142  
FXUS02 KWBC 241856  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 PM EDT TUE MAY 24 2022  
 
VALID 12Z FRI MAY 27 2022 - 12Z TUE MAY 31 2022  
   
..WEATHER PATTERN OVERVIEW
 
 
AN UPPER TROUGH WITH POSSIBLE EMBEDDED CLOSED LOW WILL BE CROSSING  
THE EASTERN U.S. LATE THIS WEEK INTO THE WEEKEND, WITH SOME  
UNCERTAINTY OVER HOW QUICKLY IT AND THE ASSOCIATED SURFACE  
WAVE/FRONTAL SYSTEM WILL ULTIMATELY CLEAR THE EAST COAST.  
MEANWHILE, A SHORTWAVE REACHING THE NORTHWESTERN U.S. BY FRIDAY  
WILL BE AT THE LEADING EDGE OF A LARGER SCALE MEAN TROUGH THAT  
SHOULD AMPLIFY OVER THE WEST DURING THE WEEKEND AND EARLY NEXT  
WEEK. A STRONG RIDGE WILL BUILD OVER AN INCREASING PORTION OF THE  
EASTERN HALF OF THE COUNTRY AS THE WESTERN TROUGH DEEPENS.  
PRIMARY REGIONS OF FOCUS FOR PRECIPITATION WILL BE OVER THE EAST  
WITH THE LATE WEEK SYSTEM, AND THEN FROM THE NORTHWEST THROUGH THE  
NORTHERN-CENTRAL PLAINS INTO WESTERN GREAT LAKES WITH A LEADING  
FRONTAL SYSTEM AND EMBEDDED WAVES THAT SET UP OVER THE CENTRAL  
U.S. AS THE PATTERN AMPLIFIES WHILE A TRAILING PACIFIC SYSTEM ALSO  
ENHANCES PRECIPITATION OVER PARTS OF THE WEST. THE SOUTHERN HIGH  
PLAINS WILL LIKELY SEE WELL ABOVE NORMAL TEMPERATURES THROUGH THE  
PERIOD. FARTHER NORTH, THE ABOVE NORMAL ANOMALIES WILL PUSH  
EASTWARD AND EXPAND WITH TIME WHILE BELOW NORMAL READINGS SPREAD  
ACROSS THE NORTHWEST AND INTO THE GREAT BASIN/NORTHERN PLAINS.  
   
..MODEL GUIDANCE AND PREFERENCES
 
 
THROUGH THE 00Z/06Z MODEL CYCLES, MOST GUIDANCE EXHIBITED A  
PRONOUNCED SLOWER TREND WITH THE UPPER TROUGH/LOW CROSSING THE  
EAST. THE CMC WAS THE ONE FASTER HOLDOUT, THOUGH THE 06Z GFS DID  
NUDGE A BIT FASTER THAN THE 00Z VERSION. NEW 12Z RUNS HAVE REALLY  
LOWERED THE CONFIDENCE IN ANY SCENARIO THOUGH, AS THE  
GFS/UKMET/ECMWF HAVE TRENDED FASTER BY WAY OF SOME COMBINATION OF  
FASTER PROGRESSION OF THE INITIAL TROUGH AND/OR GREATER  
INTERACTION WITH A MORE AMPLIFIED NORTHERN STREAM TROUGH WHILE THE  
CMC HAS JUMPED BACK TO THE 00Z ECMWF. MEANWHILE THE MODELS ARE  
STILL IN THE PROCESS OF TRYING TO RESOLVE THE DETAILS OF PACIFIC  
DYNAMICS THAT SUPPORT A SYSTEM TRACKING TOWARD THE NORTHWEST  
AROUND SATURDAY. THE 06Z GFS WAS THE DEEP EXTREME AND THE NEW 12Z  
GFS HAS TRENDED CLOSER TO OTHER SOLUTIONS. ON THE OTHER HAND THE  
12Z ECMWF HAS BECOME A WEAK/SUPPRESSED EXTREME. GUIDANCE AGREES  
FAIRLY WELL THAT INCOMING PACIFIC ENERGY WILL DIG INTO THE WESTERN  
U.S., BUT WITH TYPICAL DIFFERENCES FOR THE DETAILS. RECENT  
ENSEMBLE MEAN TRENDS IMPLY AT LEAST A MODERATE DEGREE OF SUPPORT  
FOR LATEST GFS/ECMWF/CMC RUNS THAT SHOW AN EMBEDDED CLOSED LOW FOR  
A PERIOD OF TIME.  
 
