759  
FXUS02 KWBC 180723  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
222 AM EST TUE JAN 18 2022  
 
VALID 12Z FRI JAN 21 2022 - 12Z TUE JAN 25 2022  
 
...HEAVY SNOW/ICE THREAT FOR THE SOUTHEAST/MID-ATLANTIC/NORTHEAST  
INTO FRIDAY/SATURDAY...  
   
..OVERVIEW
 
 
ARCTIC HIGH PRESSURE WILL PUSH A COLD FRONT THROUGH THE DEEP SOUTH  
AND EAST LATER THIS WEEK, LEADING TO MUCH BELOW NORMAL  
TEMPERATURES. MOIST AIR FED INTO THE SOUTHERN AND EASTERN  
PERIPHERY OF THE COLD AIRMASS IS INCREASINGLY LIKELY TO FUEL A  
HEAVY SNOW/ICE THREAT FROM THE SOUTHEAST TO THE MID-ATLANTIC INTO  
FRI. POTENTIAL COASTAL STORM DEVELOPMENT WOULD ENHANCE MID-ATLANIC  
TO NORTHEAST HEAVY SNOW POTENTIAL SAT. MEANWHILE, UPPER RIDGING  
BUILDS OFF/ALONG THE WEST COAST AS DIGGING INTERMOUTAIN  
WEST/ROCKIES SHORTWAVE ENERGY SPILLS SNOWS SOUTHWARD IN ROUTE TO  
PRODUCING A SOUTHWEST CLOSED LOW BY THE WEEKEND SLATED TO EJECT  
ACROSS THE U.S. SOUTHERN TIER EARLY NEXT WEEK.  
 
...GUIDANCE/PREDICTABILITY ASSESSMENT AND WEATHER  
HIGHLIGHTS/THREATS...  
 
GUIDANCE REMAINS IN DECENT AGREEMENT WITH THE LARGE SCALE MEAN  
FLOW OVER THE LOWER 48 HIGHLIGHTED BY AN UPPER RIDGE OFF/ALONG THE  
WEST COAST AND UPPER TROUGHING OVER THE CENTRAL AND EASTERN U.S..  
HOWEVER, THE MODELS HAVE RECENTLY BEEN HORRENDOUS WITH RUN TO RUN  
CONTINUITY WITH EMBEDDED SHORTWAVES THAT DIG THROUGH THE MEAN  
UPPER TROUGH POSITION. IN PARTICULAR, FORECAST SPREAD REMAINS A  
SIGNIFICANT TIMING AND AMPLITUDE ISSUE WITH A MAIN SHORTWAVE OVER  
THE EAST-CENTRAL TO EASTERN STATES FRI/SAT THAT PRODUCES MAJOR  
PLACEMENT DIFFERENCES WITH A POTENTIALLY IMPACTFUL COASTAL LOW  
GENESIS IN THE WESTERN ATLANTIC. THE 00 UTC ECMWF/UKMET TRENDED  
DEEPER AND LESS PROGRESSIVE WITH THE INLAND SHORTWAVE AND  
SUBSEQUENT COASTAL SYSTEM. THE 00 UTC GEFS ALSO TRENDED IN THAT  
DIRECTION. THE 00 UTC GFS WAS SLIGHTLY LESS PROGRESSIVE AND  
NORTHWARD SHIFTED. THE 00 UTC CANADIAN SEEMS IN LINE WITH ITS 12  
UTC RUN. IT DOES SEEM NOTEABLE THAT THE 00 UTC MODEL TRENDS NOW  
SEEM MORE FAVORABLE FOR SIGNIFICANT SYSTEM DEVELPMENT. HOWEVER, IT  
HAS BEEN AN ANNOYING RECENT TREND FOR 00 UTC GUIDANCE TO TREND  
SLOWER VS 12 UTC GUIDANCE, POSSIBLY DUE TO DIURNAL INITIALIZATION  
DATA SENSITIVITY. HOPEFULLY, MODEL SOLUTIONS WILL CONTINUE TO  
CONVERGE ON A MORE COMMON SOLUTION.  
 
ACCORDINGLY AND IN ANTICIPATION, THE EARLIER RELEASED WPC PRODUCT  
SUITE WAS PRIMARILY DERIVED FROM THE MOST AMPLIFIED ENSEMBLE MEAN  
SOLUTION, THE ECMWF ENSEMBLE MEAN. MANUAL ADJUSTMENTS WERE FURTHER  
APPLIED TO INCREASE SHORTWAVE AMPLITUDE SMOOTHED OUT BY THE MEAN  
AND TO MAINTAIN MAX WPC PRODUCT CONTINUITY.  
 
THERE IS POTENTIAL FOR HEAVY SNOW, SLEET, AND FREEZING RAIN  
PARTICULARLY FROM THE SOUTHERN APPALACHIANS AND  
CAROLINAS/MID-ATLANTIC INTO FRI, POTENTIALLY INTO THE NORTHEAST BY  
SAT. THE PATTERN WILL ALSO BE FAVORABLE FOR LAKE EFFECT SNOW GIVEN  
COLD AIR IN PLACE. INTO EARLY NEXT WEEK, GUIDANCE AGREES TO HOLD  
AN AMPLIFIED MEAN UPPER TROUGH OVER THE COOLED EAST-CENTRAL U.S.,  
ABLEIT WITH VARIATIONS WITH EMBEDDED SHORTWAVES SET TO DIG AND  
REINFORCED THE FEATURE UNDERNEATH A DEEP LOW CENTERED JUST EAST OF  
THE HUDSON BAY.  
 
MEANWHILE OUT WEST, MODELS GENRALLY AGREE TO DIG SHORTWAVE ENERGY  
SOUTHWARD ACROSS THE INTERMOUNTAIN WEST FRIDAY LEADING TO A  
SOUTHWEST U.S/NORTHERN MEXICO CLOSED LOW BY THE WEEKEND. LEAD FLOW  
RESPONSE IN ADVANCE OF EXPECTED SYSTEM EJECTION OUT ACROSS THE  
U.S. SOUTHERN TIER EARLY NEXT WEEK WOULD SUPPORT A MODEST SWATH OF  
OVERRUNNING PRECIPITATION WITHIN A COOLED AIRMASS FROM TEXAS  
EASTWARD ACROSS THE GULF COAST. THE BEST CHANCE FOR SNOW WILL  
FRI/SAT DOWN THROUGH THE ROCKIES AS THE SHORTWAVE IMPULSE MOVES  
THROUGH. OTHER THAN THAT, CONDITIONS SHOULD REMAIN MOSTLY DRY,  
WITH SLIGHTLY WARMER THAN NORMAL CONDITIONS FOR THE WEST COAST  
STATES UNDERNEATH THE RIDGE, AND ABOVE NORMAL TEMPERATURES ARE  
THEN EXPECTED FOR THE HIGH PLAINS EARLY NEXT WEEK.  
 
SCHICHTEL  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE 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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