509  
FXUS02 KWBC 211905  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
205 PM EST FRI JAN 21 2022  
 
VALID 12Z MON JAN 24 2022 - 12Z FRI JAN 28 2022  
   
..OVERVIEW
 
 
A STRONG EASTERN PACIFIC RIDGE WILL HELP TO MAINTAIN A BROAD MEAN  
TROUGH ACROSS A MAJORITY OF THE LOWER 48 THROUGH THE MIDDLE OF  
NEXT WEEK. LATER IN THE WEEK GUIDANCE SUGGESTS THE OVERALL  
PATTERN MAY BEGIN TO SHIFT A LITTLE EASTWARD AS PACIFIC ENERGY  
FINALLY NUDGES THE RIDGE INTO THE WESTERN U.S. THIS PATTERN WILL  
FAVOR TEMPERATURES THAT ARE SLIGHTLY ABOVE NORMAL OVER THE WEST,  
VARIABLE OVER THE PLAINS, AND MOSTLY BELOW AVERAGE OVER THE EAST.  
A SOUTHERN STREAM WAVE SHOULD PRODUCE AN AREA OF LOCALLY MODERATE  
TO HEAVY RAIN ALONG/NORTH OF THE GULF COAST EARLY IN THE WEEK  
WHILE LIGHTER PRECIPITATION SPREADS ACROSS THE REST OF THE EASTERN  
U.S. OTHERWISE EXPECT PRECIPITATION COVERAGE AND INTENSITY TO BE  
FAIRLY MODEST OVER MOST OF THE LOWER 48.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE PRIMARY FORECAST UNCERTAINTIES INVOLVE SHORTWAVE DETAILS  
WITHIN THE LOWER 48 MEAN TROUGH, AND BY LATE IN THE WEEK SPECIFICS  
OF PACIFIC ENERGY PUSHING INTO THE RIDGE THAT DRIFTS INTO THE  
WESTERN U.S. THE SOUTHERN STREAM SHORTWAVE EMERGING INTO THE  
SOUTHERN PLAINS EARLY IN THE WEEK IS FAIRLY SIMILAR IN THE  
GUIDANCE, QUICKLY SHEARING AS IT BECOMES EMBEDDED WITHIN FAST  
FLOW. SOME FINE-SCALE SURFACE DETAILS THAT HAVE LOWER  
PREDICTABILITY 4-5 DAYS OUT IN TIME WILL STILL TAKE SOME TIME TO  
BE RESOLVED. MEANWHILE GUIDANCE HAS BEEN DIFFERING FOR SPECIFICS  
OF ONE OR MORE SHORTWAVES DROPPING INTO THE GREAT BASIN/ROCKIES BY  
TUESDAY ONWARD, WITH A BLEND APPROACH LOOKING BEST GIVEN  
PERSISTENT DIFFERENCES AMONG THE MODELS AND BETWEEN CONSECUTIVE  
RUNS. AN INTERMEDIATE SOLUTION APPEARS IDEAL ALONG THE WEST COAST  
BY THURSDAY-FRIDAY. RECENT GFS RUNS THROUGH 06Z HAVE BEEN ON THE  
SLOWER/CLOSED SIDE WITH THE PACIFIC ENERGY (AS WAS THE 12Z CMC)  
AND THUS KEEP MORE RIDGING OVER THE WEST, IN CONTRAST TO THE ECMWF  
THAT HAS BEEN ON THE FAST/OPEN SIDE WITH THE SHORTWAVE. THEIR  
RESPECTIVE ENSEMBLE MEANS ARE LESS EXTREME BUT WITH A TILT TO  
THEIR MODELS' RELATIVE TIMING. THE MEANS HAVE TRENDED TOWARD A  
STRONGER AND FASTER SHORTWAVE OVER THE PAST COUPLE DAYS, WHICH  
WOULD AT LEAST FAVOR LEANING AWAY FROM THE SLOW SIDE OF THE  
SPREAD. THE NEW 12Z GFS/CMC HAVE REMAINED SLOWER AND CLOSED WHILE  
THE NEW 00Z ECMWF HAS TRENDED SLOWER (ALBEIT STRAYING TO THE  
AMPLIFIED SIDE OF THE SPREAD BY EARLY FRIDAY), ULTIMATELY LEADING  
TO BETTER CLUSTERING FOR NOW.  
 
