859  
FXUS02 KWBC 191556  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1056 AM EST SUN NOV 19 2017  
 
VALID 12Z WED NOV 22 2017 - 12Z SUN NOV 26 2017  
   
..RECORDS HIGHS LIKELY IN THE SOUTHWEST LATER THIS WEEK
 
   
..WET OVER THE NORTHWEST
 
 
   
..OVERVIEW
 
 
STRONG UPPER HIGHS NEAR SAN DIEGO AND THE DAVIS STRAIT BETWEEN FAR  
NORTHEASTERN CANADA AND GREENLAND WILL FAVOR EASTERN US TROUGHING  
AND COOLER THAN AVERAGE TEMPERATURES. RECORD WARM TEMPERATURES ARE  
LIKELY FOR PARTS OF THE SOUTHWEST BUT WEST TO SOUTHWESTERLY FLOW  
INTO THE PACIFIC NORTHWEST WILL MAINTAIN A RATHER WET PATTERN.  
ADDITIONAL WET WEATHER IS LIKELY OVER FLORIDA ASTRIDE A SLOWLY  
MOVING FRONTAL BOUNDARY. THE MIDDLE PART OF THE COUNTRY IS  
EXPECTED TO BE RATHER DRY AND MILD TO START BUT TRENDING COOLER BY  
THE WEEKEND.  
 
   
..GUIDANCE/UNCERTAINTY PREFERENCES...
 
 
MODELS/ENSEMBLES ARE IN GOOD AGREEMENT ON THE LARGE SCALE PATTERN  
BUT DIFFER ON SOME TIMING/AMPLITUDE DETAILS. THERE REMAINS SOME  
00Z/12Z GUIDANCE OSCILLATING BUT OVERALL THE LATEST 00Z GUIDANCE  
WAS RATHER AGREEABLE AND A BLEND OF THE RECENT  
GFS/ECMWF/CANADIAN/UKMET OFFERED A GOOD STARTING POINT FOR THE  
WED/THU FORECAST. AFTER THAT, THE GFS DEPARTED FROM THE  
ECMWF/CANADIAN/ENSEMBLE CLUSTERING OVER CANADA (BOTH NEAR THE  
BORDER AND FARTHER NORTH INTO THE NW TERRITORIES/NUNAVUT) AND IT  
WAS DROPPED FROM THE PREFERENCE. PREVIOUS GEFS RUNS WERE CLOSER TO  
THE ECMWF ENSEMBLES SO THE 00Z GEFS MAY BE JUST A JOG FROM  
OTHERWISE DECENT CONTINUITY. TREND HAS BEEN WAVERING IN THE GULF  
TOWARD EITHER A CLOSED LOW OR WEAKLY SEPARATED TROUGH MOVING  
ACROSS FLORIDA LATER IN THE WEEK, BUT STILL FAVORED A BIT STRONGER  
SOLUTION GIVEN THE STRENGTH OF THE UPPER HIGH BOTH UPSTREAM AND  
DOWNSTREAM. TO THE WEST, CANADIAN AND GFS STILL SHOWED A SHORTWAVE  
MOVING INTO CALIFORNIA SAT WHILE THE ENSEMBLE TREND HAS BEEN TO  
HAVE THIS ONLY SLOWLY MOVE EASTWARD LIKE THE 00Z ECMWF/CONTINUITY,  
DEPICTED AS THE APPROACHING BUT WEAKENING COLD FRONT NEXT SUNDAY  
WEST OF SAN FRANCISCO. TO THE EAST, FAVORED THE MORE  
AMPLIFIED/COOLER ECMWF ENSEMBLE SOLUTION NEXT WEEKEND WHICH SHOULD  
FOLLOW BEHIND A COLD FRONT MOVING OFF THE EAST COAST.  
 
   
..WEATHER HIGHLIGHTS
 
 
OCCASIONALLY HEAVY DAILY RAINS AND LOCALLY HEAVY ELEVATION SNOWS  
WILL PERSIST IN THE PAC NW THIS WEEK, PERHAPS EASING THIS COMING  
WEEKEND DEPENDING ON HOW QUICKLY THE NEXT SYSTEM MOVES TOWARD THE  
COAST. UPPER RIDGING WILL SUPPORT WELL ABOVE AVERAGE TEMPERATURES  
IN THE SOUTHWEST WHERE RECORD HIGHS ARE POSSIBLE WED-SAT OVER  
PARTS OF CA/NV/AZ/UT. MILD TEMPERATURES WILL EXTEND EASTWARD  
THROUGH THE CENTRAL/SOUTHERN ROCKIES AND PLAINS AHEAD OF A COLD  
FRONT THU/FRI WITH COOLER TEMPERATURE TO FOLLOW FOR THE WEEKEND.  
THERE IS A GOOD CHANCE FOR APPRECIABLE PRECIPITATION ALONG THE  
GULF COAST AS LOW PRESSURE CENTERS MEANDER ALONG A SLOW MOVING  
FRONT. EXPECT SOME RAIN/SNOW AROUND THE GREAT LAKES BUT GENERALLY  
NO PRECIPITATION FROM THE SOUTHWEST TO THE PLAINS AND MS VALLEY.  
 
   
..THANKSGIVING FORECAST
 
 
IT WILL REMAIN GENERALLY QUIET FOR MOST OF THE LOWER 48.  
PRECIPITATION WILL BE MOST CONCENTRATED IN THE PACIFIC NORTHWEST  
INTO NORTHERN CALIFORNIA AS WELL AS NORTHERN IDAHO/WESTERN  
MONTANA/NW WYOMING. SCATTERED TO PERHAPS WIDESPREAD RAIN IS ALSO  
QUITE POSSIBLE THROUGH FLORIDA AND THE COASTAL SOUTHEAST DEPENDING  
ON HOW THE SURFACE SYSTEMS EVOLVE. RECORD HIGH TEMPS ARE LIKELY IN  
THE SOUTHWEST WITH 80S AND SOME 90S. PHOENIX HAS THE CHANCE OF  
RECORDING THEIR LATEST 90 DEGREE DAY SO LATE IN THE YEAR (RECORD  
IS NOV 15 1999) INCLUDING THEIR WARMEST THANKSGIVING DAY (RECORD  
IS 87 ON NOV 23 1950 AND NOV 27 2014 - THANKS TO THE PHOENIX NWS  
OFFICE FOR THE CLIMATE/RECORD INFORMATION). COOLER 30S/40S IN THE  
UPPER MIDWEST/GREAT LAKES/NORTHEAST/MID-ATLANTIC ARE LIKELY BY  
NEXT WEEKEND BEHIND THE FRONT.  
 
FRACASSO/SCHICHTEL  
 

 
 
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