971  
FXUS02 KWBC 171917  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
216 PM EST MON JAN 17 2022  
 
VALID 12Z THU JAN 20 2022 - 12Z MON JAN 24 2022  
 
...SNOW/ICE ARE POSSIBLE ALONG THE EASTERN SEABOARD LATE THIS WEEK  
AND WEEKEND ON THE EASTERN PERIPHERY OF AN ARCTIC HIGH...  
   
..OVERVIEW
 
 
ARCTIC HIGH PRESSURE WILL PUSH A COLD FRONT ACROSS THE EAST LATE  
THIS WEEK, LEADING TO VERY COLD TEMPERATURES ACROSS THE CENTRAL  
AND EASTERN CONUS. MOIST AIR SPILLING INTO THE SOUTHERN AND  
EASTERN PERIPHERY OF THE CHILLY AIRMASS COULD PRODUCE WINTRY  
WEATHER WITH LIGHT AMOUNTS OVER TEXAS THURSDAY TO CURRENTLY BETTER  
CHANCES FOR NOTABLE AMOUNTS OVER THE CAROLINAS AND INTO THE  
MID-ATLANTIC LATE THIS WEEK, POSSIBLY SPREADING INTO THE NORTHEAST  
THIS WEEKEND, THOUGH UNCERTAINTY REMAINS HIGH WITH THE DETAILS  
GIVEN MODEL GUIDANCE DISAGREEMENTS. MEANWHILE, UPPER RIDGING IS  
EXPECTED FOR THE WEST, WITH THE EXCEPTION OF A SHORTWAVE DIGGING  
SOUTH THAT MAY PRODUCE A CLOSED LOW OVER THE SOUTHWEST THIS  
WEEKEND.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE 00Z/06Z SUITE OF MODEL GUIDANCE BEGINS THE PERIOD THURSDAY  
WITH FAIRLY GOOD AGREEMENT FOR THE OVERALL PATTERN--UPPER  
TROUGHING ACROSS THE CENTRAL AND EASTERN U.S. WITH A STRONG ARCTIC  
HIGH AT THE SURFACE, AND A HIGH OVER THE EASTERN PACIFIC WITH A  
RIDGE AXIS INTO THE WEST. A COUPLE OF SHORTWAVES THAT ARE  
SIGNIFICANT TO THE PATTERN THEN HAVE SOMEWHAT LOW PREDICTABILITY  
FRIDAY AND BEYOND. IN THE EAST, A SHORTWAVE MOVING THROUGH THE  
PERSISTENT EASTERN TROUGH SHOWS CONSIDERABLE DIFFERENCES IN  
PLACEMENT AND STRENGTH BY LATE FRIDAY INTO SATURDAY THROUGH THE  
OHIO VALLEY TO EASTERN SEABOARD, WHICH PRODUCES PLACEMENT  
DIFFERENCES WITH A POTENTIALLY IMPACTFUL SURFACE LOW IN THE  
WESTERN ATLANTIC. THE 00Z AND INCOMING 12Z ECMWF ARE GENERALLY ON  
THE WESTERN SIDE OF THE MODEL SPREAD WITH THESE FEATURES, LEADING  
TO MORE PRECIPITATION OVER THE EASTERN SEABOARD, WHILE THE GFS  
RUNS HAVE BEEN SUPPRESSED FARTHER EAST INTO THE ATLANTIC. THE 00Z  
CLUSTER ANALYSIS AND ENSEMBLE MEMBER LOW PLOTS SHOWED THAT THE  
GEFS AND EC ENSEMBLES FOLLOWED THEIR OPERATIONAL RUNS, WITH GEFS  
MEMBERS FARTHER EAST THAN EC ENSEMBLE MEMBERS. TENDED TO FAVOR A  
POSITION FOR THE SURFACE LOW NEAR THE 00Z EC ENSEMBLE MEAN AS  
SOMEWHAT OF A COMPROMISE, WHICH WAS NOT TOO FAR OFF FROM THE 00Z  
CMC POSITION, BUT THE 12Z CMC IS NOW SHOWING A MORE SUPPRESSED  
PATTERN. THIS FORECAST APPROACH LED TO A TREND WEST OF THE  
PREVIOUS WPC FORECAST WITH THE SURFACE LOW AND FRONTAL PLACEMENT,  
BUT NOT NEARLY TO THE WESTERN EXTENT OF THE ECMWF RUNS.  
 
