782  
FXUS02 KWBC 131618  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1118 AM EST SAT JAN 13 2018  
 
VALID 12Z TUE JAN 16 2018 - 12Z SAT JAN 20 2018  
 
...WINTER COASTAL STORM THREAT FOR THE ERN MID-ATLANTIC AND  
ESPECIALLY NEW ENGLAND THIS WEEK...  
...EARLY-MIDWEEK WET/UNSETTLED FLOW INTO THE NWRN U.S. SPREADS  
DOWN ACROSS THE WEST LATER WEEK...  
   
..PATTERN OVERVIEW
 
 
MID-UPPER LEVEL TROUGHING WILL LEAD TO DEVELOPMENT OF SEVERAL DEEP  
STORMS INTO THE ERN PACIFIC AND INLAND WORKING SHORTWAVE  
ENERGIES/HEIGHT FALLS ACROSS THE NWRN US TO THE ROCKIES  
EARLY-MIDWEEK AND ASSOCIATED DYNAMICS AND MOISTURE WILL FURTHER  
ENHANCE WET AND UNSETTLED CONDITIONS ACROSS THE REGION. THIS IS BE  
HIGHLIGHTED BY HEAVY COASTAL RAINS AND TERRAIN ENHANCED INLAND  
ELEVATION SNOWS.  
MUCH STRONGER AND LARGER SCALE PACIFIC TROUGH/HEIGHT FALLS SLAM  
INTO THE WEST THU-NEXT SAT THAT SHOULD LEAD TO MORE  
UNSETTLED/WIDESPREAD PRECIPITATION POTENTIAL AND POST SYSTEM  
COOLING.  
 
THE DOWNSTREAM PATTERN EARLY-MIDWEEK WILL FEATURE A HIGHLY  
AMPLIFIED E-CENTRAL U.S. TROUGH ALOFT AND AN EXPANSIVE ARCTIC  
SURFACE HIGH SETTLING WELL SOUTH ACROSS THE CENTRAL AND ERN  
US...DUG TO THE LEE OF A SHARP INTERMOUNTAIN WEST/ROCKIES  
MID-UPPER LEVEL RIDGE. AMPLE ENERGY IN ADVANCE OF THE MID-UPPER  
LEVEL TROUGH WILL HELP DEVELOP SEVERAL COASTAL LOWS THAT HAVE  
POTENTIAL TO PRODUCE HEAVY SNOW FROM THE ERN MID-ATLANTIC AND  
ESPECIALLY NEW ENGLAND. THE UPSTREAM RIDGE IS FORECAST TO BREAK  
DOWN MID-LATE WEEK AS SEVERAL PACIFIC SHORTWAVES PUNCH INLAND. THE  
SURFACE HIGH WILL STEADILY MODERATE AS THE PATTERN BECOMES LESS  
AMPLIFIED TO CLOSE OUT THE WEEK AS THE ERN TROUGH LIFTS OUT ACROSS  
THE ATLANTIC...RIDGING ALOFT WORKS OVER THE N-CENTRAL US...AND SRN  
STREAM SHORTWAVE TROUGHING MOVES TO THE SRN/SERN US. GUIDANCE MAY  
BE UNDERDOING RAINFALL POTENTIAL FOR THIS SYSTEM.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
MEDIUM RANGE MODEL AND ENSEMBLE FORECAST SPREAD AND UNCERTAINTY  
SEEM LESS THAN NORMAL. OVERALL... THE 06 UTC GFS/GEFS AND 00 UTC  
ECMWF/ECMWF ENSEMBLE MEAN SEEM FAIRLY WELL CLUSTERED FOR THE MOST  
PART THIS WEEK. THAT SAID...PERHAPS THE BIGGEST DIFFERENCE IS WITH  
RESPECT TO THE PROXIMITY AND ENHANCED THREAT POTENTIAL FOR THE  
NERN US. THE CLOSER TRACK TO THE COAST OF THE ECMWF AND ECMWF  
ENSEMBLES OFFERS BETTER RUN TO RUN CONTINUITY AND SEEM A BIT MORE  
LIKELY GIVEN THE AMPLITUDE OF THE UPSTREAM RIDGE LEADING INTO  
DEVELOPMENT. THE WPC MEDIUM RANGE PRODUCT SUITE WAS ACCORDINGLY  
PRIMARILY DERIVED FROM A BLEND OF THESE GUIDANCE PIECES...BUT THE  
ECMWF AND ECMWF ENSEMBLES WERE MORE HEAVILY WEIGHTED.  
 
SCHICHTEL  
 

 
 
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