685  
FXUS02 KWBC 310702  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
201 AM EST MON JAN 31 2022  
 
VALID 12Z THU FEB 03 2022 - 12Z MON FEB 07 2022  
 
...HEAVY RAINFALL LIKELY ACROSS THE CENTRAL GULF COAST AND  
TENNESSEE VALLEY ON THURSDAY, WITH A SIGNIFICANT WINTER STORM FROM  
THE MIDWEST TO GREAT LAKES AND INTERIOR NORTHEAST...  
 
   
..OVERVIEW
 
 
MEAN TROUGHING SHOULD DOMINATE MUCH OF THE CONUS THROUGH THE  
MEDIUM RANGE AS STRONG UPPER RIDGING BUILDS OVER BOTH THE WESTERN  
ATLANTIC AND EAST PACIFIC. A SHORTWAVE INITIALLY OVER THE ROCKIES  
ON THURSDAY WILL DRIVE A POTENT COLD FRONT EASTWARD THROUGH FRIDAY  
BRINGING WIDESPREAD HEAVY RAIN TO THE SOUTH AND A POTENTIALLY  
SIGNIFICANT WINTER STORM FROM THE OHIO VALLEY TO THE INTERIOR  
NORTHEAST. ADDITIONAL WAVES OF SHORTWAVE ENERGY DROPPING DOWN THE  
EAST SIDE OF THE RIDGE IN THE WEST, SHOULD HELP REINFORCE MEAN  
TROUGHING ACROSS THE CENTRAL U.S. THROUGH NEXT WEEKEND, WHILE  
NORTHERN STREAM SHORTWAVES SEND A SERIES OF LOW PRESSURE SYSTEMS  
ACROSS THE NORTHERN TIER STATES.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
GUIDANCE CONTINUES TO EXHIBIT OVERALL GOOD AGREEMENT REGARDING AN  
AMPLIFIED SHORTWAVE INITIALLY OVER THE ROCKIES ON THURSDAY AND  
INTO THE MID-SOUTH/EAST FRIDAY-SATURDAY. THERE REMAIN SOME  
DIFFERENCES IN THE SHORTWAVE TIMING ESPECIALLY INTO THE EAST,  
THOUGH THE CMC IS NOTABLY MORE AMPLIFIED WITH THIS SYSTEM AS A  
WHOLE. GUIDANCE SHOWS THIS ENERGY MAY ULTIMATELY COMBINE WITH A  
NORTHERN STREAM SHORTWAVE THROUGH THE GREAT LAKES/NORTHEAST LATE  
THIS WEEK TO HELP INDUCE A DEEPENING SURFACE LOW WELL OFF THE  
NORTHEAST COAST. A GENERAL NON-CMC MODEL COMPROMISE SEEMED A GOOD  
STARTING POINT FOR NOW THROUGH DAY 5 FOR THIS SYSTEM WHICH ALSO  
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST.  
 
AFTER THIS, THE GUIDANCE SHOWS ANOTHER COUPLE OF SHORTWAVES  
ROUNDING THE TOP OF THE RIDGE AND DIVING INTO THE SOUTHWEST, THE  
FIRST ON FRIDAY AND THE NEXT ON SUNDAY. THERE CONTINUES TO BE SOME  
PRETTY SIGNIFICANT VARIABILITY IN STRENGTH AND TIMING OF THESE  
SYSTEMS, ESPECIALLY THE SECOND ONE. WITH THAT ONE, THE GFS HAS  
CONSISTENTLY BEEN MUCH STRONGER IN SHOWING A DEEP CLOSED LOW  
SETTLING INTO THE SOUTHWEST/NORTHERN BAJA CALIFORNIA  
SUNDAY-MONDAY. THE ECMWF IS BACK AND FORTH BETWEEN A SIMILAR  
CLOSED LOW SOLUTION AND A WEAKER/MORE PROGRESSIVE SHORTWAVE INTO  
THE PLAINS. THE 31/12Z CMC HAS A NICE MIDDLE GROUND. AT THIS  
POINT, GIVEN THE UNCERTAINTY AND RUN TO RUN INCONSISTENCIES, IT  
SEEMED PRUDENT TO LEAN MORE ON THE ENSEMBLE MEANS DURING THE  
LATTER HALF OF THE FORECAST PERIOD, ALTHOUGH ENSEMBLE PLOTS SHOW  
ENOUGH SUPPORT AMONGST VARIOUS MEMBERS FOR EITHER SOLUTION.  
 