BASED ON THE ARRAY OF 00Z/06Z GUIDANCE, THE UPDATED FORECAST  
STARTED WITH A BLEND OF 06Z GFS AND 00Z ECMWF/UKMET/CMC EARLY IN  
THE PERIOD WITH THE LEAST WEIGHT ON THE CMC DUE TO ITS FASTER  
EASTERN UPPER TROUGH. THEN THE FORECAST TRANSITIONED TO A BLEND  
OF 06Z GFS/00Z ECMWF AND THEIR ENSEMBLE MEANS. THE NEW GUIDANCE  
IS SUGGESTING A POTENTIAL FASTER REVERSAL FOR THE INITIAL EASTERN  
SYSTEM BUT BETTER STABILITY FOR THE LARGE SCALE PATTERN BY EARLY  
NEXT WEEK.  
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
AREAS OF HEAVY RAINFALL WITH THE INITIAL EASTERN SYSTEM SHOULD BE  
TAPERING OFF BY FRIDAY, ALTHOUGH A CORRIDOR OF SHOWERS AND STORMS  
IS STILL POSSIBLE ACROSS THE EAST COAST STATES AHEAD OF A  
WEAKENING COLD FRONT. THERE IS THE POTENTIAL FOR SOME REPEATED  
ROUNDS OF CONVECTION WITH HEAVY RAIN ACROSS PORTIONS OF THE  
SOUTHERN MID-ATLANTIC/CAROLINAS BUT THE POTENTIAL FOR ANY FLOODING  
APPEARS MARGINAL. POCKETS OF HEAVY RAINFALL ARE ALSO POSSIBLE  
ACROSS PORTIONS OF THE NORTHEAST, ALTHOUGH THE SYSTEM SHOULD BE  
MORE PROGRESSIVE THERE. AS RAINFALL DIMINISHES IN  
COVERAGE/INTENSITY OVER THE EAST, THE DOMINANT FOCUS FOR  
PRECIPITATION WILL EXTEND FROM THE NORTHWEST THROUGH THE  
NORTHERN-CENTRAL PLAINS INTO WESTERN GREAT LAKES. SHOWERS AND  
STORMS WILL INITIALLY DEVELOP ACROSS THE NORTHERN PLAINS AND UPPER  
MIDWEST IN RESPONSE TO A DEVELOPING LOW PRESSURE/FRONTAL SYSTEM  
OVER THE NORTH-CENTRAL U.S. WHILE SOME PRECIPITATION EXTENDS BACK  
INTO THE NORTHERN ROCKIES AND VICINITY. A SYSTEM EXPECTED TO  
REACH THE NORTHWEST AROUND SATURDAY COULD BRING AN EPISODE OF  
ENHANCED PRECIPITATION TO PARTS OF THE REGION, FOLLOWED BY THIS  
MOISTURE STREAMING ACROSS THE ROCKIES AND INTERACTING WITH THE  
WAVY FRONTAL SYSTEM SET UP OVER THE PLAINS. COLDER TRENDS OVER  
THE NORTHWEST/NORTHERN ROCKIES SHOULD INCREASE THE POTENTIAL FOR  
SOME LATE SEASON HIGH ELEVATION SNOW BY AROUND SUNDAY-MONDAY WHILE  
SOME AREAS OF HEAVY RAINFALL COULD DEVELOP OVER NORTHERN TIER  
AREAS AS WELL. IT WILL TAKE ADDITIONAL TIME TO RESOLVE THE  
DETAILS WITHIN AN AMPLIFIED PATTERN THAT WOULD TEND TO INCREASE  
THE POTENTIAL FOR A HEAVY PRECIPITATION EVENT.  
 
TEMPERATURES WILL WARM UP CONSIDERABLY ACROSS THE PLAINS BY THE  
END OF THE WEEK WITH HIGHS REACHING 10-20F ABOVE NORMAL OVER SOME  
AREAS, INCLUDING 100-105F OR SO READINGS OVER WESTERN TEXAS WHERE  
SOME DAILY RECORDS COULD BE CHALLENGED. THE SOUTHERN HIGH PLAINS  
WILL REMAIN ON THE HOT SIDE INTO EARLY NEXT WEEK BUT WITH HIGHS  
DECLINING AT LEAST A FEW DEGREES. MEANWHILE THE HEAT WILL BUILD  
EASTWARD TO INCLUDE THE GREAT LAKES/OHIO VALLEY AND EVENTUALLY THE  
EAST COAST THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK,  
COMPLIMENTS OF THE BUILDING UPPER RIDGE AND SOUTHERLY FLOW AHEAD  
OF THE WAVY MEAN FRONT SETTING UP OVER THE PLAINS. IN CONTRAST,  
OVER THE COURSE OF THE PERIOD MUCH COOLER WEATHER WILL SPREAD  
ACROSS THE NORTHWEST/NORTHERN ROCKIES AND THEN INTO THE GREAT  
BASIN AND NORTHERN PLAINS AS UPPER TROUGHING DEEPENS OVER THE  
WESTERN U.S. WITHIN THIS AREA, HIGHS OF 10-20F BELOW NORMAL WILL  
BE MOST LIKELY SUNDAY-TUESDAY.  
 
RAUSCH/HAMRICK  
 
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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