Monday, April 23, 2012

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 230610
SWODY2
SPC AC 230609

DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0109 AM CDT MON APR 23 2012

VALID 241200Z - 251200Z

...NO SVR TSTM AREAS FORECAST...

CORRECTED FOR NDFD GRAPHIC

...SYNOPSIS...
AN AMPLIFIED LARGE SCALE PATTERN WILL REMAIN OVER MUCH OF THE
CONUS/CANADA THROUGH TUESDAY. AN UPPER RIDGE OVER THE ROCKIES WILL
BE FLANKED BY A DEEP LONGWAVE TROUGH OVER THE EASTERN PORTIONS OF
THE CONUS/CANADA AND FAR WESTERN ATLANTIC...WHILE DUAL UPPER TROUGHS
SHIFT EASTWARD OVER THE EASTERN PACIFIC AMID SPLIT UPPER FLOW.

...NORTHERN ROCKIES...
ONE OR MORE LOW-AMPLITUDE IMPULSES ARE EXPECTED TO CREST THE ROCKIES
UPPER RIDGE AS THE RIDGE OTHERWISE DAMPENS TO A DEGREE...WITH A
GRADUAL /ALBEIT MODEST/ MOISTENING OF THE AIRMASS ACROSS THE REGION
INTO TUESDAY. THIS SHOULD RESULT IN AN UPSWING OF POSSIBLE TSTMS
ESPECIALLY FROM FAR EASTERN ORE/WA INTO ID/MT. WHILE EARLY DAY
CLOUDS/PRECIPITATION MAY FURTHER HINDER THE DEGREE OF
DESTABILIZATION...STEEP LAPSE RATES AND MODEST CAPE BENEATH MODERATE
WEST-SOUTHWESTERLY FLOW ALOFT MAY BE SUFFICIENT FOR A FEW STRONGER
TSTMS CAPABLE OF HAIL/GUSTY WINDS.

...UPPER MIDWEST/MIDDLE MS VALLEY/OH VALLEY...
AN ELEVATED MIXED LAYER WILL BUILD EASTWARD AND BECOME INCREASINGLY
EXTENSIVE OVER THE NORTHERN/CENTRAL PLAINS AND ADJACENT UPPER
MIDWEST THROUGH TUESDAY. APPRECIABLE MOISTURE RETURN IS UNLIKELY
THROUGH TUESDAY GIVEN PERSISTENCE OF CONTINENTAL NEAR-GULF OF MEXICO
TRAJECTORIES...BUT A DEGREE OF MOISTENING WILL NONETHELESS OCCUR
INTO THE REGION BENEATH THE STRENGTHENING CAP.

IT IS CONCEIVABLE THAT ISOLATED TO SCATTERED TSTMS COULD DEVELOP
TUESDAY AFTERNOON NEAR A SURFACE LOW AND WEAK FRONT/SURFACE TROUGH
ACROSS THE EASTERN DAKOTAS/MN. HOWEVER...A SOMEWHAT MORE CERTAIN
SCENARIO IS FOR ISOLATED TSTMS TO DEVELOP LATE TUESDAY NIGHT ACROSS
THE MIDWEST/OH VALLEY ON THE EASTERN EDGE OF THE CAP IN AREAS
NEAR/NORTHEAST OF A WARM FRONT. IT SHOULD BE NOTED THAT CONSIDERABLE
NUMERICAL GUIDANCE VARIABILITY DOES STILL EXIST /ESPECIALLY 00Z GFS
VS 00Z NAM/12Z ECMWF -- WITH THE LATTER MORE AGGRESSIVE/. BUT EVEN
WITH THIS GUIDANCE VARIABILITY AND A MARGINAL MOISTURE INFLUX ALOFT
LATE TUESDAY...WILL INTRODUCE LOW PROBABILITIES FOR
CONDITIONAL/ISOLATED HAIL POTENTIAL TUESDAY NIGHT IF/WHERE STORMS
OCCUR ACROSS THE MIDWEST/OH VALLEY...GIVEN THE PROXIMITY OF VERY
STEEP LAPSE RATES ALOFT COUPLED WITH A HIGH DEGREE OF SHEAR.

..GUYER.. 04/23/2012

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