970  
FXUS02 KWBC 120459  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1159 PM EST SUN FEB 11 2018  
 
VALID 12Z THU FEB 15 2018 - 12Z MON FEB 19 2018  
   
..OVERVIEW
 
 
UPPER PATTERN WILL FEATURE RELOADING WESTERN CONUS TROUGHING AND A  
SLOWLY MEANDERING UPPER HIGH CENTERED NEAR FLORIDA. THIS WILL TAKE  
A LEAD SYSTEM THROUGH THE EAST THU-FRI AS A PACIFIC FRONT MOVES  
INTO BAJA CALIFORNIA. NEXT SHORTWAVE DIVING SOUTHEASTWARD OUT OF  
THE GULF OF ALASKA WILL DROP A COLD FRONT THROUGH THE PACIFIC  
NORTHWEST THIS WEEKEND AND THROUGH CALIFORNIA AND THE  
INTERMOUNTAIN WEST SUN/MON AS THE ARCTIC FRONT PUSHES THROUGH THE  
HIGH PLAINS.  
   
..GUIDANCE PREFERENCES
 
 
TREND HAS BEEN TOWARD A QUICKER EJECTION OF THE BRIEFLY CLOSED LOW  
OFF CALIFORNIA AT THE END OF THE SHORT TERM INTO THE START OF THE  
MEDIUM RANGE (12Z THU) OWING TO A STRONGER SHORTWAVE THROUGH THE  
PACIFIC NORTHWEST ALLOWING IT TO BE DRAWN EASTWARD. ECMWF  
ENSEMBLES WERE QUICKER TO PICK UP ON THAT CHANGE THAN THE GEFS  
MEMBERS, BUT LATEST ENSEMBLES WERE CLOSE ENOUGH THAT A BLEND OF  
THE RECENT GUIDANCE SUFFICED TO START. BY THE WEEKEND INTO NEXT  
MONDAY, GFS/ECMWF AND THEIR ENSEMBLE MEANS OFFERED A REASONABLE  
CLUSTER WITH THE NEXT SHORTWAVE DIVING SOUTHWARD ALONG THE WEST  
COAST WHILE THE EAST REMAINS IN WEST TO SOUTHWEST FLOW ALOFT ATOP  
THE UPPER HIGH.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PRECIPITATION WILL STREAM OUT OF THE SOUTHWEST AND ACROSS THE  
MID-MISSISSIPPI AND OHIO VALLEYS LATER THIS WEEK, GUIDED BY THE  
UPPER FLOW. MODELS AND ENSEMBLES HAVE INCREASED THE PRECIPITATION  
AMOUNTS ALONG I-64/70 FROM SOUTHERN MO TO WV AS IT GETS SQUEEZED  
BETWEEN THE HIGH TO THE SOUTH AND THE LOWER HEIGHTS TO THE NORTH.  
MILD/WARM TEMPERATURES AHEAD OF AND SOUTH OF THE FRONT (60S-70S)  
WILL TRANSITION TO 30S/40S TO THE NORTH (WITH SOME WINTRY  
PRECIPITATION). NEXT SYSTEM IN THE WEST WILL BRING IN COLDER AIR  
TO AREAS WEST OF THE DIVIDE INTO THE GREAT BASIN WITH LOWERING  
SNOW LEVELS.  
 
FRACASSO  
 

 
 
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