Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
856
FXUS02 KWBC 251535
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1134 AM EDT SUN SEP 25 2016

VALID 12Z WED SEP 28 2016 - 12Z SUN OCT 02 2016

...OVERVIEW...

ONE UPPER LOW WILL SLOWLY SWING THROUGH THE NORTHEAST CONUS WHILE
ANOTHER DROPS INTO THE PACIFIC NORTHWEST. A COLD FRONT AND
DEVELOPING SURFACE LOWS ARE FORECAST TO LIE JUST OFFSHORE THE
MID-ATLANTIC AND NORTHEAST MID/LATE WEEK PER THE ENSEMBLES BUT THE
SPREAD REMAINS LARGE. IN THE WEST, A LEAD COLD FRONT WILL LINGER
FROM OREGON ACROSS MONTANA UNTIL THE WEEKEND WHEN REINFORCING
ENERGY SHOULD MOVE IT ALONG TO THE EAST.


..MODEL PREFERENCES AND ASSESSMENT...

ENSEMBLES CONTINUE TO TREND TOWARD A MORE SLOWLY MOVING AND CLOSED
OFF UPPER LOW IN THE EAST THAT DIPS THROUGH THE CENTRAL
APPALACHIANS AND OUT THROUGH SOUTHERN NEW ENGLAND. THE SPREAD IN
SOLUTIONS RANGE FROM A MUCH WEAKER UPPER LOW LIFTING OUT QUICKLY
THROUGH NEW ENGLAND THU/FRI TO A COMPLETELY CLOSED OFF AND
ISOLATED UPPER LOW MAKING A CYCLONIC LOOP OVER THE SOUTHERN
APPALACHIANS. THE ECMWF/UKMET HAVE BEEN MOST AGGRESSIVE IN RECENT
RUNS IN A FARTHER SW AND ISOLATED CUTOFF LOW WHILE THE GFS HAS
BEEN MORE IN LINE WITH THE ENSEMBLES. THE CANADIAN AND ITS
ENSEMBLES WAS LATE TO COME IN LINE WITH THE GEFS AND ECMWF
ENSEMBLES BUT LIES CLOSE TO THE GFS IN ITS 00Z RUN. THOUGH THE
POSSIBILITY REMAINS FOR AN ECMWF/UKMET SOLUTION (THERE ARE ABOUT A
HALF DOZEN ECMWF ENSEMBLE MEMBERS THAT ARE TO THE SW OF THE ECMWF)
IT IS CONSIDERED A LOW PROBABILITY SOLUTION. JUST FOUR CYCLES AGO
THE ECMWF SHOWED NO SUCH CLOSED LOW AT ALL IN THE NORTHEAST FOR
LATER THIS WEEK. THE GFS HAS HAD BETTER CONTINUITY WITH THIS
SYSTEM (THOUGH FAR FROM PERFECT) THUS FAR BUT THAT DOES NOT
NECESSARILY MEAN IT WILL VERIFY BETTER IN FIVE DAYS.  THE
AGREEABLE ENSEMBLE MEANS PROVIDE A GOOD POSITIONING FOR FUTURE
CHANGES TOWARD EITHER A DEEPER/MORE OR WEAKER/LESS CLOSED OFF
SOLUTION.

IN THE WEST, MULTI-MODEL/ENSEMBLES BLEND SUFFICES IN AN OTHERWISE
FAIRLY PREDICTABLE PATTERN, DOWNSTREAM FROM BUILDING HEIGHTS INTO
ALASKA. UPPER LOW IN THE SW CONUS WILL LIFT INTO THE SW FLOW BY
THURSDAY IN THE GREAT BASIN. WILL HAVE TO MONITOR ANY POTENTIAL
TROPICAL DEVELOPMENT IN THE EAST PACIFIC OFF BAJA CALIFORNIA AS
REMNANT MOISTURE MAY STREAM INTO THE SOUTHWEST BEFORE UPPER
RIDGING SLIDES WESTWARD. PLEASE SEE THE NATIONAL HURRICANE CENTER
FOR THE LATEST INFORMATION. IN ADDITION, THE POTENTIAL DEVELOPMENT
OF WHAT IS CURRENTLY AL97 (WELL EAST OF THE LESSER ANTILLES) IS
STILL UNCERTAIN LATER THIS WEEK, THOUGH ITS POSITION BY NEXT
SUNDAY PER THE ENSEMBLES WOULD LIKELY BE SOUTH OF THE GREATER
ANTILLES.


...WEATHER HIGHLIGHTS...

PREFERRED SOLUTION IN THE EAST WOULD MEAN A DRIER PATTERN FOR THE
MID-ATLANTIC AND SOUTHEAST AS THE COLD FRONT WOULD BE FAR ENOUGH
OFFSHORE TO MAINTAIN NW FLOW. SHOULD A MUCH LESS PROGRESSIVE
SOLUTION VERIFY (SUCH AS THE ECMWF/UKMET) A MUCH CLOUDIER/WETTER
AND PATTERN FOR THU-SAT WOULD OCCUR FOR THE SOUTHERN APPALACHIANS
AND MID-ATLANTIC. FLORIDA WOULD STILL SEE HIGH POPS THROUGH THE
WHOLE PERIOD AS THE FRONT SINKS SLOWLY SOUTHWARD AND EVENTUALLY
WASHES OUT.

OTHERWISE, GENERALLY ABOVE AVERAGE TEMPERATURES IN THE CENTRAL
STATES WHERE THE RIDGE AXIS REMAINS MOSTLY IN PLACE WITH DRY
WEATHER FOR THE END OF THE WEEK. COOLER THAN AVERAGE TEMPERATURES
IN THE PAC NW, ESPECIALLY DAYTIME HIGHS, WITH BETTER CHANCES OF
RAIN NEXT WEEKEND SPREADING EASTWARD THROUGH THE ROCKIES AND INTO
THE PLAINS.


FRACASSO

$$





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