April 14-16th Plains/MW/OV Severe Weather, SPC Risk Level: Day 1 Slight Risk Options

[CIWeather]

Per Dr. Forbes and SPC, it seems reasonable to create a thread for the potential severe weather event later this week. Dates will likely need changed as the week progresses.

Forbes FB page: Thur Apr 14. Severe thunderstorms and isolated tornadoes in IL, northeast, central, and south MO, southeast KS, east OK, northeast TX about as far southwest as College Station, north LA, northwest MS, west TN, west KY, extreme west IN. Details could change, as numerical models differ on this.

DAY 4-8 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0410 AM CDT SUN APR 10 2011

VALID 131200Z - 181200Z

CORRECTED OUTLOOK GRAPHIC...DAY 4 LABEL SHOULD BE DAY 5

THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH AN
UPPER-LEVEL RIDGE IN THE ERN STATES AND AN UPPER-LEVEL TROUGH IN THE
ROCKIES WEDNESDAY MORNING/DAY 4. THE MODELS MOVE THIS UPPER-LEVEL
TROUGH EWD INTO THE MS RIVER VALLEY WEDNESDAY NIGHT WITH ANOTHER
TROUGH DEVELOPING FURTHER TO THE WEST IN THE ROCKIES. THE ECMWF AND
GFS ARE SIMILAR WITH THE SECOND UPPER-LEVEL TROUGH...MOVING THE
SYSTEM ACROSS THE GREAT PLAINS ON THURSDAY/DAY 5 BUT THE ECMWF IS
THE SLOWER SOLUTION. THIS WOULD SEEM THE MORE LIKELY SCENARIO WHICH
WOULD SUGGEST NUMEROUS THUNDERSTORMS DEVELOPING THURSDAY EVENING
ALONG THE MOIST AXIS FROM ERN OK AND ERN KS EWD INTO MO AND AR. DUE
TO THE NEGATIVELY-TILT OF THE UPPER-LEVEL TROUGH AND STRONG
LOW-LEVEL JET RESPONSE FORECAST BY THE MODELS...WILL INTRODUCE A
SEVERE THREAT AREA FOR PARTS OF THE SRN AND CNTRL PLAINS EWD INTO
THE OZARKS. A WIDESPREAD SEVERE WEATHER EVENT REMAINS POSSIBLE
ACROSS THIS AREA THURSDAY AFTERNOON AND EVENING. ON FRIDAY/DAY
6...THE MODELS DIVERGE WITH THE ECMWF DEVELOPING AN UPPER-LEVEL LOW
OVER THE NCNTRL PLAINS AND THE GFS DEVELOPING THE LOW FURTHER EAST
IN THE UPPER MIDWEST. STRONG THUNDERSTORMS WOULD BE POSSIBLE ON THE
ERN SIDE OF THE SYSTEM ALONG A MOIST AXIS IN THE MS VALLEY. ON
SATURDAY/DAY 7...THE UPPER-LEVEL MOVES INTO THE OH VALLEY WITH THE
ECMWF SLOWER. THIS WOULD MOVE THE SEVERE THREAT SATURDAY AFTERNOON
INTO THE ERN STATES. OTHER THAN THE DAY 5 OUTLOOK AREA...CONFIDENCE
IS NOT GREAT ENOUGH TO ADD A THREAT AREA IN THE MS VALLEY OR ERN
STATES.

..BROYLES.. 04/10/2011

Attached image(s)

 

[The Snowman]

Ohboy, here we go again.

[CIWeather]

The Day 5 area in the SPC map above is for Thursday, April 14-Friday, April 15.

[CIWeather]

I think I may have left a couple of things out in the title of the thread. If I can edit it myself I have forgotten how to do so, otherwise if someone else could edit it and fix the errors (such as a Moderator), I would greatly appreciate it. Thanks.

[jdrenken]

I think I may have left a couple of things out in the title of the thread. If I can edit it myself I have forgotten how to do so, otherwise if someone else could edit it and fix the errors (such as a Moderator), I would greatly appreciate it. Thanks.

