448  
FXUS02 KWBC 141600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST SUN JAN 14 2018  
 
VALID 12Z WED JAN 17 2018 - 12Z SUN JAN 21 2018  
 
 
...WET AND UNSETTLED NWRN US FLOW TO SPREAD DOWN ACROSS THE WEST  
THEN INTO THE CENTRAL US...  
 
   
..PATTERN OVERVIEW AND WEATHER HIGHLIGHTS/THREATS
 
 
POTENT MID-UPPER LEVEL TROUGHING WILL SUPPORT A SERIES OF DEEP ERN  
PACIFIC STORMS THIS WEEK. LEAD SHORTWAVE ENERGIES/HEIGHT FALLS  
WORKING DOWNSTREAM FROM THE NWRN US TO THE ROCKIES THROUGH MIDWEEK  
AND ASSOCIATED DYNAMICS AND MOISTURE WILL FURTHER ENHANCE WET AND  
UNSETTLED CONDITIONS ACROSS THE REGION. THIS IS BE HIGHLIGHTED BY  
LINGERING HEAVY COASTAL RAIN AND TERRAIN ENHANCED ELEVATION SNOWS  
INLAND. THERE IS A LIKELY THREAT FOR MUCH STRONGER AND LARGER  
SCALE PACIFIC TROUGHING/HEIGHT FALLS TO THEN DIG IN ERNEST FARTHER  
SOUTHEASTWARD INTO AND ACROSS MUCH OF THE WEST TO THE ROCKIES  
THU-SAT. THIS WILL PRODUCE WIDESPREAD UNSETTLED  
WEATHER/PRECIPITATION AND POST SYSTEM COOLING. AMPLE HEIGHT FALLS  
REACHING THE CENTRAL US NEXT WEEKEND MAY SPAWN CYCLOGENESIS AND AN  
INCREASINGLY FAVORABLE RETURN FLOW AND EMERGING CONVECTIVE PATTERN  
UP ACROSS THE EAST-CENTRAL US.  
 
THE MIDWEEK DOWNSTREAM PATTERN FEATURES AN AMPLIFIED ERN US TROUGH  
ALOFT AND AN EXPANSIVE ARCTIC SURFACE HIGH SETTLING WELL SOUTH  
ACROSS THE CENTRAL AND ERN US DUG TO THE LEE OF A ROCKIES SHUNTED  
MID-UPPER LEVEL RIDGE. ENERGY LIFTING ON THE ERN PERIPHERY OF THE  
MID-UPPER LEVEL TROUGH WILL HELP DEVELOP SEVERAL COASTAL  
LOWS...BUT LATEST GUIDANCE TRENDS THAT SHOW MORE OF A POSITIVE  
TILT TO THE TROUGH MIDWEEK LESSENS THE THREAT THIS PERIOD FOR  
HEAVY SNOW EXCEPT PERHAPS FOR SERN NEW ENGLAND. THE UPSTREAM RIDGE  
IS MEANWHILE FORECAST TO BREAK DOWN MID-LATE WEEK AS SEVERAL THE  
POTENT PACIFIC SYSTEMS MARCH INLAND. THE CENTRAL TO ERN US SURFACE  
HIGH WILL GRADUALLY WEAKEN AND SHIFT EASTWARD AND TEMPERATURES  
ACROSS THIS REGION WILL STEADILY MODERATE. THIS OCCURS AS THE  
PATTERN BECOMES LESS AMPLIFIED DOWNSTREAM OF THE WRN US AS THE ERN  
US TROUGH LIFTS OUT ACROSS THE ATLANTIC AND BROAD RIDGING ALOFT  
WORKS OVER THE CENTRAL THEN ERN US.  
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
MEDIUM RANGE MODEL AND ENSEMBLE FORECAST SPREAD AND UNCERTAINTY  
REMAIN LESS THAN NORMAL. THE 06 UTC GFS/GEFS AND 00 UTC  
ECMWF/ECMWF ENSEMBLE MEAN SEEM FAIRLY WELL CLUSTERED INTO NEXT  
WEEKEND AND THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED  
FROM A COMPOSITE BLEND OF THESE GUIDANCE PIECES.  
 
SCHICHTEL  
 

 
 
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