National Weather Service United States Department of Commerce

Unsettled Weather Continues for the Northern U.S., Alaska, and Hawaii

Low pressure will bring strong winds and heavy snow to the northern Plains and upper Great Lakes into Monday. Farther south, strong to severe thunderstorms accompanied by locally heavy rainfall are possible over the ArkLaTex and lower Ohio Valley through tonight. Meanwhile, a major winter storm will affect western and central Alaska. Heavy rainfall and flooding are possible for much of Hawaii. Read More >

Day 3 Severe Weather Outlook issued at 0730 UTC on 25 April 2011

SPC AC 250730
   
   DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0230 AM CDT MON APR 25 2011
   
   VALID 271200Z - 281200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF CENTRAL AND
   EASTERN KENTUCKY...MIDDLE AND EASTERN TENNESSEE...NORTHEAST
   MISSISSIPPI...CENTRAL AND NORTHERN ALABAMA...AND NORTHWEST
   GEORGIA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PORTION OF THE
   ERN U.S. FROM THE LOWER AND MID MS/OH VALLEYS EWD...
   
   ...SYNOPSIS...
   A LARGE UPPER TROUGH WILL CONTINUE SHIFTING EWD ACROSS THE U.S. THIS
   PERIOD...WITH A POTENT SHORT-WAVE TROUGH/SPEED MAX SHIFTING EWD INTO
   THE MID SOUTH REGION INTO THE AFTERNOON.  AS THIS OCCURS...SECONDARY
   SURFACE LOW DEVELOPMENT IS EXPECTED ALONG THE COLD FRONT S OF THE
   MAIN GREAT LAKES REGION LOW.  THIS SYNOPTIC-SCALE SETUP FAVORS
   SIGNIFICANT SEVERE WEATHER POTENTIAL E OF THE MS VALLEY.
   
   ...PA/NW SSWWD TO THE GULF COAST...
   YET ANOTHER DAY OF POTENTIALLY VERY SIGNIFICANT SEVERE WEATHER IS
   EXPECTED DAY 3 /WED. AND EARLY THU. APR. 27 AND 28/ -- WITH ELEVATED
   THREAT FOR A TORNADO OUTBREAK EVIDENT ACROSS THE MID SOUTH AND INTO
   PORTIONS OF THE CENTRAL GULF COAST STATES.
   
   STRONG/SEVERE STORMS SHOULD BE ONGOING AT THE START OF THE PERIOD
   ACROSS THE NWRN PORTIONS OF THE SLIGHT RISK AREA...AS THE POTENT
   SHORT-WAVE TROUGH AND ASSOCIATED MID-/UPPER-LEVEL SPEED MAX ROUNDS
   THE BASE OF THE LARGER-SCALE TROUGH.  WHILE AN INITIAL SURFACE LOW
   SHOULD SHIFT NNEWD ACROSS THE OH VALLEY/MIDWEST...SECONDARY SURFACE
   LOW DEVELOPMENT IS FORECAST DURING THE AFTERNOON IN THE KY/TN
   VICINITY...WITH LOCALLY-BACKED SURFACE FLOW VEERING/INCREASING
   SUBSTANTIALLY WITH HEIGHT RESULTING IN SHEAR PROFILES VERY
   SUPPORTIVE OF SUPERCELLS AND TORNADOES.  THE MOST FAVORABLE
   COMBINATION OF RICH LOW-LEVEL MOISTURE...STRONG SHEAR...FOCUSED
   LARGE-SCALE ASCENT...AND ANTICIPATED LACK OF APPRECIABLE PRIOR
   CONVECTION INDICATES A RELATIVELY HIGH-CONFIDENCE AREA OF
   CONCENTRATED SIGNIFICANT THREAT FOR POTENTIALLY STRONG TORNADOES AND
   WIDESPREAD WIND DAMAGE CENTERED OVER THE MID SOUTH/TN VALLEY REGION.
    THEREFORE...WILL INTRODUCE MODERATE RISK FORECAST ATTM --
   INDICATIVE OF OUTBREAK POTENTIAL.  
   
   ALONG WITH FAIRLY SUBSTANTIAL SEVERE POTENTIAL EXTENDING FARTHER
   NNEWD INTO PA/NY -- INCLUDING THREATS FOR DAMAGING WINDS AND
   ISOLATED TORNADOES...SEVERE STORMS WILL LIKELY ALSO EXTEND E OF THE
   APPALACHIANS INTO THE ATLANTIC COAST STATES.  ALONG WITH THE
   LIKELIHOOD FOR AFTERNOON SEVERE CONVECTION...SEVERE CONVECTION MAY
   CONTINUE INTO THE OVERNIGHT HOURS AS THE SURFACE FRONT CRESTS THE
   APPALACHIANS.
   
   ..GOSS.. 04/25/2011