616  
FXUS02 KWBC 011559  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1158 AM EDT MON OCT 01 2018  
 
VALID 12Z THU OCT 04 2018 - 12Z MON OCT 08 2018  
 
...PROLONGED WET PATTERN FOR THE WEST/ROCKIES AND A CENTRAL U.S.  
HEAVY RAINFALL THREAT...  
   
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE OVERALL PATTERN THROUGH THE EXTENDED PERIODS IS IN FAIRLY  
DECENT AGREEMENT WITH A DIGGING LONGWAVE TROUGH OVER THE WESTERN  
STATES, SANDWICHED BETWEEN A RIDGE OVER THE PACIFIC AND THE EAST  
COAST/ATLANTIC OCEAN. DETERMINISTIC AND ENSEMBLE MEANS DEPICT A  
DEEPENING LOW SETTING UP OVER THE GREAT BASIN REGION BY OCTOBER  
7TH, WITH A FEW SOLUTIONS SUGGESTING IT CLOSE OFF. THIS SUPPORTS  
MULTIPLE WAVES OF LOW PRESSURE LIFTING FROM THE GREAT  
BASIN/SOUTHERN AND CENTRAL ROCKIES INTO THE PLAINS.THE WPC MEDIUM  
RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A BLEND OF THE  
GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
COLDER THAN SEASONAL NORMAL TEMPERATURES AND UNSETTLED/WET WEATHER  
IS EXPECTED FOR THE NEXT SEVERAL AS A PERSISTENT AND HIGHLY  
AMPLIFIED TROUGH ALOFT SETS UP OVER THE WEST.  
TERRAIN AND UPSLOPE ENHANCED SNOWS WILL SPREAD OVER THE NORTHERN  
ROCKIES/PLAINS. WITH SUCH A STRONG HIGH IN PLACE OVER THE EAST,  
WAVES ALONG THE FRONTAL BOUNDARY (INCLUDING REMNANTS OF ROSA) WILL  
HAVE LITTLE EASTWARD PROGRESSION THROUGH NEXT WEEK. MULTIPLE  
ROUNDS OF RAIN (AND SOME NORTHERN FRINGE SNOW) TO THE SAME AREAS  
OVER SEVERAL DAYS GIVING WAY TO WETTER SOILS AND RISING RIVERS.  
TEMPERATURES TO THE SOUTH OF THE FRONT WILL BE RATHER SUMMER-LIKE  
INTO THE 80S AND SOME 90S ALONG THE GULF COAST.  
 
BY THE COMING WEEKEND, AMPLIFYING OF THE LONGWAVE TROUGH INTO THE  
WEST WILL NUDGE THE TROUGH AXIS EASTWARD INTO THE GREAT BASIN.  
THIS WILL TRIGGER CYCLONE DEVELOPMENT WHICH WILL BRINGING MORE  
RAIN AND HIGH MOUNTAIN SNOW INTO THE NORTH-CENTRAL ROCKIES. AS  
THIS SYSTEM EXITS THE ROCKIES AND AN EMERGES INTO THE  
SOUTHERN/CENTRAL HIGH PLAINS IT WILL POSE AS A HEAVY RAINFALL AND  
STRONG CONVECTION THREAT. THIS WILL PROMOTE A PROLONGED PATTERN  
THAT OFFERS A RISK OF CELL TRAINING WITHIN AN INCREASINGLY DEEP  
MOISTURE CHANNEL EAST OF THE WESTERN U.S. MEAN TROUGH AND AROUND  
THE AMPLIFIED RIDGE HOLDING IN PLACE OVER THE EAST/SOUTHEASTERN  
U.S.  
 
CAMPBELL/SCHICHTEL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND 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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