517  
FXUS02 KWBC 080542  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
141 AM EDT MON APR 08 2019  
 
VALID 12Z THU APR 11 2019 - 12Z MON APR 15 2019  
 
...MAJOR WINTER STORM LIKELY FROM THE NORTHERN HIGH PLAINS TO THE  
UPPER MIDWEST MID TO LATE THIS WEEK...  
...MAJOR SPRING CYCLONE TO PRODUCE HEAVY SNOW AND HIGH WINDS IN  
PORTIONS OF THE NORTH CENTRAL PLAINS TO UPPER MS VALLEY AND UPPER  
GREAT LAKES...  
   
..OVERVIEW AND GUIDANCE ASSESSMENT/PREFERENCES
 
 
THE MODELS ARE IN EXCELLENT AGREEMENT NOW ON THE DEVELOPING  
CYCLONE IN THE CENTRAL PLAINS THAT MOVES IN TO THE UPPER MIDWEST  
ON DAY 3 THU AND ACROSS THE UPPER LAKES FRI BEFORE EXITING UP INTO  
CANADA FRIDAY. DETERMINISTIC MODEL SOLUTIONS AND ENSEMBLE MEMBERS  
ARE NOW VERY WELL-CLUSTERED WITH RESPECT TO THE SURFACE LOW TRACK  
WED-FRI, WITH THE ECMWF AND UKMET THE TWO SOLUTIONS MOST  
WELL-CENTERED WITHIN THE BROAD CONSENSUS.  
THE TRAILING COLD FRONT MOVES OFF THE NORTHEAST/MID ATLANTIC  
COASTS EARLY SAT.  
 
IN THE WESTERN US, SHORTWAVE ENERGY IS EXPECTED TO DIVE SOUTH  
ACROSS THE PACIFIC NORTHWEST THU TO THE SOUTHWEST US FRI, PERHAPS  
CLOSING OFF AS IT CROSSES SOUTH THROUGH THE GREAT BASIN. THE 12Z  
ECMWF AND 18Z GEFS MEANS REMAIN IN BETTER THAN AVERAGE AGREEMENT,  
WHICH SERVE TO CENTER IN BETWEEN THE 12Z ECMWF WITH ITS FURTHER  
WEST TRACK OF THE 500 MB WAVE, THE GFS/GFS PARALLEL WITH ITS  
FURTHER EAST TRACK. THE WPC FORECAST BLENDED THE 2 ENSEMBLES WITH  
LESS WEIGHT TO THE OPERATIONAL ECMWF.  
 
NEXT WEEKEND, THE PRIMARY FORECAST CONCERN BECOMES HOW QUICKLY THE  
ENERGY ACROSS THE SOUTHWEST THU-FRI EJECTS EASTWARD INTO THE  
CENTRAL U.S. THE 18Z GFS CONTINUES TO MOVE THE UPPER TROUGH AND  
ASSOCIATED SFC LOW EASTWARD FASTER THAN MOST OTHER SOLUTIONS,  
SO WAS NOT USED, GIVEN THE GEFS MEAN WAS SLOWER LIKE THE 12Z ECMWF  
AND 12Z ECMWF ENSEMBLE MEAN. THE CANADIAN/CANADIAN ENSEMBLE MEAN  
WAS A FEW HOURS SLOWER IN MOVING THE UPPER TROUGH AND SFC LOW  
NORTHEAST WITH A SIMILAR TRACK TO THE GEFS/ECMWF.  
 
MOST SOLUTIONS SPIN UP A LOW PRESSURE SYSTEM ACROSS THE LOWER  
MISSISSIPPI VALLEY NEXT SUN AND MOVE THE LOW INTO THE OHIO VALLEY  
AND GREAT LAKES MON, WHEN THE SYSTEM OCCLUDES. THE TRIPLE POINT  
CROSSES THE MID ATLANTIC, WITH A NEW LOW DEVELOPING AND MOVING  
NORTHEAST TOWARDS COASTAL NEW YORK/NEW ENGLAND OR THE ADJACENT  
COASTAL WATERS.  
 
