523  
FXUS02 KWBC 102112  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
410 PM EST MON JAN 10 2022  
 
VALID 12Z THU JAN 13 2022 - 12Z MON JAN 17 2022  
   
..OVERVIEW
 
 
GUIDANCE HAS SIMILAR IDEAS FOR THE LARGE SCALE PATTERN, CONSISTING  
OF GENERAL MEAN RIDGING OVER PARTS OF THE EASTERN PACIFIC/WESTERN  
U.S. AND A MEAN TROUGH OVER THE EAST. HOWEVER THE MODELS AND  
ENSEMBLES HAVE BEEN SHOWING CONSIDERABLE DIFFICULTY IN RESOLVING  
DETAILS OF HOW PACIFIC SHORTWAVE ENERGY MAY SPLIT AS IT HEADS  
INTO/AROUND THE MEAN RIDGE. AS A RESULT, OVER THE LAST SEVERAL  
DAYS THERE HAS BEEN A LOT OF SPREAD AND VARIABILITY FOR DETAILS OF  
ONE OR MORE SHORTWAVES OR UPPER LOWS THAT COULD BECOME EMBEDDED  
WITHIN OR LINGER UNDERNEATH THE MEAN RIDGE. AT THE SAME TIME THESE  
ISSUES HAVE BEEN AFFECTING SPECIFICS OF SHORTWAVES DROPPING INTO  
THE MEAN TROUGH OVER THE EAST. THE COMBINED UNCERTAINTIES KEEP  
CONFIDENCE LOW FOR HOW POTENTIAL SURFACE LOW PRESSURE DEVELOPMENT  
MAY AFFECT THE EAST BY THE WEEKEND, THOUGH THERE IS A DECENT  
SIGNAL FOR AN AXIS OF MEANINGFUL SNOW OVER PARTS OF THE MIDWEST ON  
FRIDAY BEFORE SOLUTIONS DIVERGE.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
REVIEW OF THE 00Z/06Z MODELS AND ENSEMBLES LED TO FAVORING A BLEND  
OF THE 00Z-06Z GFS/00Z ECMWF AND SMALL INPUT OF THE 06Z GEFS/00Z  
ECMWF MEANS EARLY, TRANSITIONING TOWARD A MORE EVEN WEIGHT OF  
MODELS AND MEANS LATE WITH SOME 00Z CMC MEAN INCLUDED AS WELL.  
THIS PROVIDED THE MOST COHERENT OVERALL EVOLUTION WITH THE  
UNDERSTANDING THAT SIGNIFICANT FURTHER CHANGES MAY OCCUR. THE MOST  
NOTABLE ADJUSTMENTS FROM CONTINUITY INCLUDE REFLECTING IMPROVED  
CONSENSUS FOR AN AXIS OF FOCUSED SNOWFALL OVER THE MIDWEST AS A  
WAVE DROPS SOUTHEAST FROM THE NORTHERN TIER AND A FARTHER SOUTH  
TREND FOR LOW PRESSURE EVOLVING OVER THE EASTERN U.S. AND WESTERN  
ATLANTIC.  
 
LATEST GFS/ECMWF RUNS AND THEIR MEANS (PLUS THE CMC MEAN) HAVE  
ACTUALLY COME INTO BETTER AGREEMENT THAN THEY HAVE SHOWN IN MANY  
DAYS, AS THE GFS IN PARTICULAR GRAVITATED TO THE ENSEMBLE MEANS  
THAT HAVE BEEN DEPICTING THE ENERGY REACHING THE WEST COAST BY  
EARLY DAY 3 THURSDAY AS AN OPEN WAVE. MULTIPLE DAYS OF GFS RUNS  
HAD BEEN CLOSING OFF A LOW OVER THE EASTERN PACIFIC. CONFIDENCE IS  
STILL NOT GREAT IN SPITE OF THIS BETTER AGREEMENT AS EVEN IN THE  
NEW 12Z CYCLE THE UKMET/CMC CONTINUE TO SHOW DIFFERENT IDEAS FOR  
THIS SHORTWAVE ENERGY.  
 
