National Weather Service United States Department of Commerce

Winter Weather Across the North, Flood Potential for Pacific Northwest

Through this weekend, a clipper system will produce light to moderate snow, and gusty winds, across Great Lakes and interior northeast. Meanwhile, atmospheric river event will unfold to generate moderate-to-heavy rainfall in the Pacific Northwest. Dry weather and occasionally gusty winds will elevate the fire weather concerns across Southern California and part of the Southern Plains. Read More >

Day 4-8 Severe Weather Outlook issued at 0850 UTC on 24 April 2011

ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 240850
   SPC AC 240850
   
   DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0350 AM CDT SUN APR 24 2011
   
   VALID 271200Z - 021200Z
   
   ...DISCUSSION...
   WIDESPREAD CONVECTIVE/SEVERE WEATHER EVENT -- ONGOING FROM THE DAY 3
   /TUE. 4-26/ PERIOD -- IS LIKELY TO CONTINUE SPREADING EWD ACROSS THE
   OH/TN VALLEYS AND GULF COAST STATES DAY 4 /WED. 4-27/...AS
   MEDIUM-RANGE MODELS BOTH FORECAST EWD PROGRESSION OF THE LARGE
   CENTRAL U.S. TROUGH.  AS THE COLD FRONT SHIFTS EWD TOWARD THE
   APPALACHIANS THROUGH THE AFTERNOON AND EVENING...PRE-FRONTAL WARM
   SECTOR FEATURING MODERATE INSTABILITY AND STRONG DEEP-LAYER SHEAR
   WILL SUPPORT CONTINUATION/REDEVELOPMENT OF SEVERE STORMS INTO THE
   AFTERNOON AND EVENING.  POTENTIAL FOR SUBSTANTIAL SEVERE WEATHER --
   INCLUDING HAIL/WIND AND ISOLATED TORNADOES -- SUPPORTS CONTINUATION
   OF A LARGE SEVERE WEATHER THREAT AREA FOR DAY 4.  
   
   MODEL TIMING WITH RESPECT TO THE SURFACE FRONT AND ASSOCIATED UPPER
   TROUGH BEGINS TO DIFFER MORE SUBSTANTIALLY DAY 5 /THU. 4-28/...THUS
   CASTING SOME UNCERTAINTY WITH RESPECT TO LOCATION AND DEGREE OF
   THREAT E OF THE APPALACHIANS DAY 5.  THEREFORE...WHILE POTENTIALLY
   SEVERE CONVECTION WILL LIKELY SPREAD ACROSS THE ATLANTIC COAST
   STATES SOMEWHERE BETWEEN LATE IN THE DAY 4 PERIOD AND THE AFTERNOON
   AND EVENING OF DAY 5...WILL NOT HIGHLIGHT A SPECIFIC THREAT AREA
   THIS FORECAST.
   
   WITH THE FRONT EXPECTED TO HAVE SWEPT OFFSHORE BY THE START OF DAY 6
   /FRI. 4-29/...FOCUS SHIFTS WWD AS THE NEXT SYSTEM SHIFTS ACROSS/OUT
   OF THE ROCKIES.  MODELS ARE IN MORE SUBSTANTIAL DISAGREEMENT WITH
   THE EVOLUTION AND PROGRESSION OF THIS FEATURE...AND THUS WILL NOT
   HIGHLIGHT ANY LONGER-RANGE THREAT AREAS THIS FORECAST.
   
   ..GOSS.. 04/24/2011

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