Prognostic Meteorological Discussion
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FXUS02 KWBC 271557
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1057 AM EST FRI FEB 27 2015

VALID 12Z MON MAR 02 2015 - 12Z FRI MAR 06 2015

...MODEL PREFERENCES...
THE 27/00Z ECENS...NAEFS AND GEFS CONTINUE TO HANDLE THE TEMPORARY
PATTERN CHANGE ACROSS NORTH AMERICA DURING THIS MEDIUM RANGE
PERIOD. OF THE 27/00Z DETERMINISTIC SOLUTIONS---THE GFS/ECMWF
LOOKED REASONABLE UNTIL 4/12Z ACROSS THE MIDWEST---BEFORE THE
SEPARATION BETWEEN THE GFS/CANADIAN (FASTER SURFACE CYCLONE/WAVE
TRACK) AND ECMWF (SLOWER TRACK) BECOME VERY DIFFERENT. QUICKLY
TAPERED AWAY FROM ANY DETERMINISTIC SOLUTION BY
5/00Z---PRIMARILY...TO MITIGATE THE DIFFERENCES ALONG THE MODIFIED
ARCTIC COLD FRONT AND FOR SOUTHERN HALF OF THE CONTINENTAL DIVIDE
REGION (WEAK SOUTHERN BRANCH DISTURBANCES). ANY LINGERING
MID-LEVEL ENERGY AND DOWNSTREAM MOISTURE/DYNAMICS STREAMING OVER
THE TOP OF THE `NEW` SHALLOW MODIFIED-ARCTIC BOUNDARY COULD
PRESENT SENSIBLE WEATHER ISSUES ACROSS THE SOUTHERN TIER OF THE
US. WOULD THINK IT MIGHT TAKE A DAY OR TWO...TO GET A BETTER SENSE
OF THE TIMING AND/OR SEQUENCING OF SOUTHERN STREAM MOISTURE AND
MORE-ORGANIZED SHORTWAVE ENERGY MIGRATING FROM THE WEST COAST TO
THE SOUTHERN PLAINS.

...UNCERTAINTY ASSESSMENT...
THE `FOUR CORNERS` ENERGY MOVING AHEAD OF AN ARCTIC BOUNDARY AND
FORMING THE LEAD BOUNDARY APPEARS TO DELAY THE ARCTIC
FRONT---INITIALLY `SETTLED` OVER THE NORTHERN HIGH PLAINS AND
DAKOTAS. HOWEVER...THE MID-LEVEL SHORTWAVE`S EXIT ACROSS THE
EASTERN GREAT LAKES---SHOULD HELP BETTER TIME THE ARCTIC AIRMASS
PLUNGE AND ITS SOUTHEASTWARD SPREAD ACROSS THE CENTRAL AND EASTERN
STATES---FOR NEXT WEDNESDAY THROUGH FRIDAY.

THE FORECAST CHALLENGE DURING THE LATTER HALF OF THE
PERIOD---CONCERNS THE SOUTHERN END OF THE TROUGH AXIS AND UPSTREAM
(SOUTHERN BRANCH) ENERGY---STILL APPARENTLY LINGERING BACK ACROSS
THE SOUTHERN HIGH PLAINS AND RIO GRANDE VALLEY. THOUGH THE 27/00Z
DETERMINISTIC GUIDANCE HAS LITTLE IN COMMON WITH THE LOCATION OF
THE MID-LEVEL ENERGY THAT MAY GENERATE A LIGHT WINTRY MIX---THE
BROAD-SCALE PATTERN SUGGESTS ANOTHER `OVER-RUNNING TYPE` SCENARIO
IS POSSIBLE (HAS POTENTIAL) FROM WEST CENTRAL TEXAS EASTWARD TO
THE CAROLINAS---WEDNESDAY NIGHT INTO FRIDAY.

...SENSIBLE WEATHER HIGHLIGHTS...
THE 3/00Z TO 4/12Z TIME FRAME SHOULD BE AN ACTIVE ONE FOR THE
SOUTHERN ROCKIES...CENTRAL HIGH PLAINS AND LOWER MISSOURI
VALLEY---AS MID-LEVEL ENERGY EJECTS NORTHEASTWARD FROM THE FOUR
CORNERS AND MIGRATES INTO THE GREAT LAKES. THE SYSTEM SHOULD HAVE
A DISTINCT WINTER SIDE FOR THE PLAINS---AND A WINDY...WET AND VERY
MILD SPRING-LIKE SIDE WITHIN ITS WARM SECTOR---AS THE SYSTEM
MIGRATES EASTWARD ACROSS THE LOWER MS VALLEY...SOUTHEAST TO THE
ATLANTIC COAST BETWEEN WEDNESDAY AND THURSDAY. BEHIND THE COLD
FRONT...VERY SHARP TEMPERATURE DROPS---ON THE ORDER OF 25-35F.

VOJTESAK

$$





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