Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXUS02 KWBC 051549
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1148 AM EDT TUE MAY 05 2015

VALID 12Z FRI MAY 08 2015 - 12Z TUE MAY 12 2015

...OVERVIEW AND GUIDANCE PREFERENCES...

HAVE NOT DEVIATED SIGNIFICANTLY FROM LAST NIGHTS FORECAST PACKAGE.

ACROSS THE NORTHEAST CORNER OF THE NATION...RIDGING WILL DOMINATE
THE EARLY FLOW PATTERN.  THE COMBINATION OF RIDGING IN THE
NORTHEAST AND ACROSS NORTHWESTERN CANADA TELECONNECTS WITH
TROUGHING OVER THE WESTERN US...WHICH WILL BE THE DOMINANT FLOW
MODE BEGINNING THE MEDIUM RANGE...WHICH THEN PROGRESSES EASTWARD.

WITHIN THE EASTERN RIDGE...A SUBTROPICAL LOW IS EXPECTED TO
DEVELOP WITHIN THE EAST SOUTHEASTERLY FLOW OFF THE SOUTHEAST COAST
IN THE SHORT RANGE AND THEN THEN CONTINUE SLOWLY WESTWARD IN THE
MEDIUM RANGE. IN CONSULT WITH NHC...THIS LOW IS DEPICTED SO FAR AS
A RELATIVELY WEAK SYSTEM THAT WILL MOVE SLOWLY WESTWARD POSSIBLY
REACHING THE GEORGIA/SOUTH CAROLINA COAST BY AROUND SUNDAY TO
MONDAY.  THIS EARLY SEASON SYSTEM IS THE FIRST POTENTIAL TROPICAL
SYSTEM OF THE SEASON.

THERE IS GENERALLY DECENT AGREEMENT AMONG THE MODELS ON DAYS 3 TO
5/FRIDAY THROUGH SUNDAY DISCOUNTING THE OPERATIONAL CANADIAN.
WHILE THE EUROPEAN ENSEMBLE MEANS SEEM TO HAVE SLIGHTLY MORE CYCLE
TO CYCLE CONTINUITY WITH THE EVOLUTION OF FEATURES AFFECTING THE
US...THERE ARE SOME SIGNIFICANT DIFFERENCES THAT BEGIN TO EMERGE
DURING LATE WEEKEND INTO EARLY NEXT WEEK.  THE MAIN CONCERN IS
THAT THERE ARE A SIGNIFICANT NUMBER OF INDIVIDUAL ENSEMBLE RUNS
THAT ARE SUGGESTIVE THAT ARE AT ODDS WITH THE EXTEND OF THE
RESULTANT RIDGING OCCURRING AGAIN OVER THE NORTHEAST AND SOUTHEAST
CANADA LATE IN THE FORECAST ON DAYS 6 AND 7...WHICH WOULD IMPLY A
SIGNIFICANT WARMUP FOR THE NORTHEAST EARLY NEXT WEEK.

HOWEVER...SOME OTHER MEMBERS ARE MORE SUGGESTIVE OF A FLATTER
SOLUTION WITHIN CONFLUENT FLOW...ALLOWING COOLER AIR TO SUBSIDE
INTO THE NORTHEAST. SOME OF LAST WEEKS FORECASTS INDICATED A WARM
WEEK FOR MUCH OF THE EAST BUT AS THIS WEEK CONTINUES...COOLER AIR
IS LIKELY TO FLOW SOUTHWARD ALONG THE EAST COAST.  THIS CONTINUES
TO BE A SIMILAR KIND OF DILEMMA FOR THE FORECAST FOR EARLY NEXT
WEEK AS WELL.  NOT MUCH CONFIDENCE EITHER WAY AT THIS POINT BUT
FAVORED A MIXED SOLUTION LATE IN THE FORECAST...BUT NOT AS WARM AS
THE EUROPEAN ENSEMBLES MAY HAVE INDICATED.  TIME WILL TELL. IN
ADDITION...RECENT OPERATIONAL GFS SOLUTIONS APPEAR TO BE ON THE
EDGE OF THE SOLUTION ENVELOP IN THE EASTERN PACIFIC LATE IN THE
FORECAST...SO HAVE MINIMIZED THEIR INFLUENCE.



...SENSIBLE WEATHER HIGHLIGHTS...

TEMPERATURE DEPARTURES APPEAR COOLER THAN AVERAGE IN THE WEST AND
WARMER THAN AVERAGE IN THE EAST. THE CENTRAL STATES WILL COOL DOWN
BY EARLY NEXT WEEK AND ALLOW THE WEST TO REBOUND TO NEAR OR ABOVE
AVERAGE. PRECIPITATION WILL FOCUS ALONG AND DOWNSTREAM OF THE
CLOSED LOW THAT LIFTS FROM THE GREAT BASIN AND CENTRAL ROCKIES
INTO THE CENTRAL/SOUTHERN PLAINS AND INTO THE GREAT LAKES. THE
THREAT OF SEVERE WEATHER IS LIKELY TO BE SIGNIFICANT IN THE WARM
SECTOR OF THIS SYSTEM AS IT PROGRESSES EASTWARD.  IT DOES APPEAR
THAT PRECIPITATION WITH THE SUBTROPICAL SYSTEM OFF THE SOUTHEAST
COAST COULD MAKE ITS INFLUENCE KNOW OVER THE WEEKEND ON SATURDAY
AND SUNDAY WITH THE BULK OF THE PRECIPITATION REMAINING OFFSHORE.
AS THIS SYSTEM COULD COME ASHORE EARLY NEXT WEEK...PRECIPITATION
WILL INCREASE ACROSS THE SOUTHEAST BUT CONFIDENCE IS RELATIVELY
LOW GIVEN WHETHER IT WILL REMAIN WEAK OR POSSIBLY NOT COME ASHORE.


BECAUSE OF THE CONCERNS OF THE RELATIVE EFFECTS OF RIDGING IN THE
EAST VERSUS FLATTER MORE CONFLUENT FLOW...TEMPERATURE DEPARTURE
FORECASTS ACROSS THE NORTHEASTERN CORNER OF THE NATION WILL HAVE
LOW CONFIDENCE DUE TO CONCERNS ABOUT WHERE A BACKDOOR TYPE FRONT
MOVES ON MONDAY AND TUESDAY.


KOCIN

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.