241  
FXUS02 KWBC 261557  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1056 AM EST SAT JAN 26 2019  
 
VALID 12Z TUE JAN 29 2019 - 12Z SAT FEB 02 2019  
 
...WELL BELOW NORMAL TEMPERATURES EXPECTED ACROSS MUCH OF THE  
NORTH-CENTRAL U.S. INTO THE EASTERN U.S. NEXT WEEK...  
   
..PATTERN OVERVIEW
 
 
THE OVERALL PATTERN DURING THE MEDIUM RANGE PERIOD FEATURES QUITE  
AMPLIFIED FLOW THROUGH NEXT THURSDAY WITH A LARGE SCALE RIDGE  
SITUATED OVER THE WEST COAST, AND A LARGE AND COLD UPPER LEVEL  
ARCTIC LOW REINFORCING A LARGE TROUGH OVER MUCH OF THE CENTRAL AND  
EASTERN STATES. AS THE DEEP CLOSED LOW LIFTS OUT INTO EASTERN  
CANADA, THE PATTERN ACROSS THE CONUS SHIFTS AND WEAKENS SLIGHTLY  
AS THE WESTERN U.S. RIDGE SLIDES INLAND AND A BROAD TROUGH BECOMES  
ESTABLISHED OVER THE EASTERN PACIFIC.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
DETERMINISTIC MODELS AND ENSEMBLES REMAIN IN GOOD ENOUGH AGREEMENT  
WITH THE DEEP UPPER LEVEL VORTEX AS IT TRACKS ALONG THE  
U.S./CANADA BORDER AND LIFTS INTO EASTERN CANADA NEAR THE MIDDLE  
TO END OF NEXT WEEK. A GENERAL MODEL BLEND SUFFICED FOR THIS  
SYSTEM.  
 
MODEL DIFFERENCES IN THE MEDIUM RANGE CONCENTRATE IN THE WESTERN  
U.S. FIRST WITH A SMALL LOBE OF ENERGY EMBEDDED WITHIN THE BROAD  
UPPER LEVEL RIDGE, AND AGAIN WITH EVENTUAL TROUGHING OFF THE WEST  
COAST LATE NEXT WEEK. REGARDING THE FIRST SYSTEM, THE  
DETERMINISTIC GFS/ECMWF CONTINUE TO HANG ONTO A SMALL CLOSED LOW  
APPROACHING THE PACIFIC NORTHWEST COAST EARLY NEXT WEEK, WITH  
INDIVIDUAL MEMBER DISAGREEMENT LENDING TO A MUCH WEAKER/SUPPRESSED  
OUTPUT IN THE ENSEMBLE MEANS. TO MAINTAIN WPC CONTINUITY, DID LEAN  
MORE TOWARDS THE GFS/ECMWF SOLUTIONS DAY 3 AND 4. MODELS REALLY  
DIVERGE BY DAYS 6 AND 7 ON THE EVOLUTION OF THE EASTERN PACIFIC  
TROUGH. THERE REMAINS PLENTY OF RUN-TO-RUN CONTINUITY IN THE  
DETERMINISTIC RUNS (REGARDING BROAD TROUGHING OR A POSSIBLE CLOSED  
LOW OFF CALIFORNIA DAY 7) TO WARRANT A MOSTLY ENSEMBLE MEAN BLEND.  
LEANED VERY HEAVILY ON THE ECENS MEAN OVER THE GEFS MEAN DUE TO  
MORE PRONOUNCED TROUGHING, AND SLIGHTLY BETTER OVERALL CONTINUITY  
BOTH WITH PREVIOUS RUNS AND THE WPC FORECAST.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
A CLIPPER SYSTEM CROSSING THE GREAT LAKES INTO THE NORTHEAST EARLY  
IN THE PERIOD SHOULD RESULT IN A BAND OF MODERATE TO LOCALLY HEAVY  
SNOWFALL NORTH AND WEST OF THE SURFACE LOW ACROSS THE LOWER GREAT  
LAKES AND MUCH OF THE NORTHEAST. RAIN MAY ALSO CHANGE TO SNOW  
ALONG THE MAIN COLD FRONT AS IT CROSSES THE MID-ATLANTIC AND  
COASTAL NEW ENGLAND. LAKE EFFECT SNOWS ARE LIKELY DOWNWIND OF THE  
GREAT LAKES AS INTENSE COLD AIR ADVECTION CONTINUES ON THE  
BACKSIDE OF THE SYSTEM. OUT WEST, RAIN AND MOUNTAIN SNOWS ARE  
EXPECTED TO RETURN TO THE WEST COAST BY NEXT WEEKEND AS A LOW  
PRESSURE SYSTEM WORKS ITS WAY TOWARDS CALIFORNIA.  
 
THE BIGGER HEADLINE IN THE MEDIUM RANGE PERIOD WILL BE BRUTAL,  
POTENTIALLY DANGEROUS, COLD TEMPERATURES DIVING INTO THE  
NORTH-CENTRAL U.S. EARLY NEXT WEEK. DAILY HIGH TEMPERATURES MONDAY  
- WEDNESDAY OF NEXT WEEK ACROSS MUCH OF THE UPPER MISSISSIPPI  
VALLEY AND INTO THE MIDWEST ARE FORECAST TO BE BELOW ZERO FOR MANY  
LOCATIONS, WITH OVERNIGHT MINS 20 TO 30 BELOW ZERO! THESE  
TEMPERATURES WOULD BE 30 TO 40 DEGREES BELOW NORMAL, WITH BOTH  
DAILY LOW AND HIGH TEMPERATURE RECORDS LIKELY TO BE CHALLENGED OR  
BROKEN. ALTHOUGH THE AIRMASS SHOULD MODIFY SOME BY THE TIME IT  
REACHES THE EAST COAST DURING THE MIDDLE OF NEXT WEEK,  
TEMPERATURES ARE LIKELY TO STILL BE WELL BELOW NORMAL ON THURSDAY  
WITH DAYTIME HIGHS BELOW FREEZING FOR MOST LOCATIONS ACROSS THE  
MID-ATLANTIC AND THE NORTHEAST.  
 
SANTORELLI  
 
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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