Prognostic Meteorological Discussion
Issued by NWS

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000 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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