SPC AC 091226
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0726 AM CDT THU JUL 09 2009
VALID 091300Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS TO THE
GREAT LAKES...
...SYNOPSIS...
STRONG MID/UPPER JET CONTINUES TO TRANSLATE EWD NRN PLAINS TO UPPER
GREAT LAKES ATOP THE LARGE SRN PLAINS UPPER HIGH. TROUGH REMAINS
JUST OFF PAC NW COAST WITH EMBEDDED FAST MOVING S/WVS MOVING THRU
THE FLOW. OVERNIGHT A 40-50KT LOW LEVEL JET HAS MOVED A SUBSTANTIAL
INCREASE IN MOISTURE/INSTABILITY NWD THRU PLAINS. RESULT HAS BEEN
NUMEROUS SEVERE THUNDERSTORM COMPLEXES ACROSS THE DAKOTAS.
COLD FRONT HAS PUSHED EWD ACROSS THE DAKOTAS INTO SWRN NEB...AND
PARTICULARLY THE SRN PORTION WILL SLOW TODAY GIVEN THE STRENGTH OF
THE SRN PLAINS UPPER HIGH.
...CENTRAL U.S...
COMPLEX SCENARIO FOR THE FORECAST PERIOD AS THE STRONG UPPER HIGH
SRN PLAINS GRADUALLY EXPANDS AND ATTEMPTS TO CAP OFF THE CONVECTIVE
THREAT. THE PLAINS ARE WHERE THE GREATEST SEVERE POTENTIAL EXISTS
GIVEN THE AMOUNT OF MOISTURE AND INSTABILITY NOW IN PLACE.
IMMEDIATE CHALLENGE IS HOW LONG THE VERY IMPRESSIVE SEVERE
THUNDERSTORM COMPLEX NOW SERN SD WILL CONTINUE. IT IS RIDING DOWN
THE ERN PERIPHERY OF THE MID LEVEL CAP AND FEEDING OFF STRONG
ISENTROPIC LIFT IN THE WARM ADVECTION GENERATED BY THE LOW LEVEL
JET. GIVEN THE ACTIVE CONVECTION SWD THRU ERN KS/OK DURING THE
NIGHT...THERE REMAINS SIGNIFICANT INSTABILITY ABOVE THE CAP THIS
AREA. THUS THE POTENTIAL FOR THE SEVERE MCS NOW SERN SD CONTINUING
BASICALLY DOWN THE MO RIVER VALLEY INTO THE KC AREA IS PLAUSIBLE.
IF SO THEN AN ENHANCED THREAT OF BOTH LARGE HAIL AND DAMAGING WINDS
WILL ACCOMPANY THIS SYSTEM
REF MCD 1499.
THIS SCENARIO HAS BEEN HANDLED WELL THUS FAR BY THE NSSL WRF
MODEL...WHICH TAKES THE TRACK OF THE SYSTEM TO KC BY EARLY THIS
AFTERNOON.
WITH THE STRONG HEATING EXPECTED ACROSS MUCH OF THE CENTRAL PLAINS
TODAY THE AIRMASS BECOMES VERY TO EXTREMELY UNSTABLE WITH MLCAPES
AOA 3500 J/KG S OF FRONTAL ZONE AND CONVECTIVE BOUNDARIES...RENEWED
THUNDERSTORMS SHOULD BE ABLE TO BREECH THE CAP VICINITY FRONTAL
BOUNDARY. MORE THAN SUFFICIENT SHEAR WILL REMAIN IN PLACE ERN
NEB/NERN KS FOR SUPERCELLS AS THE LOW LEVEL JET INCREASES AGAIN THIS
EVENING TO 40-50 KT AFTER WEAKENING SOME THIS AFTERNOON.
LARGE HAIL AND DAMAGING DOWNBURSTS WINDS ARE THE PRIMARY
THREAT...WITH A SMALLER THREAT OF ISOLATED TORNADOES GIVEN THE WARM
AIRMASS AND RELATIVELY HIGH LFC.
ADDITIONALLY UPSLOPE FLOW TO THE N OF THE FRONTAL ZONE WILL DELIVER
SUFFICIENT LOW LEVEL MOISTURE AND INSTABILITY FOR POTENTIAL OF
SCATTERED STORMS...SOME SEVERE MOVING OFF THE HIGHER TERRAIN SERN
WY/WRN NEB.
...CENTRAL/ERN GULF COAST...
MID LEVEL TROUGHING WILL GRADUALLY SAG SEWD INTO THE CNTRL/ERN GULF
REGION OVER THE NEXT FEW DAYS ENHANCING THE PROSPECT FOR ROBUST
AFTERNOON PULSE-MULTICELL THUNDERSTORMS. GUSTY WINDS ARE THE
GREATEST RISK WITH STORMS THAT DEVELOP DURING THE HEAT OF THE DAY
ACROSS THIS REGION.
..HALES/GARNER.. 07/09/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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