434  
FXUS02 KWBC 240659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST MON JAN 24 2022  
 
VALID 12Z THU JAN 27 2022 - 12Z MON JAN 31 2022  
   
..OVERVIEW
 
 
LATEST GUIDANCE CONTINUES TO SHOW A MEAN UPPER LEVEL PATTERN THAT  
FEATURES TROUGHING OVER THE EAST, VARYING DEGREES OF RIDGING OVER  
THE WEST, AND A DEVELOPING NORTHEASTERN PACIFIC TROUGH THAT MAY  
APPROACH THE WEST COAST EARLY NEXT WEEK. WITHIN THIS FAIRLY  
AGREEABLE REGIME THERE ARE STILL SIGNIFICANT UNCERTAINTIES  
REGARDING SPECIFICS OF AN EASTERN U.S. AMPLIFIED TROUGH THAT WILL  
LIKELY SUPPORT A WESTERN ATLANTIC STORM FRIDAY INTO THE WEEKEND  
WITH SOME EFFECTS POSSIBLE OVER NEW ENGLAND IN PARTICULAR, AS WELL  
AS FOR A SHORTWAVE APPROACHING THE WEST COAST LATE THIS WEEK.  
ISSUES NEAR THE WEST COAST MAY HAVE SOME INFLUENCE ON THE FORECAST  
FARTHER TO THE EAST. THERE ARE ALSO DIFFERENCES WITH DETAILS OF  
THE LATE-PERIOD NORTHEASTERN PACIFIC TROUGH, AFFECTING HOW MUCH  
MOISTURE REACHES THE NORTHWEST. BETWEEN THESE AREAS OF  
CONTENTION, A SERIES OF WEAK SYSTEMS MAY BRING LIGHT PRECIPITATION  
TO SOME AREAS FROM THE NORTHERN TIER INTO THE APPALACHIANS. THE  
FORECAST TEMPERATURE PATTERN REMAINS SIMILAR WITH THE EAST  
GENERALLY BELOW NORMAL THROUGH THE WEEKEND AND THE WEST INTO  
PORTIONS OF THE PLAINS ABOVE NORMAL FOR MOST DAYS.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
EVEN THOUGH THE LARGE SCALE MEAN PATTERN HAS BEEN RATHER  
CONSISTENT IN THE GUIDANCE, THE EMBEDDED AREAS OF UNCERTAINTY  
INVOLVE ASPECTS THAT ARE SMALLER IN SCALE AND LEAD TO LOWER  
PREDICTABILITY.  
 
OVER RECENT DAYS, MOST OPERATIONAL MODELS HAVE BEEN VARYING WITH  
THE EXACT DEPICTION OF SHORTWAVE ENERGY WITHIN THE AMPLIFIED UPPER  
TROUGH THAT HEADS INTO THE EAST AND SUPPORTS ATLANTIC CYCLOGENESIS  
LATE WEEK INTO THE WEEKEND--THUS LEADING TO IMPORTANT DIFFERENCES  
IN TRACK/TIMING/STRENGTH OF THE SURFACE SYSTEM. ONE POSITIVE  
TREND IS A DEEPER DEPICTION IN THE ENSEMBLE MEANS COMPARED TO  
PREVIOUS DAYS, SUGGESTING THAT MEMBER SPREAD MAY BE DECREASING  
SOMEWHAT. HOWEVER THERE IS STILL ENOUGH TRACK VARIANCE AMONG THE  
GUIDANCE TO RESULT IN A WIDE VARIETY OF POTENTIAL EFFECTS,  
ESPECIALLY OVER NEW ENGLAND AND TO A LESSER EXTENT FARTHER SOUTH.  
ON ONE HAND THE RECENT CMC RUNS AND ASSOCIATED ENSEMBLES HAVE  
TENDED TO BE ON THE NORTHERN/NORTHWESTERN SIDE OF THE FULL  
GUIDANCE SPREAD AND THE NEW 00Z RUN ACTUALLY BRINGS THE TRACK INTO  
NEW ENGLAND. ON THE OTHER EXTREME THE 12Z ECMWF WAS SO FAR EAST  
THAT IT BROUGHT HARDLY ANY PRECIPITATION AT ALL TO NEW ENGLAND.  
REMAINING SOLUTIONS ARE BETWEEN THESE EXTREMES WITH THE CONSENSUS  
TREND AMONG 12Z/18Z AND NEW 00Z GUIDANCE APPEARING TO BE SOMEWHAT  
WESTWARD. AN INTERMEDIATE APPROACH PROVIDES THE BEST STABILITY  
FOR THE TIME BEING. A MAJOR CHANGE IN THE NEW 00Z ECMWF  
HIGHLIGHTS THE SENSITIVITY OF THE FORECAST, AS IT NOW SHOWS A VERY  
DEEP LOW JUST OFF NEW ENGLAND BY LATE SATURDAY--A LITTLE NORTH OF  
A SIMILARLY WOUND-UP UKMET.  
 
