191  
FXUS02 KWBC 171854  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
154 PM EST THU FEB 17 2022  
 
VALID 12Z SUN FEB 20 2022 - 12Z THU FEB 24 2022  
 
...INCREASING CONFIDENCE IN A SOUTHERN U.S. HEAVY RAINFALL EVENT  
WITH NORTHERN TIER HEAVY SNOWS...  
 
   
..OVERVIEW
 
 
AS NEXT WEEK BEGINS, QUASI-ZONAL FLOW ACROSS MUCH OF THE U.S. WILL  
BE TRANSITIONING TO A MORE AMPLIFIED PATTERN AS UPPER-LEVEL ENERGY  
SPILLS INTO THE WEST TO CREATE DEEP TROUGHING, WHILE RIDGING  
BUILDS IN THE EAST. THE TROUGH WILL SLOWLY TRACK EASTWARD ALONG  
WITH A STRONG FRONTAL SYSTEM, BEHIND WHICH ARCTIC HIGH PRESSURE  
SHOULD PRODUCE WELL BELOW NORMAL TEMPERATURES IN THE CENTRAL U.S.,  
WITH WARMER THAN AVERAGE TEMPERATURES IN THE EAST. LIGHT TO  
MODERATE PRECIPITATION IS LIKELY IN THE WEST UNDERNEATH THE TROUGH  
AND SPREADING INTO THE CENTRAL AND EASTERN U.S., WITH THE  
POSSIBILITY OF NORTHERN TIER SNOW AND SOUTHERN U.S. RAIN AND  
THUNDERSTORMS. A MULTI-DAY RAINY PERIOD FOR PARTS OF THE LOWER  
MISSISSIPPI AND TENNESSEE VALLEYS COULD LEAD TO FLOODING AND FLASH  
FLOODING THERE.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THROUGH THE 00Z/06Z CYCLE, MODEL GUIDANCE CONTINUES TO SHOW VERY  
GOOD AGREEMENT WITH THE LARGE SCALE PATTERN INTO THE MIDDLE OF  
NEXT WEEK, THOUGH WITH SOME LINGERING UNCERTAINTY IN THE SMALLER  
SCALE DETAILS. A COMPACT UPPER LOW LIKELY WEST OF BAJA CALIFORNIA  
TO BEGIN THE PERIOD SUNDAY SHOULD WEAKEN AS IT MOVES EASTWARD,  
WITH GOOD CONSENSUS AS WELL ON THE LARGE SCALE FOR ENERGY TO SPILL  
INTO THE WEST EAST OF AN AMPLIFIED EASTERN PACIFIC RIDGE BY NEXT  
SUNDAY-MONDAY, GRADUALLY DEEPENING AND SHIFTING SLOWLY EASTWARD.  
00Z/06Z MODELS SHOWED SOMEWHAT BETTER AGREEMENT ON WESTERN TROUGH  
TIMING, WITH THE 00Z ECMWF ADJUSTING WESTWARD WITH ITS AXIS, MORE  
IN LINE WITH THE GFS. HOWEVER, THE 12Z ECMWF AGAIN SLOWED DOWN A  
LITTLE BIT WITH THE AXIS, WHILE THE 12Z CMC IS FASTER THAN ITS  
PREVIOUS RUN. SO, QUESTIONS ON TIMING CONTINUE TO LOOM LATE  
PERIOD. ADDITIONALLY, THE EVOLUTION OF UPSTREAM ENERGY IS RATHER  
UNCERTAIN STEMMING FROM HIGH LATITUDES AND ROUNDING THE PACIFIC  
RIDGE, LEADING TO LOW CONFIDENCE IN THE SPECIFICS OF THE EMBEDDED  
ENERGIES WITHIN THE MAIN TROUGH AND ITS EVENTUAL MOVEMENT,  
ESPECIALLY BY DAY 7. THE PAST FEW RUNS OF THE GFS HAS BEEN QUITE  
SHARP AND FAST WITH THE NEXT SHORTWAVE INTO THE PACIFIC NORTHWEST  
NEXT THURSDAY, BUT THE 12Z RUN LOOKS MORE REASONABLE AND IN LINE  
WITH THE ECMWF/CMC.  
 
