668  
FXUS02 KWBC 250701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT MON APR 25 2022  
 
VALID 12Z THU APR 28 2022 - 12Z MON MAY 02 2022  
   
..OVERVIEW
 
 
A MEAN TROUGH AXIS INITIALLY NEAR THE WEST COAST AS THE MEDIUM  
RANGE PERIOD BEGINS THURSDAY WILL PUSH EASTWARD THROUGH THE REST  
OF THIS WEEK, POTENTIALLY FORMING A CLOSED UPPER LOW OVER THE  
NORTH-CENTRAL U.S. OVER THE WEEKEND. A SURFACE LOW IS LIKELY TO  
CONSOLIDATE IN CONJUNCTION WITH THE TROUGH/LOW, SPREADING RAIN TO  
MUCH OF THE CENTRAL U.S. WHILE SNOW IS FORECAST ON THE BACKSIDE OF  
THE LOW ACROSS THE NORTHERN ROCKIES WITH SOME CHANCE OF WINTRY  
WEATHER SPREADING INTO THE NORTHERN HIGH PLAINS AS WELL, ALTHOUGH  
THE DETAILS OF PRECIPITATION AMOUNTS AND PLACEMENT REMAIN  
UNCERTAIN AT THIS POINT. MEANWHILE, SURFACE AND UPPER LOWS WILL  
MOVE SLOWLY AWAY FROM THE NORTHEAST OVER THE WEEKEND AFTER  
SPREADING SOME LIGHT TO MODERATE RAIN AND SNOW ACROSS THE AREA FOR  
THE LATTER PART OF THE WEEK.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
MODEL GUIDANCE REMAINS QUITE AGREEABLE IN KEEPING A SLOW-MOVING  
LOW PRESSURE SYSTEM (BOTH IN THE UPPER LEVELS AND AT THE SURFACE)  
OVER THE CANADIAN MARITIMES THROUGH THE WEEKEND. THERE IS ALSO  
GOOD AGREEMENT ON THE BROAD RIDGE OVER THE CENTRAL U.S. THURSDAY  
NARROWING AND BECOMING SUPPRESSED FRIDAY INTO THE WEEKEND AS  
WESTERN TROUGHING COMES IN, THOUGH WITH VARIOUS DETAILS ON  
EMBEDDED SHORTWAVES TRACKING THROUGH THE OVERALL RIDGE PATTERN.  
THE MORE UNCERTAIN PART OF THE FORECAST LIES IN THE UPPER TROUGH  
OVER THE WESTERN U.S. THURSDAY PUSHING EASTWARD WITH TIME. RECENT  
MODEL GUIDANCE IS IN SOMEWHAT BETTER AGREEMENT THAN A DAY OR SO  
AGO THOUGH, WITH A GENERAL CONSENSUS FOR SHORTWAVE ENERGY TO  
CONSOLIDATE WITHIN THE TROUGH AND FORM AN UPPER LOW BY THE WEEKEND  
IN THE NORTH-CENTRAL CONUS. THERE ARE STILL SOME DIFFERENCES  
PARTICULARLY WITH THE LATITUDINAL POSITION OF THE UPPER LOW. WITH  
THE 12/18Z CYCLE, IT APPEARED THE THE 12Z GFS WAS A BIT SOUTH OF  
CONSENSUS BY AROUND SATURDAY SO PREFERRED THE 18Z GFS INSTEAD THAT  
WAS BETTER CLUSTERED, BUT SOME NEWER 00Z GUIDANCE (PARTICULARLY  
THE CMC) CAME IN FARTHER SOUTH. SIMILAR NORTH-SOUTH SPREAD WAS  
SEEN WITH THE SURFACE LOW POSITIONS THROUGH THE WEEKEND, WITH EVEN  
MORE DIVERGENCE IN POSITION BY MONDAY DEPENDING ON HOW THE UPPER  
LOW MAY LIFT AND/OR WEAKEN. UPSTREAM OF THESE FEATURES, MODELS ARE  
EVEN LESS AGREEABLE WITH THE PATTERN--THE ECMWF AND CMC RUNS HAVE  
SHOWN A STRONG SHORTWAVE SOMEWHERE IN THE NORTHWEST BY EARLY  
SUNDAY WHEREAS GFS RUNS HAVE BEEN WEAKER WITH THAT ENERGY, AND THE  
ECMWF/CMC ARE ALSO QUITE STRONG WITH POSSIBLY A LARGER CLOSED LOW  
IN THE EASTERN PACIFIC BY MONDAY WITH THE GFS RUNS SHOWING A  
DIFFERENT PATTERN.  
 
