...ALONG WITH DAMAGING WINDS AND LARGE HAIL. A FEW SEVERE STORMS ARE ALSO EXPECTED BY LATE AFTERNOON/EVENING FROM NORTHERN OKLAHOMA INTO SOUTHEAST KANSAS...WHERE A FEW TORNADOES AND LARGE HAIL WILL BE THE MAIN THREATS. STATE AND LOCAL EMERGENCY MANAGERS ARE MONITORING THIS POTENTIALLY VERY DANGEROUS SITUATION. THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE WEATHER SAFETY RULES AND TO LISTEN TO RADIO...TELEVISION...AND NOAA WEATHER RADIO FOR POSSIBLE WATCHES...WARNINGS...AND STATEMENTS LATER TODAY.

Could we see a PDS watch out of this?

Sounds like a high risk PWO

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The HRRR and RUC both have substantially-backed surface winds compared to the NAM/GFS, and considering their short-term reliability and increased resolution, they should be trusted. This could change the whole complexion of the event during the evening and overnight hours, as this makes the supercellular convective mode much more likely.

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