517  
FXUS02 KWBC 190659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 AM EST SUN NOV 19 2017  
 
VALID 12Z WED NOV 22 2017 - 12Z SUN NOV 26 2017  
 
...RECORDS HIGHS LIKELY IN THE SOUTHWEST LATER NEXT WEEK AND WET  
OVER THE NWRN US...  
 
   
..OVERVIEW
 
 
AN AMPLIFIED MEAN FLOW PATTERN WILL BE HIGHLIGHTED BY AN ERN  
PACIFIC UPPER TROUGH...A VERY STRONG UPPER HIGH NEAR THE DAVIS  
STRAIT...AND A SECONDARY UPPER HIGH NEAR SRN CALIFORNIA WILL  
CONTINUE TO FAVOR ERN CONUS TROUGHING ALOFT NEXT WEEK. A LEAD  
SYSTEM WILL PUSH OFF THE EAST COAST WEDNESDAY AS PROPELLED BY  
AMPLE APPROACHING NRN STREAM TROUGH ENERGY. HOWEVER...THE FRONT  
SHOULD LINGER THROUGH THE WEEK OVER WETTENED FLORIDA AS MORE SRN  
STREAM ENERGY DIGGING TO THE LEE OF THE WRN US RIDGE OFFERS SOME  
FLOW SEPARTION POTENTIAL. MEANWHILE...ANOTHER SYSTEM WILL ENTER  
THE PACIFIC NORTHWEST BY THURSDAY/THANKSGIVING AND MOVE EASTWARD  
THROUGH THE HIGH PLAINS ON FRIDAY AND ACROSS THE EAST-CENTRAL THEN  
ERN US NEXT WEEKEND.  
 
   
..GUIDANCE/UNCERTAINTY PREFERENCES...
 
 
MODELS/ENSEMBLES ARE IN GOOD AGREEMENT ON THE LARGE SCALE  
PATTERN...BUT HAVE LINGERING ISSUES WITH THE DETAILS. SURFACE HIGH  
AND LOW SYSTEM RESPONSES TO UNCERTAIN AND CHANGING STRENGTH/TIMING  
ISSUES OF EMBEDDED IMPULSES ALOFT CONTINUE TO WRECK HAVIC WITH  
ASSOCIATED SENSIBLE WEATHER FOCUS AT LOWER LEVELS OF THE  
ATMOSPHERE. THIS IS PRODUCING HIGHLY ERRATIC AND MAINLY UNRESOLVED  
RUN TO RUN MODEL LOCAL CONSISTENCY ISSUES...ESPECIALLY WITH  
RESPECT TO FLOW SEPARATION EXTENT AND PROGRESSION NEAR/OFF THE  
GULF COAST AND SERN US/FL. WHILE SOME INPUT FROM MODEL GUIDANCE  
CAN BE CONSIDERED...MAINLY FAVOR AN ENSEMBLE MEAN BASED FORECAST  
STRATEGY USING REASONABLY COMPATABLE AND CONSISTENT GEFS/ECMWF  
ENSEMBLE MEANS.  
 
   
..WEATHER HIGHLIGHTS
 
 
MORE WET FLOW IS ON TAP FOR THE PACIFIC NW WITH OCCASIONALLY HEAVY  
DAILY RAINS AND LOCALLY HEAVY ELEVATION SNOWS. 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. COOLER THAN  
AVERAGE TEMPERATURES ARE EXPECTED IN THE EASTERN US BEHIND THE  
INITIAL COLD FRONT WEDNESDAY. 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. RAIN IS ALSO QUITE POSSIBLE THROUGH FLORIDA  
AND THE COASTAL SOUTHEAST DEPENDING ON HOW THE SURFACE SYSTEMS  
EVOLVE. RECORD HIGH TEMPS ARE POSSIBLE IN THE SOUTHWEST WITH  
WIDESPREAD 80S AND SOME 90S...BUT COOLER 30S/40S IN THE UPPER  
MIDWEST/GREAT LAKES/NORTHEAST/MID-ATLANTIC.  
 
SCHICHTEL/FRACASSO  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page