252  
FXUS02 KWBC 211855  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
254 PM EDT MON MAR 21 2022  
 
VALID 12Z THU MAR 24 2022 - 12Z MON MAR 28 2022  
   
..OVERVIEW
 
 
EXPECT AN AMPLIFIED UPPER LEVEL PATTERN FROM LATE THIS WEEK INTO  
EARLY NEXT WEEK, WITH SOME DEGREE OF PROGRESSION. AN EASTERN  
PACIFIC TROUGH SHOULD MOVE INTO THE WEST BY AROUND NEXT MONDAY  
WHILE THE MEAN RIDGE PERSISTING OVER THE WEST INTO THE WEEKEND  
PUSHES INTO THE CENTRAL U.S. THIS GRADUAL SHIFT IN THE PATTERN  
WILL EVENTUALLY BRING SOME MOISTURE INTO THE WEST AND MODERATION  
OF POTENTIAL RECORD WARMTH OVER CALIFORNIA AND THE GREAT  
BASIN/SOUTHWEST. MEANWHILE THE ELONGATED UPPER LOW/TROUGH OVER THE  
EAST-CENTRAL U.S. AS OF EARLY THURSDAY AND THE ASSOCIATED  
PRECIPITATION WILL LIFT AWAY FAIRLY QUICKLY BUT UPSTREAM  
SHORTWAVES WILL REINFORCE A FAIRLY DEEP MEAN TROUGH OVER THE EAST,  
PRODUCING CHILLY TEMPERATURES ALONG WITH ONE OR MORE EPISODES OF  
MOSTLY LIGHT RAIN/SNOW OVER THE NORTHERN HALF OF THE REGION.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST CYCLE OF GUIDANCE SHOWS DECENT AGREEMENT WITH THE LARGE  
SCALE PATTERN BUT THERE ARE PERSISTENT DETAIL UNCERTAINTIES. FOR  
THE SYSTEM OVER THE EAST AS OF EARLY THURSDAY, CONSENSUS SHOWS A  
TRIPLE POINT WAVE OVER THE MID-ATLANTIC BECOMING THE MORE DOMINANT  
FEATURE FRIDAY-SATURDAY AS IT TRACKS OVER/NEAR NEW ENGLAND AND  
INTO THE CANADIAN MARITIMES. TRACK DIFFERENCES ARE GENERALLY  
WITHIN TYPICAL SPREAD FOR A FEW DAYS OUT IN TIME. INTO SATURDAY, A  
FASTER TREND IN THE 12Z CMC VERSUS ITS QUESTIONABLY SLOW 00Z  
VERSION HAS IMPROVED CLUSTERING FOR THE SHORTWAVE INITIALLY  
ROUNDING THE WESTERN RIDGE AND THEN DIGGING INTO THE EASTERN MEAN  
TROUGH. THUS FAR THERE IS NOT MUCH OF A SIGNAL FOR FLOW TO  
SEPARATE WITHIN THE TROUGH AS DEPICTED IN THE NEW 12Z UKMET BY  
EARLY SUNDAY. THE REINFORCING TROUGH ENERGY SHOULD SUPPORT  
OFFSHORE LOW PRESSURE BY EARLY SUNDAY, MOST LIKELY OFF THE  
NORTHEAST AND THEN TRACKING INTO/NEAR THE CANADIAN MARITIMES PER  
THE MODEL AND ENSEMBLE MAJORITY.  
 
AT LEAST BEFORE TODAY'S 12Z CYCLE, OVER THE PAST COUPLE DAYS THE  
ECMWF/ECMWF MEAN HAVE GENERALLY BEEN MORE CONSISTENT THAN THE  
GFS/GEFS WITH THE HANDLING OF THE EASTERN PACIFIC UPPER TROUGH  
MOVING INTO THE WEST. THE MAIN ADJUSTMENT IN THE ECMWF/ECMWF MEAN  
HAS BEEN A SLIGHTLY FASTER TREND. ON THE OTHER HAND GFS RUNS HAVE  
VARIED CONSIDERABLY FOR THE HANDLING OF INDIVIDUAL COMPONENTS OF  
THE OVERALL TROUGH AND UPSTREAM FLOW. 12Z/20 THROUGH 00Z/21 RUNS  
WERE QUICK TO SEPARATE FLOW WITHIN THE TROUGH, LEADING TO AN UPPER  
LOW HANGING BACK WELL OFFSHORE INTO EARLY NEXT WEEK. MORE RECENT  
06Z/12Z RUNS HAVE ADJUSTED FASTER AND BETTER FIT WITHIN THE  
ECMWF-ECENS/CMC-CMCENS CLUSTER. HOWEVER THE 06Z GFS DIFFERED FROM  
MOST SOLUTIONS IN BRINGING ENOUGH SOUTHERN STREAM ENERGY INTO THE  
PLAINS LATE IN THE PERIOD TO RAISE EASTERN U.S. HEIGHTS MORE THAN  
CONSENSUS (00Z AND NEW 12Z RUNS APPEARED MORE REASONABLE). THE  
GEFS MEAN HAS TRENDED A BIT SLOWER OVER THE PAST DAY. INDIVIDUAL  
ENSEMBLE MEMBER SPREAD BECOMES VERY BROAD LATE IN THE PERIOD SO  
CONFIDENCE IN ANY PARTICULAR SOLUTION IS ONLY MODERATE AT BEST,  
AND NOW THE 12Z ECMWF'S CHANGE TO MORE FLOW SEPARATION AND SLOWER  
UPPER LOW FURTHER HIGHLIGHT THE UNCERTAINTY HERE.  
 
