Wednesday, July 20, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 210058
SWODY1
SPC AC 210057

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0757 PM CDT WED JUL 20 2011

VALID 210100Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE UPPER GREAT LAKES...

...THERE IS A SLGT RISK OF SVR TSTMS FOR NORTHERN MAINE...

...UPPER GREAT LAKES...
EARLY EVENING SURFACE OBSERVATIONS SHOW A COLD FRONT STEADILY
PROGRESSING EWD ACROSS THE UPPER MS RIVER VALLEY AS THE SRN
EXTENSION OF STRONGER FORCING FOR ASCENT ASSOCIATED WITH MCV OVER
SRN ONTARIO/MN ARROW HEAD CONTINUES TO SHEAR NEWD INTO INTERIOR SRN
ONTARIO N OF LAKE SUPERIOR. ENOUGH CINH REMAINS IN PLACE TO AREAS S
IN MN/WI WHERE VERY WEAK CONVERGENCE ALONG THE WIND SHIFT AND LACK
OF APPRECIABLE LARGE SCALE FORCING FOR ASCENT HAVE PRECLUDED STORM
INITIATION OVER THIS REGION THUS FAR. WHILE AN ISOLD STORM STILL
CANNOT BE RULED OUT LATER THIS EVENING...CURRENT THINKING IS STORM
COVERAGE SHOULD REMAIN SPARSE AND LIMIT SEVERE POTENTIAL. FARTHER
NE OVER THE LAKE SUPERIOR/MI UPPER PENINSULA VICINITY...GLANCING
INFLUENCE OF THE AFOREMENTIONED IMPULSE NOW EMBEDDED WITHIN THE
LARGER SCALE UPPER TROUGH OVER THE CANADIAN PRAIRIE PROVINCES SEEMS
TO SUPPORT A CONTINUED RISK FOR PRIMARILY ISOLD DMGG WINDS/LARGE
HAIL AS ONGOING ACTIVITY UNDERGOES FURTHER INTENSIFICATION/FORWARD
PROPAGATING CHARACTER THROUGH THE EVENING HOURS.

...NRN NEW ENGLAND...
POTENT MID LEVEL VORT MAX NOW EXITING FROM QUEBEC TO THE CANADIAN
MARITIMES HAS DRIVEN A COLD FRONT INTO THE LOWER ST. LAWRENCE RIVER
VALLEY/NRN NEW ENGLAND. A SQUALL LINE HAS DEVELOPED ALONG THIS
PORTION OF THE FRONT AND IS MOVING THROUGH THIS REGION THIS EVENING.
ALTHOUGH THE SHORTWAVE TROUGH IS MOVING AWAY IN COMBINATION WITH THE
LOSS OF DAYTIME HEATING...AN ISOLD DMGG WIND THREAT MAY PERSIST
THROUGH THE EARLY EVENING WITH ANY BOWING SEGMENTS--OWING TO 40 KT 2
KM AGL WLY FLOW BEFORE A RENEWED THREAT FOR STORMS TOWARDS DAYBREAK.

...CNTRL HIGH PLAINS...
INFLUENCE OF EXPANSIVE UPPER RIDGE CENTERED OVER THE MS RIVER VALLEY
HAS SO FAR LARGELY SUPPRESSED STORM DEVELOPMENT ALONG THE TRAILING
PORTION OF THE FRONT AND SURFACE CONFLUENCE ACROSS NEB/KS...WITH
HIGH-BASED STORMS PRIMARILY INITIATING OVER THE HIGHER TERRAIN AND
MOVING EWD IN THE CO HIGH PLAINS. VERY STEEP LOW LEVEL LAPSE RATES
RESULTANT FROM LARGE TEMP/DEWPOINT SPREADS IN EXCESS OF 40 DEG F MAY
ENABLE A FEW STORMS TO PRODUCE ISOLD STRONG-SEVERE WIND GUSTS
THROUGH THE EARLY EVENING HOURS.

...MID OH RIVER VALLEY...
A FEW MULTICELLULAR STORMS MAY CONTINUE TO POSE PRIMARILY AN ISOLD
STRONG WIND GUST RISK FOR THE NEXT HOUR OR TWO AS A RICH PW AIRMASS
/AOA 2 INCHES/ MAY SUPPORT A WET MICROBURST OR TWO BEFORE STORMS
DIMINISH IN COVERAGE/INTENSITY DUE TO DIURNAL COOLING. FARTHER SE
ACROSS THE CAROLINAS INTO THE DEEP SOUTH...CONVECTIVE
OVERTURNING/BOUNDARY LAYER STABILIZATION SHOULD LIMIT DMGG WIND
POTENTIAL.

..SMITH/KERR.. 07/21/2011

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