A 00Z/06Z OPERATIONAL MODEL BLEND WAS EFFECTIVE FOR MOST OF THE  
PERIOD. SOME WEIGHTING WAS OFFERED TO THE ENSEMBLES BY DAY 5 DUE  
TO UNCERTAINTIES WITH THE SOUTHWEST SHORTWAVE. THIS WEIGHTING WAS  
INCREASED TO 60 PERCENT BY THE END OF THE PERIOD TO ACCOUNT FOR  
SPREAD IN THE DETERMINISTICS WITH RESPECT TO THE INCOMING PACIFIC  
SHORTWAVE.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A SOUTHERN STREAM SYSTEM TRACKING NEAR THE GULF COAST MONDAY INTO  
TUESDAY SHOULD PRODUCE AN AREA OF LOCALLY MODERATE TO HEAVY  
RAINFALL ACROSS THE FAR SOUTHERN TIER. HIGHEST TOTALS ARE LIKELY  
BE FROM AROUND EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY  
DURING MONDAY-MONDAY NIGHT WITH A LIGHTER TREND FARTHER EASTWARD.  
ALSO EARLY IN THE WEEK A SEPARATE WAVE/FRONT CROSSING THE EAST  
WILL SPREAD MOSTLY LIGHT TO MODERATE SNOW FROM THE GREAT LAKES  
INTO THE NORTHEAST. MOISTURE IN THE NORTHERN PERIPHERY OF THE  
SOUTHERN SYSTEM INTERACTING WITH THE FRONT MAY LEAD TO SOME SNOW  
FROM THE OHIO VALLEY INTO CENTRAL APPALACHIANS AND COULD PROVIDE  
SOME ENHANCEMENT FARTHER NORTHEAST AS WELL. SOME LAKE EFFECT SNOW  
WILL BE POSSIBLE AFTER THE SYSTEM PASSES BY. ANOTHER FRONTAL  
SYSTEM REACHING THE GREAT LAKES LATE IN THE WEEK COULD BRING SOME  
LIGHT SNOW TO THE REGION. AIDED BY LOW LEVEL UPSLOPE FLOW AS HIGH  
PRESSURE BUILDS INTO THE CENTRAL U.S., AN AREA OF SNOW WILL DROP  
SOUTHWARD THROUGH THE ROCKIES AND HIGH PLAINS DURING THE FIRST  
HALF OF THE WEEK. THE REST OF THE WEST SHOULD BE DRY EXCEPT FOR  
POSSIBLY SOME LIGHT PRECIPITATION REACHING THE PACIFIC NORTHWEST  
LATE IN THE WEEK.  
 
WITHIN THE GENERALLY COLD PATTERN OVER THE EASTERN HALF OF THE  
COUNTRY, THE EAST COAST WILL START OUT CHILLY ON MONDAY WITH  
FLORIDA AND THE NORTHEAST MOST LIKELY TO SEE MIN AND/OR MAX  
TEMPERATURES AT LEAST 10F BELOW NORMAL. THE NEXT ARCTIC SURGE  
WILL BRING READINGS DOWN TO 15-25F BELOW NORMAL OVER THE  
MIDWEST/UPPER MISSISSIPPI VALLEY TUESDAY INTO EARLY WEDNESDAY  
WHILE WELL BELOW NORMAL READINGS SPREAD SOUTH AND EAST THROUGH THE  
PLAINS AND EASTERN U.S. INTO THURSDAY WITH SOME MODERATION OVER  
THE EAST BY LATE WEEK. THE PLAINS WILL SEE A WARMING TREND  
WEDNESDAY-FRIDAY WITH INCREASING COVERAGE OF PLUS 10F OR GREATER  
ANOMALIES FROM NORTHERN INTO CENTRAL AREAS. EXPECT THE WEST TO  
SEE MODERATELY ABOVE NORMAL TEMPERATURES NEXT WEEK. ISOLATED  
LOCATIONS COULD SEE PLUS 10F OR SO ANOMALIES.  
 
KEBEDE/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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