332  
FXUS02 KWBC 132010  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
309 PM EST THU JAN 13 2022  
 
VALID 12Z SUN JAN 16 2022 - 12Z THU JAN 20 2022  
 
...HEAVY SNOW LIKELY FROM THE APPLACHIANS TO THE INTERIOR  
MID-ATLANTIC AND NORTHEAST WITH SIGNIFICANT ICING POSSIBLE FOR  
PARTS OF THE CAROLINAS...  
 
   
..OVERVIEW
 
 
THE MOST NOTABLE WEATHER FEATURE DURING THE MEDIUM RANGE PERIOD IS  
A DEVELOPING SURFACE LOW PRESSURE SYSTEM THAT SLIDES ACROSS THE  
SOUTHEAST ON SUNDAY AND THEN PIVOTS NORTHWARD NEAR/ALONG THE EAST  
COAST AHEAD OF A POTENT MID-UPPER SHORTWAVE TROUGH. THIS WILL  
CAUSE IMPACTFUL WINTRY WEATHER TO SPREAD ACROSS MUCH OF THE EAST  
EARLY NEXT WEEK. HOWEVER, SOME LINGERING UNCERTAINTY REMAINS WITH  
THE EXACT LOW TRACK, LENDING TO LOW CONFIDENCE IN PRECIPITATION  
TYPE (WHICH COULD CHANGE IN SOME LOCATIONS AS THE EVENT  
PROGRESSES), THE AXIS OF THE HEAVIEST SNOW, AND THE WESTWARD  
EXTENT OF THE SNOW. MEANWHILE IN THE WEST, MAINLY DRY CONDITIONS  
ARE EXPECTED UNDERNEATH SURFACE HIGH PRESSURE, WITH THE EXCEPTION  
OF LIGHT PRECIPITATION IN THE PACIFIC NORTHWEST AND NORTHERN  
ROCKIES AS WEAK FRONTS TRACK THROUGH.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE MODEL GUIDANCE FOR THE 00Z/06Z CYCLE SHOW REASONABLE AGREEMENT  
REGARDING THE SOUTHEAST/EAST COAST SURFACE LOW SUNDAY-TUESDAY. THE  
NEW 12Z GUIDANCE STICKS PRETTY CLOSE TO PREVIOUS RUNS, WITH JUST  
THE TYPICAL RUN-TO-RUN WOBBLE VARIANCE. ALL OF THE DETERMINISTIC  
SOLUTIONS NOW KEEP THE LOW INLAND, WITH THE 06Z/12Z GFS A HAIR  
EAST, AND THE UKMET CONTINUING TO STICK FARTHER SOUTH. THE  
ENSEMBLE MEANS ARE ALSO A BIT EAST OF THE DETERMINISTIC SOLUTIONS,  
THOUGH STILL MOSTLY ALONG OR JUST INLAND OF THE COAST.  
INTERESTINGLY ENOUGH, THE 06Z/12Z GEFS MEAN CONTINUES TO KEEP IT'S  
LOW CENTER OFFSHORE AND DISPLACED WELL TO THE EAST OF ITS  
DETERMINISTIC COUNTERPART, THOUGH THERE ARE A FAIR NUMBER OF  
ENSEMBLE MEMBERS WITH AN ONSHORE LOW. WPC PREFERS A TRACK A LITTLE  
CLOSER TO THE DETERMINISTIC SOLUTIONS, GIVEN THE TREND OVER THE  
PAST COUPLE OF DAYS HAS BEEN WESTWARD. THE CLOSEST PROXY TO THE  
FORECAST WAS A BLEND OF THE 00Z ECMWF AND CMC, WHICH PLACES THE  
LOW OVER THE PHILADELPHIA REGION ON MONDAY MORNING, AND VERY CLOSE  
TO THAT OF THE PREVIOUS WPC FORECAST AS WELL. GIVEN THE SPREAD IN  
THE INDIVIDUAL ENSEMBLE MEMBERS, THERE STILL A FAIR AMOUNT OF  
UNCERTAINTY IN THE EXACT LOW TRACK AND EVEN SUBTLE SHIFTS EAST OR  
WEST COULD CREATE LARGE CHANGES IN THE IMPACTS FOR ESPECIALLY THE  
MAJOR METROPOLITAN CITIES ALONG THE I-95 CORRIDOR.  
 
