Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 010637
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 AM EDT SAT OCT 01 2016

VALID 12Z TUE OCT 04 2016 - 12Z SAT OCT 08 2016

...OVERVIEW...

UPPER PATTERN WILL TREND TOWARD TROUGHING IN THE WEST AND THE EAST
LATE NEXT WEEK. THE PATH OF HURRICANE MATTHEW WILL BE IN FOCUS FOR
THE SOUTHEAST. HOW THE LARGE SCALE PATTERN INTERACTS WITH MATTHEW
IS STILL UNDETERMINED.


...GUIDANCE PREFERENCES AND UNCERTAINTY ASSESSMENT...

UPPER LOW WILL LIFT INTO CANADA OUT OF NORTH DAKOTA ON WEDNESDAY
WHICH IS QUICKER THAN 24 HRS AGO, IN RESPONSE TO STRONGER RIDGING
TO ITS EAST OVER NEW ENGLAND. GFS  TRENDED A BIT QUICKER IN ITS
18Z RUN (AND THEN 00Z RUN) TO FOLLOW ALONG WITH THE 12Z
ECMWF/UKMET. THEREAFTER, THE TREND HAS BEEN FOR A WEAKER TROUGH TO
PUSH EASTWARD, WITH ITS PROGRESSION NORTHEASTWARD INTO CANADA.
THIS PLAYS A PART IN THE EVENTUAL TRACK OF MATTHEW OFF FLORIDA
LATER IN THE WEEK. THE GEFS TREND HAS BEEN TO SLOW DOWN THE
NORTHWARD MOVEMENT OF MATTHEW WHILE THE ECMWF ENSEMBLES HAS SPED
UP A BIT (BY NEXT FRI/SAT), THOUGH THEY STILL REMAIN RATHER
SEPARATED BY DAY 7. OPTED FOR A POSITION ABOUT 2/3 OF THE WAY TO
THE ECMWF ENSEMBLE MEAN WHICH WOULD TAKE MATTHEW JUST OFF NC NEXT
SAT. PLEASE CONSULT THE NATIONAL HURRICANE CENTER FOR THE LATEST
INFORMATION AND THE WPC 19Z SURFACE FRONTS/PRESSURES THAT
INCORPORATES A COORDINATED WPC/NHC POSITION VALID NEXT FRI/SAT.

BACK TO THE PAC NW, THE 12Z ECMWF FELL OUT OF LINE WITH THE
CONSENSUS BY THU OR SO OVER THE NE PACIFIC. UPSTREAM FLOW REMAINS
COMPLICATED BY THE EXTRATROPICAL TRANSITION OF TROPICAL STORM
CHABA OFF JAPAN IN ADDITION TO A ROBUST LEAD SYSTEM IN THE BERING
SEA. THE FLOW IS FORECAST TO BE STRONGLY ZONAL ON EITHER SIDE OF
THE DATELINE LATE NEXT WEEK WITH A STRONG JET OFF ASIA. THIS COULD
SUPPORT A SPLIT FLOW EAST OF 150W THAT COMPLICATES THE CONUS FLOW
AS WELL. ENSEMBLE MEANS CONTINUE TO BE A MORE RELIABLE SOLUTION.


...WEATHER HIGHLIGHTS...


DECREASING PRECIPITATION WILL ACCOMPANY THE FRONT MOVING OUT OF
THE PLAINS AS ITS UPPER SUPPORT LIFTS INTO CANADA. TUE/WED WOULD
BE THE BEST CHANCE FOR WIDESPREAD MODEST RAIN FROM OKLAHOMA
NORTHWARD TO MINNESOTA. SOUTHERN PORTION OF THE FRONT MAY BE JUST
A WIND SHIFT WITH SOME LIGHT SHOWERS BY FRIDAY IN THE LOWER MS
VALLEY. TEMPERATURES WILL COOL BEHIND THE FRONT AFTER SURGING
AHEAD OF IT. AGAIN, HOW QUICKLY OR SLOWLY MATTHEW DEPARTS OR
MEANDERS WILL AFFECT THE SENSIBLE WEATHER IN THE SOUTHEAST.


FRACASSO

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