Prognostic Meteorological Discussion
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000
FXUS02 KWBC 261620
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1120 AM EST MON JAN 26 2015

VALID 12Z THU JAN 29 2015 - 12Z MON FEB 02 2015


...GENERAL FLOW PATTERN...

MID-LEVEL ENERGY PHASING OVER THE MID-WEST LATE THIS WEEK WILL
AMPLIFY OVER THE EAST BEFORE SWINGING OFF THE ATLANTIC COAST ON
SATURDAY.  UPSTREAM...A NORTHERN STREAM RIDGE BUILDING INTO THE
NORTHWEST/BRITISH COLUMBIA WILL ALLOW SHORTWAVE IMPULSES TO DIVE
SOUTHEASTWARD INTO THE NORTH CENTRAL U.S....EVENTUALLY CARVING OUT
BROAD TROUGHING FROM THE NORTHERN/CENTRAL PLAINS TO THE NORTHEAST
AND MID-ATLANTIC REGION BY EARLY NEXT WEEK.  IN THE SOUTHERN
STREAM...MID-LEVEL ENERGY EDGING IN OVER CALIFORNIA ON THURSDAY
SHOULD GRADUALLY AMPLIFY WHILE SLOWLY SINKING SOUTHEASTWARD
TOWARDS NORTHERN MEXICO THIS WEEKEND.


...MODEL DIFFERENCES AND PREFERENCES...

DETAIL DIFFERENCES WITH THE PHASING OF ENERGY OVER THE MID-WEST ON
THURSDAY LEAD TO SOME MODEL SPREAD WITH THE RESULTING SURFACE LOW
WHILE IT TRACKS THROUGH THE OHIO VALLEY AND ESPECIALLY AS IT
DEEPENS OFF THE NEW ENGLAND COAST FRIDAY INTO SATURDAY.  IN
GENERAL...THE DETERMINISTIC ECMWF HAS BEEN MORE
PHASED/SLOWER/DEEPER WITH THE SURFACE LOW...WHILE THE GFS HAS BEEN
FASTER/WEAKER WITH THE LOW.  THE DAY 3-4 FORECAST RELIED HEAVILY
ON THE 00Z ECMWF ENSEMBLE MEAN SINCE IT FIT WELL WITHIN THE MIDDLE
OF MODEL SPREAD AND MATCHED WELL WITH WPC CONTINUITY.

TOWARDS THE LATER HALF OF THE FORECAST PERIOD...THE GEFS MEAN AND
ECMWF ENSEMBLE MEAN ARE IN DECENT AGREEMENT WITH THE MEAN FLOW
OVER THE LOWER-48...HOWEVER...DETERMINISTIC GUIDANCE IS
ADVERTISING A WIDE RANGE OF SOLUTIONS FOR SOME OF THE SMALLER
SCALE FEATURES OVER THE CONUS.  BY MONDAY MORNING...THE 00Z GFS
DEVELOPS A DEEP SURFACE CYCLONE OVER THE UPPER MIDWEST WHILE THE
00Z ECMWF FAVORS THE IDEA OF DEVELOPING A LOW IN THE NORTHERN GULF
AND TRACKING IT TOWARDS THE SOUTHEAST/SOUTHERN MID-ATLANTIC COAST.
 WITH SUCH A WIDE RANGE OF SOLUTIONS IN THE DETERMINISTIC
GUIDANCE...THE WPC DAY 3-7 FORECAST RELIED ON ENSEMBLE MEAN
GUIDANCE.


...SENSIBLE WEATHER HIGHLIGHTS...

LIGHT TO MODERATE SNOW WILL BE POSSIBLE WITH THE SURFACE WAVE
TRACKING THROUGH THE OHIO VALLEY THURSDAY.  DEPENDING ON WHERE AND
WHEN THE SYSTEM DEEPENS OFFSHORE...IT WILL HAVE THE POTENTIAL TO
BRING STRONG WINDS AND SNOW TO COASTAL NEW ENGLAND...ON THE HEELS
OF A MAJOR NORTHEAST SNOWSTORM IN THE SHORT RANGE PERIOD.  BEHIND
THIS FEATURE...THE BIG STORY WILL BE ARCTIC AIR SURGING SOUTH AND
EASTWARD WITH THE BROAD TROUGH CARVING OUT OVER THE
CENTRAL/EASTERN U.S..  THE EPICENTER OF THE COLD AIR SHOULD BE
FROM THE UPPER GREAT LAKES INTO INTERIOR NEW ENGLAND...WHERE
TEMPERATURE ANOMALIES COULD BE IN THE -15 TO -20 RANGE BY MONDAY.
THE RUSH OF COLD AIR SHOULD ALSO CHURN SNOW SHOWERS DOWNWIND OF
THE UPPER GREAT LAKES.

IN THE LOWER LATITUDES...THE ENERGY EDGING IN OVER CALIFORNIA WILL
PRODUCE WIDESPREAD PRECIPITATION OVER THE SOUTHWESTERN CORNER OF
THE NATION LATE THIS WEEK.  A LOT OF UNCERTAINTY STILL EXIST AS
THE ENERGY SINKS SOUTHEASTWARD AND PRECIPITATION SPREADS
EAST...BUT BOTH THE 00Z ECMWF ENSEMBLE MEAN AND GEFS MEAN SIGNAL A
WIDE SWATH OF PRECIPITATION EXTENDING FROM THE WESTERN GULF INTO
THE SOUTHERN MID-ATLANTIC STATES EARLY NEXT WEEK.  GIVEN THE FRESH
SURGE OF ARCTIC AIR SPREADING INTO THE CENTRAL/EASTERN U.S. THIS
WEEKEND...WINTER WEATHER WILL BE POSSIBLE WITHIN THE NORTHERN EDGE
OF THE PRECIPITATION SHIELD.


GERHARDT


$$





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