831  
FXUS02 KWBC 090709  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
307 AM EDT SAT APR 09 2022  
 
VALID 12Z TUE APR 12 2022 - 12Z SAT APR 16 2022  
 
...ACTIVE WEATHER IS LIKELY NEXT WEEK, WITH HEAVY SNOW SPREADING  
FROM HIGHER ELEVATIONS OF THE WEST INTO THE NORTHERN PLAINS AND  
HEAVY RAIN AND SEVERE THUNDERSTORM CHANCES ACROSS THE SOUTH...  
   
..OVERVIEW
 
 
THE LATEST GUIDANCE CONTINUES TO SUPPORT AN AMPLIFIED AND ACTIVE  
WEATHER PATTERN ACROSS THE LOWER 48 NEXT WEEK. A REINFORCED  
WESTERN U.S. TROUGH LOOKS TO EMERGE INTO THE PLAINS BY AROUND  
MIDWEEK AS A VIGOROUS CLOSED LOW AND ASSOCIATED SURFACE LOW  
DEVELOP OVER THE PLAINS/UPPER MIDWEST. INITIALLY, THIS SHOULD  
BRING HEAVY MOUNTAIN SNOWS OUT WEST, WITH HEAVY SNOW AND POSSIBLE  
BLIZZARD CONDITIONS SPREADING NORTH AND WEST OF THE LOW TRACK INTO  
THE NORTHERN PLAINS. IN THE WARM SECTOR OF THE SYSTEM, SEVERE  
WEATHER AND HEAVY TO EXCESSIVE RAIN IS LIKELY ACROSS PARTS OF THE  
DEEP SOUTH AND POTENTIALLY EASTWARD. BY LATE WEEK, A BLOCKY RIDGE  
IN THE WESTERN ATLANTIC SHOULD STEER THE CLOSED UPPER LOW IN A  
MORE NORTHERLY DIRECTION INTO EASTERN CANADA AS THE NEXT TROUGH  
MOVES INTO THE WEST.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THOUGH MODEL GUIDANCE IS UNITED IN SHOWING THE DEVELOPING WESTERN  
TROUGH BECOMING A DEEP CLOSED UPPER LOW AS IT TRACKS INTO THE  
CENTRAL U.S., AMPLE DIFFERENCES REMAIN WITH THE TIMING AND TRACK  
OF THE UPPER AND SURFACE LOW FEATURES. FOR A FEW DAYS NOW, THE GFS  
HAS BEEN AND CONTINUES TO BE A FAST AND NORTH OUTLIER, WITH THE  
ECMWF AND CMC THE FARTHEST WEST/SOUTH WITH THE SURFACE LOW  
WEDNESDAY INTO THURSDAY. THE LAST COUPLE OF RUNS OF THE ECMWF  
HOWEVER, INCLUDING TONIGHTS NEW 00Z RUN, SEEM TO BE TRENDING  
FASTER WITH THE SYSTEM. NOT QUITE AS FAST STILL AS THE GFS, BUT  
THE TWO MAY BE COMING INTO SOMEWHAT BETTER AGREEMENT AND THIS  
WARRANTS WATCHING. THE ENSEMBLE MEANS GENERALLY FOLLOW THEIR  
DETERMINISTIC COUNTERPARTS, WHICH DOES NOT INCREASE CONFIDENCE IN  
ONE SOLUTION OVER THE OTHER. ALL OF THIS SEEMS TO BE RELATED TO  
STRENGTH AND INTERACTIONS OF PIECES OF ENERGY EMBEDDED WITHIN THE  
LARGER WESTERN U.S. TROUGH AS EARLY AS DAY 3/TUESDAY. SO PERHAPS,  
ONCE THESE DETAILS GET RESOLVED, MODELS MAY START CONVERGING ON A  
SOLUTION AS IT MOVES FARTHER DOWNSTREAM. WPC CONTINUITY HAS BEEN  
FAVORING THE MORE SOUTHERLY/SLOWER TRACK AND SO WITH NO CLEAR  
INDICATION TO SHIFT THAT THINKING, TONIGHTS FORECAST ALSO LEANED  
HEAVILY ON THE ECMWF/CMC AND RESPECTIVE ENSEMBLE MEANS.  
 
