Prognostic Meteorological Discussion
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000
FXUS02 KWBC 271600
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT TUE SEP 27 2016

VALID 12Z FRI SEP 30 2016 - 12Z TUE OCT 04 2016

...GUIDANCE/UNCERTAINTY ASSESSMENT AND PATTERN
HIGHLIGHTS/THREATS....

A WET UPPER LEVEL CLOSED/CUTOFF LOW WILL VERY SLOWLY LIFT OUT OF
THE OHIO VALLEY THROUGH THE WEEKEND WHILE TROUGHING IS REINFORCED
INTO THE UNSETTLED WRN US. THE MIDDLE SECTION OF THE COUNTRY WILL
START DRY AND MILD BUT WILL SEE AN INCREASED CHANCE OF RAIN LATE
WEEKEND INTO EARLY NEXT WEEK.

MEANWHILE...THE POTENTIAL FOR SHORT TERM TROPICAL LOW DEVELOPMENT
ACROSS THE CARRIBEAN MAY LEAD TO A THREAT FOR THE SERN US EARLY
NEXT WEEK. THIS IS BEING MONITORED BY THE NHC AND WPC.

MODELS AND ENSEMBLES HAVE INCREASINGLY SETTLED ON A COMMON
SOLUTION REGARDING THE EVOLUTION OF AN UPPER/CLOSED LOW IN THE
EAST. THERE IS AGREEMENT THAT A CLOSED LOW WILL COMPLETELY CUT OFF
FROM THE WESTERLIES NEAR THU/FRI AND THEN SLOWLY LIFT NORTHWARD
THIS WEEKEND. A +2 SIGMA HEIGHT ANOMALY NEAR JAMES BAY IS FORECAST
TO SLOWLY MOVE NORTHEASTWARD THROUGH THE PERIOD WHICH FAVORS A
SLOW EXODUS OF THE CLOSED LOW TO ITS SOUTH THROUGH NEW ENGLAND
AROUND MONDAY. THE 00 UTC ECMWF/ECMWF ENSEMBLES REMAIN THE SLOWEST
TO MOVE THE CLOSED LOW AWAY FROM THE GREAT LAKES COMPARED TO THE
GFS/CANADIAN AND RESPECTIVE ENSEMBLES. PREFER A COMPOSITE 06 UTC
GFS...00 UTC ECMWF...AND 00 UTC NAEFS ENSEMBLE BLEND GIVEN THE
DISAGREEMENT IN THE WEST AS TO THE ORIENTATION OF THE TROUGH AND
UNCERTAINTY IN EMBEDDED SHORTWAVES.

WITH THE CLOSED LOW NEARLY STUCK IN THE EAST FOR SEVERAL DAYS...AN
INFLUX OF MOISTURE FROM THE ATLANTIC WILL BE CHANNELED INTO THE
MID-ATLANTIC AND NORTHEAST IN WAVES. COOLER THAN AVERAGE DAYTIME
HIGHS ARE EXPECTED WITH ABUNDANT CLOUDINESS. AS THE UPPER LOW
WEAKENS AND FILLS OVER TIM...PRECIPITATION COVERAGE WILL GRADUALLY
DECREASE INTO NEXT WEEK. COLD POOL ALOFT SUGGESTS LINGERING CLOUDS
AROUND THE DECAYING CIRCULATION WITH AFTERNOON HEATING. THE
ENSEMBLES FOCUS THE PRECIPITATION INITIALLY ON THE MID-ATLANTIC
LATER THIS WEEK (THU-FRI) AND THEN NORTHWARD INTO THE NORTHEAST AS
THE UPPER AND SFC SYSTEMS MOVE NORTHWARD. TAIL END OF THE FRONTAL
BOUNDARY WILL LINGER AROUND FLORIDA WHICH WILL KEEP RAIN IN THE
FORECAST NEARLY EVERY DAY FOR CENTRAL/SOUTH PORTIONS. THIS COULD
BECOME A RENEWED FOCUS FOR TROPICAL MOISTURE EARLY NEXT WEEK WITH
POSSIBLE LOW DEVELOPMENT AND APPROACH FROM THE CARIBBEAN AS
EFFECTED BY A GENERAL MEAN WEKANESS TO LIFT FEATURES.

THE WEST WILL SEE A WAVY LEAD FRONT LINGER INTO FRI AND THEN
SLOWLY PROGRESS EASTWARD THIS WEEKEND...BRINGING COOLER
TEMPERATURES TO THE N-CENTRAL INTERMOUNTAIN WEST/ROCKIES AND
EVENTUALLY INTO THE HIGH PLAINS. MUCH OF THE PACIFIC NORTHWEST
INTO NORTHERN/CENTRAL CALIFORNIA AND THE REST OF THE GREAT BASIN
WILL SEE BELOW AVERAGE TEMPERATURES AS THE TROUGH GETS REINFORCED
THIS WEEKEND INTO NEXT WEEK. PRECIPITATION WILL SPREAD EASTWARD
THROUGH THE CENTRAL AND NORTHERN ROCKIES AS THE FRONT MOVES SOUTH
AND EAST. THE POTENTIAL EXISTS FOR EVEN MORE ENERGY TO DIG INTO
THE BASE OF THE TROUGH WITH MORE SEPARATION THAT MOST GUIDANCE
EARLY NEXT WEEK GIVEN RECENT PATTERN TRENDS AND UPSTREAM RIDGE
AMPLITUDE. WPC PROGS UTILIZE THE 00 UTC NAEFS BY DAYS 6/7 TO
BETTER DEPICT THIS POTENITAL. THIS HOLDS HEIGHTS LOWER THAN THE 00
UTC ECMWF AND 06 UTC GFS BUT NOT AS MUCH AS SHOWN BY THE 00 UTC
CANADIAN.

SCHICHTEL

$$





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