067  
FXUS02 KWBC 271557  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1057 AM EST SUN JAN 27 2019  
 
VALID 12Z WED JAN 30 2019 - 12Z SUN FEB 03 2019  
 
...ARCTIC AIRMASS EXPECTED TO BRING RECORD BREAKING TEMPERATURES  
AND DANGEROUSLY COLD WIND CHILLS TO THE NORTH-CENTRAL U.S...  
 
   
..OVERVIEW
 
 
AN AMPLIFIED FLOW REGIME IS EXPECTED TO PERSIST ACROSS THE CONUS  
THROUGH THE MEDIUM RANGE, BUT WITH SOME CHANGES TO THE STRUCTURE  
BY NEXT WEEKEND. A DEEP UPPER LOW EXPECTED TO BE CENTERED ACROSS  
THE GREAT LAKES ON DAY 3 (WED) WILL SUPPORT RAPID PROGRESSION OF A  
FEW SHORTWAVES FROM THE NORTHERN PLAINS TO THE NORTHEAST. ONE  
SHORTWAVE AND DEEPENING LOW PRESSURE SYSTEM WILL EXIT THE  
NORTHEAST ON WED WHILE A SECONDARY WAVE/FRONT CROSSES THE OHIO  
VALLEY QUICKLY MOVING TOWARD THE EASTERN SEABOARD. FARTHER WEST, A  
COMPACT BUT ENERGETIC PACIFIC UPPER LOW APPEARS LIKELY TO REACH  
THE WEST COAST ON WED AND THEN DIG INTO THE GREAT BASIN/SOUTHWEST  
BY THU-FRI, REACHING THE SOUTHERN PLAINS AS AN OPEN WAVE BY THE  
WEEKEND, WHEN ANOTHER VIGOROUS PACIFIC TROUGH REACHES THE WEST  
COAST. THE LARGE UPPER LOW SHOULD BEGIN TO LIFT OUT BY THU-FRI,  
OPENING MUCH OF THE CONUS UP TO PACIFIC SHORTWAVE ENERGY, WITH  
PERIODIC AMPLIFICATION OF PROGRESSIVE NORTHERN STREAM ENERGY,  
LIKELY BRINGING ANOTHER FRONTAL SYSTEM INTO THE CENTRAL U.S. BY  
NEXT WEEKEND.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS CONSENSUS HAS IMPROVED OVER RECENT DAYS WITH A CONSISTENT  
PICTURE OF THE DEEP VORTEX CROSSING THE GREAT LAKES BY MID TO LATE  
WEEK EVIDENT ACROSS THE GUIDANCE. ADDITIONALLY, SOLUTIONS SEEM TO  
HAVE SETTLED TOWARD FAVORING THE COMPACT UPPER LOW REACHING THE  
WEST COAST ON WED AND DIGGING INTO THE SOUTHWEST AFTER THAT. A  
BLEND OF THE 00Z ECMWF/CMC AND 06Z GFS REPRESENTED THIS CONSENSUS  
WELL, AND SERVED AS A FORECAST STARTING POINT THROUGH MUCH OF THE  
FORECAST PERIOD DURING DAYS 3-5 (WED-FRI). SIGNIFICANT MODEL  
DIFFERENCES BEGIN TO EMERGE DURING DAYS 6-7 (SAT-SUN). TIMING  
DIFFERENCES DEVELOP WITH THE NEXT AMPLIFIED WAVE REACHING THE WEST  
COAST, WITH THE GFS MUCH FASTER TO BRING THE TROUGH INLAND  
RELATIVE TO THE ECMWF/CMC. AT THIS TIME, WPC FAVORED THE SLOWER  
SOLUTION HERE. IN THE NORTHERN STREAM, A NUMBER OF SOLUTIONS  
SUGGEST AMPLIFICATION OF A SHORTWAVE ACROSS THE CANADIAN PRAIRIES  
NEXT WEEKEND, WITH AN ASSOCIATED SURFACE LOW PASSING ALONG THE  
U.S./CANADA BORDER TOWARD THE GREAT LAKES. MODEL CONSENSUS WAS A  
