DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT SUN APR 24 2011
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PORTION OF THE
ERN U.S. FROM THE NORTHEAST SWWD INTO ERN TX/ERN OK...
...SYNOPSIS...
AS ONE FEATURE ALOFT EJECTS NEWD ACROSS THE OH VALLEY INTO THE GREAT
LAKES AREA...A SECOND WILL DIG QUICKLY SEWD OUT OF THE ROCKIES AND
INTO THE SRN PLAINS -- BOTH WITHIN THE LARGER-SCALE TROUGH WHICH
WILL KEEP BROAD CYCLONIC FLOW IN PLACE ACROSS A LARGE PORTION OF THE
U.S. THROUGH THE PERIOD.
WHILE THE INITIAL SURFACE LOW LIFTS NEWD INTO THE GREAT LAKES AND
WEAKENS...LEAVING BEHIND A TRAILING FROM THE OH VALLEY SWWD ACROSS
THE MID MS VALLEY INTO TX...A SECOND FRONTAL LOW WILL DEVELOP -- AND
QUICKLY DEEPEN -- AS IT SHIFTS ACROSS TX AND INTO AR LATE. THIS
DEVELOPING LOW WILL CONTRIBUTE TO A POTENTIALLY SUBSTANTIAL SEVERE
WEATHER EVENT ACROSS THE ARKLATEX AND MID MS VALLEY REGION.
...ARKLATEX REGION INTO THE MID MS VALLEY AREA...
COMPLEX -- BUT POTENTIALLY SIGNIFICANT -- SCENARIO APPEARS TO BE
UNFOLDING ACROSS THIS REGION...AS PERSISTENT WARM ADVECTION INVOF A
SURFACE WARM FRONT RESULTS IN A SLOW INCREASE IN STORM COVERAGE
AHEAD OF A RAPIDLY-APPROACHING UPPER FEATURE DIGGING SEWD FROM THE
ROCKIES INTO THE SRN PLAINS. WHILE SEVERE POTENTIAL IS APPARENT
ACROSS PORTIONS OF THE AREA -- PARTICULARLY INVOF THE WARM FRONT --
THROUGH MUCH OF THE PERIOD...THREAT SHOULD RAMP UP RAPIDLY FROM W TO
E BY LATE AFTERNOON ACROSS SERN OK/E TX...AND THEN INTO THE EVENING
ACROSS THE ARKLATEX INTO NRN LA/AR AND EVENTUALLY THE MID MS VALLEY
REGION.
FLOW ALOFT IS FORECAST TO INCREASE AS THE UPPER SYSTEM
APPROACHES...AND AS BACKING/INCREASING LOW LEVEL FLOW EVOLVES IN
RESPONSE...SHEAR WILL BECOME HIGHLY-FAVORABLE FOR SUPERCELLS. IN
ADDITION...IT APPEARS THAT LOW-LEVEL SHEAR WILL BECOME QUITE
FAVORABLE FOR LOW-LEVEL ROTATION -- AND THUS THE POSSIBILITY OF
STRONG TORNADOES...ESPECIALLY OVERNIGHT FOCUSED ON AR AND VICINITY.
GIVEN THIS POTENTIAL...UPGRADE TO HIGHER CATEGORY RISK APPEARS
LIKELY IN LATER FORECASTS.
...SRN APPALACHIANS WWD ACROSS THE TN VALLEY REGION...
PERSISTENT CYCLONIC FLOW ALOFT -- AND THE PASSAGE OF SEVERAL
WEAK/EMBEDDED FEATURES -- ATOP A MOIST BOUNDARY LAYER DESTABILIZING
THROUGH THE AFTERNOON SHOULD RESULT IN WIDESPREAD THUNDERSTORM
DEVELOPMENT ACROSS A LARGE PORTION OF THE SERN U.S. -- FROM VA AND
THE CAROLINAS WWD INTO THE TN VALLEY AND SOUTHEAST. WITH MODEST BUT
SUFFICIENT FLOW ALOFT ACROSS A BROAD AREA...MULTICELL/LOCAL
SUPERCELL ORGANIZATION CAN BE EXPECTED WITH STORMS ACROSS A LARGE
PORTION OF THIS REGION. DETAILS REMAIN UNCLEAR ATTM...BUT WILL
INCLUDE A LARGE PORTION OF THIS REGION IN SLIGHT RISK FORECAST --
MAINLY FOR DAMAGING WIND AND HAIL POTENTIAL...THOUGH AN ISOLATED
TORNADO OR TWO IS ALSO POSSIBLE.