Done

[CIWeather]

Done

Thanks

[Illinois blizzar...]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0352 AM CDT MON APR 11 2011

VALID 141200Z - 191200Z

THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH AN
UPPER-LEVEL TROUGH ENTERING THE GREAT PLAINS ON THURSDAY/DAY 4.
AHEAD OF THE SYSTEM...THE MODELS BRING LOW-LEVEL MOISTURE NWD INTO
THE ARKLATEX AND OZARKS WITH BOTH THE ECMWF AND GFS DEVELOPING
MODERATE INSTABILITY THURSDAY AFTERNOON FROM EAST TX NWD INTO ERN
OK...ARK AND SRN MO. THE CURRENT THINKING IS THAT STORMS WILL
INITIATE ALONG THE WRN EDGE OF THE MOIST AXIS IN ERN OK AND MOVE
ENEWD INTO THE OZARKS BY THURSDAY EVENING. THE EXIT REGION OF AN
APPROACHING MID-LEVEL JET AND A STRONG LOW-LEVEL JET RESPONSE COULD
RESULT IN AN ENHANCED SEVERE THREAT IN ERN OK AND WRN AR. THE MODELS
CONTINUE TO MOVE THE SYSTEM EWD ON FRIDAY/DAY 5 WITH AN UPPER-LEVEL
LOW CLOSING OFF IN THE MID T0 UPPER-MS VALLEY. STRONG THUNDERSTORMS
WILL BE POSSIBLE TO THE EAST OF THE SYSTEM IN THE OH AND TN VALLEYS
AS A COLD FRONT MOVES QUICKLY EWD. THIS POTENTIAL FOR STRONG STORMS
MAY CONTINUE EWD INTO THE MID-ATLANTIC AND NERN STATES ON
SATURDAY/DAY 6 AS A WELL-DEVELOPED UPPER-LEVEL SYSTEM AND MID-LEVEL
JET APPROACHES THE REGION FROM THE WEST. OTHER THAN THE DAY 4 SEVERE
THREAT AREA...CONFIDENCE REMAINS LOW IN THE ERN STATES CONCERNING
THREAT COVERAGE AND TIMING SO WILL NOT OUTLOOK AN AREA BEYOND
THURSDAY.

..BROYLES.. 04/11/2011

[Superstorm93]

I've never seen a 4-8 so small before.

[WeatherMonger]

Thunderstorms to snow, winter not giving in without a fight. Pulling for the Euro

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
306 PM CDT MON APR 11 2011


LONG TERM...THURSDAY THROUGH MONDAY.

THE NEXT LONG WAVE TROUGH WILL BEGIN TO AFFECT OUR AREA ON
THURSDAY...AS A CUTOFF LOW BREAKS FREE FROM THE NORTHERN STREAM
AND OCCLUDES OVER THE CENTRAL PLAINS. BY THURSDAY AFTERNOON...LOW
PRESSURE AT THE SURFACE WILL REACH EASTERN KANSAS...WITH A WARM
FRONT EXTENDING FROM THE LOW INTO NW IL. RAIN AND A FEW
THUNDERSTORMS WILL BE POSSIBLE THUR...MAINLY IN THE WEST AND
NORTH...CLOSER TO THE WARM FRONT. DRY EASTERLY FLOW WILL WORK TO
KEEP THE SOUTH AND EAST DRIER LONGER.

BY THURSDAY NIGHT...MORE WIDESPREAD RAIN AND STORMS ARE EXPECTED
AS THE SFC LOW DRIFTS INTO MISSOURI. THE NEW 12Z ECMWF JUST LOADED
INTO THE DATABASE WITH SOME BIG CHANGES FROM THE 00Z RUN. IT NOW
KEEPS THE RAIN WEST OF US UNTIL AFTER 12Z FRIDAY. THE CONSENSUS OF
OTHER MODELS STILL POINT TOWARD THUR NIGHT AS THE MOST LIKELY
PERIOD...SO WE WILL NOT ALTER PRECIP TRENDS LATER JUST YET. RAIN
SHOWERS WILL LINGER THROUGH FRIDAY...WITH COLDER AIR EXPECTED TO
ARRIVE FRIDAY NIGHT. SOME OF THE RAIN MAY CHANGE TO SNOW AS LOW
TEMPS FALL THROUGH THE 30S BY 12Z SAT...WITH A FEW FLURRIES EVEN
ON SATURDAY MORNING.

