436  
FXUS02 KWBC 230707  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
305 AM EDT SAT APR 23 2022  
 
VALID 12Z TUE APR 26 2022 - 12Z SAT APR 30 2022  
   
..OVERVIEW
 
 
AN UPPER TROUGH IS FORECAST TO TRACK FROM THE MIDWEST EASTWARD AND  
DEVELOP AN EMBEDDED UPPER LOW SPINNING OVER THE NORTHEAST FOR THE  
LATTER PART OF THE WEEK. THIS WILL INITIALLY PUSH A COLD FRONT  
WITH RAINFALL ALONG IT ACROSS THE EASTERN SEABOARD TUESDAY, THEN  
STRENGTHENING SURFACE LOW PRESSURE COULD PROMOTE LINGERING  
PRECIPITATION IN THE NORTHEAST AS THE WEEK PROGRESSES. MEANWHILE,  
MEAN TROUGHING IS LIKELY IN THE WEST WITH MULTIPLE SHORTWAVES  
TRACKING THROUGH CAUSING ROUNDS OF PRECIPITATION, WHILE RIDGING IN  
BETWEEN WILL PROMOTE WARM TEMPERATURES ACROSS THE SOUTHWEST TO  
SOUTHERN/CENTRAL HIGH PLAINS.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
MODEL GUIDANCE HAS REMAINED CONSISTENT WITH BETTER THAN AVERAGE  
AGREEMENT FOR THE EASTERN TROUGH DEVELOPING INTO AN UPPER LOW.  
THERE IS STILL SOME VARIABILITY IN THE TIMING OF THE UPPER LOW  
FORMING (DEPENDING IN PART ON WHAT HEIGHT CONTOUR INTERVAL IS  
USED), WITH THE 12Z ECMWF ON THE SLOWER SIDE TO DEVELOP IT BUT THE  
00Z EC SHOWING ITS DEVELOPMENT MORE IN LINE WITH OTHER GUIDANCE.  
MODELS ALSO CONTINUE TO SHOW A STRENGTHENING SURFACE LOW WEDNESDAY  
INTO THURSDAY NEAR NEW ENGLAND, WITH GOOD CLUSTERING IN POSITION  
FOR A MEDIUM RANGE FORECAST. BY FRIDAY INTO SATURDAY, THERE IS  
SOME UNCERTAINTY WITH THE TIMING OF THE UPPER LOW LIFTING OUT  
NORTHEASTWARD, WITH GFS RUNS FASTER WHILE THE CMC RUNS APPEARED  
SLOW INITIALLY, BUT THE 00Z ECMWF CLUSTERS WITH IT. THE LATTER  
CLUSTER IS SLOWER THAN THE ENSEMBLE MEANS AT THIS POINT THOUGH.  
 
GREATER MODEL DIFFERENCES ARE SEEN WITH THE PATTERN OVER THE WEST  
DESPITE GENERAL AGREEMENT INITIALLY FOR TROUGHING STEMMING FROM AN  
UPPER LOW CENTERED NEAR BRITISH COLUMBIA. ONE UNCERTAIN SHORTWAVE  
REACHING THE NORTHWEST AROUND TUESDAY SHOULD CONTINUE ONWARD INTO  
SOUTHERN CANADA, POSSIBLY FORMING A COMPACT UPPER LOW, AS IT  
TRACKS AROUND THE NORTHERN PERIPHERY OF THE CENTRAL U.S. MEAN  
RIDGE. THE EXACT TIMING/TRACK HAVE VARIED A FAIR AMOUNT FROM RUN  
TO RUN AND MODEL TO MODEL. THERE IS ALSO SOME SUGGESTION OF A WEAK  
SHORTWAVE REACHING THE SOUTHWEST AROUND WEDNESDAY BUT IT SHOULD  
HAVE AT MOST MODEST EFFECT AND SHEAR OUT AS IT HEADS DOWNSTREAM  
INTO THE MEAN RIDGE. BY THURSDAY, ANOTHER SHORTWAVE IS LIKELY TO  
DROP INTO THE WEST COAST WHILE THE BULK OF GUIDANCE FAVORS THE  
TROUGH AXIS SHIFTING EASTWARD BY FRIDAY-SATURDAY. THERE HAS BEEN A  
GENERAL TREND IN RECENT GUIDANCE TOWARDS LESS OF A PERSISTENT AND  
STRONG UPPER LOW WITHIN THE TROUGH, THOUGH CONSIDERING THE  
UNCERTAIN PACIFIC ORIGINS OF THE ASSOCIATED SHORTWAVES, CONFIDENCE  
IS LOW. AT THIS POINT, THE MAIN OUTLIER WITH THE PATTERN APPEARS  
TO BE THE CMC RUNS, ESPECIALLY THE 00Z, WHICH SHOWS STRONGER  
ENERGY IN THE EAST PACIFIC AROUND FRIDAY THAT CAUSES THE TROUGH TO  
SLOW DOWN CONSIDERABLY COMPARED TO OTHER GUIDANCE THAT SHOWS  
TROUGHING MOVING INTO THE NORTH-CENTRAL U.S. ON SATURDAY. AT LEAST  
MODEL AGREEMENT REMAINS FAIRLY GOOD FOR UPPER RIDGING IN BETWEEN  
THE WEST AND EAST TROUGH/LOW FEATURES.  
 
