Prognostic Meteorological Discussion
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FXUS02 KWBC 261619
PMDEPD

EXTENDED FORECAST DISCUSSION ... CORRECTED PARAGRAPH 2
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1218 PM EDT THU MAY 26 2016

VALID 12Z SUN MAY 29 2016 - 12Z THU JUN 02 2016

THE 26/00Z DETERMINISTIC ECMWF/GFS WERE IN VERY GOOD AGREEMENT
UNTIL 30/00Z ALONG THE SC COAST---BEFORE THE LOW-LEVEL WIND
FORECASTS (SFC-850MB LAYER) DIFFER SIGNIFICANTLY ENOUGH TO TREND
TOWARDS THE ECMWF. THE RESULTING DIFFERENCES APPEARING TO BE TIED
TO A MID-LATITUDE TROUGH MIGRATING ACROSS THE CENTRAL
APPALACHIANS...OHIO VALLEY AND NORTHEAST.

PREFER TO LEAN TOWARDS THE DETERMINISTIC ECMWF (AT LEAST A 30%
CONTRIBUTION) TO THE BLEND---TO KEEP A MORE REALISTIC TRAJECTORY
OF THE `DISTURBANCE` (INVEST AL912016) RELATIVE TO THE
SYNOPTIC-SCALE FEATURES SURROUNDING IT. LIKEWISE...THOUGHT THE
ECENS/ECMWF COMBINATION WAS CONSISTENT UPSTREAM ACROSS THE
NORTHERN PLAINS...OFF THE WASHINGTON COAST AND ALONG THE US/MEXICO
BORDER---CORRELATING STRONGLY WITH THE FULL ENSEMBLE PACKAGE (BY
1/12Z) INVOF 48N 100W VERSUS A `SLOWER` GEFS/GFS SOLUTION. PLEASE
REFER TO THE ---NATIONAL HURRICANE CENTER--- FOR THE LATEST
INFORMATION CONCERNING INVEST AL912016.

FROM A SENSIBLE WEATHER PERSPECTIVE---THE TROPICAL `DISTURBANCE`
SHOULD ALLOW FOR A RATHER HUMID AND UNSTABLE AIRMASS TO MIGRATE
NORTHWESTWARD AND ASHORE ACROSS THE SOUTHEAST...TO THE EASTERN
SLOPES OF THE APPALACHIANS. THE FRONTAL BOUNDARY TO ITS
NORTH---WILL LIKELY PRODUCE A SHARP DEMARCATION BETWEEN THIS
AIRMASS AND A CANADIAN ONE --- WEST OF THE APPALACHIAN SPINE. SO
THE GENERAL RULE WOULD BE TO CARRY AN AIRMASS-TYPE HIT-N-MISS
SHOWER PATTERN---OUTSIDE OF THE MORE ORGANIZED AND WESTWARD-
MOVING 850-700MB LAYERED SHORTWAVE ENERGY THAT ROTATES INLAND IN
COUNTER-CLOCKWISE FASHION. MIX IN A SEA BREEZE FRONT...AND IT
BECOMES A CHALLENGE FROM A QPF PERSPECTIVE FROM THE FIRST COAST OF
FLORIDA NORTHWARD TO THE PIEDMONT.

ACROSS THE PLAINS AND WEST OF THE DIVIDE---WHAT TRANSPIRES WILL BE
A `PERSISTENCE-TYPE` MEDIUM RANGE FORECAST. GIVEN THE DOWNSTREAM
PATTERN EAST AND SOUTH OF THE MISSISSIPPI/OHIO RIVER
CONFLUENCE---THE CONVECTIVE PATTERN WILL BE `SUMMER-LIKE` IN ITS
DEVELOPMENT...CHARACTER AND INTENSITY. THE FOCAL POINT FOR
SYNOPTIC-SCALE PRECIPITATION WILL BE TIED TO A MODERATE SURFACE
CYCLONE THAT DEVELOPS EAST OF THE MONTANA/ALBERTA PORTION OF THE
DIVIDE---MEMORIAL HOLIDAY WEEKEND (30TH-31ST) AND ITS
SOUTHEASTWARD-MIGRATING CANADIAN COLD FRONT (A JUNE FRONT...MIND
YOU) THAT PRESSES INTO THE MID MS VALLEY AND CENTRAL GREAT LAKES
ON WEDNESDAY AND THURSDAY.

VOJTESAK




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