ELSEWHERE, RIDGING IS LIKELY TO HAVE HOLD OF THE WEST EARLY THIS  
WEEK, OTHER THAN A MEANDERING SOUTHERN STREAM UPPER LOW CENTERED  
OFFSHORE OF CALIFORNIA. WHICH SHOULD TRACK EASTWARD AND EVENTUALLY  
JOIN WITH THE MAIN FLOW BY AROUND TUESDAY. THEN THERE IS GOOD  
MODEL AGREEMENT FOR AN AMPLIFIED RIDGE OVER THE WEST COAST BY  
THURSDAY DRIFTING EASTWARD FROM THE PACIFIC, WITH SOME MODEL  
DIFFERENCES IN POSSIBLE EMBEDDED SHORTWAVES PARTICULARLY SHOWN BY  
THE GFS RUNS. MEANWHILE, ADDITIONAL SHORTWAVES REINFORCE TROUGHING  
CENTERED OVER THE GREAT LAKES WEDNESDAY-THURSDAY, FOR WHICH THERE  
IS REASONABLE MODEL AGREEMENT ON THE NEXT WELL DEFINED CYCLONE TO  
TRAVERSE THE UPPER MIDWEST/GREAT LAKES AND INTO EASTERN  
CANADA/NORTHERN NEW ENGLAND BY NEXT THURSDAY.  
 
THE WPC MEDIUM RANGE FORECAST WAS BASED ON AN INITIAL BLEND OF THE  
00Z/06Z DETERMINISTIC GUIDANCE FAVORING THE ECMWF AND CMC FOR DAYS  
3-4. AFTER THIS, ADDED INTRODUCED INCREASING AMOUNTS OF THE  
ENSEMBLE MEANS TO HELP MITIGATE SOME OF THE LATER PERIOD SMALLER  
SCALE DETAILS DIFFERENCES. OVERALL, THIS PRESENTED A FORECAST VERY  
CLOSE TO PREVIOUS WPC CONTINUITY.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE SURFACE LOW LIFTING FROM THE SOUTHEAST AND UP THE EAST COAST  
WILL BRING WITH IT A FULL ARRAY OF WEATHER HAZARDS AND THREATS. AT  
THIS POINT, HEAVY SNOWS ARE MOST LIKELY IN THE TENNESSEE  
VALLEY/SOUTHERN APPALACHIANS BEGINNING THIS WEEKEND, SPREADING  
NORTHWARD ALONG/ON THE BACKSIDE OF THE DEEPENING LOW AND GENERALLY  
WEST OF THE I-95 CORRIDOR IN THE MID-ATLANTIC AND THE NORTHEAST  
SUNDAY NIGHT INTO MONDAY. FOR LOCATIONS EAST/ALONG I-95 (INCLUDING  
THE MAJOR METRO AREAS OF DC, PHILADELPHIA, AND NEW YORK CITY),  
PRECIPITATION MAY START OUT AS A QUICK BURST OF ACCUMULATING SNOW,  
WITH A CHANGEOVER TO SLEET AND/OR PLAIN RAIN AS WARMER AIR FILTERS  
IN FROM THE EAST. CHANCES ARE ALSO INCREASING FOR A POTENTIALLY  
SIGNIFICANT ICING EVENT, ESPECIALLY FROM PARTS OF NORTHEAST  
GEORGIA, THROUGH PARTS OF THE CAROLINAS, AND INTO CENTRAL VIRGINIA  
WHERE WARM AND MOIST GULF OF MEXICO INFLOW WILL OVERRUN INITIALLY  
COLD AIR AT THE SURFACE. WPC HAS BOTH THE SNOW AND ICE THREATS  
HIGHLIGHTED IN TODAYS HAZARD OUTLOOK. TO THE SOUTH, MODERATELY TO  
LOCALLY HEAVY RAIN LIKELY MOVES UP THE IMMEDIATE EAST COAST SUNDAY  
INTO MONDAY. GUSTY WINDS SURROUNDING THE SURFACE LOW MAY CREATE  
HIGH WAVES OFF THE COAST LEADING TO POSSIBLE COASTAL FLOOD  
CONCERNS ALONG THE NORTHEAST COASTLINE. OF COURSE, ALL OF THIS IS  
HIGHLY DEPENDENT ON THE EXACT TRACK OF THE SURFACE LOW AND EVEN  
SMALL ADJUSTMENTS BACK TO THE EAST COULD BRING HEAVY SNOW  
POTENTIAL INTO EVEN COASTAL PARTS OF THE EAST.  
 