THE WPC FORECAST WAS BASED ON A MULTI-MODEL BLEND OF DETERMINISTIC  
12/18Z GUIDANCE FAVORING THE ECMWF EARLY IN THE PERIOD, GRADUALLY  
TRANSITIONING TO A BLEND INCLUDING THE ENSEMBLE MEANS  
(PARTICULARLY THE EC MEAN) AS SPREAD AND UNCERTAINTY INCREASED  
CONSIDERABLY. THE RESULTS WERE PRETTY SIMILAR TO THE PREVIOUS  
FORECAST THROUGH SUNDAY.  
 
   
..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. PERIODS OF  
PRECIPITATION 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 DURING THE NIGHT BUT  
MIXING WITH RAIN DURING THE DAY. SOME RAIN IS LIKELY IN THE  
CENTRAL U.S. ON THURSDAY, WHICH SHOULD INCREASE IN COVERAGE AND  
AMOUNTS FRIDAY OVER NORTHERN/CENTRAL PARTS OF THE PLAINS AS THE  
MAIN UPPER TROUGH EXITS THE ROCKIES AND CONSOLIDATES A LOW  
PRESSURE SYSTEM IN THE CENTRAL U.S. 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. IN  
PORTIONS OF THE DAKOTAS, PRECIPITATION MAY BEGIN AS RAIN AND  
TRANSITION TO MIXED PRECIPITATION OR SNOW. HOWEVER, THE EXACT  
DETAILS OF THESE THREATS MAY NOT BE DETERMINED FOR A FEW MORE DAYS  
GIVEN CONTINUED MODEL UNCERTAINTY. BY THE WEEKEND, THE CURRENT  
EXPECTATION IS THAT RAIN WILL SPREAD INTO THE EAST AND COULD  
LINGER OVER THE SOUTHERN PLAINS AS THE FRONT THERE MAY STALL.  
 
THE NORTHEASTERN QUADRANT OF THE U.S. CAN EXPECT COOLER THAN  
NORMAL TEMPERATURES BY AROUND 10-15 DEGREES ON THURSDAY WITH A FEW  
DAILY RECORD LOWS POSSIBLE, BUT TEMPERATURES THERE SHOULD  
GRADUALLY MODERATE CLOSER TO NORMAL BY THE WEEKEND AND EARLY NEXT  
WEEK. BUT BELOW AVERAGE TEMPERATURES ESPECIALLY IN TERMS OF HIGHS  
WILL BE REINFORCED WITH THE INCOMING TROUGH/LOW ACROSS THE  
NORTH-CENTRAL U.S, WITH HIGHS POTENTIALLY AROUND 15-25F BELOW  
NORMAL THROUGH MUCH OF THE MEDIUM RANGE PERIOD. MEANWHILE THE FOUR  
CORNERS STATES TO THE CENTRAL/SOUTHERN HIGH PLAINS WILL SEE WARMER  
THAN NORMAL TEMPERATURES ESPECIALLY THURSDAY AND FRIDAY BEFORE THE  
UPPER RIDGE PROMOTING THE WARMTH IS SUPPRESSED OVER THE WEEKEND.  
SLIGHTLY ABOVE NORMAL TEMPERATURES SHOULD THEN STRETCH ACROSS MUCH  
OF THE SOUTHERN TIER.  
 
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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