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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0444Z Aug 31, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 AM EDT SUN AUG 31 2014

VALID 12Z WED SEP 03 2014 - 12Z SUN SEP 07 2014

...OVERVIEW AND GUIDANCE PREFERENCES...

SUBTROPICAL RIDGING OVER THE SOUTHERN CENTRAL/EASTERN STATES WILL
EXPAND AND THEN CONTRACT DURING THE MEDIUM RANGE. NORTHERN STREAM
FLOW ACROSS SOUTHERN CANADA WILL REMAIN ACTIVE... CARRYING A
COUPLE SYSTEMS ACROSS THE CONUS. THE MODELS/ENSEMBLES BROADLY
AGREE ON THE MID-LEVEL EVOLUTION... BUT THE 12Z/18Z GFS RUNS AGAIN
LAG THE QUICKER 12Z ECMWF/CANADIAN/UKMET WHICH IS ALSO NEAR WHERE
THE 18Z GEFS AND 12Z ECENS/NAEFS MEANS LIE. HARD TO ARGUE AGAINST
THAT LARGE CLUSTER SO OPTED TO BLEND THE 12Z ECMWF WITH THE MEANS
THROUGH SAT/D6 BEFORE USING JUST THE THREE MEANS FOR SUN/D7. TREND
HAS BEEN TOWARD A MORE DEFINED SYSTEM MOVING THROUGH THE UPPER
MIDWEST AND GREAT LAKES THU-FRI/D4-5 OWING TO MORE ENERGY SLIDING
EASTWARD RATHER THAN LINGERING OVER THE WESTERN STATES. BY NEXT
WEEKEND... QUESTION WILL BE HOW MUCH THE FRONT CAN PROGRESS SOUTH
OF THE OH VALLEY/MID-ATLANTIC AS THE UPPER RIDGING WILL ONLY
BEGRUDGINGLY SPLIT... RETREATING BACK WESTWARD TO TX AND ALSO INTO
THE NW ATLANTIC.


...SENSIBLE WEATHER HIGHLIGHTS...

WELL ABOVE AVERAGE TEMPERATURES... ABOUT +5 TO +15F... WILL
PRECEDE THE COLD FRONT MOVING OUT OF THE ROCKIES WED/D3. LEAD COLD
FRONT EXITING THE NORTHEAST WILL HAVE LITTLE AFFECT ON
TEMPERATURES POST FROPA AS HEIGHTS BUILD ON THU/D4. WARMEST DAY IN
THE EASTERN THIRD OF THE NATION WILL BE FRI/D5 WITH THE SFC HIGH
OFF THE COAST AND THE COLD FRONT BACK THROUGH THE LAKES. IN ITS
WAKE... MUCH COOLER AIR SHOULD PUSH SOUTHWARD THROUGH THE HIGH
PLAINS INTO THE FRONT RANGE... THOUGH THERE IS A VERY LARGE SPREAD
IN FORECAST MAX TEMPERATURES INVOF DENVER WITH THE SLOWER GFS A
FULL 20F WARMER THAN THE PREFERRED ECMWF-LED CLUSTER. TEMPERATURES
BEHIND THE FRONT SHOULD AVERAGE 5-10F BELOW CLIMO. PRECIPITATION
WILL BE CONTAINED TO THE EASTERN THREE QUARTERS OF THE COUNTRY...
ALONG/AHEAD OF THE FRONTAL BOUNDARY AND IN THE SOUTHEAST/FLORIDA
AS A WEAKNESS PROGRESSES WESTWARD. MORE MOISTURE MAY CREEP INTO
THE SW STATES... AZ AND SE CA... WHILE INTERIOR TX STAYS DRY UNDER
THE UPPER HIGH.


FRACASSO