Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 060502
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
101 AM EDT WED MAY 06 2015

VALID 12Z SAT MAY 09 2015 - 12Z WED MAY 13 2015

...OVERVIEW AND GUIDANCE PREFERENCES...

RIDGE/TROUGH/RIDGE PATTERN OVER NW CANADA/FOUR CORNERS/NORTHEAST
TO START THE PERIOD THIS SAT WILL SHIFT EASTWARD BY MIDWEEK NEXT
WEEK. THIS WILL LEAD TO TROUGHING NEAR BOTH COASTS AND RIDGING IN
THE PLAINS. THE MODELS AND ENSEMBLES HAVE HAD A PRETTY GOOD HANDLE
ON THE SETUP THE PAST SEVERAL DAYS... WITH EXPECTED DETAIL
DIFFERENCES DOMINANT THROUGH ABOUT 132HRS. THE 12/18Z RUNS SHOWED
A LITTLE LESS CLUSTERING RIGHT FROM SAT/D3 ONWARD... BUT ARE STILL
WITHIN REASON. HOWEVER... THE ECMWF/ECENS MEAN OFFERED A BETTER
BLEND FOR SAT-MON/D3-5 OVER THE INCLUSION OF THE GFS/GEFS MEAN...
ESPECIALLY WITH THE HANDLING OF THE INCOMING PAC NW TROUGH BUT
ALSO THE NEXT UPPER LOW TO EXIT COLORADO... WHERE THE 12Z GFS WAS
QUITE SLOW... AND LASTLY THE PESKY LOW PRESSURE OFF THE SE COAST.
ANY MODEL BECAME SUSPECT BY NEXT TUE/WED AS LOW PRESSURE SHOULD
MOVE EASTWARD THROUGH THE GREAT LAKES/NORTHEAST PER THE ECENS
MEMBERS OR PERHAPS JUST NORTH OF THE OHIO VALLEY PER THE GEFS.
OPTED TO PUT MORE WEIGHT IN THE MORE NORTHERLY TRACK SINCE THAT IS
WHERE MOST OF THE DETERMINISTIC RUNS HAVE LIED. TRACK OF THE
POTENTIALLY SUBTROPICAL LOW OFF/NEAR THE COAST IS STILL A BIT
UNCERTAIN... BUT SHOULD MEANDER AROUND THE NC/SC BORDER SAT/SUN
BEFORE WASHING OUT.


...SENSIBLE WEATHER HIGHLIGHTS...

THE COOLER THAN AVERAGE WEST AND WARMER THAN AVERAGE EAST PATTERN
WILL SHIFT EASTWARD IN TIME THIS PERIOD. RECORD MAX OR HIGH MIN
TEMPS MAY BE POSSIBLE AHEAD OF THE SFC FRONT. PRECIPITATION WILL
FOCUS AROUND AND DOWNSTREAM OF THE EXITING CLOSED LOW FROM THE
FOUR CORNERS REGION -- CENTRAL ROCKIES/PLAINS SOUTHWARD AND THEN
NORTHEASTWARD TOWARD THE GREAT LAKES. GEFS REFORECAST DATA SHOWS
NE COLORADO INTO WESTERN AND CENTRAL NEBRASKA IN THE 99.5
PERCENTILE -- M-CLIMATE RELATIVE -- WHICH LINES UP WITH THE ECMWF
AND ECENS MEAN RELATIVE MAX QPF AMOUNTS. NEXT TROUGH INTO THE PAC
NW EARLY NEXT WEEK WILL BRING SOME SHOWERS TO WA/OR/ID AND
NORTHERN CA/NV. ALONG THE CAROLINA COAST... MODELS CONTINUE TO BE
ALL OVER THE PLACE FROM SEVERAL TENTHS OF AN INCH OF RAIN TO
SEVERAL INCHES OF RAIN... SOME OFFSHORE AND SOME INLAND. WILL
CONTINUE TO BE SUSPICIOUS OF ANY ONE RUN AND WILL FOLLOW THE
ENSEMBLES UNTIL THIS IS BETTER RESOLVED... PROBABLY IN THE SHORT
RANGE.



FRACASSO

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