462  
FXUS02 KWBC 221900  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 PM EST WED JAN 22 2025  
 
VALID 12Z SAT JAN 25 2025 - 12Z WED JAN 29 2025  
 
   
..OVERVIEW
 
 
IT REMAINS GENERALLY THE CASE THAT BY THE START OF THE PERIOD  
SATURDAY, UPPER TROUGHING WILL BE EXITING THE EAST COAST WITH WEAK  
UPPER RIDGING DEVELOPING BEHIND FOR THE WEEKEND, FINALLY HELPING  
TO MODERATE THE BITTERLY COLD SHORT RANGE TEMPERATURES. MEANWHILE,  
A SHORTWAVE DROPPING INTO THE NORTHERN ROCKIES LATE THIS WEEK WILL  
SPLIT, SENDING NORTHERN STREAM ENERGY ACROSS THE NORTHERN TIER OF  
THE NATION WHILE TRAILING ENERGY DIVES SOUTH TO FORM A CLOSED LOW  
OVER THE SOUTHWEST THAT WILL LINGER AND SLOWLY DRIFT EAST INTO THE  
SOUTHWEST BY EARLY-MID NEXT WEEK. THE UPPER LOW WILL LIKELY BRING  
BENEFICIAL PRECIPITATION PARTS OF SOUTHERN CALIFORNIA THAT HAVE  
BEEN DEALING WITH DEVASTATING WILDFIRES AND ALSO SOME ORGANIZED  
RAINS/TERRAIN SNOWS DOWNSTREAM INTO PARTS OF THE SOUTHWEST.  
 
MEANWHILE, MODERATE TO LOCALLY HEAVY RAINFALL WILL DEVELOP  
DOWNSTREAM ACROSS THE LOWER MISSISSIPPI VALLEY SUNDAY AND MONDAY AS  
A SLOW MOVING FRONTAL BOUNDARY MOVES THROUGH THE REGION.  
ADDITIONAL FRONTAL WAVE GENESIS OVER THE SOUTHERN PLAINS INTO THE  
MIDDLE OF NEXT WEEK GIVEN SOUTHWEST LOW SLOWL APPROACH MAY AGAIN  
INCREASE LEAD RETURN FLOW AND EMERGING RAINFALL TO MONITOR.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
ON THE LARGE SCALE, THE GUIDANCE CONTINUES TO SHOW REASONABLE  
AGREEMENT, BUT THERE REMAINS PLENTY OF UNCERTAINTY IN THE DETAILS  
AND TIMING OF INDIVIDUAL SYSTEMS. RELATIVELY GOOD CLUSTERING EARLY  
PERIOD AS THE SHORTWAVE AMPLIFIES AND A LOW CUTS OFF OVER THE WEST  
COAST SATURDAY-SUNDAY. BY MONDAY THOUGH, SOME GUIDANCE HOLDS THE  
LOW FARTHER WEST (RECENT CMC AND UKMET RUNS), WHILE OTHER GUIDANCE  
(RECENT GFS, ECMWF AND ENSEMBLE MEAN RUNS) PULLS IT FARTHER EAST  
FASTER. MEAN NORTHERN STREAM TROUGHING OVER THE NORTHERN PLAINS-  
GREAT LAKES-NORTHEAST SHOWS UNCERTAINTY IN THE AMPLITUDE OF  
INDIVIDUAL SHORTWAVES DROPPING THROUGH AND RECENT GFS RUNS REMAIN THE  
MOST BULLISH WITH ONE SHORTWAVE FROM THE NORTHERN PLAINS TO THE  
MIDWEST NEXT WEDNESDAY-THURSDAY. ALL THESE SOLUTIONS ARE VIABLE,  
WITH THESE TRENDS OVERALL REMAINING WITH LATEST 12 UTC GUIDANCE.  
 
