DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 211555
SWODY1
SPC AC 211552

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1052 AM CDT SUN APR 21 2013

VALID 211630Z - 221200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

A BROAD...CYCLONIC FLOW REGIME WILL BE MAINTAINED OVER THE CONUS
THROUGH THE D1 PERIOD. WITHIN THIS LARGE-SCALE PATTERN...A
SHORT-WAVE TROUGH FROM THE OZARK PLATEAU TO NWRN GULF COAST WILL
TRANSLATE EWD ACROSS THE GULF COAST STATES. THIS SYSTEM WILL
PRECEDE MID AND UPPER-LEVEL JET STREAKS AND AN ASSOCIATED SHORT-WAVE
TROUGH WHICH WILL AMPLIFY WHILE PROGRESSING SEWD FROM THE BRITISH
COLUMBIA COAST INTO PACIFIC NW AND NRN INTERMOUNTAIN REGION.
ELSEWHERE...A SERIES OF WEAKER PERTURBATIONS WILL ADVANCE FROM THE
NRN/CNTRL PLAINS INTO THE UPPER GREAT LAKES AND OH VALLEY.

IN THE LOW LEVELS...A COLD FRONT FROM THE CNTRL DAKOTAS INTO NRN
INTERMOUNTAIN REGION WILL PROGRESS ESEWD THROUGH THE UPPER MS AND
MID MO VALLEYS...AND SWD INTO THE CNTRL ROCKIES BY MONDAY MORNING.

...FL THIS AFTERNOON AND EVENING...

THE 12Z MIAMI SOUNDING SHOWS THAT NOTABLE COOLING HAS OCCURRED ABOVE
600 MB SINCE 00Z...WHICH WHEN COUPLED WITH A COMPARABLY MORE MOIST
BOUNDARY LAYER...WILL RESULT IN A MORE UNSTABLE AIR MASS THAN
YESTERDAY WITH MLCAPE APPROACHING 1500 J/KG. MOREOVER...AN ELY
COMPONENT TO THE LOW-LEVEL WIND FIELD WILL AUGMENT MODEST /20-30 KT/
WLY WINDS IN THE MID LEVELS TO YIELD SUFFICIENT VERTICAL SHEAR FOR
SOME STORM ORGANIZATION.

INCREASED LARGE-SCALE FORCING/DCVA ASSOCIATED WITH A WEAK MIDLEVEL
VORTICITY MAXIMUM CURRENTLY OVER THE CNTRL G.O.M. WILL ENHANCE
LOW-LEVEL CONVERGENCE ALONG DEVELOPING SEA BREEZE FRONTS AND
CONVECTIVE OUTFLOW BOUNDARIES /OBSERVED OVER THE E-CNTRL/SERN
PENINSULA/ TO YIELD SCATTERED TO NUMEROUS STORMS THIS AFTERNOON.
GIVEN THE MODERATE INSTABILITY AND RELATIVELY COOL MIDLEVEL
TEMPERATURES...A RISK FOR ISOLATED DAMAGING WIND GUSTS AND HAIL WILL
EXIST THROUGH THIS EVENING.

...MID MO VALLEY THIS AFTERNOON AND EVENING...

DESPITE THE PRESENCE OF A RELATIVELY DRY AIR MASS /I.E. PW VALUES
GENERALLY LESS THAN .6 INCH/...DAYTIME HEATING COUPLED WITH
700-500-MB LAPSE RATES OF 7.0-7.5 C/KM WILL SUPPORT MODEST
DESTABILIZATION TODAY AHEAD OF THE COLD FRONT. FORCING FOR ASCENT
ATTENDANT TO MIGRATORY IMPULSES MOVING ACROSS THE REGION WILL
COMBINE WITH LOW-LEVEL UPLIFT ALONG THE FRONT TO FOSTER WIDELY
SCATTERED TSTMS LATE THIS AFTERNOON INTO EVENING. GUSTY WINDS AND
SOME SMALL HAIL MAY ACCOMPANY THE STRONGEST STORMS...THOUGH THE
LIMITED INSTABILITY WILL PRECLUDE ORGANIZED...SEVERE STORM
POTENTIAL.

..MEAD/CARBIN.. 04/21/2013

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