SWODY1
SPC AC 221620
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1120 AM CDT TUE MAY 22 2007
VALID 221630Z - 231200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PART OF THE CENTRAL
PLAINS...
..SERN SD INTO THE CENTRAL PLAINS...
MORNING DETERMINISTIC AND OVERNIGHT SREF/HIGH-RES WRF GUIDANCE ARE
IN AGREEMENT IN FOCUSED SEVERE THREAT AREA FROM PORTIONS OF CENTRAL
NEB INTO NWRN KS...SIMILAR TO PREVIOUS FORECASTS. THUS...VERY FEW
CHANGES ARE NEEDED TO PREVIOUS DAY 1 OUTLOOKS. 70-80M HEIGHT FALLS
AT H5 AT RIW AND GJT INDICATE MID LEVEL TROUGH WILL CONTINUE TO
DEEPEN/DIG ACROSS THE INTERMOUNTAIN WEST/CENTRAL ROCKIES...WITH AN
IMPULSE EJECTING ACROSS THE CENTRAL HIGH PLAINS THIS EVENING.
SURFACE PATTERN IS SOMEWHAT MUDDLED BY PRE-FRONTAL GRAVITY WAVE
WHICH HAS SURGED EWD WELL AHEAD OF PRIMARY COLD FRONT THIS MORNING
OVER NWRN KS/SRN NEB. EXPECT HEATING/MIXING WITHIN THE BOUNDARY
LAYER WILL ERODE/LIFT CAP AND DIMINISH THIS WAVE BY THE
AFTERNOON...REFOCUSING ATTENTION ALONG COLD FRONT/DRY LINE WHICH IS
FORECAST TO MOVE SLOWLY EWD ACROSS CENTRAL SD AND WRN NEB/KS.
THOUGH LOW LEVEL MOISTURE WILL REMAIN MODEST FOR LATE MAY...COOL
TEMPERATURES ALOFT AND SUFFICIENT HEATING WILL SUPPORT MODERATE
INSTABILITY INTO CENTRAL NEB. COMBINATION OF STRONG UPPER LEVEL
DIFFLUENCE ALONG NOSE OF 100+ KT H25 JET AND CONVERGENCE INVOF COLD
FRONT WILL OVERCOME WEAKENING CAP. THIS WILL SUPPORT THUNDERSTORM
DEVELOPMENT FROM THE NEB SAND HILLS /AND POSSIBLY SCENTRAL-SERN SD
EAST OF THE MO RIVER/ INTO NWRN KS BETWEEN 21-00Z. DEEP LAYER SHEAR
WILL BE MORE THAN ADEQUATE FOR DISCRETE SUPERCELLS...ESPECIALLY
WITHIN THE FIRST FEW HOURS AFTER INITIATION...WITH ATTENDANT THREAT
OF A FEW TORNADOES. IN ADDITION...RELATIVELY STEEP LAPSE RATES AND
COLD MID LEVEL TEMPERATURES SHOULD ENHANCE HAIL GROWTH AND COULD
SUPPORT VERY LARGE HAIL. ACTIVITY IS EXPECTED TO EVOLVE INTO SMALL
LINEAR SEGMENTS DURING THE MID TO LATE EVENING...WITH SEVERE THREAT
WANING LATE THIS EVENING/OVERNIGHT AS STORMS EVOLVE INTO ONE OR TWO
MCSS AND SHIFT EWD ACROSS KS/ERN NEB.
..ERN ND/WRN MN/NERN SD...
EJECTING MID LEVEL IMPULSE IS MOVING NNEWD INTO SERN ND LATE THIS
MORNING. ATTENDANT 40+ KT LLJ WILL ALSO SPREAD NWD AND EXTEND
ACROSS WRN MN FOR MUCH OF THE DAY. BROKEN CLOUDS AHEAD OF THIS
IMPULSE OVER NWRN MN/NERN ND MAY INCREASE THUNDERSTORM
COVERAGE/INTENSITY BY THE EARLY TO MID AFTERNOON. THOUGH AN
ISOLATED SEVERE THUNDERSTORM IS POSSIBLE...RELATIVELY WEAK LAPSE
RATES/INSTABILITY AND MARGINAL SHEAR SUGGEST SEVERE THREAT REMAINS
LOW.
..SRN HIGH PLAINS...
PRESENCE OF MODEST WSWLY FLOW OVERSPREADING THE DRY LINE OVER THE
OK/ERN TX PANHANDLES AND SWRN KS TODAY WARRANTS MAINTAINING
CONDITIONAL SEVERE THREAT. CAPPING APPEARS TO BE FAIRLY STRONG AND
MAY INHIBIT INITIATION ALTOGETHER. HOWEVER WITH AFTERNOON HEATING
INTO THE MID 80S AND MODEST CONVERGENCE...AN ISOLATED SEVERE
THUNDERSTORM IS NOT OUT OF THE QUESTION EARLY THIS EVENING.
FORECAST SOUNDINGS FROM THE NAMKF AND RUC YIELD MLCAPE IN EXCESS OF
2000 J/KG...WITH NAMKF AND NAM BOTH GENERATING BRIEF QPF BETWEEN
00Z-03Z OVER THE SERN TX PANHANDLE/FAR SWRN OK. OTHER MODELS KEEP
THINGS DRY/MAINTAIN CAP SOUTH OF TRIPLE POINT LOW OVER NWRN KS.
SHOULD A STORM FIRE...IT WILL MOST CERTAINLY BECOME
SUPERCELLULAR/SEVERE VERY QUICKLY WITH MULTITUDE OF SEVERE THREATS.
SLOW MOVING STORMS WOULD THEN DIMINISH QUICKLY AFTER SUNSET.
.EVANS/CROSBIE.. 05/22/2007
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@PO.UIUC.EDU with
"unsub wx-storm" in the body of your message. For more information write chris@lib.siu.edu.
No comments:
Post a Comment