MEANWHILE IN THE WEST, MODELS ALL TEND TO SHOW SHORTWAVE ENERGY  
COMING INTO BRITISH COLUMBIA THURSDAY WITH AT LEAST A PORTION OF  
THE ENERGY DIVING SOUTH ACROSS THE INTERMOUNTAIN WEST FRIDAY, AND  
COULD CLOSE OFF A SOUTHERN STREAM LOW IN THE SOUTHWEST BY AROUND  
SATURDAY. THERE HAS BEEN GOOD MODEL AGREEMENT FOR A COUPLE CYCLES  
NOW FOR THE LOW TO CLOSE OFF AT SOME POINT THIS WEEKEND (RECENT  
12Z GUIDANCE IS SHOWING LATER COMPARED TO THE 00Z/06Z GUIDANCE),  
SO FELT IT WAS PRUDENT TO INCLUDE A CLOSED LOW FOR THE FORECAST  
UPDATE, BUT THERE IS INHERENT UNCERTAINTY AS THE SHORTWAVE ENERGY  
IS STEMMING FROM THE DATA-POOR PACIFIC OCEAN.  
 
EARLY NEXT WEEK, GUIDANCE ALL SHOWS TROUGHING REMAINING STRONG  
ACROSS THE EAST GIVEN A DEEP LOW CENTERED JUST EAST OF THE HUDSON  
BAY, BUT WITH SOME VARIATIONS IN SHORTWAVES AROUND IT. THE WPC  
FORECAST WAS BASED ON A BLEND OF DETERMINISTIC GUIDANCE EARLY ON,  
INCLUDING AND INCREASING WEIGHTING OF THE GEFS AND ESPECIALLY THE  
EC ENSEMBLE GUIDANCE AS THE PERIOD PROGRESSED.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A MASSIVE ARCTIC HIGH WILL SPREAD FROM THE CENTRAL TO EASTERN U.S.  
THURSDAY THROUGH SATURDAY BEHIND A POTENT COLD FRONT, PRODUCING  
MUCH BELOW NORMAL TEMPERATURES. LOWS OF 15-25F BELOW AVERAGE ARE  
LIKELY ACROSS THE NORTH-CENTRAL U.S. THURSDAY AND FRIDAY MORNING  
AND ACROSS THE INTERIOR NORTHEAST FRIDAY AND SATURDAY. LOWS IN THE  
TEENS ARE LIKELY AS FAR SOUTH AS TEXAS, WHILE IN PARTS OF THE  
MIDWEST TEMPERATURES COULD STAY BELOW 0F EVEN FOR HIGHS ON  
THURSDAY. HIGH TEMPERATURES SHOULD BE 20-30F BELOW NORMAL FOR THE  
PLAINS TO THE EASTERN SEABOARD LATE THIS WEEK BEFORE MODERATING  
EARLY NEXT WEEK. ON THE SOUTHERN AND EASTERN PERIPHERY OF THIS  
HIGH, MOIST AIR SPILLING INTO THE COLD AIR COULD LEAD TO WINTRY  
WEATHER ON THE NORTHERN PERIPHERY OF PRECIPITATION SPREADING  
ACROSS THE GULF COAST STATES AND THEN POSSIBLY UP THE EASTERN  
SEABOARD. ONCE AGAIN, UNCERTAINTY WITH THE EVOLUTION OF SHORTWAVES  
AND SURFACE LOWS LEADS TO LOW CONFIDENCE IN PLACEMENT OF WINTRY  
PRECIPITATION AND PRECIPITATION TYPE IN SOME LOCATIONS AT THIS  
TIME, BUT THE CURRENT FORECAST SHOWS THE POTENTIAL FOR NOTABLE  
SNOW, SLEET, AND FREEZING RAIN PARTICULARLY IN THE CAROLINAS AND  
SOUTHERN PORTIONS OF THE MID-ATLANTIC FOR THE LATTER PART OF THE  
WEEK, WITH SOME CHANCE OF SPREADING INTO THE NORTHEAST THIS  
WEEKEND. THE PATTERN WILL ALSO BE FAVORABLE FOR LAKE EFFECT SNOW  
GIVEN COLD AIR IN PLACE AND GENERALLY WESTERLY WINDS.  
 
IN THE WEST, THE BEST CHANCE FOR PRECIPITATION WILL BE THURSDAY  
AND FRIDAY WITH MOUNTAIN SNOW IN THE ROCKIES AS THE SHORTWAVE  
IMPULSE MOVES THROUGH. OTHER THAN THAT, CONDITIONS SHOULD REMAIN  
MOSTLY DRY, WITH SLIGHTLY WARMER THAN NORMAL CONDITIONS FOR THE  
WEST COAST STATES UNDERNEATH THE RIDGE, AND ABOVE NORMAL  
TEMPERATURES ARE THEN EXPECTED FOR THE HIGH PLAINS EARLY NEXT WEEK.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page