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Extended Forecast Discussion
 
(Latest Discussion - Issued 1600Z Mar 02, 2015)
 
Version Selection
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST MON MAR 02 2015

VALID 12Z THU MAR 05 2015 - 12Z MON MAR 09 2015

...SYNOPTIC PATTERN...

DEEP CYCLONIC FLOW WILL REMAIN IN PLACE ACROSS THE NORTHEASTERN
CORRIDOR OF THE CONTINENT WITH STRONG HEIGHT FALLS QUICKLY MOVING
ACROSS THE GREAT LAKES AND MID-ATLANTIC REGION ON THURSDAY. AFTER
THIS SYSTEM MIGRATES TOWARD THE CANADIAN MARITIMES...THE UPPER
FLOW BEGINS TO RELAX DURING THE FOLLOWING FEW DAYS. HOWEVER...THE
GENERAL PATTERN DOES KEEP A TROUGH ACROSS THE EAST WHICH HAS
SEEMINGLY BEEN IN PLACE FOR WEEKS. ACROSS THE WESTERN U.S...THE
MID-LATITUDE PATTERN IS MORE SPLIT IN NATURE WITH SOUTHERN STREAM
ENERGY SLOWLY MOVING FROM BAJA CA TOWARD WEST TX. BASED ON THE
AVAILABLE GUIDANCE...IT COULD TAKE MULTIPLE DAYS FOR THIS SYSTEM
TO WORK ITS WAY EASTWARD IF IT DOES NOT BECOME SHEARED OUT BY
THEN. TO THE NORTH...A MAJORITY OF THE MODELS SUPPORT MAINTAINING
A BROAD UPPER RIDGE ACROSS THE WESTERN U.S. ALTHOUGH THERE IS SOME
HINT THAT SHORTWAVES MOVING OFF THE NORTHEASTERN PACIFIC MAY DENT
THE NORTHERN EXTENT OF THE RIDGE. BUT OVERALL...THE GENERAL
CONSENSUS IS TO MAINTAIN A TROUGH IN THE EAST AND A RIDGE IN THE
WEST THROUGHOUT THE MEDIUM RANGE PERIOD.


...GUIDANCE ASSESSMENT AND PREFERENCES...

WHILE GENERAL AGREEMENT IS NOTED IN THE EAST WITH THE INITIAL
AMPLIFIED FLOW...THE LARGER DIFFERENCES ARE OUT WEST WITHIN THE
SPLIT FLOW REGIME. THERE IS A GREAT DEAL OF UNCERTAINTY WITH BOTH
ASPECTS OF THIS PATTERN...BOTH REGARDING TIMING AND STRENGTH OF
THESE FEATURES. THE TREND IN THE PAST FOUR RUNS OF THE GFS HAS
BEEN TO SHEAR THE SYSTEM WHILE THE ECMWF SOLUTIONS MAINTAIN A
RATHER ROBUST SHORTWAVE CROSSING NORTHERN MX. THE 00Z UKMET SEEMS
TO AGREE WITH THE FLATTER/QUICKER GFS SOLUTION WHILE THE 00Z
CMC/CMC ENSEMBLE MEAN ARE OFF ON THEIR OWN BEING MUCH SLOWER
THROUGHOUT THE EVOLUTION. LOOKING TO THE NORTH...THERE ARE ALREADY
A SLEW OF MODEL DIFFERENCES REGARDING THE UPSTREAM WAVE TRACKING
ACROSS THE EASTERN PACIFIC. MODEL CONTINUITY IS POOR WITH VERY
LITTLE SIMILARITIES AMONG THE GUIDANCE BY AS EARLY AS DAY 3. HOW
THESE SHORTWAVES MOVE EASTWARD TOWARD THE PRONOUNCED WESTERN RIDGE
AND THE TRAJECTORY THESE SYSTEMS TAKE FARTHER DOWNSTREAM
DEFINITELY PLAY A ROLE IN THE PATTERN AHEAD. THE PAST FEW RUNS OF
THE ECMWF SHOW A STRENGTHENING SHORTWAVE RACING TOWARD THE CENTRAL
HIGH PLAINS BY 08/0000Z. THE 00Z UKMET SHOWS SUBTLE SUPPORT FOR
THIS IDEA BUT THE CONFIDENCE IS LOW UTILIZING ANY DETERMINISTIC
GUIDANCE HERE. OVERALL...WPC LEANED IN THE DIRECTION OF THE
ENSEMBLE MEANS THROUGHOUT THE PERIOD GIVEN THE UNCERTAINTY ACROSS
THE WESTERN SIDE OF THE MAP DOMAIN. FAVORED AN EQUAL BLEND OF THE
00Z ECMWF ENSEMBLE/NAEFS MEAN THROUGHOUT THE MEDIUM RANGE WITH
AVERAGE CONFIDENCE.


...SENSIBLE WEATHER HIGHLIGHTS...

WELL BELOW NORMAL TEMPERATURES WILL BE THE MAIN THEME OF THE
PERIOD FROM MARCH 5-9 WITH SOME VERY LARGE ANOMALIES IN THE
FORECAST. DAYS 3 AND 4 WILL BE QUITE COLD FROM THE NORTHERN PLAINS
ACROSS THE GREAT LAKES/OH VALLEY AND INTO THE NORTHEASTERN U.S.
PROJECTED ANOMALIES ON BOTH THE MINIMA/MAXIMA MAY BE IN THE 20 TO
30 DEGREE RANGE AS HIGHS ON THURSDAY REMAIN IN THE TEENS ACROSS
THE UPPER MIDWEST...GREAT LAKES...UPPER OH VALLEY...AND INTERIOR
NORTHEAST. LOW TEMPERATURES ON DAYS 3 AND 4 WILL EASILY PLUNGE
NEAR -10 DEGREES ACROSS THE UPPER MIDWEST WITH BELOW ZERO READINGS
POSSIBLE BY THE FOLLOWING NIGHT ACROSS THE GREAT LAKES...OH
VALLEY...AND SECTIONS OF NEW ENGLAND.

REGARDING PRECIPITATION...A FRONTAL ZONE MOVING ACROSS THE EAST
COAST SHOULD BRING A PERIOD OF RAIN CHANGING TO SOME MIXTURE OF
WINTRY PRECIPITATION TYPES EARLY THURSDAY. ONCE THIS SYSTEM MOVES
OFFSHORE...THE PATTERN GETS RATHER DRY ACROSS THE CONUS. A BRIEF
PERIOD OF WET CONDITIONS ARE POSSIBLE ACROSS FL AS THE COLD FRONT
SLOWLY SAGS SOUTHWARD. THEREAFTER...THE UNCERTAINTY ACROSS THE
WESTERN U.S. MAKES IT DIFFICULT TO RESOLVE HOW MUCH RETURN FLOW
FROM THE GULF OF MX WILL TAKE PLACE. THE ECMWF SOLUTIONS
DEFINITELY OFFER A WETTER PERIOD TOWARD THE END OF THE MEDIUM
RANGE PERIOD.


RUBIN-OSTER