Prognostic Meteorological Discussion
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FXUS02 KWBC 031551
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1151 AM EDT SUN MAY 03 2015

VALID 12Z WED MAY 06 2015 - 12Z SUN MAY 10 2015


...MULTI-DAY HEAVY RAINFALL EVENT FOR THE SOUTHERN AND CENTRAL
PLAINS...

A BLOCKING PATTERN IS PROGGED TO TAKE SHAPE ACROSS NORTH AMERICA
THIS WEEK, WITH A MEAN TROUGH SETTING UP IN THE WESTERN UNITED
STATES. USED A BLEND OF THE 00Z/03 ENSEMBLE MEANS AS A SYNOPTIC
GUIDE THIS FORECAST, AS THE EVOLUTION OF THE FLOW HAS BEEN WILDLY
HANDLED BY THE VARIOUS OPERATIONAL MODELS. DID INCORPORATE SOME OF
THE 00Z/03 GFS TO ADD SOME DEFINITION TO THE POSSIBLE SUBTROPICAL
LOW OFF THE SOUTHEAST COAST, WHICH THE NATIONAL HURRICANE CENTER
ESTIMATES AS HAVING A 30 PERCENT CHANCE OF DEVELOPMENT PAST 48
HOURS IN THEIR SPECIAL TROPICAL OUTLOOK. A DEEPER WESTERN TROUGH
MEANS A GREATER CHANCE OF BACKDOOR MARITIME POLAR FLOW INTO THE
NORTHEAST AND MID-ATLANTIC, SO NOT SURE HOW FAR NORTH ANY LOW OFF
THE ATLANTIC COAST WILL BE ABLE TO ULTIMATELY DRIFT.

THE STAGNATION OF THE PATTERN MEANS THAT WHAT YOU SEE IS WHAT YOU
WILL GET FOR SOME TIME TO COME. THE GREATEST IMPACT OF THE BLOCK
SHOULD BE OVER THE SOUTHERN AND CENTRAL PLAINS, WHERE PROLONGED
INFLOW FROM THE GULF OF MEXICO SHOULD FUEL DAY AFTER DAY OF
SOAKING SHOWERS AND THUNDERSTORMS. EVENTUALLY, THE MOISTURE SHOULD
WRAP BACK INTO THE HIGH PLAINS OF NORTHEASTERN COLORADO AND
EASTERN WYOMING WHEN THE UPPER LOW OVER THE SOUTHWEST BEGINS TO
KICK OUT.

THE SOUTHEAST SHOULD GRADUALLY MOISTEN UP AS THE OFFSHORE
DISTURBANCE TENDS TO RETROGRESS IN THE TIGHTENING BLOCK--MAINLY
SOUTH OF VIRGINIA.


CISCO

$$




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