[jdrenken]

Thunderstorms to snow, winter not giving in without a fight. Pulling for the Euro

I went ahead and created a thread for the other aspects.

[SEMIweather]

I believe the 00z NAM would result in a decent severe wx event Thursday evening in Eastern Kansas and Oklahoma, eventually extending into Southwest Missouri and Western Arkansas.

For starters, you have a 996mb low in SE Kansas at 21z, which the NAM shows deepening 8mb in 9 hours during the day on Thursday.



Then, you have the cap either fully eroded or very close to eroded in Eastern Kansas and Oklahoma at 21z, and anywhere from 1000-2500 J/kg of CAPE to work with, which is enough instability to support storms.





You then have low LCLs and some backing of the surface winds, which could result in a tornado threat, although being 3 days out I will not count my chickens before they hatch.






Now selfishly I hope this slows down a bit so Norman can get in on the action, as Thursday is likely not a good chase day for me, as I have a 1:30-2:20 p.m. class that I absolutely need to attend, but either way my bet is that this is going to be a decent severe wx event for someone on Thursday.

[SEMIweather]

The GFS also comes in w/ favorable severe parameters on Thursday; not as much CAPE as the NAM but I'm fairly certain it is way underdoing surface temps in the warm sector and therefore CAPE is also underdone.

I tend to not bother making my own severe weather outlooks but with what the models are showing and just the overall setup of a surface low deepening fairly rapidly on Thursday I'd be pretty surprised if I didn't see a 30% risk area somewhere around Eastern OK/Western AR extending northward to SE Kansas/SW Missouri tomorrow morning in the SPC's Day 3 Outlook.

[melissa from ill...]

Dr Forbes on FB: FRIDAY
A substantial upper-air disturbance and surface low should give a severe thunderstorm and tornado outbreak threat in central and southeast IL, west-central and southwest IN, west and central KY, west and middle TN, AL, MS, southeast LA, west FL panhandle.

[jdrenken]

DAY 3 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0336 AM CDT TUE APR 12 2011

VALID 141200Z - 151200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...CNTRL PLAINS...OZARKS AND MID-MO VALLEY...

CORRECTED TO CHANGE WEDNESDAY TO THURSDAY IN 1ST PARAGRAPH

...SRN AND CNTRL PLAINS/OZARKS AND MID-MO VALLEY...
AN IMPRESSIVE UPPER-LEVEL TROUGH WITH A NEGATIVE TILT IS FORECAST TO
MOVE INTO THE SRN HIGH PLAINS THURSDAY. A WELL-DEFINED 70 TO 90 KT
MID-LEVEL JET IS FORECAST TO MOVE THROUGH THE BASE OF THE TROUGH
WITH THE EXIT REGION SPREADING EWD ACROSS THE SRN PLAINS. THIS
FEATURE WILL CREATE STRONG DEEP LAYER SHEAR PROFILES CREATING A
FAVORABLE SHEAR ENVIRONMENT FOR SEVERE STORMS. AHEAD OF THE
SYSTEM...A STRENGTHENING LOW-LEVEL JET SHOULD TRANSPORT MOISTURE NWD
WITH THE MODELS DEVELOPING AN AXIS OF MODERATE INSTABILITY ACROSS
ERN OK AND ERN KS THURSDAY AFTERNOON. FORECAST SOUNDINGS DIMINISH A
STRONG CAPPING INVERSION AROUND 21Z WITH STORMS INITIATING JUST TO
THE EAST OF A DRYLINE ORIENTED NORTH TO SOUTH ALONG THE I-35
CORRIDOR. AS STORM COVERAGE INCREASES DURING THE LATE AFTERNOON AND
EARLY EVENING...THE ENVIRONMENT SHOULD SUPPORT SUPERCELL DEVELOPMENT
ESPECIALLY BENEATH THE EXIT REGION OF THE MID-LEVEL JET WHERE 0-6 KM
SHEAR VALUES ARE FORECAST TO BE IN THE 50 TO 60 KT RANGE.

