DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 230547
SWODY1
SPC AC 230545

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT MON APR 23 2012

VALID 231200Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
HIGHLY AMPLIFIED UPPER FLOW PATTERN TO CONTINUE ACROSS THE U.S. THIS
PERIOD...WITH THE LARGE ERN U.S. UPPER TROUGH PROGGED TO MAKE VERY
SLOW EWD PROGRESS AS THE EMBEDDED UPPER LOW SHIFTS NWD INTO/ACROSS
THE LOWER GREAT LAKES REGION WITH TIME. MEANWHILE FARTHER W...A
STRONG UPPER RIDGE OVER THE ROCKIES WILL LIKEWISE MAKE LIMITED/SLOW
EWD PROGRESS...AS AN UPPER LOW OVER THE ERN PACIFIC SHIFTS SWD --
REMAINING OFFSHORE THROUGH THE PERIOD.

AT THE SURFACE...A DEEP/OCCLUDING LOW INVOF NY CITY AT THE START OF
THE PERIOD IS FORECAST TO SHIFT STEADILY NWWD...REACHING SOUTHERN
ONTARIO THROUGH THE LATTER STAGES OF THE PERIOD. WITH THE
ASSOCIATED FRONT OFFSHORE PRIOR TO THE START OF THE PERIOD...SEVERE
WEATHER IS NOT EXPECTED WITH THIS SYSTEM.

FARTHER W...A MUCH WEAKER SURFACE PATTERN WILL PREVAIL AS THE LARGE
UPPER RIDGE DOMINATES.

...PAC NW VICINITY...
ENHANCED FLOW ALOFT WILL CONTINUE AT THE INTERFACE BETWEEN THE ERN
PACIFIC UPPER TROUGH/LOW AND THE ROCKIES RIDGE. THIS COMBINED WITH
MODEST LOW-LEVEL MOISTURE AND DIURNAL HEATING SHOULD WILL RESULT IN
THE DEVELOPMENT OF 500 TO 1000 J/KG MIXED-LAYER CAPE ACROSS THIS
REGION...AND THUS AN ENVIRONMENT SUPPORTIVE OF THUNDERSTORMS AND
POSSIBLE SEVERE POTENTIAL.

A LIMITING FACTOR WITH RESPECT TO CONVECTIVE INITIATION/COVERAGE
REMAINS THE GENERAL INFLUENCE OF THE LARGE-SCALE RIDGE. HOWEVER...A
WEAK/LEAD IMPULSE IS FORECAST TO SHIFT NNEWD ACROSS THE CA AND THE
GREAT BASIN THROUGH THE PERIOD...POSSIBLY PROVIDING AMPLE ASCENT
WITHIN AN OTHERWISE GENERALLY SUBSIDENT REGIME TO SUPPORT SCATTERED
TO ISOLATED SHOWER/THUNDERSTORM INITIATION.

GIVEN THE AFOREMENTIONED KINEMATIC/THERMODYNAMIC
ENVIRONMENT...LIMITED THREAT FOR MARGINAL SEVERE WEATHER REMAINS
APPARENT -- WITH A FEW AFTERNOON CELLS POSSIBLY STRENGTHENING TO
SEVERE LEVELS. THUS...WILL MAINTAIN 5% PROBABILITY FOR SEVERE
HAIL/WIND IN A ZONE FROM NRN CA/OREGON NEWD INTO NRN ID/WRN MT --
PRIMARILY FOR AFTERNOON AND EARLY EVENING STORMS.

..GOSS.. 04/23/2012

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