ELSEWHERE, AFTER THE MAIN LOW EXITS NORTHEAST OF THE U.S. ON  
TUESDAY, ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO TRACK OVER THE  
NORTH-CENTRAL U.S. IN RESPONSE TO A MID-UPPER SHORTWAVE AND BRING  
SOME SNOW TO THE UPPER MIDWEST AND GREAT LAKES, WITH POSSIBLY  
HIGHER TOTALS NEAR TYPICAL LAKE ENHANCEMENT AREAS. THE WEST COULD  
SEE SOME LIGHT PRECIPITATION DURING THE PERIOD, PARTICULARLY OVER  
THE PACIFIC NORTHWEST AND INTO THE NORTHERN ROCKIES EARLY NEXT  
WEEK, WITH MAINLY DRY CONDITIONS ELSEWHERE. RAIN COULD DEVELOP  
AGAIN ACROSS THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST BEGINNING  
TUESDAY AND INCREASING WEDNESDAY WITH RETURN FLOW FROM THE GULF OF  
MEXICO.  
 
COOLER THAN NORMAL TEMPERATURES ARE EXPECTED GENERALLY OVER THE  
EASTERN U.S. EARLY NEXT WEEK, WITH PARTICULARLY CHILLY LOWS BELOW  
0F IN THE INTERIOR NORTHEAST SUNDAY MORNING, ABOUT 15-25 DEGREES  
BELOW AVERAGE. THE WEST TO THE PLAINS CAN EXPECT GENERALLY ABOVE  
AVERAGE CONDITIONS THROUGH TUESDAY. THEN AS A COLD SURFACE HIGH  
DROPS INTO THE NORTH-CENTRAL U.S. WEDNESDAY AND THURSDAY,  
TEMPERATURES WILL FALL TO 10-20F BELOW NORMAL IN THE UPPER MIDWEST.  
 
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  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE MID-ATLANTIC AND THE  
NORTHEAST, SUN-MON, JAN 16-JAN 17.  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST AND THE  
MID-ATLANTIC, SUN-MON, JAN 16-JAN 17.  
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHEAST, THE CENTRAL  
APPALACHIANS, THE TENNESSEE VALLEY, THE MID-ATLANTIC, THE SOUTHERN  
APPALACHIANS, THE SOUTHEAST, THE GREAT LAKES, AND THE OHIO VALLEY,  
SUN-MON, JAN 16-JAN 17.  
- FREEZING RAIN ACROSS PORTIONS OF THE SOUTHEAST, THE  
MID-ATLANTIC, AND THE SOUTHERN APPALACHIANS, SUN, JAN 16.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE LOWER  
MISSISSIPPI VALLEY, THE PACIFIC NORTHWEST, AND THE OHIO VALLEY.  
- HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF THE  
MID-ATLANTIC AND THE NORTHEAST, SUN-MON, JAN 16-JAN 17.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page