GUIDANCE ALSO CONTINUES TO HAVE DIFFICULTY WITH THE DETAILS OF  
SHORTWAVE ENERGY APPROACHING THE WEST COAST LATE THIS WEEK AND  
THEN FILTERING THROUGH THE WESTERN MEAN RIDGE. LATEST  
GFS/UKMET/CMC RUNS HAVE BEEN SUGGESTING THE POTENTIAL FOR AN UPPER  
LOW TO CLOSE OFF WHILE RECENT ECMWF RUNS AND THE ENSEMBLE MEANS  
HAVE KEPT IT AS AN OPEN WAVE. THE NEW 12Z ECMWF HAS TRENDED MORE  
TO THE OTHER MODELS IN PRINCIPLE. THESE DIFFERENCES FIRST AFFECT  
THE COVERAGE AND AMOUNTS OF PRECIPITATION NEAR THE WEST COAST.  
THEN THE VARIED HANDLING OF THIS ENERGY LEADS TO VARIOUS IDEAS FOR  
HOW MUCH PRECIPITATION MAY DEVELOP OVER THE SOUTHERN  
PLAINS/WESTERN HALF OF THE GULF COAST LATE IN THE PERIOD. FOR THE  
PURPOSES OF A SINGLE DETERMINISTIC FORECAST, PREFER TO MAINTAIN  
THE OPEN WAVE DEPICTION FOR BETTER CONTINUITY BUT WITH FAIRLY LOW  
CONFIDENCE.  
 
ELSEWHERE, THERE IS DECENT MODEL/MEAN CONSENSUS FOR THE DEVELOPING  
NORTHEASTERN PACIFIC TROUGH BUT ITS EVOLUTION HAS SOME COMPLEXITY  
INVOLVING MULTIPLE FEATURES, SO DETAILS MAY TAKE A WHILE TO  
RESOLVE BETTER. THIS FAVORS A MODEL/MEAN BLEND FOR THE TIME  
BEING. AN INITIAL FRONT SHOULD BE DROPPING INTO THE NORTHERN TIER  
BY THURSDAY FOLLOWED BY A WAVE TRACKING FROM THE NORTHERN PLAINS  
THROUGH THE MIDWEST AND GREAT LAKES SATURDAY-MONDAY. SPREAD AND  
RUN-TO-RUN VARIABILITY HAVE BEEN FAIRLY TYPICAL THUS FAR, WITH  
SOME GRADUAL DETAIL ADJUSTMENTS IN CONSECUTIVE CONSENSUS BLENDS.  
 