ALSO CONSIDERABLE DIFFERENCES LATE PERIOD REGARDING THE NEXT  
SYSTEM INTO THE WEST. GFS RUNS MUCH WEAKER/FASTER WITH ENERGY  
DROPPING OUT OF THE GULF OF ALASKA INTO THE PACIFIC NORTHWEST.  
ECMWF MUCH STRONGER, WITH ANOTHER COMPACT CLOSED LOW OVER THE  
PACIFIC NORTHWEST BY NEXT FRIDAY. ENSEMBLES ALSO SHOW CONSIDERABLE  
SPREAD, SO SEEMS PRUDENT TO STICK CLOSE TO THE ENSEMBLE MEANS AT  
THIS POINT, ESPECIALLY GIVEN THE LATE PERIOD TIMING.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
BEGINNING TUESDAY, MOUNTAIN SNOW WILL BE ONGOING ACROSS THE  
WASHINGTON/OREGON CASCADES AS WELL AS FARTHER INLAND ACROSS THE  
INTERMOUNTAIN WEST. MEANWHILE, THE LOW PRESSURE SYSTEM SHOULD  
REALLY BEGIN TO RAMP UP AND SO A FAVORABLE COMBINATION OF UPPER  
TROUGH DYNAMICS AND LOW LEVEL UPSLOPE FLOW SHOULD INCREASE  
PRECIPITATION AND A SPRINGTIME HEAVY SNOW THREAT INTO THE ROCKIES  
AND ESPECIALLY THE NORTHERN HIGH PLAINS. STRONG LOW PRESSURE LOOKS  
TO TRACK FROM THE PLAINS INTO THE UPPER MIDWEST WEDNESDAY INTO  
THURSDAY WITH SNOW SPREADING INTO THE NORTHERN PLAINS ALONG WITH  
STRONG WINDS, POSSIBLY CREATING BLIZZARD CONDITIONS. MEANWHILE IN  
THE WARM SECTOR, THERE WILL BE INCREASING COVERAGE AND INTENSITY  
OF RAINFALL AHEAD OF THE ATTENDENT COLD FRONT FROM THE MISSISSIPPI  
VALLEY EASTWARD. THE GREATEST THREAT FOR HEAVY TO EXCESSIVE RAINS  
AND SEVERE WEATHER LOOKS TO CONVERGE OVER OR NEAR THE LOWER  
MISSISSIPPI VALLEY/TENNESSEE VALLEY WITH SEVERAL DAYS OF  
PERSISTENT GULF MOISTURE AND INSTABILITY. FARTHER NORTH, DYNAMICS  
WRAPPING AROUND THE LOW MAY SUPPORT AN ADDITIONAL AREA OF MODEST  
RAINFALL ACROSS THE UPPER MISSISSIPPI VALLEY. WHILE THIS OVERALL  
PATTERN CERTAINLY SUGGESTS A HEAVY RAIN/SEVERE WEATHER/WINTRY  
WEATHER THREAT, BUT DETAILS ON WHERE THESE HAZARDS OCCUR AND WHEN  
REMAINS UNCERTAIN STILL, WITH PLENTY OF FORECAST REFINEMENTS TO  
COME.  
 
THE WESTERN U.S. SHOULD SEE SEVERAL DAYS OF BELOW NORMAL  
TEMPERATURES, WITH DAYTIME HIGHS 20+ DEGREES BELOW NORMAL SHIFTING  
EASTWARD WITH TIME. SOME MODERATION IS LIKELY BY LATER IN THE WEEK  
ACROSS THE WEST, THOUGH STILL BELOW NORMAL WITH ADDITIONAL  
TROUGHING MOVING IN. BY NEXT THURSDAY-SATURDAY, THE CORE OF THE  
COLD SHOULD BE OVER THE NORTHERN PLAINS WITH LOW TEMPERATURES  
10-20F BELOW NORMAL AND HIGHS EVEN APPROACHING 30F BELOW AVERAGE.  
MEANWHILE, AHEAD OF THE BIG STORM, EXPECT TEMPERATURES FROM THE  
SOUTH-CENTRAL U.S. TO THE EAST TO BE ABOVE NORMAL, BUT TRENDING  
BACK TOWARDS NORMAL FOLLOWING PASSAGE OF THE COLD FRONT.  
 
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, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, 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/#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  
 

 
 

 
 
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