292  
FXUS02 KWBC 071601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST WED FEB 07 2018  
 
VALID 12Z SAT FEB 10 2018 - 12Z WED FEB 14 2018  
   
..OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
MODEL GUIDANCE THIS MORNING AGREES THAT THE LARGE-SCALE TROUGHING  
OVER THE EASTERN U.S. WILL GRADUALLY SHIFT TOWARD THE WESTERN  
U.S. OVER THE COURSE OF THE NEXT 7 DAYS. THE GFS...WHICH HAS  
BEGUN TO ADVERTISE THE FORMATION OF A CUT-OFF LOW OVER THE DESERT  
SOUTHWEST DURING THE WEEKEND...HAS BACKED OFF ON THIS IDEA FOR THE  
LAST COUPLE OF RUNS MORE IN LINE WITH THE ECMWF. A SIMILAR  
SITUATION IS NOTED BY DAY 6 AND 7...TUE AND WED OF NEXT WEEK. THE  
GFS IS STILL YET TO SETTLE WITH A STABLE SOLUTION REGARDING THIS  
FEATURE WHILE THE LAST COUPLE OF RUNS OF THE ECMWF HAS BEEN  
TRENDING TOWARD A MORE AMPLIFIED SHORTWAVE TROUGH DIGGING FURTHER  
TO THE SOUTH AND FASTER INTO THE DESERT SOUTHWEST BY DAY 7...AS  
THE UPPER-LEVEL FLOW BECOMES MORE SOUTHWESTERLY OVER THE EASTERN  
U.S. THEIR ENSEMBLE MEANS LOOK QUITE AGREEABLE HOWEVER.  
THEREFORE...THE WPC MEDIUM-RANGE PACKAGE USES A 50-50 BLEND OF THE  
06Z GFS WITH 00Z ECMWF SOLUTIONS...TRENDING TOWARD THEIR  
RESPECTIVE ENSEMBLE MEANS BY DAY 7.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
ACROSS THE WEST EXPECT AN AREA OF SNOW TO DESCEND ALONG THE  
NORTHERN-CENTRAL ROCKIES EARLY IN THE WEEKEND. TRAILING PACIFIC  
SHORTWAVES ALOFT SHOULD BRING A COUPLE PERIODS OF PRECIP FROM THE  
PACIFIC NORTHWEST EASTWARD/SOUTHEASTWARD THROUGH THE ROCKIES. A  
MAJORITY OF THIS ACTIVITY SHOULD BE OF LIGHT-MODERATE INTENSITY  
AND IN THE FORM OF SNOW ASIDE FROM COASTAL/LOW ELEVATION RAIN IN  
THE NORTHWEST. EXPECT TEMPS TO BE NEAR TO ABOVE NORMAL AT MOST  
LOCATIONS WITH WARMEST ANOMALIES POSSIBLE NEXT WED AS HEIGHTS  
ALOFT BRIEFLY RISE BETWEEN SHORTWAVES.  
 
FARTHER EAST THE OVERALL PATTERN WILL PROMOTE A WET PERIOD FOR THE  
SOUTHEASTERN THIRD TO HALF OF THE LOWER 48. THE GREATEST COVERAGE  
OF MODERATE TO HEAVY RAINFALL SHOULD BE DURING THE WEEKEND AS  
GULF/ATLANTIC INFLOW INTERACTS WITH ONE OR TWO WAVY FRONTS OVER  
THE EASTERN STATES. HIGHEST TOTALS ARE MOST LIKELY TO BE WITHIN  
AN AREA FROM THE GULF COAST INTO PARTS OF THE MID ATLANTIC. THERE  
MAY BE A BRIEF DRYING TREND AFTER THE WEEKEND EVENT BUT  
PERSISTENCE OF SOUTHWESTERLY FLOW ALOFT THROUGH THE MIDDLE OF NEXT  
WEEK AND POSSIBLE APPROACH OF ANOTHER FRONT WILL LIKELY PROMOTE  
ADDITIONAL WAVES OF MOISTURE/RAINFALL OF VARYING INTENSITY WITHIN  
THE SAME GENERAL AREA. TO THE NORTHWEST OF THE RAINFALL AREA, THE  
BEST POTENTIAL FOR ONE OR MORE PERIODS OF SNOW EXTENDS FROM THE  
CENTRAL PLAINS THROUGH THE GREAT LAKES AND NORTHERN NEW ENGLAND.  
COLD TEMPS OVER THE PLAINS DURING THE WEEKEND, INCLUDING SOME  
HIGHS 20-30F BELOW NORMAL ON SAT, WILL MODERATE CONSIDERABLY  
THEREAFTER. THE WET PATTERN OVER THE SOUTH AND EAST SHOULD LEAD  
TO ABOVE AVERAGE TEMPS. EXPECT MINS TO BE PARTICULARLY WARM WITH  
ANOMALIES OF PLUS 10-20F MOST DAYS AND POSSIBLY AS HIGH AS PLUS  
20-30F AT SOME LOCATIONS ON SUN.  
 
KONG/RAUSCH  
 

 
 
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