895  
FXUS02 KWBC 111909  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
209 PM EST TUE JAN 11 2022  
 
VALID 12Z FRI JAN 14 2022 - 12Z TUE JAN 18 2022  
 
...HEAVY SNOW LIKELY ACROSS PARTS OF THE MIDWEST ON FRIDAY, WITH  
LINGERING UNCERTAINTIES DOWNSTREAM ALONG THE EAST COAST THIS  
WEEKEND...  
   
..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, ONE  
SHORTWAVE WILL EXIT THE EAST COAST EARLY FRIDAY AS THE NEXT ONE  
DROPS THROUGH THE MIDWEST, BRINGING THE POTENTIAL FOR HEAVY  
SNOWFALL TO PARTS OF THE AREA. THE SHORTWAVE SHOULD SLIDE THROUGH  
THE SOUTHEAST AND PIVOT OFF THE EAST COAST TO SUPPORT ANOTHER EAST  
COAST LOW THIS WEEKEND INTO EARLY NEXT WEEK. THIS COULD BRING  
POTENTIALLY IMPACTFUL WINTRY WEATHER ACROSS PARTS OF THE  
MID-ATLANTIC AND THE NORTHEAST, BUT CONFIDENCE IN THE DETAILS  
REMAIN VERY LOW.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE LATEST MODEL GUIDANCE SHOWS FAIRLY GOOD AGREEMENT FOR THE  
LARGE-SCALE PATTERN, BUT WITH SOME LINGERING UNCERTAINTIES IN SOME  
POTENTIALLY IMPACTFUL DETAILS. AN INITIAL SURFACE LOW OFF THE EAST  
COAST ON FRIDAY LOOKS TO REMAIN WELL OFFSHORE TO LIMIT ANY  
SIGNIFICANT IMPACTS TO THE NORTHEAST, BUT MAY AFFECT THE CANADIAN  
MARITIMES THIS WEEKEND. FARTHER UPSTREAM, THE MODELS AGREE THAT  
SHORTWAVE ENERGY WILL BE SPILLING INTO THE MIDWEST ON FRIDAY. MOST  
OF THE 00Z GUIDANCE (AND INCOMING 12Z GUIDANCE) CONTINUE TO TREND  
SOUTHWARD WITH THE LOW AND ASSOCIATED HEAVY SNOW AXIS ACROSS THE  
MIDWEST ON FRIDAY.  
 
BY THIS WEEKEND, THE SHORTWAVE SHOULD PIVOT ACROSS THE SOUTHEAST  
INDUCING DEVELOPMENT OF LOW PRESSURE AT THE SURFACE WHICH  
EVENTUALLY MOVES UP THE EAST COAST EARLY NEXT WEEK. COMPARED TO  
YESTERDAYS 12Z/18Z GUIDANCE, THE 00Z/06Z (AND THE NEW 12Z)  
GUIDANCE SHOWS A VERY NOTABLE WESTWARD SHIFT, NOW BRINGING THE LOW  
CLOSER TO OR OVER THE EAST COAST NEXT SUNDAY-TUESDAY. THE 06Z GFS  
WAS THE FARTHEST WEST WITH THE LOW, WHILE THE 00Z ECMWF AND CMC  
KEPT IT WELL OFFSHORE. HOWEVER, THE NEWEST 12Z RUNS HAVE NOW  
SHIFTED SIGNIFICANTLY WESTWARD AND MUCH CLOSER TO THE GFS. THERE  
ALSO REMAINS CONSIDERABLE SPREAD IN INDIVIDUAL ENSEMBLE MEMBERS AS  
WELL, ALTHOUGH THE MEANS ARE FASTER THAN THE DETERMINISTIC RUNS  
(LIKELY DUE TO LOWER AMPLITUDE IN THE UPPER PATTERN). THE WPC  
BLEND FOR TODAY WAS CLOSER TO THE 00Z ECMWF, 00Z CMC, AND 00Z  
UKMET KEEPING THE LOW OFF THE EAST COAST BUT STILL CLOSER THAN THE  
PREVIOUS WPC FORECAST. ALTHOUGH, GIVEN THE NEWEST 12Z GUIDANCE  
(WHICH ARRIVED AFTER THE FORECAST WAS ISSUED), THE WPC FORECAST IS  
NOW EAST OF THE CONSENSUS. NEEDLESS TO SAY, THE DETAILS OF ANY  
POTENTIAL WINTER WEATHER IMPACTS TO PARTS OF THE MID-ATLANTIC THE  
NORTHEAST REMAIN HIGHLY UNCERTAIN AT THIS TIME AS MOST NEW MODEL  
RUNS CONTINUE TO CHANGE AND SHIFT AND WILL LIKELY DO SO IN THE  
COMING DAYS.  
 
OUT WEST, PERIODIC AND WEAK SHORTWAVE INTRUSIONS SHOULD BRIEFLY  
BREAK UP THE RIDGE OUT WEST THROUGH THE PERIOD. THERE'S GOOD  
AGREEMENT IN THE DETERMINISTIC RUNS THROUGH AT LEAST THE FIRST  
HALF OF THE PERIOD, WITH LESS UNCERTAIN TIMING AND DETAIL  
DIFFERENCES ARISING LATE. ONE SHORTWAVE SHOULD TRAVERSE THE FAR  
NORTHERN TIER OF THE U.S., EVENTUALLY MOVING ACROSS THE GREAT  
LAKES AND AMPLIFYING OVER THE EAST LATER IN THE PERIOD. THERE  
REMAINS PLENTY OF UNCERTAINTY AROUND HOW THIS ENERGY  
INTERACTS/COMBINES WITH THE SHORTWAVE MOVING UP THE EAST COAST IN  
THE DAYS PRIOR, SO A TREND TOWARDS THE ENSEMBLE MEANS LATER IN THE  
PERIOD SEEMED IDEAL AT THIS TIME.  
   
..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, GUSTY WINDS MAY 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 LOW FOR LOCATIONS, COVERAGE, AND AMOUNTS OF WINTRY  
PRECIPITATION FARTHER EAST. LATEST TRENDS CONTINUE TO SUGGEST A  
FARTHER WEST AXIS OVER THE EAST WHICH BRINGS THE HEAVIEST  
PRECIPITATION ALONG THE EAST COAST, WITH POTENTIAL FOR HEAVY SNOW  
FARTHER INLAND. AGAIN, THIS IS HIGHLY UNCERTAIN AND SUBJECT TO  
CHANGE, BUT THE POTENTIAL IS THERE. 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.  
 
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 5-10  
DEGREES OF NORMAL, WITH A TENDENCY TOWARD SLIGHTLY WARMER THAN  
AVERAGE CONDITIONS ESPECIALLY FOR LOWS.  
 
SANTORELLI/TATE  
 
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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