...LOWER GREAT LAKES/OH VALLEY REGION...
AS A STRONG SHORT-WAVE TROUGH AND SURFACE WARM FRONT LIFT QUICKLY
NEWD ACROSS THE REGION...EXPECT WIDESPREAD SHOWERS AND THUNDERSTORMS
EARLY IN THE PERIOD...WHICH SHOULD CONTINUE/REDEVELOP THROUGH THE
PERIOD. NARROWING DOWN EXACT AREAS OF SEVERE WEATHER POTENTIAL
REMAIN DIFFICULT AT THIS TIME WITH WIDESPREAD AREA OF AT LEAST
MARGINAL INSTABILITY AND A BROAD AREA OF STRONG FLOW ALOFT/FAVORABLE
SHEAR. DETAILS SHOULD BECOME CLEARER IN LATER FORECASTS...BUT
ATTM...WILL INCLUDE A LARGE PORTION OF THE LOWER GREAT LAKES REGION
SWWD INTO THE OH VALLEY AREA...WHERE POTENTIAL FOR MULTIPLE EPISODES
OF STRONG/OCCASIONALLY SEVERE STORMS APPEARS TO EXIST -- INCLUDING
THREATS FOR HAIL...DAMAGING WINDS...AND A COUPLE OF TORNADOES.
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0350 AM CDT SAT APR 23 2011
VALID 261200Z - 011200Z
...DISCUSSION...
SUBSTANTIAL SEVERE WEATHER POTENTIAL IS EXPECTED TO SHIFT SLOWLY EWD
ACROSS THE ERN U.S. DAYS 4-6 /TUE. 4-26 THROUGH THU. 4-28/...AS A
LARGE UPPER TROUGH PROGRESSES FROM THE CENTRAL U.S. DAY 4 ACROSS THE
MS VALLEY DAY 5...AND THEN ON EWD THROUGH DAYS 6/7. MODEL
DIFFERENCES WITH RESPECT TO TIMING OF THIS FEATURE BEGIN TO EMERGE
DAY 5...BUT BECOME INCREASINGLY PRONOUNCED THROUGH DAYS 6 AND 7 AS
THE TROUGH APPROACHES THE E COAST STATES/ERN ATLANTIC.
THE PRIMARY SEVERE THREAT DAY 4 IS PROGGED FROM E TX NEWD ACROSS THE
ARKLATEX INTO THE MID MS VALLEY...AS A SHORT-WAVE TROUGH DIGS ESEWD
INTO THIS REGION...WITHIN THE LARGER-SCALE TROUGH. UNSTABLE AIRMASS
COMBINED WITH THE ENERGETIC SHORT-WAVE FEATURE AND ASSOCIATED/STRONG
FLOW FIELD SUGGESTS WIDESPREAD SEVERE WEATHER POTENTIAL -- INCLUDING
RISKS FOR LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES.
THE THREAT SHOULD SHIFT E OF THE MS VALLEY INTO THE MID
SOUTH/SOUTHEAST DAY 5...AS THE SHORT-WAVE FEATURE TAKES ON A NEUTRAL
TO EVEN NEGATIVE TILT AS IT CROSSES THIS REGION. AGAIN -- AMPLY
UNSTABLE AIRMASS COMBINED WITH THE STRENGTH OF THE UPPER SYSTEM AND
ASSOCIATED FLOW FIELD SUGGESTS WIDESPREAD SEVERE WEATHER CAN BE
EXPECTED...INCLUDING THE POTENTIAL FOR TORNADOES.