REVIEW OF 00Z/06Z GUIDANCE LED TO USING THE 06Z GFS/ECMWF AND  
LESSER WEIGHT OF THE 00Z UKMET/CMC FOR THE FIRST HALF OF THE  
FORECAST, AND DOWNPLAYING THE SLOW CMC FOR THE REINFORCING EASTERN  
U.S. TROUGH. THE REST OF THE PERIOD TRANSITIONED TO A MODEL/MEAN  
BLEND AND EVENTUALLY SPLIT GFS INPUT AMONG THE 00Z/06Z RUNS AS ONE  
RUN OR THE OTHER HAD MORE OR LESS APPEALING TRAITS DEPENDING ON  
THE REGION. THE END RESULT PROVIDED GOOD CONTINUITY IN PRINCIPLE.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
AN OCCLUDED LOW PRESSURE SYSTEM WILL BE IN PLACE OVER THE UPPER  
GREAT LAKES EARLY THURSDAY, WITH LINGERING LIGHT PRECIPITATION  
THERE BUT WITH HEAVIER AMOUNTS POSSIBLE ALONG ITS ASSOCIATED COLD  
FRONT NEAR THE EAST COAST. EXPECT MAINLY RAIN BUT SNOW WILL BE  
POSSIBLE OVER NORTHERN NEW ENGLAND, AND THE SNOW COULD LINGER INTO  
FRIDAY OVER MAINE NEAR A DEVELOPING COASTAL LOW. SHORTWAVE ENERGY  
AND WEAK LOW PRESSURE/FRONTAL SYSTEMS COULD LEAD TO LIGHT  
PRECIPITATION SPREADING FROM THE NORTHERN ROCKIES/PLAINS THURSDAY  
INTO THE GREAT LAKES REGION TO THE CENTRAL/NORTHERN APPALACHIANS  
AND NORTHEAST LATE WEEK INTO THE WEEKEND. SOME OF THIS  
PRECIPITATION MAY BE IN THE FORM OF SNOW OVER HIGHER  
ELEVATIONS/NORTHERN LATITUDES. THE CENTRAL/EASTERN U.S. EVOLUTION  
MAY LEAD TO A PERIOD OF BRISK TO STRONG WINDS FROM THE NORTHERN  
PLAINS LATE THIS WEEK INTO THE EAST DURING THE WEEKEND.  
PRECIPITATION AHEAD OF THE APPROACHING EASTERN PACIFIC UPPER  
TROUGH WILL LIKELY REACH THE PACIFIC NORTHWEST AROUND FRIDAY AND  
THEN SPREAD ACROSS MORE OF THE WEST THEREAFTER. MOST OF THIS  
ACTIVITY SHOULD BE IN THE LIGHT TO MODERATE RANGE BUT SOME LOCALLY  
HEAVIER TOTALS COULD BE POSSIBLE DEPENDING ON EXACT SYSTEM  
DETAILS. COVERAGE AND INTENSITY OF THIS PRECIPITATION BECOMES  
INCREASINGLY UNCERTAIN BY LATE WEEKEND INTO EARLY NEXT WEEK.  
 
UNSEASONABLY WARM TEMPERATURES WILL BUILD AND EXPAND UNDERNEATH  
UPPER RIDGING FROM THE WESTERN U.S. INTO THE PLAINS. HIGHS THAT  
ARE 10-20F ABOVE NORMAL WILL BE COMMON OVER CALIFORNIA AND THE  
CENTRAL GREAT BASIN/SOUTHWEST THURSDAY AND FRIDAY, WITH SOME PLUS  
20-25F ANOMALIES APPEARING IN THE GREAT BASIN SATURDAY AND MOVING  
TO THE NORTHERN/CENTRAL HIGH PLAINS EARLY NEXT WEEK AS THE UPPER  
RIDGE AXIS SHIFTS. DAILY RECORD TEMPERATURES COULD BE TIED OR SET  
ACROSS CALIFORNIA AND EASTWARD. THE MOST LIKELY SCENARIO HAS AN  
INCREASING PORTION OF THE WEST SEEING HIGHS CLOSER TO NORMAL BY  
NEXT MONDAY BUT THERE IS LOWER POTENTIAL THAT ABOVE NORMAL  
READINGS COULD PERSIST A LITTLE LONGER. MEANWHILE, COOLER AIR  
UNDERNEATH THE UPPER TROUGH/LOW OVER THE CENTRAL INTO EASTERN U.S.  
SHOULD MODERATE AS IT MOVES EASTWARD, WITH TEMPERATURES GENERALLY  
10F OR LESS BELOW NORMAL. HOWEVER, ADDITIONAL COLD FRONTS AND  
UPPER ENERGY WILL BRING BELOW NORMAL TEMPERATURES TO PARTS OF THE  
EASTERN THIRD OF THE U.S. BY SUNDAY, WITH THE GREAT LAKES AND  
CENTRAL APPALACHIANS SEEING 10-15F BELOW NORMAL HIGHS.  
 
RAUSCH/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  
 
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  
 

 
 

 
 
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