FORECAST SOUNDINGS BY EARLY EVENING ACROSS ERN OK...WRN AR AND SERN
KS SHOW LOOPED HODOGRAPHS WITH 0-3 KM STORM RELATIVE HELICITIES IN
THE 400 TO 450 M2/S2 RANGE. THE LOW-LEVEL SHEAR SHOULD INCREASE BY
EARLY EVENING AS THE LOW-LEVEL JET STRENGTHENS...SUPPORTING A
TORNADO THREAT WITH THE MORE DOMINANT SUPERCELL STORMS. IN
ADDITION...MODERATE INSTABILITY...STEEP MID-LEVEL LAPSE RATES AND
500 MB TEMPS OF -14 TO -16 C SHOULD BE FAVORABLE FOR LARGE HAIL. A
THREAT FOR VERY LARGE HAIL...>= 2 INCHES IN DIAMETER...WILL ALSO BE
POSSIBLE WITH THE BETTER ORGANIZED SUPERCELLS. THE SEVERE THREAT
SHOULD EXTEND AS FAR NORTH AS KANSAS CITY WHERE THE NAM SHOWS A 995
MB SFC LOW JUST TO THE EAST OF THE UPPER-LEVEL LOW. BACKED SELY
WINDS AHEAD OF THE SFC LOW AND STRONG LOW-LEVEL SHEAR SHOULD ALSO BE
SUFFICIENT FOR A TORNADO THREAT IN NE KS AND WRN MO WHERE COLD TEMPS
ALOFT WILL ALSO MAKE LARGE HAIL POSSIBLE AS WELL.

ON THE SRN EDGE OF THE SLIGHT RISK AREA ABOUT 100 STATUTE MILES
SOUTH OF THE RED RIVER...FORECAST SOUNDINGS MAINTAIN A STRONG
CAPPING INVERSION THROUGH THE AFTERNOON AND EVENING. THIS SUGGESTS
THE THREAT FOR SEVERE STORMS SHOULD DROP OFF QUICKLY FROM NORTH TO
SOUTH ACROSS THE ARKLATEX. THE SEVERE THREAT IN THE OZARKS IS
EXPECTED TO WEAKEN DURING THE LATE EVENING BUT A MARGINAL SEVERE
THREAT COULD CONTINUE INTO THE OVERNIGHT PERIOD AS AN MCS OR
CONVECTIVE CLUSTER MOVES EWD INTO THE LOWER TO MID-MS VALLEY.

..BROYLES.. 04/12/2011

[jdrenken]

Dr Forbes on FB: FRIDAY
A substantial upper-air disturbance and surface low should give a severe thunderstorm and tornado outbreak threat in central and southeast IL, west-central and southwest IN, west and central KY, west and middle TN, AL, MS, southeast LA, west FL panhandle.

This surprises me. Granted, if the cold core option is open I guess it could happen.

[SEMIweather]

That was a pretty ominous sounding Day 3 Outlook from the SPC.

[WeatherMonger]

A dry period will take hold for Tuesday and Wednesday with warmer conditions each day. The next chance for showers and thunderstorms will be Thursday through Friday as a powerful storm moves through. Much cooler air will then begin to filter in for the weekend with the threat of rain expected to linger into Friday night and Saturday.

[SEMIweather]

NWS Tulsa AFD

THE NEXT STORM SYSTEM WILL AFFECT THE AREA THURSDAY. THE LATEST
TRENDS SUPPORT THE UPPER SYSTEM CLOSING OFF QUICKER AND FURTHER
SOUTHWEST THAN PREVIOUSLY EXPECTED. THE RESULT FOR OUR AREA WILL
BE A HIGHER SEVERE RISK LATE THURSDAY AFTERNOON AND EVENING.

