181  
FXUS02 KWBC 110716  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
215 AM EST TUE JAN 11 2022  
 
VALID 12Z FRI JAN 14 2022 - 12Z TUE JAN 18 2022  
   
..OVERVIEW
 
 
MEAN RIDGING IS LIKELY OVER THE WEST DURING THE MEDIUM RANGE  
PERIOD, THOUGH WITH THE POSSIBILITY OF SHORTWAVES TRACKING THROUGH  
THE MEAN FLOW WHILE SOUTHERN STREAM TROUGHING LINGERS NEAR OR  
OFFSHORE THE CALIFORNIA/BAJA CALIFORNIA COAST. MEANWHILE IN THE  
NORTH-CENTRAL TO EASTERN U.S., ROUNDS OF UPPER TROUGHING ARE  
EXPECTED, WITH SURFACE LOWS DEVELOPING IN RESPONSE. THESE FEATURES  
COULD CAUSE MEANINGFUL SNOW OVER PARTS OF THE MIDWEST ON FRIDAY  
BEFORE MODEL SOLUTIONS DIVERGE WITH THE SHORTWAVE/LOW TRACKS,  
WHICH KEEPS CONFIDENCE LOW FOR ANY IMPACTFUL WINTRY WEATHER  
FARTHER EAST IN THE APPALACHIANS AND EASTERN SEABOARD.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE FOR THE 12/18Z CYCLE SHOWS OKAY AGREEMENT FOR THE  
LARGE-SCALE PATTERN BUT WITH DIFFERENCES IN SOME IMPACTFUL  
DETAILS. AT THE BEGINNING OF THE PERIOD FRIDAY, A SURFACE LOW IN  
THE ATLANTIC DEMONSTRATES REASONABLY GOOD AGREEMENT THAT IT WILL  
BE WELL OFF THE EASTERN SEABOARD GIVEN A TROUGH AXIS BASICALLY  
OVER THE EAST COAST. THAT SURFACE LOW SHOULD DEEPEN CONSIDERABLY  
AND MAY AFFECT THE CANADIAN MARITIMES BY SATURDAY. FARTHER  
UPSTREAM, MODELS AGREE THAT SHORTWAVE ENERGY WILL BE SPILLING INTO  
THE MIDWEST ON FRIDAY AND CONTINUING TO DIG SATURDAY. HOWEVER, THE  
SHORTWAVES AND ASSOCIATED SURFACE LOW(S) SHOW MORE VARIABILITY IN  
THEIR TRACKS. OVERALL THE TREND CONTINUES TO BE SOUTHWARD IN THE  
DETERMINISTIC MODELS ESPECIALLY, AS SHOWN BY THE 12/18Z GFS AND  
ECMWF, WHILE THE 12Z CMC WAS WELL NORTH (00Z CMC HAS COME SOUTH).  
GUIDANCE FOR THE MOST PART TAKES THE SURFACE LOW ACROSS THE  
SOUTHEAST BEFORE TURNING NORTHEASTWARD OVER THE ATLANTIC. ENSEMBLE  
MEAN GUIDANCE IS A BIT FARTHER NORTH WITH THE LOW CENTER, AND FELT  
LIKE FOLLOWING CLOSER TO THEIR TRACK FOR THE SURFACE LOW WAS A  
SAFER BET GIVEN THE ENSEMBLE MEMBER SPREAD. AFTER THAT ON  
SUNDAY-TUESDAY, THERE IS DECENT CLUSTERING IN THE GUIDANCE FOR A  
SOUTHERN CANADA/GREAT LAKES SYSTEM WITH ASSOCIATED FRONTS, AS  
ANOTHER SHORTWAVE ORIGINATING FROM THE NORTHERN PACIFIC DROPS INTO  
THE NORTH-CENTRAL AND THEN EAST-CENTRAL U.S. THIS SHORTWAVE SHOULD  
REMAIN MORE CONSOLIDATED AS IT ROUNDS THE PACIFIC RIDGE, WHICH  
HOPEFULLY WILL PROVIDE BETTER PREDICTABILITY (AT LEAST FOR THE  
FRONT IF NOT LOW PRESSURE) THAN HAS BEEN THE CASE FOR OTHER  
SHORTWAVES.  
 
FOR THE WEST, EVEN ON DAY 3/FRIDAY THERE IS UNCERTAINTY ABOUT  
SHORTWAVE ENERGY BREAKING UP THE MEAN RIDGE. THE 12Z EC/CMC  
CENTERED A MID-UPPER LOW OVER THE NORTHERN CA/NV BORDER, RIGHT  
OVER THE RIDGE AXIS IN THE GFS RUNS. IT LOOKS LIKE THE NEWER SUITE  
OF 00Z GUIDANCE DEMONSTRATES BETTER AGREEMENT. SOUTHERN STREAM  
ENERGY ALSO SHOWS DIFFERENCES IN POSITIONING AMONG MODEL GUIDANCE  
AS IT MEANDERS, FROM WELL OFFSHORE IN THE PACIFIC TO THE WESTERN  
U.S. THE 12Z CMC APPEARED TO BE A PARTICULAR OUTLIER AS IT TAKES  
THE ENERGY EASTWARD EVEN INTO THE SOUTHERN PLAINS BY TUESDAY,  
AGAINST CONSENSUS AND BASICALLY ALL ENSEMBLE MEMBERS.  
 
