606  
FXUS02 KWBC 241902  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT SUN APR 24 2022  
 
VALID 12Z WED APR 27 2022 - 12Z SUN MAY 01 2022  
   
..OVERVIEW
 
 
FOR THE LATTER HALF OF THIS WEEK, A SURFACE LOW CONSOLIDATING NEAR  
NEW ENGLAND IN CONJUNCTION WITH A SLOW-MOVING UPPER LOW WILL CAUSE  
PRECIPITATION CHANCES TO PERSIST OVER THE NORTHEAST. MEANWHILE,  
MEAN TROUGHING WITH MULTIPLE SHORTWAVES IS LIKELY IN THE WEST, AND  
THIS TROUGH AXIS SHOULD EVENTUALLY TRACK EASTWARD BY THE END OF  
THE WEEK, PUSHING A BROAD UPPER RIDGE INITIALLY OVER THE CENTRAL  
U.S. EASTWARD. THE TROUGH WILL SUPPORT FORMATION OF A CENTRAL U.S.  
SURFACE LOW AND POSSIBLY ANOTHER ROUND OF SNOW IN THE NORTHERN  
ROCKIES/HIGH PLAINS ON ITS BACKSIDE, WHILE RAIN IS LIKELY FARTHER  
SOUTH ACROSS THE CENTRAL PLAINS/MISSISSIPPI VALLEY. THE DETAILS OF  
THESE THREATS REMAIN QUITE UNCERTAIN AT THIS POINT, HOWEVER.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
MODEL GUIDANCE REMAINS QUITE AGREEABLE WITH THE PATTERN IN THE  
EASTERN U.S. THROUGH THE END OF THE WEEK WITH THE AFOREMENTIONED  
UPPER LOW TRACKING SLOWLY FROM THE GREAT LAKES TO NORTHEAST AND  
STALLING/SPINNING, WITH AN ASSOCIATED COASTAL SURFACE LOW. THERE  
IS ALSO REASONABLY GOOD AGREEMENT FOR GENERAL BROAD RIDGING BEHIND  
IN THE CENTRAL U.S., THOUGH WITH SOME UNCERTAINTY IN EMBEDDED  
SHORTWAVES. BUT MODELS ARE CONSIDERABLY MORE VARIED WITH THEIR  
HANDLING OF THE WESTERN TROUGHING, FIRST WITH A SHORTWAVE/POSSIBLY  
A COMPACT UPPER LOW MOVING THROUGH SOUTHWESTERN TO SOUTH-CENTRAL  
CANADA WEDNESDAY-THURSDAY AND HOW AND WHEN THE ENERGY GETS  
ABSORBED, AND THEN WITH THE TROUGH'S TRACK EASTWARD AROUND FRIDAY  
INTO THE WEEKEND. GFS RUNS HAD BEEN ON THE FASTER SIDE OF  
CONSENSUS THROUGH THE 12Z RUN, BUT FORTUNATELY THE 18Z GFS SLOWED  
TO BE MORE IN LINE WITH OTHER GUIDANCE. HOWEVER, EVEN BY FRIDAY  
THERE ARE STILL SOME DIFFERENCES, WITH THE CMC AND ECMWF SHOWING  
ENERGY SPILLING INTO THE PACIFIC NORTHWEST TO PROMPT THE TROUGH TO  
MOVE AROUND FRIDAY, WHILE THE GFS IS ORIENTED MORE INLAND WITH THE  
ENERGY AND SHOWS RIDGING ACROSS THE PACIFIC NORTHWEST. DIFFERENCES  
IN ENERGY THERE AND ELSEWHERE LEAD TO CONSIDERABLE MODEL AND  
ENSEMBLE MEMBER VARIABILITY WITH TIMING OF THE TROUGH MOVEMENT  
EASTWARD AS WELL AS ITS EXTENT SOUTHWARD, AFFECTING THE SURFACE  
LOW POSITION AS WELL. THE NEWER 00Z GUIDANCE LIKE THE GFS AND  
ECMWF SHOW A MORE NORTHERN TRACK OF THE UPPER AND SURFACE LOWS  
OVER THE WEEKEND COMPARED TO THE 12/18Z CYCLE USED FOR THIS  
FORECAST, FURTHER INDICATING THE UNCERTAINTY.  
 
