952  
FXUS02 KWBC 010653  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
153 AM EST SAT JAN 1 2022  
 
VALID 12Z TUE JAN 4 2022 - 12Z SAT JAN 8 2022  
 
...MULTI-DAY COASTAL HEAVY RAIN AND MOUNTAIN FOCUSING HEAVY SNOW  
THREAT FOR THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA TO THE  
NORTHERN GREAT BASIN/ROCKIES NEXT WEEK...  
...ARCTIC BLAST TO FOCUS OVER THE NORTH-CENTRAL U.S.  
TUESDAY-FRIDAY WITH SNOW LIKELY FOR THE GREAT LAKES STATES THROUGH  
THE INTERIOR NORTHEAST...  
 
   
..WEATHER PATTERN OVERVIEW
 
 
A COLD CANADIAN SURFACE HIGH WILL BE IN PLACE ACROSS THE EASTERN  
U.S. ON TUESDAY IN THE WAKE OF THE STRONG COLD FRONT THAT WILL BE  
EXITING THE EAST COAST FOR THE BEGINNING OF THE WEEK. SURFACE  
CYCLOGENESIS ENSUES OVER THE NORTHERN PLAINS IN RESPONSE TO AN  
AMPLIFYING UPPER TROUGH, AND ANOTHER SURGE OF ARCTIC AIR BEHIND  
IT. A POTENTIALLY STRONG LOW PRESSURE SYSTEM IS ON THE HORIZON TO  
CLOSE OUT THE WEEK ACROSS THE EAST COAST, AND MULTIPLE  
DISTURBANCES ALSO TAKE AIM AT THE PACIFIC NORTHWEST WITH AN  
ATMOSPHERIC RIVER EVENT LIKELY FOR PORTIONS OF NORTHERN CALIFORNIA  
AND SOUTHERN OREGON.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE 00Z MODEL GUIDANCE SUITE APPEARS TO BE IN ABOVE AVERAGE  
AGREEMENT ON THE SYNOPTIC SCALE WITH MORE DIFFERENCES NOTED IN  
MESOSCALE FEATURES REGARDING THE LOW PRESSURE SYSTEMS EXPECTED TO  
AFFECT THE CONTINENTAL U.S. THROUGH THE MIDDLE OF THE WEEK. THE  
12Z UKMET STRAYED FROM THE MODEL CONSENSUS AS EARLY AS TUESDAY  
NIGHT AND EVEN MORE SO BY WEDNESDAY AND THURSDAY ACROSS THE GREAT  
LAKES REGION, BUT THE 00Z IS MORE IN LINE WITH THE ECMWF/CMC/GEFS  
MEAN. THE 00Z GFS IS A BIT SOUTH OF THE ENSEMBLE MEANS WITH THE  
LOW CROSSING THE GREAT LAKES WEDNESDAY WITH A SHARPER SHORTWAVE  
TROUGH AXIS. REGARDING THE NEXT SYSTEM, THE CMC/GFS ARE FAVORING  
A FASTER SOLUTION THAN THE ECMWF. THE GREATEST MODEL  
UNCERTAINTIES ARE EVIDENT OVER THE EASTERN PACIFIC AND WEST COAST  
REGION BY FRIDAY AND INTO SATURDAY WITH BOTH NORTHERN AND SOUTHERN  
STREAM SHORTWAVE ENERGY BREAKING DOWN THE WESTERN U.S. RIDGE BY  
THAT TIME.  
 
TAKING THESE FACTORS INTO ACCOUNT, THE WPC FORECAST WAS PRIMARILY  
BASED ON A CMC/ECMWF/GFS BLEND THROUGH EARLY THURSDAY, AND THEN  
ECMWF/GFS/SOME CMC WITH GRADUALLY INCREASING USE OF THE GEFS/ECENS  
FOR FRIDAY AND SATURDAY.  
   
