398  
FXUS02 KWBC 300705  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
305 AM EDT SUN SEP 30 2018  
 
VALID 12Z WED OCT 03 2018 - 12Z SUN OCT 07 2018  
   
..CENTRAL U.S. HEAVY RAINFALL THREAT
 
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
BLEND OF THE LATEST GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS. THESE  
GUIDANCE SOLUTIONS HAVE BECOME QUITE WELL CLUSTERED COMPARED TO  
YESTERDAYS EDITIONS WED INTO SAT, BOLSTERING FORECAST CONFIDENCE.  
INCREASING FORECAST SPREAD PORTENDS STRONGER WEIGHTING ON THE  
COMPATABLE ENSEMBLE MEANS LATER SAT/SUN. HOWEVER, FORECAST  
CONFIDENCE IS STILL NEAR/ABOVE NORMAL AS ADDITIONAL FLOW  
AMPLIFICATION SEEMS TO MAKE SENSE CONSIDERING THE AMPLIFIED  
UPSTREAM PATTERN OVER THE PACIFIC/ALASKA ENHANCED WITH ENTRAINMENT  
OF PACIFIC TROPICAL SYSTEM ENERGIES.  
   
..PATTERN OVERVIEW AND WEATHER HIGHLIGHTS
 
 
IN THIS PATTERN, A CLOSED NORTH-CENTRAL CANADIAN UPPER VORTEX  
EJECTS AT AN UNUSUALLY FAST PACE TO THE CANADIAN MARITIMES  
WED-FRI. TROUGHING UNDERNEATH DIGS A COOLING CANADIAN SURFACE HIGH  
AND LEAD COLD FRONTS/PRECIPITATION ACROSS THE NORTHERN HALF OF THE  
CENTRAL AND EASTERN U.S. ON THE WESTERN AND NORTHERN PERIPHERIES  
OF AN AMPLIFIED SOUTHEAST U.S. UPPER RIDGE. EJECTING  
MOISTURE/ENERGY FROM THE REMNANTS OF ROSA MAY ENHANCE RAINFALL  
NEAR THE FRONT. SUFFICIENTLY COLD AIR IN PLACE NORTH OF THE  
FRONTAL BOUNDARY ALSO SUPPORTS SOME NORTHERN ROCKIES TO THE  
NORTHERN PLAINS SNOWS. IN ADDITION, AMPLE SOUTHERN STREAM CLOSED  
LOW/UPPER TROUGHING MOVES INLAND OVER A WETTENED SOUTH-CENTRAL  
CALIFORNIA MIDWEEK BEFORE EJECTING NORTHEASTWARD ALONG WITH A  
SWATH OF PRECIPITATION FROM THE SOUTHWEST AND SOUTH-CENTRAL GREAT  
BASIN/ROCKIES TO OVERTOP THE WARMING/DRYING SOUTHEAST U.S. RIDGE  
THU-FRI. THE RIDGE HOLDS THROUGH NEXT WEEKEND, BOLSTERED BUILDING  
OF AN UNSETTLING/AMPLIFIED WESTERN U.S. UPPER TROUGH. IN ADDITION  
TO A RENEWED PRECIPITATION PATTERN SPREAD OVER MUCH OF THE WEST, A  
DOWNSTREAM CHANNEL OF DEEPENING GULF OF MEXICO MOISTURE AROUND THE  
PERIPHERY OF THE SOUTHEAST U.S. RIDGE WILL RENEW HEAVIER  
PRECIPITATION FOCUS ALONG/NEAR THE SLOWLY MOVING AND WAVY  
SOUTH-CENTRAL TO NORTHEASTERN U.S. FRONT/SHARP BAROCLINIC ZONE.  
THIS PRESENTS A CONTINUED HEAVY RAINFALL THREAT AND HEIGHT FALLS  
WORKING OUT THROUGH THE ROCKIES NEXT WEEKEND MAY ACT TO  
SIGNIFICANTLY INVIGORATE PLAINS CONVECTION.  
 
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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page