260  
FXUS02 KWBC 110623  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
122 AM EST SUN FEB 11 2018  
 
VALID 12Z WED FEB 14 2018 - 12Z SUN FEB 18 2018  
   
..WIDESPREAD PRECIPITATION EXPECTED IN THE SOUTHWEST WED-FRI
 
 
   
..OVERVIEW AND GUIDANCE PREFERENCES
 
 
A CLOSED LOW INITIALLY OFF THE COAST OF SOUTHERN CALIFORNIA ON  
WEDNESDAY WILL MOVE EASTWARD THROUGH THE SOUTHWEST BRINGING  
WIDESPREAD RAIN AND HIGH ELEVATION SNOW TO THE REGION. BROAD  
CYCLONIC FLOW OVER MOST OF THE REST OF THE LOWER 48 WILL BRING IN  
COLDER AIR TO MONTANA AND THE HIGH PLAINS WHILE MOST OF THE  
COUNTRY SEES ABOVE AVERAGE TEMPERATURES. LATEST GFS/ECMWF  
SOLUTIONS WERE IN GENERAL AGREEMENT WITH THEIR ENSEMBLE MEANS  
THROUGH THE PERIOD WITH THE OVERALL FLOW PATTERN. THERE WERE  
SIGNIFICANT DIFFERENCES IN THE PACIFIC NORTHWEST INTO IDAHO WITH  
THE STRENGTH OF HEIGHT FALLS THAT MAY INFLUENCE HOW QUICKLY THE  
UPPER LOW OFF CALIFORNIA WOULD PUSH EASTWARD. ENSEMBLES HAVE  
TRENDED AWAY FROM A BETTER CONSENSUS 24 HOURS AGO, BUT A MIDWAY  
SOLUTION WAS STILL PREFERRED GIVEN THE RECENT CHANGE. MAY NEED A  
COUPLE MORE CYCLES TO SHAKE OUT THE UPSTREAM PACIFIC FLOW WHICH  
HAS BEEN THE CULPRIT OF THE UNCERTAINTY (AS IS TYPICAL).  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PRECIPITATION WILL EXPAND INTO AND THROUGH THE SOUTHWEST AS THE  
UPPER LOW NUDGES EASTWARD WED-FRI. CONTINUED SOUTHWESTERLY FLOW  
ALOFT WILL HELP RAISE PW VALUES TO +2 TO +4 STANDARD DEVIATIONS  
WHICH SUGGESTS SOME LOCALLY HEAVY RAINFALL, DEPENDING ON OTHER  
FACTORS OF COURSE. AMOUNTS MAY VARY FROM A TENTH OR TWO IN THE  
LOWER DESERTS AROUND THE COLORADO RIVER TO ABOUT A HALF INCH NEAR  
OR JUST N/NE OF PHOENIX/TUCSON TO PERHAPS AN INCH OR MORE IN THE  
MOUNTAINS. TEMPERATURES WILL GENERALLY BE ABOVE AVERAGE OVERNIGHT  
BUT NEAR TO BELOW AVERAGE DURING THE DAY GIVEN CLOUD COVER AND  
PRECIPITATION.  
 
TO THE NORTH, GENERALLY BELOW AVERAGE TEMPERATURES ARE EXPECTED  
FROM MONTANA AND THE HIGH PLAINS INTO THE UPPER MIDWEST AS A  
COUPLE WEAKER SHORTWAVES GET SWEPT ALONG THE QUASI-ZONAL  
UPPER-LEVEL FLOW FORECAST TO PERSIST OVER THE CENTRAL/EASTERN US.  
ABOVE AVERAGE TEMPERATURES ARE EXPECTED ACROSS MUCH OF THE EASTERN  
THIRD OF THE CONUS AS UPPER RIDGING MEANDERS ACROSS FLORIDA. 70S  
MAY REACH AS FAR NORTH AS CENTRAL VIRGINIA ON THURSDAY WITH 60S  
PAST THE MASON-DIXON LINE. A COLD FRONT WILL KNOCK DOWN  
TEMPERATURES LATER IN THE WEEK, ESPECIALLY UP NORTH ALONG THE  
US/CANADIAN BORDER, BUT THE SOUTHEAST WILL REMAIN MILD FOR  
MID-FEBRUARY. PRECIPITATION BY NEXT WEEKEND WILL EXPAND ACROSS THE  
LOWER MISSISSIPPI VALLEY INTO THE OHIO/TENNESSEE VALLEYS WITH SOME  
WINTRY PRECIPITATION ON ITS NORTH SIDE.  
 
FRACASSO  
 

 
 
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