056  
FXUS02 KWBC 010645  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
245 AM EDT MON OCT 01 2018  
 
VALID 12Z THU OCT 04 2018 - 12Z MON OCT 08 2018  
 
...A WET PATTERN FOR THE WEST/ROCKIES AND A CENTRAL U.S. HEAVY  
RAINFALL THREAT...  
   
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
BLEND OF THE GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS. THESE  
GUIDANCE SOLUTIONS REMAIN WELL CLUSTERED, BOLSTERING FORECAST  
CONFIDENCE. FLOW AMPLIFICATION MAKES SENSE CONSIDERING THE  
AMPLIFIED UPSTREAM PACIFIC/ALASKAN FLOW ENHANCED IN PART WITH  
ENTRAINMENT OF WESTERN PACIFIC TROPICAL LOWS.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PERSISTENT AND HIGHLY AMPLIFIED TROUGHING ALOFT OVER THE WEST WILL  
BE REINFORCED FROM THE NORTHEAST PACIFIC AND WESTERN CANADA THAT  
ACTS TO KEEP COLDER THAN NORMAL TEMPERATURES AND UNSETTLED/WET  
WEATHER FOR MUCH OF THE WEST AND INTO THE PLAINS TO THE NORTH OF A  
WAVY SURFACE FRONT WITH POST-FRONTAL CANADIAN HIGH PRESSURES  
SURGES. THIS WILL INCLUDE TERRAIN AND UPSLOPE ENHANCED SNOWS OVER  
THE NORTHERN ROCKIES/PLAINS. WITH THE UPPER RIDGE IN THE  
EAST/SOUTHEAST ANCHORED IN PLACE, THE FRONT WILL BE PREVENTED FROM  
MOVING MUCH TO THE SOUTHEAST AS WAVES OF LOW PRESSURE (INCLUDING  
THE REMNANTS OF ROSA) LIFT ALONG A SIMILAR PATH FROM THE CENTRAL  
PLAINS TO THE GREAT LAKES. THIS WILL BRING 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, ADDITIONAL  
TROUGHING INTO THE WEST WILL NUDGE THE TROUGH AXIS EASTWARD INTO  
THE GREAT BASIN WITH MORE RAIN AND HIGH MOUNTAIN SNOW INTO THE  
NORTH-CENTRAL ROCKIES AND AN EMERGING HEAVY RAINFALL AND STRONG  
CONVECTION THREAT SPREAD DOWN INTO THE SOUTHERN PLAINS WITH  
MID-LEVEL SOUTHWEST FLOW ATOP THE LINGERING SURFACE FRONT. 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.  
 
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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