ACCORDINGLY, WPC GUIDANCE USED A GENERAL MODEL AND ENSEMBLE BLEND,  
GRADUALLY TRANSITIONED MAJORITY WEIGHTLY FROM THE MODELS TO THE  
ENSEMBLE MEANS AMID SLOWLY GROWING FORECAST SPREAD. THIS PROVIDED  
A GOOD STARTING POINT FOR THE SOUTHWEST UPPER LOW EVOLUTION AND  
NORTHERN STREAM TROUGHING/SHORTWAVES. WPC CONTINUITY WAS GOOD.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
COLDER THAN NORMAL TEMPERATURES WILL LINGER THROUGH SATURDAY FOR  
PARTS OF THE SOUTH AND SOUTHEAST WITH DAYTIME HIGHS STILL 5-15F  
BELOW NORMAL WITH OVERNIGHT LOWS BELOW FREEZING. TEMPERATURES WILL  
GRADUALLY MODERATE, RETURNING TO NEAR NORMAL SUNDAY THROUGH EARLY  
NEXT WEEK. ANOMALOUSLY COLD TEMPERATURES WILL ALSO DEVELOP IN THE  
HIGH PLAINS, ROCKIES, AND MUCH OF THE WEST THIS WEEKEND UNDER THE  
INFLUENCE OF UPPER TROUGHING. THE COLDEST ANOMALIES WILL BE IN THE  
HIGH PLAINS AND ROCKIES WHERE HIGH TEMPERATURES COULD BE 10-20  
DEGREES BELOW NORMAL. LATE PERIOD RIDGING OVER THE NORTHERN TIER  
COULD ALLOW TEMPERATURES TO RISE ABOVE NORMAL NEXT WEEK.  
 
PRECIPITATION WISE, A COUPLE OF CLIPPER SYSTEMS AND REINFORCING  
COLD FRONTS WILL PERIODICALLY ENHANCE LAKE EFFECT SNOWS DOWNWIND  
OF THE GREAT LAKES. MEANWHILE, MORE WIDESPREAD RAIN AND MOUNTAIN  
FOCUSING SNOWS WILL BE DROPPING THROUGH THE GREAT BASIN TO  
SOUTHWEST THIS WEEKEND BRINGING BENEFICIAL RAIN TO SOUTHERN  
CALIFORNIA OVER THE WEEKEND. A TIGHTENED GRADIENT BEHIND THE COLD  
FRONT DROPPING SOUTH MAY PRODUCE SOME GUSTY WINDS ALONG PARTS OF  
THE ROCKIES LATE THIS WEEK AND CALIFORNIA AND NEVADA ON SATURDAY  
WITH OFFSHORE FLOW AND MODESTLY FAVORABLE FIRE WEATHER CONDITIONS  
POSSIBLE AGAIN BEHIND THE UPPER LOW NEXT WEEK TO KEEP AN EYE ON.  
 
FARTHER EAST, GULF MOISTURE WILL INTERACT WITH A FRONT APPROACHING  
THE LOWER MISSISSIPPI VALLEY TO TENNESSEE AND OHIO VALLEYS BY THIS  
COMING WEEKEND/EARLY NEXT WEEK. LATEST GUIDANCE CONTINUES TO TREND  
HEAVIER WITH RAINFALL TOTALS OVER PARTS OF THE SOUTHERN U.S., WITH  
THE POTENTIAL FOR HEAVY RAIN AND THUNDERSTORMS ON SUNDAY ACROSS  
THE LOWER MISSISSIPPI VALLEY. THERE WAS ENOUGH SUPPORT FOR A  
MARGINAL RISK IN THE DAY 5/SUNDAY EXCESSIVE RAINFALL OUTLOOK FROM  
EASTERN TEXAS INTO MISSISSIPPI WHERE STORMS MAY TRAIN ALONG A SLOW  
MOVING FRONTAL BOUNDARY. THERE WAS A SEEMINGLY REASONABLE  
CONVECTIVE SIGNAL SHIFT SLIGHTLY TO THE SOUTHWEST COMPARED TO  
EARLIER GUIDANCE THAT WAS INCORPORATED. SNOW OR A WINTRY MIX IS  
POSSIBLE ON THE NORTHERN SIDE OF THIS PRECIPITATION SHIELD MAINLY  
OVER THE OHIO VALLEY, SOUTH-CENTRAL APPALACHIANS, AND POSSIBLY THE  
TENNESSEE VALLEY AND VICINITY. PRECIPITATION MAY SPREAD TOWARDS  
THE EAST COAST EARLY NEXT WEEK AS THE FRONTAL SYSTEM PROGRESSES  
WITH SOME RAINFALL REDEVELOPMENT OF ACROSS THE SOUTHERN PLAINS AND  
LOWER MISSISSIPPI VALLEY AS WELL. THIS SIGNAL IS INCREASING WITH  
DEVELOPMENT OF AN ORGANIZED FRONTAL WAVE WITH SOUTHWEST UPPER  
SYSTEM APPROACH.  
 
SANTORELLI/SCHICHTEL  
 
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 FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 
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