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FXUS02 KWBC 041931
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
330 PM EDT FRI SEP 04 2009
VALID 12Z MON SEP 07 2009 - 12Z FRI SEP 11 2009
SIMILAR TO YESTERDAY ENSEMBLES/MODELS GENERALLY SHOW A PROGRESSIVE
PATTERN ABOVE LATITUDE 45N ACROSS NOAM. HOWEVER THE DEVIL IS IN
THE DETAILS AT LOWER LATITUDES. WEAK YET SIGNIFICANT UPPER
VORTICITY MAXIMA COVERING A BROAD AREA FROM THE OH VLY ESE INTO
THE CAROLINAS AND THE MID ATLANTIC STATES COULD PLAY A ROLE IN
DETERMINING IF ANY MOISTURE FROM REMNANTS OF TS ERIKA MIGHT AFFECT
THE E COAST NEXT WED-FRI. MUCH WILL DEPEND ON THE BLOCKING
POTENTIAL OF A HIGH PRES SYS SINKING SE FROM QB ACROSS NEW ENG
LATE NEXT WEEK. THIS SURFACE HIGH WILL BE SUPPORTED BY A VERY
STRONG RIDGE AT 500 MILLIBARS.
12Z/04 MODELS ARE IN DECENT AGREEMENT THRU WED DAY 5 WITH FEATURES
IN THE POLAR JET WAVETRAIN ABOVE LATITUDE 45N....BUT OUR
CONFIDENCE PLUMMETS IN THE 12Z/04 GFS THEREAFTER. THE GFS GETS TOO
AMPLIFIED WITH A SHORTWAVE PASSING N OF THE GREAT LAKES AROUND THU
DAY 6 GIVEN THE PROGRESSIVE NATURE OF THE FLOW. PREFER TO STAY
WITH THE MOSTLY ECMWF BASED CONTINUITY OF OUR UPDATED PRELIMS
SINCE THE 12Z ECMWF WAS FAIRLY CONSISTENT ACROSS THE CONUS WITH
ITS PREVIOUS RUN. THE EXCEPTION TO THIS CONSISTENCY WAS THAT THE
NEW ECMWF RUN WAS FARTHER N WITH A SRN CANADIAN SHORTWAVE DAYS
6-7. ITS HIGH AMPLITUDE WITH STILL ANOTHER WAVE DROPPING INTO THE
NRN PLAINS DAY 7 IS SUSPECT.
CONCERNING SENSIBLE WEATHER...WE AGAIN SEE THE SAME PLAYERS AS
YESTERDAY
MONSOONAL MOISTURE WILL IGNITE DIURNALLY OVER THE CENTRAL AND SRN
ROCKIES/INTERMOUNTAIN REGIONS DAYS 3-4. MEANWHILE NRN/CENTRAL
PLAINS CONVECTION WILL BECOME BETTER ORGANIZED ALONG /AHEAD OF THE
COLD FRONT ASSOCIATED WITH THE HEIGHT FALLS MOVING ACROSS THE NWRN
QUADRANT OF THE NATION BY TUE EVE. THEY SHOULD CONTINUE EWD IN
TANDEM WITH THE FRONT THEREAFTER...WITH A TENDENCY FOR CONVECTION
TO LINGER OVER TX. HEIGHT RISES IN THE WAKE OF THE DEPARTING WRN
500MB TROF WILL PUT A DAMPER ON MOST MONSOONAL PRECIP IN THE SRN
ROCKIES/INTERMOUNTAIN REGIONS FROM DAY 5 ONWARDS. SOME LESS
ORGANIZED SHOWERS ARE LIKELY EACH DAY FROM THE WRN GULF STATES
THRU THE OH VLY. THE BIG QUESTION MARK WILL BE THE WWD AND NWD
EXTENT OF ATLANTIC MOISTURE INTO THE CAROLINAS AND MID ATLANTIC
STATES IN CONJUNCTION WITH THE REMNANTS OF ERICA OFFSHORE AND
EASTERLY LOW LEVEL FLOW S OF A DEPARTING SURFACE HIGH OFF THE NEW
ENG COAST.
ROTH/FLOOD
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