030  
FXUS02 KWBC 170604  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
103 AM EST THU JAN 17 2019  
 
VALID 12Z SUN JAN 20 2019 - 12Z THU JAN 24 2019  
 
...MAJOR WINTER STORM SHIFTS FROM GREAT LAKES/OHIO  
VALLEY/APPALACHIANS TO MID-ATLANTIC/NORTHEAST SUNDAY INTO MONDAY...  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM  
REASONABLY CLUSTERED 12 UTC ECMWF/GEFS/ECENS GUIDANCE. THIS HOLDS  
GOOD WPC CONTINUITY. HOWEVER, LATEST GFS/GEFS RUNS TRENDED MORE  
PROGRESSIVE WITH THE FLOW. A MAJOR LEAD WEEKEND WINTER STORM STILL  
OFFERS HIGH PREDICTABILITY, BUT THE TIMING/DETAILS OF AN UPSTREAM  
MAIN SOUTHERN STREAM SYSTEM NEXT WEEK IS MORE UNCERTAIN.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
DEEP GULF OF MEXICO AND ATLANTIC MOISTURE WILL LIFT OVER THE  
EASTERN U.S. SUNDAY. HEAVY PRECIPITATION FOCUSES AROUND A MAIN  
LOW/FRONTAL SYSTEM, OVERRUNNING ARCTIC AIR TO THE NORTH. HEAVY  
SNOWS SHIFT FROM THE GREAT LAKES/OHIO VALLEY AND APPALACHIANS  
THROUGH THE NORTHERN MID-ATLANTIC/NORTHEAST, EXITING MONDAY. SOME  
LOCATIONS COULD SEE BLIZZARD CONDITIONS IN THE TIGHT PRESSURE  
GRADIENT BETWEEN THE SURFACE LOW AND THE STRONG ARCTIC HIGH.  
MEANWHILE, LINGERING HEAVY WARM-SECTOR RAINS/STRONG CONVECTION  
MOVES THROUGH THE SOUTHEAST/MID-ATLANTIC SUNDAY, WITH A TRANSITION  
ZONE BETWEEN SNOW AND RAIN TO INCLUDE SIGNIFICANT SLEET AND  
FREEZING RAIN.  
 
MEANWHILE, PACIFIC STORM SYSTEMS WILL RELOAD WITH NEW FOCUS AS A  
HEAVY PRECIPITATION THREAT INTO THE PACIFIC NORTHWEST THIS  
WEEKEND. WINTRY WEATHER SPREADS/MODERATES INLAND ACROSS THE  
NORTH-CENTRAL GREAT BASIN/ROCKIES LATER IN THE HOLIDAY WEEKEND AND  
ACROSS THE FULL U.S. NORTHERN TIER NEXT WEEK. THERE IS A SIGNAL  
FOR INCREASED MID-UPPER LEVEL TROUGH AMPLITUDE/SEPARATION OVER THE  
SOUTH-CENTRAL U.S., BUT THERE IS MORE UNCERTAINTY WITH THE  
SPECIFICS OF THIS FLOW AND ASSOCIATED SURFACE SYSTEM RESPONSE.  
HOWEVER, MOST GUIDANCE SUPPORTS AN INCREASING LEAD GULF THEN  
ATLANTIC MOISTURE INFLOW AND PRECIPITATION PATTERN NEXT TUE-THU  
THAT WILL INCLUDE THE THREAT FOR A WIDESPREAD SWATH OF SNOW/ICE IN  
THE COOLED NORTHERN PERIPHERY OF THE LARGE PRECIPITATION SHIELD.  
 
UPSTREAM, SHARP SHORTWAVE DIGGING NEXT WED/THU OVER THE WEST TO  
THE LEE OF A BUILDING/AMPLIFIED EASTERN PACIFIC UPPER RIDGE MAY  
PROVIDE COOLING AND RISK OF A WINTRY WEATHER SWATH FROM THE  
NORTHWEST TO THE NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES/PLAINS.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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