695  
FXUS02 KWBC 211856  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
155 PM EST MON FEB 21 2022  
 
VALID 12Z THU FEB 24 2022 - 12Z MON FEB 28 2022  
 
...HEAVY TO EXCESSIVE RAINFALL THREAT FROM THE MID-SOUTH TO THE  
CENTRAL APPALACHIANS THURSDAY ALONG WITH A SIGNIFICANT HEAVY  
SNOW/ICE THREAT FROM THE MID-MISSISSIPPI VALLEY NORTHEASTWARD TO  
THE NORTHEAST THURSDAY-FRIDAY...  
   
..OVERVIEW
 
 
A POTENT SHORTWAVE IS FORECAST TO TRACK FROM THE FOUR CORNERS  
REGION THURSDAY AND LIKELY COMBINE WITH A NORTHERN STREAM  
SHORTWAVE IN THE GREAT LAKES/OHIO VALLEY FRIDAY, WHILE MOISTURE  
STREAMS AHEAD OF THE TROUGH INTO THE VICINITY OF A FRONTAL  
BOUNDARY TO CAUSE PRECIPITATION ACROSS THE SOUTH-CENTRAL TO  
NORTHEASTERN U.S. THROUGH FRIDAY. COLD HIGH PRESSURE WILL CAUSE  
SNOW AND ICE ON THE NORTHERN/WESTERN SIDE OF THE PRECIPITATION  
SHIELD, ALONG WITH MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF THE  
COUNTRY. THE PATTERN SHOULD CALM DOWN SOMEWHAT BY THE WEEKEND INTO  
EARLY NEXT WEEK, THOUGH COLD TEMPERATURES WILL PERSIST FOR MOST  
AREAS OTHER THAN FLORIDA AND A GRADUALLY WARMING WEST.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT MODEL GUIDANCE CONTINUES TO SHOW REASONABLY GOOD AGREEMENT  
FOR THE OVERALL LARGE-SCALE PATTERN INTO THE WEEKEND WITH THE  
AFOREMENTIONED INITIAL SHORTWAVE TRACK, ADDITIONAL  
TROUGHING/ENERGY DROPPING INTO THE NORTHERN/CENTRAL ROCKIES FRIDAY  
INTO SATURDAY, AND AMPLIFIED RIDGING OVER THE EASTERN PACIFIC.  
MINOR DIFFERENCES REMAIN WITH THE TRACK OF THESE FEATURES, WITH  
THE GFS SUITE (INCLUDING THE DETERMINISTIC RUNS AND ENSEMBLE MEAN  
AS WELL AS THE BULK OF ENSEMBLE MEMBERS AS INDICATED BY SPAGHETTI  
PLOTS AND CLUSTER ANALYSIS) SHIFTED A BIT EAST FOR BOTH FEATURES  
AS WELL AS WEAKER WITH THE SECOND SHORTWAVE COMPARED TO THE ECMWF  
SUITE. THESE ARE CONSISTENT WITH TYPICAL MODEL BIASES, AND  
CONSENSUS IS CLOSE ENOUGH FOR THE WPC FORECAST TO USE A  
MULTI-MODEL BLEND OF THE LATEST AVAILABLE DETERMINISTIC GUIDANCE  
(00Z/06Z) FOR THE FIRST HALF OF THE FORECAST PERIOD.  
 