THE WPC BLEND FOR TODAYS PROGS FEATURED A MULTI DETERMINISTIC  
MODEL SOLUTION FOR DAYS 3-5 AMIDST ABOVE AVERAGE AGREEMENT. FOR  
DAYS 6 AND 7, THE ENSEMBLE MEANS WERE PHASED INTO THE BLEND WITH  
INCREASING PROPORTIONS TO HELP ACCOUNT FOR THE UNCERTAINTIES IN  
THE WESTERN U.S. TROUGH TIMING AND MITIGATE THE SMALLER SCALE  
DETAILS. THE RESULTING SOLUTION PROVIDES A MIDDLE GROUND SOLUTION  
FOR THE TROUGH AND MAINTAINS GOOD CONTINUITY WITH THE OVERNIGHT  
WPC PACKAGE AS WELL.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PRECIPITATION WILL BE INCREASING IN THE PACIFIC NORTHWEST AND  
NORTHERN ROCKIES OVER THE WEEKEND WITH THE UPPER TROUGH COMING IN.  
COASTAL AND VALLEY RAIN AND MODERATE TO HEAVY MOUNTAIN SNOW ARE  
LIKELY OVER THE PACIFIC NORTHWEST SPREADING INTO CALIFORNIA, THE  
GREAT BASIN, AND THE ROCKIES AND PERSISTING THERE INTO THE MIDDLE  
OF NEXT WEEK. AS THE WESTERN TROUGH DEEPENS, IT SHOULD TAP INTO  
GULF OF MEXICO MOISTURE TO FUEL A HEAVY TO POSSIBLY EXCESSIVE  
RAINFALL EVENT FROM PORTIONS OF THE LOWER MISSISSIPPI VALLEY INTO  
THE TENNESSEE VALLEY DURING THE EARLY TO MIDDLE PART OF NEXT WEEK.  
A MULTI-DAY EVENT OVER ROUGHLY THE SAME AREAS IS POSSIBLE AS  
ADDITIONAL ENERGY GETS RELOADED INTO THE TROUGH OUT WEST. THIS  
LIKELY INCREASES THE THREAT FOR FLOODING AND FLASH FLOODING INTO  
AT LEAST NEXT WEDNESDAY. SPC CONTINUES TO MENTION THE THREAT FOR  
SEVERE WEATHER WITHIN THIS PATTERN AS WELL ACROSS PARTS OF THE  
SOUTH. ON THE NORTH SIDE OF THIS SYSTEM, CONFIDENCE IS INCREASING  
THAT A SWATH OF MODERATE TO HEAVY SNOWFALL WILL BE PRESENT  
STRETCHING FROM THE NORTHERN PLAINS INTO THE UPPER MIDWEST/GREAT  
LAKES MONDAY AND TUESDAY, AND EVENTUALLY AFFECTING PARTS OF FAR  
NORTHERN NEW ENGLAND AS WELL, THOUGH THE EXACT AXIS OF HEAVY SNOWS  
REMAINS SOMEWHAT UNCERTAIN.  
 
TEMPERATURES AS NEXT WEEK BEGINS ARE EXPECTED TO BE ABOVE NORMAL  
FOR PARTS OF THE WEST INTO THE PLAINS, WITH THE LARGEST ANOMALIES  
OF HIGHS 20+ DEGREES ABOVE AVERAGE OVER NEBRASKA. AS THE PATTERN  
AMPLIFIES, THE SOUTH-CENTRAL U.S. TO THE EAST COAST WILL FURTHER  
WARM THROUGH THE FIRST HALF OF NEXT WEEK, WITH WIDESPREAD HIGHS  
10-20F AND LOWS 20-30F ABOVE NORMAL. MEANWHILE, A COLD ARCTIC HIGH  
IS FORECAST TO EXPAND ACROSS THE NORTH-CENTRAL U.S., LEADING TO  
WELL BELOW AVERAGE TEMPERATURES INITIALLY ACROSS THE NORTHERN HIGH  
PLAINS AND SPREADING SOUTHWARD (AS FAR SOUTH AS TEXAS) THROUGH  
MIDWEEK. TEMPERATURES IN SOME PLACES COULD BE 30-40 DEGREES BELOW  
NORMAL, AND HIGHS IN THE SINGLE DIGITS TO EVEN BELOW 0F ARE  
EXPECTED FOR MONTANA, THE DAKOTAS, AND NORTHERN MINNESOTA MONDAY  
AND TUESDAY, WITH COLD TEMPERATURES LINGERING THROUGH WEDNESDAY  
AND THURSDAY AS WELL.  
 
SANTORELLI/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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