Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 030329
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1129 PM EDT SAT MAY 02 2015

VALID 12Z WED MAY 06 2015 - 12Z SUN MAY 10 2015

...OVERVIEW AND GUIDANCE PREFERENCES...

UPPER RIDGING IS FORECAST TO PERSIST IN THE GREAT LAKES AND
NORTHEAST CONUS FOR THE SECOND HALF OF THE WEEK INTO NEXT WEEKEND.
UPSTREAM... RIDGING SOUTH OF THE GULF OF ALASKA IS FORECAST TO
MOVE INTO NW CANADA. THIS WILL FAVOR TROUGHING IN THE WESTERN
STATES VIA SPLIT ENERGY INITIALLY IN WASHINGTON/BRITISH COLUMBIA.
OFF THE SOUTHEAST/FL COAST... A DISTURBANCE WILL MEANDER JUST
OFFSHORE... CAUGHT UNDERNEATH THE RIDGE TO ITS NORTH IN A WEAK
FLOW ENVIRONMENT. OVERALL PATTERN WILL RESULT IN ONLY SLOWLY
CHANGEABLE DAY-TO-DAY `WEATHER` FOR MUCH OF THE LOWER 48. THE
MODELS AND ENSEMBLES HAVE MOSTLY BEEN ON THE SAME PAGE AS FAR AS
THE SYNOPTIC FLOW GOES SINCE ABOUT TWO DAYS AGO... THOUGH THE
DETAILS ALMOST NEVER AGREE. A MODEL/ENSEMBLE BLEND HAS BEEN A GOOD
STARTING POINT AND WILL CONTINUE THIS TACTIC AGAIN USING THE 18Z
GFS/GEFS AND 12Z ECMWF/ECENS MEAN. OFF THE SE COAST... THE GFS
RUNS ARE A BIT CLOSER TO THE COAST AND DEEPER THAN THE BALANCE OF
THE GUIDANCE... BUT NOTHING CAN REALLY BE RULED OUT SINCE IT FALLS
WITHIN THE MULTI-CENTER/DAY ENSEMBLE SPREAD. BIGGEST DIFFERENCES
LIE TO THE NORTH IN THE UPPER MIDWEST WITH THE TRACK/EVOLUTION OF
THE SFC LOW LATE THU INTO FRI. ENSEMBLES FAVOR THE GFS OVER THE
ECMWF AT THIS POINT. BY NEXT SUN... NE PAC GETS A BIT MESSY AS THE
RIDGE MAY PUSH FAR ENOUGH INTO INTERIOR NW CANADA TO ALLOW ENERGY
TO SLIDE IN UNDERNEATH IT INTO THE PAC NW. ECMWF REPRESENTS A
RATHER EXTREME EXAMPLE OF THIS... AND TRENDED TOWARD A NAEFS/ECENS
MEAN BLEND BY NEXT SUN GIVEN THE SPREAD HERE AS WELL AS IN THE
SOUTHEAST... WHERE THE SFC LOW OF SOME FLAVOR -- BE IT SUBTROPICAL
OR OTHERWISE -- MAY CREEP TOWARD OR ONTO THE COAST BUT PERHAPS IN
A WEAK FORM.


...SENSIBLE WEATHER HIGHLIGHTS...

MILD OVERNIGHT TEMPS IN THE EAST AHEAD OF THE FRONT AND COOLER
THAN AVERAGE DAYTIME MAX TEMPS IN THE WEST WILL BE THE BIGGEST
ANOMALIES THIS PERIOD. FRONTAL BOUNDARY IN THE NORTHEAST WILL
WREAK HAVOC WITH TEMPERATURES FOR COASTAL AREAS FROM VA/MD UP INTO
SE NEW ENGLAND GIVEN STILL CHILLY OCEAN TEMPS. ENSEMBLES SHOW A
RANGE OF ABOUT 45 DEGREES FOR MAX TEMPS IN COASTAL NEW ENGLAND
NEXT WEEKEND... FROM THE 40S TO THE 80S... DEPENDING ON WHERE THE
FRONT LIES AND FROM WHERE THE WIND BLOWS. PRECIPITATION SHOULD BE
ON THE LIGHTER SIDE GENERALLY NORTH OF THE BOUNDARY LATE THIS WEEK
BEFORE WANING... ONLY TO PICK UP AGAIN ONCE THE COLD FRONT PUSHES
THROUGH FROM THE WEST NEXT WEEKEND.

THE WEST -- OUTSIDE THE DESERT SW -- SHOULD SEE A FAIR AMOUNT OF
SHOWERS/STORMS AND WIND AS IT WILL TAKE A FEW DAYS FOR THE TROUGH
TO DIG AND THEN LIFT OUT OF THE GREAT BASIN. DAYTIME MAX TEMPS
SHOULD BE SUPPRESSED WITH ALL THE CLOUDINESS... BUT SHOULD
MODERATE BACK TOWARD AVERAGE BY THE END OF NEXT WEEKEND. PRECIP
FOCUS SHOULD SHIFT TOWARD THE HIGH PLAINS AS THE UPPER LOW DEPARTS
NEXT WEEKEND.

DOWNSTREAM OF THE UPPER TROUGH... PERSISTENT SOUTHERLY FLOW SHOULD
ALLOW SOME JUICY AIR TO INFILTRATE OVER THE SOUTHERN/CENTRAL
PLAINS. MODELS/ENSEMBLES CONTINUE TO SHOW A FOCUS FROM N-CENTRAL
TX NORTHWARD TO MINNESOTA LATER THIS WEEK... THEN BACK TOWARD THE
SOUTHERN PLAINS NEXT WEEKEND AS THE TROUGH PUSHES PAST THE DIVIDE.

THE AFFECT OF THE SOUTHEAST OCEAN LOW MAY BE NOTHING MORE THAN
INCREASED CLOUDINESS... BUT IF IT TRACKS AS FORECAST TOWARD THE
COAST THEN AN INCREASE IN AT LEAST SOME SHOWER ACTIVITY IS
PROBABLE.

FRACASSO

$$




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