SPC AC 071618
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1118 AM CDT MON APR 07 2008
VALID 071630Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SRN AND
CENTRAL PLAINS...
...SYNOPSIS...
BROAD TROUGHING CONTINUES TO EVOLVE OVER THE WESTERN U.S. POTENT
UPPER LOW WILL BE TRACKING NEWD FROM WI TO ERN UP OF MI TODAY AND TO
SERN ONTARIO OVERNIGHT. UPSTREAM LOW AMPLITUDE IMPULSES WILL BE
TRACKING THROUGH DEVELOPING WRN U.S. TROUGH. W/V IMAGERY SUPPORTS
THE NAM BRINGING A S/WV ACROSS CENTRAL/SRN ROCKIES TO HIGH PLAINS BY
THIS EVENING WITH ANOTHER SYSTEM REACHING CENTRAL PAC COAST LATER
TONIGHT.
SURFACE LOW GRADUALLY DEEPENS TX/OK PANHANDLE THIS AFTERNOON IN
RESPONSE TO STRENGTHENING UPSTREAM WESTERLIES AND APPROACHING MID
LEVEL TROUGH. SHALLOW FRONTAL ZONE FROM SRN LA NWWD TO NWRN TX WILL
MIX/LIFT NWD AS A WARM FRONT TODAY IN RESPONSE TO STRENGTHENING SLY
LOW LEVEL JET AND STRONG SURFACE HEATING AS A DRY LINE DEVELOPS IN
SURFACE TROUGH WRN TX.
...SRN/CNTRL PLAINS...
EVOLUTION OF SEVERE THUNDERSTORM POTENTIAL DISCUSSED IN THE 13Z DY1
STILL VALID. A POTENT SUPERCELL ENVIRONMENT IS EXPECTED TO DEVELOP
DURING THE AFTERNOON AS THE COMBINATION OF RAPID DESTABILIZATION AND
EXPANDING HODOGRAPHS VICINITY OF RETURNING WARM FRONT TAKE PLACE.
WITH STEEP/COOL MID LEVEL LAPSE RATES IN PLACE THE SURFACE HEATING
COUPLED WITH LOW LEVEL MOISTURE RETURN WILL INCREASE MLCAPES TO NEAR
2000 J/KG BY LATE AFTERNOON SRN OK INTO N TX E OF DRY LINE.
MODELS IN BASIC AGREEMENT THAT STORMS SHOULD INITIATE BY LATE
AFTERNOON VICINITY LOW LEVEL CONVERGENCE NEAR THE WARM FRONT AS WELL
AS THE DRY LINE WHICH SHOULD EXTEND SWD FROM NEAR WRN OK/TX BORDER.
THE LIMITED LARGE SCALE FORCING BUT WITH FAVORABLE UPPER
DIVERGENCE/LARGE SCALE ASCENT WITH APPROACHING S/WV TROUGH SUPPORTS
DISCRETE STORMS VS A LINEAR MODE.
INITIALLY SUPERCELLS ACCOMPANIED BY VERY LARGE HAIL WILL BE THE
PRIMARY THREAT BY LATER THIS AFTERNOON. HOWEVER TORNADO CONCERN WILL
INCREASE TOWARD EVENING AS LOW LEVEL JET TO 50KT DEVELOPS. WITH GULF
MOISTURE WHICH THIS AFTERNOON WILL STILL BE SOMEWHAT
LIMITED...INCREASES THRU THE NIGHT...SUPERCELLS ARE EXPECTED TO
CONTINUE WELL AFTER DARK. THIS WILL MAINTAIN BOTH A LARGE HAIL AND A
TORNADO THREAT...PARTICULARLY VICINITY OF E/W WARM FRONT ACROSS OK.
GIVEN THE STILL UNCERTAINTY WITH REGARDS TO THE NUMBER OF STORMS AND
THE TIMING OF DEVELOPMENT...THE FORECAST WILL REMAIN A STRONG
SLIGHT...WITH A POTENTIAL UPGRADE TO MDT THIS AFTERNOON.
...ERN LWR MI...
GOOD HEATING OCCURRING ACROSS LOWER MI AHEAD OF STRONG UPPER LOW AND
COLD FRONT. WITH SURFACE TEMPERATURES WARMING INTO 60S AND LOW 40S
DEWPOINTS A MARGINALLY UNSTABLE AIR MASS WILL BE AVAILABLE FOR STORM
INITIATION ALONG COLD FRONT BY EARLY THIS AFTERNOON. STRONG SHEAR
AHEAD OF UPPER LOW SUPPORTS ORGANIZED LOW TOPPED THUNDERSTORM
DEVELOPMENT BY EARLY AFTERNOON. WITH MLCAPES OF 200-400 J/KG PRIMARY
THREAT WILL BE HAIL AND DAMAGING WINDS GIVEN THE STEEP/COOL LAPSE
RATES. SEVERE COVERAGE WILL BE LIMITED BY SMALL TIME AND SPACE
WINDOW AVAILABLE FOR OCCURRENCE AND THE WEAK INSTABILITY.
..HALES/BOTHWELL.. 04/07/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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