..SENSIBLE WEATHER AND HAZARDS
 
 
HEAVY COASTAL RAIN AND HEAVY MOUNTAIN SNOW IS EXPECTED FROM  
NORTHERN CALIFORNIA TO WESTERN WASHINGTON FOR EARLY TO MIDDLE PART  
OF THE WEEK AS A STORM SYSTEM MOVES INLAND ACROSS THE PACIFIC  
NORTHWEST, LIKELY THE RESULT OF AN ATMOSPHERIC RIVER EVENT. THIS  
MOISTURE IS EXPECTED TO REACH THE CENTRAL AND NORTHERN ROCKIES  
WITH HEAVY SNOW, MAINLY ON WEDNESDAY AND THURSDAY. UNLIKE RECENT  
EVENTS, THIS STORM IS NOT CURRENTLY EXPECTED TO PRODUCE HEAVY  
PRECIPITATION FOR CENTRAL/SOUTHERN CALIFORNIA. THE SURFACE LOW  
OVER THE NORTH-CENTRAL U.S. FOR TUESDAY-WEDNESDAY WILL LIKELY HAVE  
A SWATH OF LIGHT TO MODERATE SNOW, AND LAKE ENHANCED SNOW ACROSS  
MUCH OF MICHIGAN WITH SOME BLOWING/DRIFTING SNOW AS WINDS INCREASE  
WITH THE ARCTIC AIRMASS MOVING INTO THE REGION. DEPENDING ON WHAT  
HAPPENS ALONG THE EAST COAST LATE IN THE WEEK, MODERATE TO LOCALLY  
HEAVY RAIN FOR THE SOUTHEAST U.S. AND SNOW FOR THE APPALACHIANS  
AND PORTIONS OF THE OHIO VALLEY CAN BE EXPECTED.  
 
IN THE TEMPERATURE DEPARTMENT, THERE WILL BE A RETURN TO  
SEASONABLY COLD CONDITIONS ACROSS MUCH OF THE DEEP SOUTH AND THE  
EAST COAST FOR EARLY IN THE WEEK AFTER DAYS OF WELL ABOVE AVERAGE  
TEMPERATURES AND HUMIDITY LEVELS. THERE IS LIKELY A BRIEF  
MODERATION ACROSS THE PLAINS AND MIDWEST STATES ON TUESDAY AHEAD  
OF THE NEXT ARCTIC FRONT, WHICH WILL HERALD A RETURN TO FRIGID  
CONDITIONS ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST BY  
WEDNESDAY AND BEYOND, WITH HIGHS RUNNING A GOOD 15-30 DEGREES  
BELOW SEASONAL AVERAGES IN MANY CASES. PORTIONS OF MONTANA MAY BE  
UP TO 40 DEGREES BELOW NORMAL BY WEDNESDAY! THIS WILL EQUATE TO  
SUBZERO HIGH TEMPERATURES ONCE AGAIN ACROSS PORTIONS OF NORTHERN  
MONTANA, NORTH DAKOTA, AND NORTHERN MINNESOTA, WITH A FEW RECORD  
LOWS POSSIBLE. WIND CHILLS WILL ALSO REACH HAZARDOUS LEVELS FOR  
THESE SAME AREAS, AND WIND CHILL RELATED WEATHER BULLETINS WILL  
LIKELY BE NEEDED FOR MUCH OF THE NORTH-CENTRAL U.S. AS THE ARCTIC  
AIRMASS SETTLES INTO THE REGION. THE GOOD NEWS IS THE SEVERITY OF  
THE COLD SHOULD MODERATE QUITE A BIT BY THE TIME THIS AIRMASS  
REACHES THE EAST COAST, BUT STILL 5-15 DEGREES BELOW AVERAGE BY  
THE END OF THE WEEK FOR MANY AREAS. OUT WEST, READINGS ARE LIKELY  
TO BE WITHIN 10 DEGREES EITHER SIDE OF AVERAGE FOR MOST AREAS NEXT  
WEEK WEST OF THE CONTINENTAL DIVIDE.  
 
HAMRICK  
 
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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