THE UPDATED FORECAST STARTED WITH A BLEND OF 12Z/18Z MODEL RUNS  
EARLY IN THE PERIOD AND THEN STARTED TO INCORPORATE 18Z GEFS/12Z  
ECMWF MEANS BY DAY 5 SATURDAY, REACHING 50 PERCENT TOTAL WEIGHT BY  
DAYS 6-7 SUNDAY-MONDAY.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
CONTINUE TO MONITOR FORECASTS FOR THE LIKELY ATLANTIC STORM  
DEVELOPMENT LATE THIS WEEK AND WEEKEND. RECENT TRENDS ARE  
INCREASING THE POTENTIAL THAT NEW ENGLAND COULD SEE MEANINGFUL  
PRECIPITATION AND WIND EFFECTS FROM THIS SYSTEM. WITH LESSER  
MAGNITUDES OF EACH, THERE IS ALSO UNCERTAINTY FOR WHAT PORTIONS OF  
THE MID-ATLANTIC MAY EXPERIENCE. TYPICAL GUIDANCE ERRORS FOR SUCH  
SYSTEMS AT THIS TIME FRAME STILL ALLOW FOR SIGNIFICANT CHANGES TO  
THE CURRENT FORECAST. IT IS HOPED THAT ARRIVAL OF SOME OF THE  
SUPPORTING DYNAMICS INTO WESTERN CANADA BY TUESDAY MAY START TO  
PROVIDE IMPROVED REFINEMENT TO THE FORECAST AROUND THEN OR SHORTLY  
THEREAFTER. BEFORE THIS STORM DEVELOPS, LOCATIONS ACROSS THE FAR  
SOUTHERN TIER MAY SEE SOME MOSTLY LIGHT PRECIPITATION. SOME  
LOCATIONS NEAR THE WEST COAST MAY SEE AN INCREASE IN PRECIPITATION  
WITH AN APPROACHING SHORTWAVE/POSSIBLE COMPACT UPPER LOW LATE WEEK  
INTO THE WEEKEND BUT WITH LOW CONFIDENCE IN DETAILS. THIS ENERGY  
COULD EVENTUALLY SUPPORT SOME PRECIPITATION OVER THE SOUTHERN  
PLAINS/WESTERN HALF OF THE GULF COAST EARLY NEXT WEEK. FLOW AHEAD  
OF A NORTHEASTERN PACIFIC UPPER TROUGH SHOULD BRING RAIN AND  
MOUNTAIN SNOW INTO THE NORTHWEST BUT AGAIN WITH LOW CONFIDENCE FOR  
TIMING AND AMOUNTS. A WAVY FRONTAL SYSTEM SHOULD BRING MOSTLY  
LIGHT SNOW TO THE GREAT LAKES AND APPALACHIANS LATE THIS WEEK.  
ONE OR MORE TRAILING WEAK WAVES MAY ALSO PRODUCE SCATTERED LIGHT  
SNOW OVER AREAS FROM THE EXTREME NORTHERN TIER INTO THE GREAT  
LAKES.  
 
ON THURSDAY NORTHERN PARTS OF THE EAST WILL SEE LOWS 10-20F BELOW  
NORMAL AND LOCATIONS NEAR THE EAST COAST WILL SEE HIGHS 10F OR  
MORE BELOW NORMAL. REINFORCING COLD AIR REACHING THE EAST-CENTRAL  
U.S. FRIDAY WILL BRING A BROAD AREA OF TEMPERATURES AT LEAST  
10-15F BELOW NORMAL OVER THE EAST BY SATURDAY. MOST AREAS SHOULD  
REBOUND TOWARD MORE NORMAL READINGS BY NEXT MONDAY. MUCH OF THE  
WEST SHOULD CONTINUE TO SEE MODERATELY ABOVE NORMAL TEMPERATURES  
(LOCALLY PLUS 10-15F ANOMALIES) WHILE THE NORTHERN AND CENTRAL  
PLAINS WILL LIKELY SEE ONE OR MORE DAYS WITH TEMPERATURES 10-20F  
ABOVE NORMAL (ESPECIALLY FRIDAY-SATURDAY). LESSER WARMTH MAY  
EXTEND INTO THE SOUTHERN PLAINS BY THE WEEKEND.  
 
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, 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/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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