SURFACE LOW PRESSURE WILL INTENSIFY THURSDAY AS IT MOVES ACROSS
WESTERN OKLAHOMA INTO NORTHERN OKLAHOMA OR SOUTHERN KANSAS BY LATE
AFTERNOON. A DRYLINE WILL TRAIL SOUTH FROM THE SURFACE LOW AND
WILL REACH NEAR OF EAST OF THE INTERSTATE 35 CORRIDOR BY LATE
AFTERNOON. THE UPPER LOW WILL BE IN THE PROCESS OF CLOSING OFF
OVER KANSAS AT THE SAME TIME. SHOULD THE DRYLINE MOVE FURTHER EAST
THAN CURRENTLY EXPECTED AND ENTER OUR FORECAST AREA BEFORE
DARK...FIRE WEATHER HEADLINES WOULD BECOME NECESSARY.

MOISTURE QUALITY WILL IMPROVE DRAMATICALLY DURING THE DAY THURSDAY
WITH A NARROW TONGUE OF 60-65 DEGREE DEWPOINTS SURGING NORTH AHEAD
OF THE DRYLINE. THIS SHOULD BE SUFFICIENT TO ALLOW AT LEAST
SCATTERED SEVERE THUNDERSTORMS TO ERUPT ALONG AND AHEAD OF THE
DRYLINE LATE THURSDAY AFTERNOON WITH STORM COVERAGE BECOMING
GREATER FURTHER TO THE EAST THURSDAY EVENING AS THE DRYLINE AND A
TRAILING COLD FRONT SURGE ACROSS THE AREA. ALL MODES OF SEVERE
WEATHER WILL BE POSSIBLE LATE THURSDAY AFTERNOON AND EVENING.

[SEMIweather]

NWS Wichita AFD

BY THU AFTERNOON THE UPPER TROUGH WILL BE MOVING OUT ACROSS WESTERN
KS. ONE OF THE CHANGES COMPARED TO THE 00Z RUNS FROM LAST NIGHT IS
THAT THE TROUGH IS TAKING ON A MORE NEGATIVE TILT WHICH IS ALLOWING
THE SURFACE LOW TO DEVELOP FURTHER WEST THUS DRAWING-IN BETTER
MOISTURE OVER EASTERN OK/EASTERN KS. THIS SLIGHT CHANGE HAS RESULTED
IN AN INCREASED THREAT FOR SEVERE STORMS OVER FAR EASTERN KS ON THU
AFTERNOON/EVENING. FEEL THE MAIN QUESTION WILL BE HOW EXTENSIVE LOW
CLOUDS ARE ACROSS EASTERN OK/EASTERN KS. GIVEN THE STRONG MID LEVEL
COOLING AND UPPER DYNAMICS THE CLOUD COVER MAY NOT STOP INITIATION
BUT MAY LIMIT THE SEVERITY. SO FOR THU THINK THERE WILL BE TWO MAIN
PRECIP AREAS...ONE WITH THE STORMS OVER EASTERN KS AND THE OTHER IN
THE WRAP AROUND REGION OVER CENTRAL KS.

[SEMIweather]

NWS Springfield AFD

BIG CHANGES BEGIN STARTING WEDNESDAY NIGHT AS MODELS PROG A STRONG
UPPER LEVEL JET TO PUNCH ONSHORE ACROSS THE PACIFIC NORTHWEST.
AS THIS JET DIVES SOUTHEAST THROUGH THE FOUR CORNERS REGION AND
EMERGES ACROSS THE SOUTHERN PLAINS...MODELS ARE CONSISTENT IN
SHORT WAVE ENERGY BECOMING NEGATIVELY TILTED AND THEN CLOSING OFF
SOMEWHERE ACROSS THE CENTRAL PLAINS BY THURSDAY NIGHT. AS WOULD BE
EXPECTED...STRONG CYCLOGENESIS WILL TAKE PLACE ACROSS THE SOUTHERN
HIGH PLAINS STARTING THURSDAY MORNING. IT IS STILL A BIT TOO FAR
OUT TO PEG THE EXACT TRACK OF THE SURFACE LOW...BUT THE SYNOPTIC
SCALE PATTERN WILL FAVOR A NORTH-NORTHEAST TRACK AS IT QUICKLY
DEEPENS.