FOR THE MEDIUM RANGE FORECAST, FAVORED AN INITIAL BLEND OF THE 12Z  
ECMWF, UKMET, CMC AND 18Z GFS FAVORING THE ECMWF SOMEWHAT. THEN AS  
THE PERIOD PROGRESSED, INCREASED WEIGHTING OF THE GEFS AND EC  
ENSEMBLE MEANS TO ABOUT HALF THE BLEND BY DAYS 6/7, WHILE TAKING  
OUT THE 12Z CMC FROM THE BLEND. THIS PROVIDED THE MOST COHERENT  
OVERALL EVOLUTION, AND WHILE SIGNIFICANT FURTHER CHANGES MAY  
OCCUR, CONTINUITY FROM THE PREVIOUS FORECAST ON DAYS 3-6 WAS  
FAIRLY GOOD.  
   
..WEATHER HIGHLIGHTS
 
 
WHILE DEEPENING ATLANTIC LOW PRESSURE LATE THIS WEEK SHOULD STAY  
FAR ENOUGH OFFSHORE TO KEEP A MAJORITY OF PRECIPITATION EAST OF  
NEW ENGLAND ON FRIDAY, STRONG WINDS WILL BE POSSIBLE DUE TO THE  
TIGHT GRADIENT BETWEEN THIS STORM AND EASTERN CANADA HIGH  
PRESSURE. THE SHORTWAVE AND SURFACE LOW DROPPING SOUTHEASTWARD  
FROM THE NORTHERN TIER LATE THIS WEEK WILL LIKELY BRING A SWATH OF  
WINTRY PRECIPITATION ACROSS PORTIONS OF THE MIDWEST, FOLLOWED BY  
SOME OF THIS PRECIPITATION EXTENDING ACROSS THE EASTERN U.S. THIS  
WEEKEND. GUIDANCE SIGNALS ARE IMPROVING FOR A BAND OF SIGNIFICANT  
SNOW THAT MAY COVER PARTS OF MINNESOTA/WISCONSIN/IOWA/ILLINOIS  
AROUND FRIDAY-FRIDAY NIGHT, ALBEIT WITH SOME UNCERTAINTY REMAINING  
FOR LOCATION AND MAGNITUDE AS WELL AS EXACT TIMING. CONFIDENCE  
REMAINS FAIRLY LOW FOR COVERAGE AND AMOUNTS OF ANY WINTRY  
PRECIPITATION FARTHER EAST. LATEST TRENDS CONTINUE TO SUGGEST A  
FARTHER SOUTH AXIS OVER THE EAST WITH LOWER PROBABILITIES OVER THE  
NORTHEAST INITIALLY, THOUGH IF THE LOW TURNS SIGNIFICANTLY  
NORTHWARD, SNOW COULD SPREAD INTO THE NORTHEAST SUNDAY ON THE  
BACKSIDE OF THE LOW TRACK. THE SOUTH-CENTRAL AND SOUTHEASTERN U.S.  
SHOULD SEE MOSTLY LIGHT TO MODERATE RAIN ALONG THE SOUTHERN SIDE  
OF THE PRECIPITATION SHIELD. AN AREA OF LIGHT SNOW MAY EXTEND  
ACROSS THE UPPER MIDWEST INTO THE GREAT LAKES AROUND SUNDAY-MONDAY  
WITH THE SYSTEM MOVING INTO THE REGION. THE MOST LIKELY FORECAST  
SCENARIO HAS GENERALLY LIGHT AND SCATTERED PRECIPITATION OVER THE  
WEST DURING THE PERIOD. THERE IS A LOWER PROBABILITY OF MORE  
ORGANIZED ACTIVITY OVER A LARGER AREA IF UPPER FLOW DETAILS END UP  
GRAVITATING TO THE LESS LIKELY SIDE OF THE GUIDANCE SPREAD.  
 
TEMPERATURE-WISE, THE CENTRAL U.S. WILL SEE MILD CONDITIONS ON  
FRIDAY, WITH LOWS 10-20F ABOVE AVERAGE WHILE 10-15F ABOVE NORMAL  
HIGHS ARE EXPECTED FOR THE SOUTHERN PLAINS. WARMER THAN AVERAGE  
TEMPERATURES SHOULD CONTINUE INTO EARLY NEXT WEEK FOR PORTIONS OF  
THE PLAINS. MEANWHILE, COLDER THAN AVERAGE TEMPERATURES ARE LIKELY  
FOR THE GREAT LAKES TO THE NORTHEAST THROUGH THE WEEKEND, WITH  
SATURDAY THE COLDEST DAY IN THE NORTHEAST WITH TEMPERATURES 15-25F  
BELOW NORMAL. THE WEST SHOULD SEE TEMPERATURES WITHIN ABOUT 10  
DEGREES OF NORMAL, WITH A TENDENCY TOWARD SLIGHTLY WARMER THAN  
AVERAGE CONDITIONS ESPECIALLY FOR LOWS.  
 
TATE/RAUSCH  
 
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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