267  
FXUS02 KWBC 260659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 AM EST SAT JAN 26 2019  
 
VALID 12Z TUE JAN 29 2019 - 12Z SAT FEB 2 2019  
 
***EXTREMELY COLD WEATHER EXPECTED ACROSS THE NORTH-CENTRAL U.S.  
NEXT WEEK***  
 
   
..OVERVIEW
 
 
THE OVERALL FLOW PATTERN ACROSS THE CONTINENTAL U.S. AND CANADA  
WILL REMAIN HIGHLY AMPLIFIED GOING THROUGH THURSDAY WITH A LARGE  
SCALE RIDGE SITUATED JUST OFF THE WEST COAST AND A PRONOUNCED  
UPPER LEVEL TROUGH ENCOMPASSING MUCH OF THE CENTRAL AND EASTERN  
U.S. A LARGE AND COLD UPPER LOW, WHICH IS BASICALLY A LOBE OF THE  
POLAR VORTEX, WILL REINFORCE THE TROUGH THROUGH THURSDAY, AND  
AFTER THIS FEATURE LIFTS OUT ACROSS SOUTHEAST CANADA, THE PATTERN  
SHOULD NOT BE QUITE AS AMPLIFIED WITH THE WEST COAST RIDGE MOVING  
INLAND AND A BROAD TROUGH BECOMING ESTABLISHED OVER THE EASTERN  
PACIFIC.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
A CLIPPER SYSTEM CROSSING THE GREAT LAKES REGION WILL BE MOST  
SIGNIFICANT LOW PRESSURE SYSTEM DURING THE BEGINNING OF THE MEDIUM  
RANGE PERIOD, WITH MODELS IN GOOD AGREEMENT REGARDING A POWERFUL  
COLD FRONT AND PERHAPS A SECONDARY LOW FORMING ALONG THE BOUNDARY  
NEAR THE MID-ATLANTIC REGION. THERE WAS GOOD DETERMINISTIC MODEL  
AGREEMENT ON TUESDAY AND CONTINUING INTO WEDNESDAY, WITH THE MAIN  
DIFFERENCE BEING THAT THE GFS/GEFS MEAN ARE FASTER WITH THE  
PROGRESSION OF THE VORTEX ACROSS THE GREAT LAKES REGION, AND THE  
ECMWF/CMC/EC MEAN SLOWER.  
 
THE EVENTUAL DECAY OF THE WEST COAST UPPER LEVEL RIDGE IS WHERE  
GREATER MODEL DIFFERENCES EMERGE AS A COMPACT UPPER LOW TRIES TO  
UNDERCUT THE RIDGE AS SUGGESTED BY THE ECMWF AND GFS, BUT ABSENT  
ON THE CMC. THE ECMWF BECOMES STRONGER WITH THE RIDGE OVER THE  
INTERMOUNTAIN WEST COMPARED TO A BROADER GFS SOLUTION. BY THE END  
OF THE FORECAST PERIOD ON SATURDAY, THERE IS A STRONG MODEL SIGNAL  
FOR AN ORGANIZED LOW PRESSURE SYSTEM OFF THE COAST OF CALIFORNIA,  
WITH THE GFS NEAR THE NORTHERN CALIFORNIA COAST AND THE ECMWF MUCH  
FARTHER TO THE WEST. THE EC MEAN IS CLOSE TO THE MODEL CONSENSUS  
AND PROVIDES A GOOD STARTING POINT FOR THE LOW POSITION.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE STRONG ALBERTA CLIPPER SYSTEM IS EXPECTED TO REACH THE EASTERN  
GREAT LAKES BY THE BEGINNING OF THE FORECAST PERIOD TUESDAY  
MORNING, ALONG WITH A VERY STRONG ARCTIC FRONT. THIS WILL BRING A  
BAND OF LIGHT TO MODERATE SNOW FROM THE CENTRAL APPALACHIANS TO  
THE NORTHEAST U.S., AND RAIN CHANGING TO SNOW FOR MUCH OF THE  
MID-ATLANTIC REGION AND COASTAL NEW ENGLAND. AFTER THIS SYSTEM  
DEPARTS, MORE LAKE EFFECT SNOW IS LIKELY DOWNWIND OF THE GREAT  
LAKES WITH INTENSE COLD AIR ADVECTION BEHIND THE LOW.  
 
ANOTHER THING THAT WILL BE MAKING WEATHER HEADLINES BY THE MIDDLE  
OF THE UPCOMING WEEK WILL BE AN IMPRESSIVE ROUND OF FRIGID  
TEMPERATURES AS A LOBE OF THE POLAR VORTEX SINKS SOUTHEASTWARD  
ACROSS CANADA AND THEN REACHES THE NORTHERN GREAT LAKES.  
TEMPERATURES ARE EXPECTED TO PLUMMET WELL BELOW ZERO ACROSS THE  
UPPER MIDWEST, MOST OF THE GREAT LAKES REGION, AND THE NORTHERN  
OHIO VALLEY BY WEDNESDAY AND THURSDAY. ANOMALIES ON THE ORDER OF  
25 TO 35 DEGREES BELOW NORMAL ARE A GOOD POSSIBILITY FOR THESE  
REGIONS, AND IT IS QUITE LIKELY THAT THIS WOULD WARRANT WIND CHILL  
WARNINGS FOR MANY OF THESE AREAS. NUMEROUS RECORD LOW  
TEMPERATURES ARE EXPECTED. ALTHOUGH THE AIRMASS WILL MODIFY SOME  
BY THE TIME IT REACHES THE EAST COAST, IT SHOULD STILL BE QUITE  
COLD FOR THE MID-ATLANTIC AND NORTHEAST U.S. ON THURSDAY WITH  
HIGHS BELOW FREEZING FOR MOST AREAS. RAIN AND MOUNTAIN SNOW IS  
EXPECTED TO RETURN TO THE WEST COAST BY NEXT WEEKEND AS A LOW  
PRESSURE SYSTEM WORKS ITS WAY TOWARDS CALIFORNIA.  
 
D. HAMRICK  
 
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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page