AS FOR CONVECTIVE TRIGGERS...RIGHT NOW THE MAIN PLAYER APPEARS
THAT IT WILL BE A DRY LINE PUSHING OUT OF SOUTH CENTRAL KANSAS AND
CENTRAL OKLAHOMA. FORECAST SOUNDINGS INDICATE THAT A STRONG CAP
WILL INITIALLY BE IN PLACE ACROSS THE REGION THURSDAY
MORNING...LIKELY BEING A RESULT OF AN ELEVATED MIXED LAYER. THIS
CAP WILL QUICKLY ERODE BY LATE THURSDAY AFTERNOON AS STRONG
COOLING OCCURS IN THE MID LEVELS AND THE LEFT EXIT REGION OF THAT
UPPER LEVEL JET OVERSPREAD THE REGION. AT THIS TIME...THUNDERSTORM
INITIATION LOOKS LIKE A GOOD BET ALONG THE DRY LINE FROM LATE
THURSDAY AFTERNOON INTO THURSDAY EVENING.

CONVECTIVE MODE WILL BE HIGHLY DEPENDENT ON THE MOVEMENT OF THE
DRY LINE. CURRENT INDICATIONS ARE THAT THIS FEATURE MAY SURGE
NORTHEAST ACROSS WEST CENTRAL MISSOURI TOWARDS THE INTERSTATE 70
CORRIDOR. THIS MAY MAKE LINE SEGMENTS WITH EMBEDDED SUPERCELLS
THE PREFERRED MODES. FARTHER SOUTH ACROSS EASTERN OKLAHOMA AND
SOUTHWEST MISSOURI...MODELS ARE HINTING AT SLIGHTLY SLOWER
PROGRESS OF THE DRY LINE. THE NAM AND EVEN MULTIPLE GLOBAL MODELS
EVEN INDICATE SOME KIND OF SECONDARY SURFACE LOW DEVELOPMENT. IF
THE DRY LINE IS INDEED SLOWER TO PUSH EAST...SUPERCELLS WILL BE
THE PREFERRED CONVECTIVE MODE ACROSS THIS REGION.

MODERATE AMOUNTS OF INSTABILITY WILL BE PRESENT AS UPPER 50 AND
LOWER 60 DEW POINTS SPREAD NORTH INTO THE REGION. WHILE THESE DEW
POINTS MAY NOT BE ALL THAT IMPRESSIVE...THE STRONGLY COOLING MID
LEVELS WILL MORE THAN COMPENSATE FOR THAT. LARGE AMOUNTS OF CAPE
IN THE HAIL GROWTH ZONE AND THE PRESENCE OF A STRONG MID AND UPPER
LEVEL JET WILL CREATE THE POTENTIAL FOR VERY LARGE HAIL WITH ANY
SUPERCELLS. AS THAT PARENT SURFACE LOW DEEPENS AND TRACKS WEST OF
THE OZARKS...IT IS ALSO QUITE POSSIBLE THAT SURFACE WINDS REMAIN
BACKED. WITH A STRENGTHENING LOW LEVEL JET THURSDAY
EVENING...WIND PROFILES APPEAR SUPPORTIVE OF A TORNADO THREAT. ONE
ITEM THAT WILL HAVE TO BE WATCHED CLOSELY WITH RESPECT TO THE
TORNADO THREAT WILL BE QUALITY MOISTURE RETURN. LOWER LCLS AND
HIGHER AMOUNTS OF LOW LEVEL CAPE WOULD FURTHER INCREASE THE
THREAT FOR TORNADOES. NEEDLESS TO SAY...AM IN FULL AGREEMENT WITH
THE SPC DAY 3 OUTLOOK...THAT IS THE 30 PERCENT HATCHED AREA.