FXUS01 KWBC 120757
PMDSPD

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
357 AM EDT TUE JUL 12 2011

VALID 12Z TUE JUL 12 2011 - 12Z THU JUL 14 2011

....EXCESSIVE HEAT WARNINGS AND ADVISORIES COVER MUCH OF THE
EASTERN HALF OF THE COUNTRY...

....COLD FRONT TO BRING RELIEF TO OVERHEATED OHIO VALLEY ON
TUESDAY...

....HEAVY RAINS TO IMPACT ALREADY FLOODED RIVER VALLEYS ACROSS
NORTHERN AND CENTRAL PLAINS...


A PERSISTENT UPPER-LEVEL RIDGE OVER THE SOUTHERN PLAINS AND
MISSISSIPPI VALLEY WILL KEEP THE MIDDLE U.S. LATITUDES WET AND THE
SOUTHEASTERN U.S. HOT. TO THE SOUTH OF A SURFACE BOUNDARY DRAPED
ACROSS THE CENTRAL PLAINS AND OHIO VALLEY...MOIST AIR FROM THE
GULF WILL COMBINE WITH HOT SUMMER TEMPERATURES TO PERPETUATE THE
DANGEROUS HEAT ILLNESS THREAT ACROSS THE SOUTH AND EAST. A SLEW OF
HEAT WARNINGS AND ADVISORIES HAVE BEEN ISSUED FOR A LARGE PORTION
OF THE COUNTRIES MID-SECTION AND NOW EXTEND EASTWARD TO THE
MID-ATLANTIC COAST. IN ADDITION TO THE TRIPLE DIGIT TEMPERATURES
AND HEAT INDICES HOVERING AROUND THE 115 DEGREE MARK...AIR QUALITY
IS ALSO A MAJOR CONCERN.

THE GOOD NEWS IS THAT FOR SOME OF THE AFFECTED AREA RELIEF IS ON
THE WAY. AN UPPER-LEVEL JET IS POISED TO MOVE THROUGH THE GREAT
LAKES REGION ON TUESDAY...MOVING THE SURFACE FRONT THROUGH THE
OHIO VALLEY AND UPPER-MID ATLANTIC. HIGH TEMPERATURES WILL DROP BY
AS MUCH AS 10 DEGREES AND THE HUMIDITY WILL LESSEN.

UNFORTUNATELY FOR THE CENTRAL PLAINS AND TENNESSEE VALLEY THE
UPPER-LEVEL ENERGY WILL NOT PROVIDE THE THRUST NECESSARY TO PUSH
THIS STUBBORN BOUNDARY FURTHER SOUTH IN THE SHORT TERM. THE
WESTERN HALF OF THIS FRONT...WINDING THROUGH THE INTERMOUNTAIN
WEST...WILL ALSO REMAIN STATIONARY. THIS BOUNDARY WILL BE THE
FOCUS FOR DRENCHING RAINS OVER THE CENTRAL AND NORTHERN
PLAINS...ADDING TO THE FLOODING ISSUES ALREADY PLAGUING THE
REGION. HOWEVER...THE TROUGH THAT HAS BEEN A PERSISTENT FEATURE
OVER THE PACIFIC NORTHWEST WILL FINALLY BREAK LOSE AT THE END OF
THE FORECAST PERIOD...GIVING THE BOUNDARY OVER THE CENTRAL ROCKIES
AND PLAINS A HEFTY EASTWARD SHOVE.

GARRETT


GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
$$

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