NORTHERN STREAM SHORTWAVES WILL DRIVE A TRAIN OF LOW PRESSURE  
SYSTEMS ACROSS THE NORTHERN PLAINS/GREAT LAKES REGION THROUGH THE  
PERIOD. THE MODELS SHOW BETTER AGREEMENT OVERALL ON THESE THAN IN  
THE MORE VOLATILE SOUTHERN STREAM, BUT GIVEN TIMING AND  
INTERACTION WITH THAT SOUTHERN STREAM, THERE REMAINS PLENTY OF  
UNCERTAINTY IN THE DETAILS. SOME INCORPORATION OF THE  
DETERMINISTIC SOLUTIONS LATE PERIOD HELPED TO BRING SOME ADDED  
DEFINITION TO THESE SYSTEMS WHERE THE ENSEMBLE MEANS MAY TEND TO  
WASH OUT.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
AMPLIFIED TROUGH OUT OF THE SOUTHWEST ON THURSDAY WILL CONTINUE TO  
THREAT FOR HEAVY RAINFALL AND A SIGNIFICANT WINTER STORM TO THE  
NORTH INTO THE THURSDAY-FRIDAY TIME PERIOD. AMPLE GULF MOISTURE  
WILL BE DRAWN NORTHWARD AHEAD OF THE TROUGH AND ASSOCIATED SURFACE  
COLD FRONT RESULTING IN WIDESPREAD MODERATE TO HEAVY PRECIPITATION  
FROM THE LOWER MISSISSIPPI VALLEY INTO THE NORTHEAST. BEST CHANCE  
FOR HEAVY RAINFALL EXTENDS FROM THE CENTRAL GULF COAST ON THURSDAY  
INTO THE SOUTHERN/CENTRAL APPALACHIANS AND INTERIOR EAST. THE  
OVERALL PATTERN CONTINUES TO SUPPORT A THREAT FOR EXCESSIVE  
RAINFALL/FLASH FLOODING. ALTHOUGH PLENTY OF UNCERTAINTIES IN THE  
DETAILS LINGER, MODELS SEEM TO BE BETTER LATCHING ONTO THE  
GREATEST THREAT FROM THE CENTRAL GULF COAST INTO THE TENNESSEE  
VALLEY WHERE ANOMALOUS PRECIPITABLE WATER VALUES, LIFT, AND  
MODERATE INSTABILITY SHOULD SUPPORT SEVERAL INCHES OF RAINFALL  
ACROSS THIS REGION.  
 
ON THERE NORTH SIDE, THE THREAT FOR A SIGNIFICANT WINTER STORM  
INTO PARTS OF THE OHIO VALLEY/GREAT LAKES/INTERIOR NORTHEAST WILL  
CONTINUE FROM THE SHORT RANGE PERIOD. HEAVY ACCUMULATING SNOW IS  
LIKELY, WHILE POSSIBLE IMPACTFUL SLEET AND FREEZING RAIN JUST TO  
THE SOUTH WITHIN THE TRANSITION ZONE BETWEEN THE RAIN TO THE SOUTH  
AND SNOW TO THE NORTH. EXACT AMOUNTS OF ANY WINTRY PRECIPITATION  
REMAIN HIGHLY DEPENDENT ON THE LOWER-CONFIDENCE DETAILS OF  
EJECTING SHORTWAVE ENERGY, FRONTAL WAVES, AND TIMING OF COLDER  
TEMPERATURES.  
 
ABOVE AVERAGE TEMPERATURES (GENERALLY +10-15F) WILL SPREAD ACROSS  
THE EAST THURSDAY-FRIDAY. MEANWHILE, AS ARCTIC HIGH PRESSURE DIVES  
INTO THE CENTRAL U.S. BEHIND THE COLD FRONT MIDWEEK, DOWNRIGHT  
CHILLY AND MUCH BELOW NORMAL TEMPERATURES WILL SPREAD FROM THE  
CENTRAL U.S. TO THE MIDWEST AND EVENTUALLY THE EAST BY THE  
WEEKEND. WIDESPREAD DAYTIME HIGHS (AND SLIGHTLY LESS EXTREME  
OVERNIGHT LOWS) AS MUCH AS 10-25 DEGREES BELOW AVERAGE ARE LIKELY  
WITH VALUES AS MUCH AS 30-35 BELOW NORMAL AS FAR SOUTH AS OKLAHOMA  
AND NORTH/CENTRAL TEXAS. THESE TEMPERATURES MAY MODERATE SLIGHTLY  
AS THEY SHIFT EAST INTO THE OHIO VALLEY/GULF COAST STATES NEXT  
FRIDAY AND THE EAST ON SATURDAY. THE WEST COAST STATES SHOULD BE  
NEAR NORMAL INTO WEEKEND, TRENDING SLIGHTLY WARMER THE REST OF THE  
PERIOD OWING TO AMPLIFIED RIDGING ACROSS THE EAST PACIFIC.  
 
SANTORELLI  
 
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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