471
FXUS02 KWBC 311930
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
330 PM EDT SAT MAY 31 2008
VALID 12Z TUE JUN 03 2008 - 12Z SAT JUN 07 2008
..FINAL MEDIUM RANGE DISCUSSION
THE NEW 12Z/31 GFS HAS FOLLOWED ITS 06Z CONTINUITY IN THE EAST BY
BEING WEAKER THAN ITS 00Z RUN WITH THE TROF MOVING INTO THE NERN
CONUS ON THU DAY 5. OUT WEST...IT IS SLOWER AND FARTHER S WITH THE
NEW SHORTWAVE TROF THAN THE 00Z/31 RUNS OF THE ECMWF AND
GFS...RESPECTIVELY. THE NEW CANADIAN/UKMET RUNS ARE SLOWER THU DAY
5 THAN THE ECMWF BUT THE CANADIAN IS NOT AS FAR S THEN AS THE NEW
GFS. THE NEW UKMET DAY 6 GETS EVEN FARTHER S THAN THE ECMWF.
PREFER TO STAY WITH OUR EARLIER PROGS CONCERNING THE CONFIGURATION
OF THE WRN CONUS TROF DAYS 4-6. MODELS CONSISTENTLY SHOW A FAIR
AMOUNT OF WESTERLY FLOW UPSTREAM OFF THE PACIFIC NW COAST DAY 5
THAT WOULD TEND TO KEEP THE DIGGING SYS OVER THE WEST FROM SLOWING
DOWN TOO MUCH OR GETTING TOO FAR S. THE FLAW IN THAT REASONING
MIGHT BE IF THE SHORTWAVE RIDGE RIGHT OFF THE W COAST JUST BELOW
THE MAIN JET WERE SHARPER THAN CONSENSUS OF MODELS...IT COULD
ALLOW FOR A SLOWER DEEPER UPPER SYS DOWNSTREAM. A QUICK LOOK AT
THE NEW 12Z/31 ECMWF SHOWED IT TO BE REASONABLY CLOSE TO ITS 00Z
CONTINUITY OVER THE LOWER 48 THU-SAT DAYS 5-7. AN AVERAGE OF NEW
12Z MODEL SOLUTIONS WITH THE TR0F IN THE WEST/PLAINS DAYS 5-6
MIGHT BE QUITE REASONABLE.
..REGIONAL HIGHLIGHTS
...CENTRAL PLAINS...OH VLY...MID ATLANTIC...NEW ENG
THE CENTRAL PLAINS....OH VLY...AND MID ATLANTIC WILL LINE IN A
MEAN WAVY FRONTAL ZONE ALONG THE SRN EDGE OF THE WESTERLIES AS THE
WRN TROF/ERN RIDGE LONGWAVE PATTERN REALLY BEGINS TO AMPLIFY. MCS
CLUSTERS WILL TRAVEL THROUGH THIS ZONE GENERATING MODERATE TO
LOCALLY HEAVY PRECIP AMOUNTS EN ROUTE. DEEPER INTO THE COLD SIDE
OF THE FRONT...A MORE GENERAL RAIN WITH SOME EMBEDDED CONVECTION
SHOULD OCCUR FROM SD ACROSS THE SRN GRT LAKES INTO NEW ENG.
RIDGING ALOFT SHOULD DECREASE CONVECTIVE ACTIVITY OVER THE ERN
QUARTER OF THE NATION FRI-SAT DAYS 6-7...WHILE SOME STRONG
CONVECTION IS EXPECTED IN THE N CENTRAL PLAINS FRI AND THE MID MS
VLY TO THE W CENTRAL GRT LAKES SAT.
..WEST
A LOT DEPENDS ON THE DETAILS OF THE SHORTWAVES THAT WILL BE
CARVING OUT THE NEXT MAJOR UPPER TROF IN THE WEST DAYS 4-5...ALSO
LATER DAY 6 OR 7. USING OUR BLEND OF ECMWF AND GEFS ENSEMBLES...WE
EXPECT TERRAIN-ENHANCED QPF OVER THE NWRN STATES DIRECTLY UNDER
THE UPPER TROF/VORT MAX...ALSO IN THE LEFT FRONT QUADRANT OF THE
JET ON S-SE SIDE OF THE TROF. SOME OF THIS MAY FALL AS SN OVER
HIGHEST ELEVATIONS. THE FATE OF THE NEXT SYS DROPPING INTO THE
LONGWAVE TROF DAYS 6-7 IS A BIT TRICKER...AND THE GFS/ECMWF
ENSEMBLE MEAN SPREAD HINTS THAT THE DAY 6-7 SYS COULD BE AN INSIDE
SLIDER THAT DROPS INTO NV. NEW ECMWF AND GFS AIM MORE FOR THE PAC
NW COAST BY DAY 7.
..TROPICS
WHILE TS ARTHUR IS EXPECTED TO DISSIPATE OVER THE YUCATAN
PENINSULA ON WED DAY 4...THE GFS AND ECMWF STILL SHOW AN AREA OF
UNSETTLED WX AND A PSBL LOW CENTER IN THE BAY OF CAMPECHE ON FRI.
PLEASE REFER TO STATEMENTS FROM NHC ON ANY PSBL NEW DEVELOPMENT
WITHIN THIS AREA OF UNSETTLED WEATHER.
FLOOD
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