THE MODELS ALSO SHOW THE NEXT UPPER TROUGH OVER THE NORTHEAST  
PACIFIC SET TO MOVE ONSHORE AND INLAND LATE SUN INTO MON 15 APR.  
TIMING AND PHASING DIFFERENCES PERSIST WITH THE ECMWF/GFS/CANADIAN  
ALL OFFERING DIFFERING SOLUTIONS, AS MORE WEIGHTING WAS GIVEN TO  
THE ENSEMBLE MEANS UNTIL BETTER AGREEMENT DEVELOPS.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE LOW PRESSURE SYSTEM CROSSING THE CENTRAL U.S. THU-FRI IS  
EXPECTED TO BRING MAJOR WINTER WEATHER IMPACTS FROM PORTIONS OF  
THE NORTH CENTRAL PLAINS TO THE UPPER MIDWEST/UPPER GREAT LAKES.  
MODELS SHOW STRONG SIGNAL FOR A BAND OF HEAVY SNOW NORTH OF THE  
SURFACE LOW TRACK. PEAK PROBABILITIES FOR HEAVY SNOW COVER SD,  
NORTHERN NE, SOUTHERN TO CENTRAL MN, NORTHERN WI, AND THE UP OF  
MI. STRONG AND GUSTY WINDS WILL LIKELY RESULT IN BLOWING SNOW AND  
PERHAPS BLIZZARD CONDITIONS FOR SOME AREAS. ON THU-THU NIGHT,  
INCREASING MOISTURE RETURN SHOULD LEAD TO SCATTERED TO NUMEROUS  
SHOWERS AND THUNDERSTORMS IN THE MID MS VALLEY TO THE OH VALLEY,  
SOME OF WHICH COULD BE STRONG TO SEVERE. SEE THE STORM PREDICTION  
CENTER OUTLOOKS FOR SEVERE CONVECTIVE WEATHER PROBABILITIES.  
 
THE SYSTEM ACROSS THE WESTERN U.S. THU-FRI SHOULD PRODUCE  
SCATTERED AREAS OF VALLEY RAIN AND MOUNTAIN SNOW FROM THE WEST  
COAST TO THE GREAT BASIN AND ROCKIES. AS THE SYSTEM ENTERS THE  
CENTRAL U.S. NEXT WEEKEND, A DEVELOPING FRONTAL WAVE ALONG THE  
GULF COAST/LOWER MISSISSIPPI VALLEY SHOULD PROMOTE STRONG MOISTURE  
RETURN AND WIDESPREAD RAIN AND THUNDERSTORMS FROM THE LOWER  
MISSISSIPPI VALLEY TO THE TENNESSEE/OHIO VALLEYS AND THE  
APPALACHIANS AND MID ATLANTIC, WITH AREAS OF HEAVY RAINFALL  
POSSIBLE.  
 
HIGH TEMPERATURES ARE FORECAST TO BE 10-15 DEG ABOVE AVERAGE  
ACROSS PORTIONS OF THE MID MS VALLEY TO SOUTHEAST AND  
TENNESSEE/OHIO VALLEYS ON THU. THE ANOMALOUS WARMTH SPREADS EAST  
INTO THE APPALACHIANS TO THE SOUTHEAST ON FRI, AND THEN ALONG THE  
EAST COAST SAT, THEN THE SOUTHEAST AND FL SUN.  
 
IN THE WAKE OF THE LOW PRESSURE SYSTEM, MUCH COLDER AIR IS  
EXPECTED TO SPREAD INTO THE ROCKIES AND THE CENTRAL U.S., WITH  
HIGH TEMPERATURES 15-25 DEG BELOW AVERAGE POSSIBLE LATE IN THE  
WEEK. THE ANOMALIES TAPER ON SUN, WITH THE PRIMARY AREA OF BELOW  
NORMAL TEMPS NEXT MON 15 APR UNDER THE UPPER TROUGH IN THE PLAINS  
TO THE MS VALLEY.  
 
PETERSEN  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS 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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