BY EARLY NEXT WEEK, TROUGHING SHOULD BE SHIFTING INTO THE CENTRAL  
AND THEN EASTERN U.S. AS ENERGY SPINS AROUND AN UPPER LOW IN  
EASTERN CANADA, THOUGH WITH MORE DIFFERENCES IN THE PHASING  
DETAILS. RIDGING WILL MOVE IN BEHIND THE TROUGH, THOUGH WITH  
UNCERTAINTY IN THE SHORTWAVES COMING IN ON THE RIDGE'S BACKSIDE.  
AS THE MEDIUM RANGE PERIOD PROGRESSED, SHIFTED TO A BLEND OF  
DETERMINISTIC (MAINLY MAINTAINING THE ECMWF) AND ENSEMBLE (LEANING  
TOWARD THE EC ENSEMBLE MEAN) GUIDANCE TO LEAN TOWARD THE ECMWF  
SUITE, MINIMIZE INDIVIDUAL MODEL DIFFERENCES, AND MAINTAIN GOOD  
FORECAST CONTINUITY FROM THE PREVIOUS CYCLE.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
AS THE PERIOD BEGINS THURSDAY WITH UPPER TROUGHS DIGGING OVER THE  
WEST/SOUTHWEST AND RIDGING OVER THE SOUTHEAST, SOUTHERLY INFLOW  
INTO A LOW PRESSURE/FRONTAL SYSTEM WILL PROVIDE MOISTURE FOR  
WIDESPREAD PRECIPITATION FROM THE MISSISSIPPI VALLEY TO TENNESSEE  
AND OHIO VALLEYS INTO THE MID-ATLANTIC AND NORTHEAST. CURRENT  
FORECASTS SHOW THE THREAT FOR EXCESSIVE RAINFALL IS MAXIMIZED  
ACROSS NORTH-CENTRAL TENNESSEE INTO EASTERN KENTUCKY AND WESTERN  
WEST VIRGINIA THURSDAY INTO THURSDAY NIGHT. TO THE NORTH AND WEST,  
THERE IS A SIGNIFICANT THREAT FOR SNOW AND ICE FROM THE  
MID-MISSISSIPPI AND OHIO VALLEYS INTO THE NORTHEAST THURSDAY AND  
FRIDAY. SOME MOISTURE RETURN INTO THE SOUTHEASTERN QUADRANT OF THE  
COUNTRY IS POSSIBLE OVER THE WEEKEND, BUT WITH LIKELY LIGHTER  
PRECIPITATION AMOUNTS COMPARED TO THE PREVIOUS EVENTS. MEANWHILE  
SOME LIGHT SNOW IS POSSIBLE ACROSS THE GREAT LAKES REGION FOR THE  
WEEKEND, WHILE APPROACHING FRONTAL SYSTEMS AND SHORTWAVES SHOULD  
LEAD TO INCREASING PRECIPITATION CHANCES OVER THE PACIFIC  
NORTHWEST.  
 
COLD CANADIAN HIGH PRESSURE WILL AFFECT MUCH OF THE CONTIGUOUS  
U.S. THROUGH THE PERIOD, SPREADING MUCH BELOW AVERAGE TEMPERATURES  
TO THE BULK OF THE COUNTRY, WHICH COULD BE RECORD-SETTING.  
ESPECIALLY FRIGID TEMPERATURES ARE LIKELY FROM THE NORTHERN HIGH  
PLAINS TO THE NORTHERN/CENTRAL PLAINS WHERE DAYTIME HIGHS AND  
OVERNIGHT LOWS COULD BE 30-40+ DEGREES BELOW NORMAL THROUGH  
FRIDAY. AFTER A WARMER THAN AVERAGE COUPLE OF DAYS LATE THIS WEEK  
IN THE SOUTHEASTERN U.S. WITH A FEW RECORD WARM MAXES AND MINS  
POSSIBLE UNDER THE RIDGE AND AHEAD OF THE FRONT, THE COLD AIR WILL  
SPREAD INTO THE EAST OVER THE WEEKEND, BUT MODIFIED/MODERATED. THE  
FLORIDA PENINSULA WILL BE THE MAIN SPOT HANGING ONTO ABOVE AVERAGE  
TEMPERATURES. CHILLY WEATHER COULD BE REINFORCED BY UPPER-LEVEL  
ENERGY ACROSS THE NORTH-CENTRAL U.S. INTO THE OHIO VALLEY AND  
GREAT LAKES EARLY NEXT WEEK. MEANWHILE THE WEST CAN EXPECT COOL  
TEMPERATURES TO BEGIN THE PERIOD BUT SHOULD WARM TO NEAR/ABOVE  
AVERAGE EARLY NEXT WEEK GIVEN OVERALL RIDGING.  
 
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  
 
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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