SPC AC 201258
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0658 AM CST SUN FEB 20 2011
VALID 201300Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
WRN U.S. TROUGH EXPECTED TO PROGRESS STEADILY E THIS PERIOD AS
UPSTREAM DISTURBANCE AMPLIFIES SE TO FORM A CLOSED LOW OFF THE ORE
CST. THE MAIN PART OF THE WRN TROUGH...I.E. UPR LOW AND ASSOCIATED
JET STREAK NOW OVER WY...SHOULD REACH CNTRL SD/NE NEB BY EVE...AND
SRN MN EARLY MON...WITH FAST WSW FLOW PREVAILING FROM THE CNTRL PLNS
INTO THE OH VLY.
AT LWR LVLS...LOW NOW OVER NW KS SHOULD MOVE ENE TO SRN IA BY THIS
EVE...BEFORE THE SYSTEM PARTLY OCCLUDES AND EVOLVES INTO AN
ELONGATED AREA OF LOW PRESSURE ALONG THE WARM/STNRY FRONT EXTENDING
THROUGH CNTRL PORTIONS OF IL/IND AND OH BY 12Z MON. COLD FRONT
TRAILING SW FROM THE LOW SHOULD REACH ERN KS THIS EVE...AND EXTEND
FROM CNTRL IL THROUGH SRN MO INTO ERN OK EARLY MON.
...CNTRL PLNS TO SRN GRT LKS...
TWO MAIN AREAS OF LOW LVL WAA EXPECTED TO SUPPORT EPISODES OF SCTD
TO BKN TSTMS THIS PERIOD. THE FIRST OF THESE WILL BE ASSOCIATED
WITH MAIN BRANCH OF SW TO WSWLY LLJ NOW EXTENDING FROM THE SRN PLNS
TO THE LWR MO/MID MS VLYS. THE ELEVATED STORMS IN THE EXIT REGION
OF THIS JET SHOULD SHIFT E OR ENE THROUGH THE PERIOD. WHILE
SUBSTANTIAL MOISTURE TRANSPORT WILL CONTINUE ALONG THE JET...A
GRADUAL WEAKENING TREND IN THE CONVECTION IS EXPECTED AS THE EXIT
REGION MOVES BEYOND PLUME OF STEEPER MID LVL LAPSE RATES.
THE SECOND AREA OF STORMS IS EXPECTED TO FOCUS IN AREA OF STRONGER
FORCING FOR ASCENT/FRONTAL UPLIFT OVER THE CNTRL PLNS/LWR MO
VLY...AHEAD OF POSITIVE-TILT SHORTWAVE TROUGH SWEEPING ENE WITH
AFOREMENTIONED UPR LOW. ASCENT ALSO MAY BE ENHANCED BY LOW LVL
CONVERGENCE INVOF SFC LOW/COLD FRONT. WIND PROFILES WILL BE
FAVORABLE FOR SUSTAINED STORMS ALONG COLD FRONT IN ERN KS/WRN MO
LATER TODAY/EARLY TONIGHT. BUT FCST SOUNDINGS CONTINUE TO SHOW
WARM/STABLE LAYER AROUND 500-600 MB THAT SHOULD PROHIBIT DEEP
CONVECTION IN THE WARM SECTOR....WITH STORMS LIKELY TO BE CONFINED
TO AREA OF ELEVATED CAPE N OF WARM FRONT IN PARTS OF IA/IL/WI.
SOME POTENTIAL FOR TSTMS MAY EVOLVE LATE IN THE PERIOD /AFTER ABOUT
09Z/ IN SRN MO...NW AR...AND NE OK AS MID LVL COOLING AND ASCENT
ASSOCIATED WITH UPR TROUGH OVERTAKE TRAILING PORTION OF COLD FRONT.
WHILE THIS WILL WEAKEN CINH...BY THIS TIME THE LLJ OVER THE REGION
LIKELY WILL HAVE VEERED TO WSWLY AND WEAKENED. THIS SHOULD TEND TO
MINIMIZE STORM COVERAGE/INTENSITY. NEVERTHELESS...ANY SUSTAINED
STORMS THAT DO FORM OVER THE AREA WOULD TEND TO BE SFC-BASED...OR
NEARLY SO. GIVEN STRENGTH OF WIND FIELD...THESE COULD YIELD A
LOCALLY DMGG GUST TOR TWO. THE NRN OZARKS WILL CONTINUE TO BE
MONITORED FOR POSSIBLE UPGRADE TO INCLUDE GEN TSTM AND POSSIBLY LOW
CONDITIONAL SVR PROBABILITIES IN LATER OTLKS.
...GRT BASIN...
SCTD MAINLY DIURNAL STORMS EXPECTED OVER PARTS OF THE GREAT BASIN
THIS PERIOD IN ZONE OF STEEP LOW TO MID LVL LAPSE RATES BENEATH UPR
TROUGH.
..CORFIDI/GARNER.. 02/20/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
|