BIT BETTER HERE AND ENSEMBLE MEMBERS SHOWED REASONABLE CLUSTERING  
WITH RESPECT TO THE SURFACE LOW TRACK, EVEN WITH SOME  
TIMING/INTENSITY VARIABILITY EVIDENT IN DETERMINISTIC SOLUTIONS.  
GIVEN THESE CONSIDERATIONS, THE FORECAST DURING DAYS 6-7 CONTINUED  
TO EMPHASIZE THE ECMWF/CMC BUT SHIFTED CONSIDERABLY MORE EMPHASIS  
TOWARD THE ENSEMBLE MEANS (ECENS/GEFS), WITH MAJORITY WEIGHT PLACE  
ON THE MEANS BY DAY 7.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE DEEPENING LOW PRESSURE SYSTEM EXITING NEW ENGLAND ON WED COULD  
PRODUCE HEAVY SNOW FOR PORTIONS OF NORTHERN NEW ENGLAND. A  
SECONDARY COLD FRONT CROSSING THE CENTRAL/EASTERN U.S. IN THE WAKE  
OF THIS LEADING SYSTEM WILL USHER A FRIGID ARCTIC AIR MASS INTO  
MUCH OF THE CENTRAL/EASTERN U.S. TEMPERATURES ACROSS A LARGE AREA  
FROM THE NORTHERN PLAINS AND MIDWEST TO THE OHIO VALLEY ARE  
FORECAST TO BE 30-40 DEG F BELOW AVERAGE ON WED. HIGH TEMPERATURES  
WILL REMAIN WELL BELOW ZERO ACROSS MOST OF THE MIDWEST ON WED,  
WITH LOW TEMPERATURES SURPASSING -30 DEG FOR SOME AREAS ACROSS THE  
NORTHERN PLAINS/UPPER MIDWEST. A NUMBER OF RECORD LOWS AND RECORD  
LOW MAX TEMPERATURES WILL LIKELY BE BROKEN BOTH WED AND THU. A  
TIGHT PRESSURE GRADIENT BETWEEN THE ARCTIC SURFACE HIGH AND THE  
DEEPENING LOW PRESSURE SYSTEM ACROSS NEW ENGLAND ON WED INTO THU  
WILL RESULT IN POTENTIALLY GUSTY WINDS FOR MUCH OF THE  
MIDWEST/GREAT LAKES, WITH DANGEROUS WIND CHILLS SURPASSING -40 DEG  
F FOR MANY AREAS - WHICH CAN PRODUCE FROSTBITE ON EXPOSED SKIN IN  
A MATTER OF MINUTES. THE AIR MASS WILL MODERATE SOME AS IT MOVES  
EAST BY THU, WITH MAX/MIN TEMPS FROM 20-30 DEG F BELOW AVERAGE  
SPREADING INTO THE MID-ATLANTIC/NORTHEAST. A NUMBER OF TEMPERATURE  
RECORDS MAY ALSO BE IN JEOPARDY ON THU ACROSS THESE AREAS.  
TEMPERATURE WILL QUICKLY MODERATE BY LATE WEEK INTO NEXT WEEKEND  
AS THE UPPER LOW QUICKLY LIFTS NORTHEASTWARD INTO CANADA, ALLOWING  
TEMPERATURES TO GRADUALLY RETURN CLOSER TO SEASONAL NORMS.  
 
ALONG THE WEST COAST, THE ARRIVAL OF A COUPLE PACIFIC SYSTEMS WILL  
KEEP PRECIPITATION (RAIN AND MOUNTAIN SNOW) FAIRLY WIDESPREAD,  
STARTING IN THE NORTHWEST AND GRADUALLY SHIFTING SOUTH ACROSS  
CALIFORNIA. RAIN/SNOW WILL GRADUALLY SPREAD INTO THE GREAT  
BASIN/ROCKIES BY NEXT WEEKEND AS THE SECOND/LARGER UPPER TROUGH  
MOVES INLAND.  
 
RYAN  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION AND WINTER WEATHER OUTLOOK  
PROBABILITIES 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  
 

 
 
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