THE WPC FORECAST UTILIZED A MULTI-MODEL 12/18Z DETERMINISTIC BLEND  
EARLY IN THE FORECAST PERIOD, PHASING OUT THE CMC AND UKMET IN  
FAVOR OF THE PRETTY AGREEABLE ENSEMBLE MEANS AS THE PERIOD  
PROGRESSED. THIS APPROACH YIELDED MINIMAL CHANGES IN CONTINUITY.  
 
   
..SENSIBLE WEATHER/THREATS
 
 
THE COLD FRONT MOVING ACROSS THE EASTERN SEABOARD TUESDAY AS THE  
PERIOD BEGINS WILL PROMOTE RAIN AND POSSIBLY THUNDERSTORMS ALONG  
IT, BUT ITS REASONABLY FAST PROGRESSION SHOULD KEEP RAINFALL  
AMOUNTS IN THE LIGHT TO MODERATE RANGE. THEN AS SURFACE LOW  
PRESSURE CONSOLIDATES AND PIVOTS, PRECIPITATION WILL REMAIN IN THE  
FORECAST ACROSS THE NORTHEAST THROUGH THE END OF THE WORKWEEK.  
THERE IS SOME POTENTIAL FOR HIGHER ELEVATIONS OF NEW ENGLAND TO  
RECEIVE SNOW WITH THIS PRECIPITATION ACTIVITY. HOW MUCH  
PRECIPITATION FALLS WILL BE SENSITIVE TO EXACT SYSTEM DETAILS.  
MEANWHILE IN THE WEST, UNSETTLED WEATHER IS LIKELY AS SHORTWAVE  
ENERGY MOVES THROUGH THE MEAN TROUGH SOUTH OF A CLOSED UPPER LOW  
POSITIONED OFF BRITISH COLUMBIA THROUGH THURSDAY. GUIDANCE HAS  
PERSISTED IN SHOWING A BETTER DEFINED EPISODE OF RAIN AND HIGH  
ELEVATION SNOW IN THE EARLY-MID PART OF THE WEEK WITH A LEADING  
SHORTWAVE FOLLOWED BY ANOTHER LATER IN THE WEEK WITH A SEPARATE  
SHORTWAVE AND THEN INLAND PROGRESSION OF THE OVERALL TROUGH BY  
FRIDAY. HEAVIER PRECIPITATION IS LIKELY WITH THE LATTER SHORTWAVE,  
WHICH SHOULD BE IN THE FORM OF SNOW OVER THE NORTHERN ROCKIES, AND  
THERE IS ONCE AGAIN SOME POTENTIAL FOR THE NORTHERN HIGH PLAINS TO  
SEE SNOW BY THE LATTER PART OF NEXT WEEK, THOUGH PRECIPITATION  
TYPE IN THE LOWER ELEVATIONS WILL BE QUITE SENSITIVE TO SYSTEM  
DETAILS. MEANWHILE A FRONTAL BOUNDARY DRAPED OVER THE CENTRAL  
PLAINS MAY HELP TO FOCUS SOME RAINFALL AS FAR SOUTHEAST AS THE MID  
MISSISSIPPI VALLEY LATE IN THE WEEK.  
 
THE CORE OF POST-FRONTAL COLD AIR IS FORECAST IN THE  
DAKOTAS/MIDWEST ON TUESDAY AND SPREADING INTO THE GREAT LAKES  
REGION BY WEDNESDAY-THURSDAY, WITH TEMPERATURES 10-25F BELOW  
AVERAGE. AS THE COLD FRONT SWEEPS ACROSS THE EAST, TEMPERATURES  
WILL TRANSITION FROM WARMER THAN NORMAL ON TUESDAY TO BELOW NORMAL  
MIDWEEK, THOUGH WITH SOME TEMPERATURE MODERATION. THE NORTHWEST  
SHOULD SEE NEAR TO SLIGHTLY BELOW AVERAGE TEMPERATURES, BUT BY  
LATE WEEK TEMPERATURES IN THE NORTHERN ROCKIES/PLAINS MAY BECOME  
MUCH BELOW NORMAL ESPECIALLY IN TERMS OF HIGHS WITH THE  
POSSIBILITY OF MORE POTENT TROUGHING ALOFT. MEANWHILE FARTHER  
SOUTH, RIDGING IN PLACE WILL SPREAD WARMER THAN NORMAL  
TEMPERATURES FROM THE SOUTHWEST/FOUR CORNERS STATES INTO NORTHERN  
AND CENTRAL PARTS OF THE PLAINS, WITH TEMPERATURES IN THE 90S IN  
MANY AREAS.  
 
TATE/RAUSCH  
 
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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