THE WPC FORECAST WAS ABLE TO USE A MULTI-MODEL DETERMINISTIC BLEND  
FAVORING THE ECMWF AND GFS EARLY IN THE PERIOD, BUT GRADUALLY  
ADDING IN GEFS AND EC ENSEMBLE MEAN INFLUENCE TO ABOUT HALF BY THE  
LATTER PART OF THE PERIOD AS UNCERTAINTY IN ANY PARTICULAR  
SOLUTION INCREASED. BUT ENSEMBLE MEAN GUIDANCE WAS CERTAINLY  
FLATTER/LESS AMPLIFIED THAN PREFERRED GIVEN THE AMPLE DIFFERENCES  
IN THE INDIVIDUAL ENSEMBLE MEMBERS IN A PATTERN SENSITIVE TO  
SMALLER SCALE SHORTWAVES THAT MAY NOT BE HANDLED TOO WELL. THUS  
FUTURE CHANGES TO THE FORECAST ESPECIALLY BY NEXT WEEKEND MAY BE  
CONSIDERABLE AS GUIDANCE EVOLVES OVER THE NEXT FEW DAYS.  
 
   
..SENSIBLE WEATHER/THREATS
 
 
THE NORTHEASTERN U.S. COULD RECEIVE MULTIPLE ROUNDS OF  
PRECIPITATION THROUGH MUCH OF THE WEEK AS THE UPPER LEVEL AND  
SURFACE LOWS PIVOT AND LINGER OVER THE AREA. INDIVIDUAL  
PRECIPITATION EVENTS SHOULD GENERALLY BE LIGHT TO MODERATE;  
AMOUNTS WILL ADD UP OVER TIME BUT STILL ARE NOT EXPECTED TO BE TOO  
HAZARDOUS. HIGHER ELEVATIONS OF NEW ENGLAND MAY SEE SNOW WITH THE  
PRECIPITATION ACTIVITY. SOME RAIN MAY BEGIN IN THE CENTRAL U.S. AS  
EARLY AS WEDNESDAY NEAR A WARM FRONT AND SURFACE LOW, BUT RAIN IS  
LIKELY TO INCREASE IN COVERAGE AND AMOUNTS AS THE WEEK PROGRESSES  
GIVEN BETTER UPPER-LEVEL SUPPORT AND STRENGTHENING LOW PRESSURE  
THAT WILL EVENTUALLY PUSH EASTWARD INTO THE WEEKEND. UNSETTLED  
WEATHER SHOULD ALSO OCCUR IN THE WESTERN TO NORTH-CENTRAL U.S.,  
WITH AMOUNTS INCREASING FROM THURSDAY INTO FRIDAY AND SATURDAY.  
CONDITIONS WILL LIKELY BE COLD ENOUGH FOR SNOW IN THE NORTHERN  
ROCKIES ON THE BACKSIDE OF THE SURFACE LOW, AND THERE IS ONCE  
AGAIN SOME THREAT OF WINTRY PRECIPITATION SPREADING INTO THE  
NORTHERN HIGH PLAINS AS WELL. BUT THE DETAILS OF THESE THREATS MAY  
NOT COME INTO FOCUS FOR A FEW MORE DAYS GIVEN CONSIDERABLE MODEL  
UNCERTAINTY.  
 
COOLER THAN AVERAGE TEMPERATURES ARE FORECAST FOR THE EASTERN  
THIRD OF THE U.S. WEDNESDAY INTO THURSDAY, WITH THE CORE OF THE  
COLD AIR IN THE GREAT LAKES/CENTRAL APPALACHIANS, WITH  
TEMPERATURES 10-20F BELOW NORMAL AND THE POSSIBILITY OF A FEW  
DAILY RECORD LOWS ON WEDNESDAY. ON THE OTHER HAND WARMER THAN  
NORMAL TEMPERATURES SHOULD SPREAD FROM THE SOUTHWEST/FOUR CORNERS  
STATES INTO SOUTHERN AND CENTRAL PARTS OF THE PLAINS UNDERNEATH  
UPPER RIDGING. BY FRIDAY INTO THE WEEKEND, THE PATTERN SHOULD  
GENERALLY SHIFT TO COOLER THAN AVERAGE TEMPERATURES IN THE NORTH  
AND WARMER THAN AVERAGE IN THE SOUTH. THE NORTHERN PLAINS TO  
MIDWEST ARE FORECAST TO SEE HIGHS NEARING 20F BELOW AVERAGE, BUT  
LOWS MAY BE CLOSER TO NORMAL. MEANWHILE THE SOUTHERN TIER SHOULD  
BE AROUND 10F ABOVE AVERAGE.  
 
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, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, 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/#PAGE=ERO  
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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