AS MODELS BEGIN DIVERGING SOMEWHAT WITH RESPECT TO TIMING AND
SMALLER-SCALE DETAILS...DEGREE OF THREAT SHIFTING ACROSS THE
APPALACHIANS LATE DAY 5 AND INTO DAY 6 BECOMES LESS CERTAIN. WHILE
SEVERE WEATHER WILL BE LIKELY WITH THE FRONT EXPECTED TO REACH THE
ATLANTIC COAST BY THE END OF THE PERIOD...WILL REFRAIN FROM
HIGHLIGHTING A THREAT AREA THIS FORECAST.
WITH THE FRONT LIKELY OFFSHORE BY THE START OF DAY 7... SEVERE
WEATHER POTENTIAL ACROSS THE U.S. APPEARS LESS
WIDESPREAD/SIGNIFICANT AND MUCH MORE UNCERTAIN THROUGH THE END OF
THE PERIOD.
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT SAT APR 23 2011
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN PORTIONS OF THE SRN
PLAINS EWD/NEWD INTO THE MID OH AND TN VALLEYS...
...SYNOPSIS...
PROGRESS OF THE LARGE-SCALE UPPER TROUGH WILL SLOW OVER THE CENTRAL
U.S. THIS PERIOD...AS ONE EMBEDDED SHORTER-WAVELENGTH TROUGH EJECTS
NEWD ACROSS THE MO VALLEY INTO THE UPPER MIDWEST/UPPER GREAT LAKES
AND A SECOND DIGS ESEWD OUT OF THE ERN PACIFIC AND INTO THE SRN
ROCKIES BY THE END OF THE PERIOD.
AT THE SURFACE...FRONTAL ZONE WHICH HAS PERSISTED FROM THE
MID-ATLANTIC REGION WSWWD INTO THE SRN PLAINS WILL REMAIN THE FOCUS
FOR SEVERE STORMS THIS PERIOD. HOWEVER...SOME NWD MOVEMENT OF THE
FRONT IS FORECAST THROUGH THE END OF THE PERIOD AS A FRONTAL WAVE
SHIFTS NEWD OUT OF THE SRN PLAINS AND INTO THE UPPER MIDWEST.
...ERN OK/NERN TX ENEWD ACROSS THE LOWER AND MID MS/TN/LOWER AND MID
OH VALLEY REGION...
RELATIVELY WIDESPREAD CONVECTION SHOULD BE ONGOING ACROSS MUCH OF
THE AREA AT THE START OF THE PERIOD...AND SHOULD INCREASE/EXPAND
THROUGH THE AFTERNOON AS AIRMASS DIURNALLY HEATS/DESTABILIZES.
WITH MODERATELY STRONG/VEERING FLOW WITH HEIGHT FORECAST ATOP THE
SURFACE WARM SECTOR...EXPECT ORGANIZED/SUPERCELL STORMS TO AGAIN
BECOME MOST INTENSE THROUGH AFTERNOON AND EVENING -- SIMILAR TO
PRIOR DAYS. ALONG WITH POTENTIAL FOR VERY LARGE HAIL...LOCALLY
DAMAGING WINDS AND A COUPLE OF TORNADOES WILL AGAIN BE POSSIBLE.
ATTM...THE FORECAST AMOUNT OF CONVECTION ONGOING THROUGH THE END OF
DAY 2 AND INTO DAY 3 RESULTS IN UNCERTAINTY WITH RESPECT TO PRECISE
LOCATION AND DEGREE OF MORE CONCENTRATED CONVECTIVE/SEVERE THREATS.
HOWEVER...THREAT APPEARS SUBSTANTIAL ENOUGH ACROSS THE ARKLATEX
REGION TO WARRANT CONTINUATION OF PROBABILITIES REFLECTIVE OF A
FAIRLY ACTIVE SEVERE THREAT.
Sounds like they wanted to go Mod but too many question marks at this junction to go mod.
Probably the GFS, its the hot hand right now. Although the Euro 12z has came in line with the GFS fairly nicely, so if that were to continue you would have inter/intramodel consistency from 2 of the best models.
Wait this cant be a true, a chase potential on my day off ?
Talk about a high octane potential too. Like Baro said its been a while since we have seen a pattern like this. Compounded by what has already happened so far this month.