SPC AC 211249
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0749 AM CDT SUN JUN 21 2009
VALID 211300Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE MID MS VLY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN
INTERMOUNTAIN REGION/NRN RCKYS...
...SYNOPSIS...
RIDGE WILL REMAIN STNRY OVER THE LWR MS VLY THIS PERIOD AS LOW
FURTHER AMPLIFIES OFF THE NJ CST AND BROAD TROUGH PERSISTS FROM FAR
WEST INTO THE NRN PLNS/UPR MS VLY. SATELLITE DATA SHOW SEVERAL VORT
MAXIMA IN THE TROUGH THAT LIKELY WILL IMPACT STORM DEVELOPMENT OVER
THE NRN INTERMOUNTAIN REGION AND THE N CNTRL STATES. COMPLEX
IMPULSE NOW OVER THE CNTRL HI PLNS SHOULD CONTINUE NE INTO ERN
ND/NRN MN BY THIS EVE...WITH TRAILING SRN PART EXTENDING S INTO IA.
VORT MAX NOW IN MT WILL CONTINUE NNE INTO SK...WHILE ELONGATED
DISTURBANCE NOW OVER SW ORE/CNTRL CA/WRN NV CONSOLIDATES OVER NRN NV
AND CONTINUES NE INTO MT EARLY MON.
AT THE SFC...NE MT LOW SHOULD MOVE NE INTO SK THROUGH THE
DAY...WHILE A WEAKER CIRCULATION NOW IN NEB MOVES SLOWLY NE TOWARD
NW IA. IN ASSOCIATION WITH THE TWO LOWS...A WEAK WARM FRONT WILL
PROGRESS E/NE ACROSS THE DAKOTAS AND MI/UPR MS VLY.
...IA/NW IL AND VICINITY...
WEAK ELEVATED CONVECTION NOW OVER IA/NE NEB SHOULD CONTINUE
GENERALLY NE INTO THE UPR MS VLY TODAY AS LEAD PORTION OF CNTRL HI
PLNS IMPULSE CONTINUES NEWD. CONVECTION ON THE SRN FRINGE OF THIS
ACTIVITY MAY BECOME SFC-BASED AND DEVELOP MORE E OR ESE INTO PARTS
OF IL/IND AS SFC HEATING DESTABILIZES AXIS OF MODEST LOW LVL WAA ON
NRN FRINGE OF UPR RIDGE. WHILE AMPLE INSTABILITY WILL EXIST FOR
STRONG/POSSIBLY LOCALLY SVR STORMS...MODEST SHEAR SHOULD LIMIT
OVERALL SVR THREAT.
IN WAKE OF MORNING ACTIVITY...SFC HEATING AND UVV ASSOCIATED WITH
MAIN LOBE OF HI PLNS DISTURBANCE SHOULD FOSTER SFC-BASED STORM
DEVELOPMENT ACROSS IA/SRN MN AND PERHAPS NW MO BY EARLY AFTN...ALONG
AND SW OF WEAK WARM FRONT. MID LVL LAPSE RATES WILL REMAIN
COMPARATIVELY WEAK. BUT COMBINATION OF RICH MOISTURE /PW UP TO 2
INCHES/...MODERATE DESTABILIZATION...AND 30 KT DEEP WLY SHEAR WILL
SUPPORT SUSTAINED STORMS/SUPERCELLS WITH DMGG WIND AND POSSIBLY
HAIL. MORE SIGNIFICANTLY...BACKED/SELY LOW-LVL FLOW AND LOW LCLS
NEAR WARM FRONT WILL BE FAVORABLE FOR TORNADOES...ESPECIALLY OVER
NRN/ERN IA AND ADJACENT PARTS OF IL LATER THIS AFTN AND EVE.
FARTHER SW...BOTH SHEAR AND INSTABILITY SHOULD DIMINISH WITH SW
EXTENT INTO NRN/ERN KS...WHERE SVR WEATHER LIKELY WILL BE MORE
LIMITED.
...NRN GREAT BASIN/NRN RCKYS...
COOL CYCLONIC FLOW WILL PREVAIL OVER THE NRN INTERMOUNTAIN REGION
TODAY...DOWNSTREAM FROM CONSOLIDATING TROUGH IN ORE/NV. MODEST
DESTABILIZATION AHEAD OF TROUGH SHOULD LEAD TO AFTN STORM
DEVELOPMENT FROM NE NV/NRN UT NEWD INTO PARTS OF ID/WRN MT AND WRN
WY. 30-40 KT DEEP SSWLY SHEAR WILL FOSTER ORGANIZATION OF
CONVECTION INTO ONE OR MORE BANDS/CLUSTERS. EMBEDDED STRONGER/
SUSTAINED STORMS COULD YIELD DMGG SFC WINDS AND MARGINALLY SVR HAIL
THROUGH EARLY EVE.
...LWR OH VLY/TN VLY TO SRN APPALACHIANS...
WEAK DISTURBANCES AND/OR POCKETS OF ENHANCED MID LVL MOISTURE
CIRCULATING AROUND NE SIDE OF UPR RDG MAY YIELD A FEW SMALL CLUSTERS
OF STRONG STORMS FROM PARTS OF KY/TN SE INTO N GA/NRN SC. MODEST
MID LVL LAPSE RATES AND WEAK FORCING FOR ASCENT SHOULD LIMIT STORM
INTENSITY/COVERAGE...ALTHOUGH A FEW STRONG AFTN/EARLY EVE CELLS MAY
OCCUR.
..CORFIDI/GRAMS.. 06/21/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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