457  
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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