Preliminary Forecasts
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FXUS02 KWNH 110627
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
126 AM EST THU FEB 11 2016

VALID 12Z SUN FEB 14 2016 - 12Z THU FEB 18 2016

...POTENT WINTER STORM NEXT TUE-WED IN THE EAST...


...OVERVIEW...

UPPER RIDGE AXIS JUST OFF THE WEST COAST ON SUNDAY WILL GRADUALLY
WORK ITS WAY PAST THE CONTINENTAL DIVIDE IN NON-CONTINUOUS FASHION
BY NEXT THURSDAY. THIS WILL ALLOW ANOTHER TROUGH TO SWING THROUGH
THE EASTERN CONUS BUT UNLIKE ITS NORTHERN STREAM PREDECESSOR THIS
WILL WRAP UP A MUCH MILDER AIRMASS WITH LOTS OF MOISTURE. END
RESULT WILL BE A POTENTIALLY SIGNIFICANT WINTER STORM FOR THE
EASTERN THIRD OF THE COUNTRY WITH A VARIETY OF CHANGEABLE
PRECIPITATION TYPES. BACK TO THE WEST, ENSEMBLES INDICATE THAT
TROUGHING SHOULD PUSH INTO CALIFORNIA WHICH SHOULD END THE STRING
OF RECORD WARMTH.

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...

WEST: THE GFS AND ECMWF ENSEMBLES HAVE BEEN CONSISTENTLY DIFFERENT
FOR SEVERAL DAYS RUNNING, AND THIS CONTINUES TODAY. THEY EACH
CLUSTER AROUND THEIR OWN MEAN SOLUTION, AND ALTHOUGH THEY ARE NOT
TERRIBLY DIFFERENT IN THE SYNOPTIC SENSE THE AMOUNT OF
NON-OVERLAPPING ENSEMBLES IS CURIOUS AND PROBABLY A RESULT OF
RATHER ZONAL FLOW ACROSS THE NORTH PACIFIC. THAT SHOULD CHANGE BY
NEXT WEEK AS RIDGING BUILDS NORTHWEST AND THEN NORTH OF HAWAI`I
WHICH SHOULD HELP PUSH THAT TROUGHING INTO CALIFORNIA. HOWEVER,
NORTHERN STREAM FLOW THROUGH THE ALEUTIANS HAS COMPLICATED THINGS
AS WELL WHICH IS EVIDENT IN THE RATHER LARGE SHIFTS IN THE GEFS
GUIDANCE. ECMWF/ECENS MEAN GUIDANCE SEEMS TO AT LEAST BE MORE
STABLE BUT NOT IMMUNE TO SHIFTS FROM CYCLE TO CYCLE. THUS, A
COMPROMISE SOLUTION IS STILL PREFERRED UNTIL MORE CLARITY EXISTS.
BLEND OF THE 18Z GEFS MEAN AND 12Z ECENS MEAN WERE ACCEPTABLE.

EAST: MODELS HAVE BEEN SHOWING A SHORTWAVE DIVING THROUGH THE
SOUTHERN PLAINS AND SOUTHEAST BEFORE TURNING UP THE COAST NEXT
TUESDAY/WEDNESDAY FOR SEVERAL DAYS. GFS HAS MOSTLY BEEN FARTHER
EAST THAN THE ECMWF WHILE THE CMC AND RECENT UKMET RUNS HAVE
WAVERED E-W. TREND IN RECENT WINTER STORMS HAS BEEN FARTHER
NORTHWEST RATHER THAN SOUTHEAST BUT ANTECEDENT COLD AIR -- RECORD
COLD -- SHOULD HAVE AT LEAST SOME AFFECT IN LIMITING A FAR WESTERN
TRACK WEST OF THE APPALACHIANS AS COLD AIR IS USUALLY SLOW TO EXIT
-- SLOWER THAN WHAT THE MODELS PREDICT. IN ADDITION, EVOLUTION OF
NORTHERN STREAM THROUGH THE GREAT LAKES AND AN UPPER LOW IN CANADA
ALL PLAY A PART IN HOW MUCH TO DIG THE SHORTWAVE INTO THE
SOUTHEAST AND WHERE IT MAY CLOSE OFF. ENSEMBLES HAVE GONE FROM
NEARLY UNANIMOUS AGREEMENT ON A CLOSE-IN COASTAL TRACK TO A SPLIT
-- THE ECMWF ENSEMBLES MOSTLY INLAND AND THE GEFS/CANADIAN
ENSEMBLES MOSTLY OFFSHORE. OPTED TO TAKE THE LOW BASICALLY ALONG
I-95 FROM SC TO RICHMOND THEN PHILLY AND INTO CENTRAL NEW ENGLAND.


...SENSIBLE WEATHER HIGHLIGHTS...

RECORD COLD IN THE EAST WILL EASE ON MONDAY BUT TEMPERATURES ARE
STILL FORECAST TO BE BELOW AVERAGE. THE WEST WILL SEE A CONTINUED
STRETCH OF ABOVE AVERAGE TEMPERATURES WHICH WILL SPREAD EASTWARD
MIDWEEK NEXT WEEK AS THE UPPER RIDGE STUMBLES EASTWARD. SHARP E-W
TEMPERATURE GRADIENT WILL DEVELOP IN THE SOUTHEAST AND
MID-ATLANTIC AS THE SURFACE LOW DEEPENS ON TUESDAY AND A COASTAL
FRONT PUSHES WESTWARD AND NORTHWARD. THAT WILL TRANSLATE NORTHWARD
AS THE LOW PUSHES INTO NEW ENGLAND WEDNESDAY. MAINE SHOULD SEE
QUITE THE TEMPERATURE RISE FROM SUNDAY IN THE -10S TO WEDNESDAY IN
THE 40S... DEPENDING ON THE STORM TRACK.

PRECIPITATION WILL FOCUS INITIALLY IN THE WASHINGTON CASCADES AND
COASTAL RANGE NEAR THE STORM TRACK BUT THEN SINK SOUTHWARD INTO
CALIFORNIA BY THURSDAY. SIGNAL SEEMS GOOD FOR PRECIP TO EVENTUALLY
MAKE IT TO SOUTHERN CALIFORNIA THU/FRI. NORTHERN STREAM FLOW WILL
WRING OUT SOME LIGHT SNOW IN THE NORTHERN TIER EARLY IN THE PERIOD
BEFORE THE SOUTHEAST SYSTEM EXPANDS ITS PRECIPITATION SHIELD.
ICING THREAT REMAINS A STRONG POSSIBILITY IN THE SOUTHEAST WHERE
COLD AIR IS RELUCTANT TO BE SCOURED OUT AS WARM ADVECTION PRECIP
IS PULLED IN FROM THE SOUTH AND EAST. SNOW IS FORECAST TO THE
NORTH, DEEPER INTO THE COLD AIR, BUT A CHANGEOVER IS LIKELY FOR
MANY AREAS AS THE SURFACE HIGH WILL BE WELL EAST OF NOVA SCOTIA
TUESDAY INTO WEDNESDAY. TOO SOON TO STATE HOW FAR WEST THAT MAY
BE. PLEASE CONSULT THE WPC EXPERIMENTAL DAY 4-7 WINTER WEATHER
OUTLOOK GRAPHICS -- LINKED FROM OUR HOME PAGE -- WHICH ARE
PROBABILISTIC IN NATURE.


FRACASSO

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