THE DETAILS OF THE INITIAL WEST COAST ENERGY AFFECT LOW PRESSURE  
THAT SHOULD TRACK SOUTHEASTWARD FROM THE NORTHERN TIER INTO THE  
EASTERN U.S. AND THEN CONTINUE OVER THE WESTERN ATLANTIC. LATEST  
CMC RUNS HAVE BEEN MOST DIFFERENT FROM CONSENSUS WITH BOTH ASPECTS  
OF THE FORECAST. GENERAL TRENDS OVER THE PAST 12-24 HOURS HAVE  
BEEN FOR THE EASTERN U.S. SURFACE PATTERN TO BECOME MORE  
SUPPRESSED IN RESPONSE TO MORE AMPLIFIED DIGGING OF SHORTWAVE  
ENERGY AS IT REACHES THE AXIS OF THE MEAN TROUGH. THE 06Z GFS/GEFS  
WERE ON THE WEAK SIDE WITH ATLANTIC DEVELOPMENT BY SUNDAY,  
FAVORING SOME 00Z GFS AND 00Z CMCENS INPUT.  
 
AHEAD OF THIS EVOLUTION, GUIDANCE IS STEADILY CONSOLIDATING FOR  
DEEP WESTERN ATLANTIC DEVELOPMENT EXPECTED TO REACH NEAR THE  
CANADIAN MARITIMES BY SATURDAY. OVER THE PAST DAY GFS RUNS HAVE  
TRENDED EAST WITH THEIR HEAVIEST PRECIPITATION WHILE GUIDANCE  
AGREES ON THE POTENTIAL FOR WINDY CONDITIONS BETWEEN THIS STORM  
AND STRONG EASTERN CANADA HIGH PRESSURE.  
 
BY SUNDAY-MONDAY THERE IS DECENT CLUSTERING IN THE GUIDANCE FOR A  
SOUTHERN CANADA/GREAT LAKES SYSTEM WITH ASSOCIATED FRONTS, AS  
ANOTHER SHORTWAVE ORIGINATING FROM THE PACIFIC DROPS INTO THE  
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 THE INITIAL SHORTWAVE NEAR THE WEST  
COAST.  
   
..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, 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 SUGGEST A FARTHER SOUTH AXIS OVER THE  
EAST WITH LOWER PROBABILITIES OVER THE NORTHEAST. 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 VERY MILD CONDITIONS  
ON THURSDAY AND INTO FRIDAY, WITH WIDESPREAD PLUS 10-25F ANOMALIES  
FOR HIGHS. LOWS WILL BE 15-25F ABOVE NORMAL IN THE NORTHERN  
PLAINS. TEMPERATURES SHOULD MODERATE SOMEWHAT OVER THE PLAINS BY  
THE WEEKEND BUT MAY STILL STAY SOMEWHAT ABOVE NORMAL. COLDER THAN  
AVERAGE TEMPERATURES WILL PREVAIL OVER THE NORTHEAST ON FRIDAY  
INTO THE WEEKEND. EXPECT SATURDAY TO BE THE COLDEST DAY WITH HIGHS  
10-20F BELOW NORMAL.  
 
RAUSCH/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  
 
HAZARDS:  
- HEAVY SNOW ACROSS PORTIONS OF THE UPPER/MIDDLE MISSISSIPPI  
VALLEY, AND THE GREAT LAKES, FRI, JAN  
14.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE LOWER  
MISSISSIPPI VALLEY AND THE PACIFIC  
NORTHWEST.  
- HIGH WINDS ACROSS PORTIONS OF THE PLAINS, THE NORTHEAST, THE  
CENTRAL APPALACHIANS, THE  
MID-ATLANTIC, THE GREAT LAKES, AND THE OHIO VALLEY, FRI, JAN 14.  
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE  
MID-ATLANTIC, THE NORTHEAST, AND THE GREAT  
LAKES, SAT, JAN 15.  
 
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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