640  
FXUS02 KWBC 300701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT THU AUG 30 2018  
 
VALID 12Z SUN SEP 02 2018 - 12Z THU SEP 06 2018  
   
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
A SERIES OF SHORTWAVES ALOFT WILL PROGRESS OVER SOUTHERN CANADA  
AND THE U.S. NORTHERN TIER STATES OVERTOP BOTH AN EMERGING  
SOUTHERN STREAM ENERGY UNDERNEATH INTO A DEVELOPING TROUGH OVER  
THE WEST AND A SPRAWLING LATE SUMMER RIDGE CENTERED OVER THE  
MID-LATITUDES OF THE CENTRAL AND EASTERN U.S. THE LARGE SCALE  
PATTERN IS REASONABLY DEPICTED IN GUIDANCE AS IMPULSES AND  
DEEPENED MOISTURE EMERGE FROM THE SOUTHWEST AND NORTHWEST TO  
INTERACT AND TRACK AROUND THE WESTERN PERIPHERY AND OVERTOP THE  
AFOREMENTIONED HOT RIDGE. HOWEVER, MODELS AND ENSEMBLES ARE QUITE  
UNCERTAIN WITH THE TIMING/AMPLITUDE/INTERACTION OF THESE  
CONVECTION DRIVING SMALL-MODERATE SCALE EMBEDDED WEATHER FEATURES.  
WITHIN THE SUBTROPICS, SEVERAL TROPICAL WAVES/DISTURBANCES ARE  
SLATED TO MOVE WESTWARD ACROSS THE FLORIDA PENINSULA AND THE  
NORTHERN GULF OF MEXICO/GULF COASTAL AREAS.  
 
GIVEN LINGERING UNCERTAINTY, THE WPC MEDIUM RANGE PRODUCT SUITE  
WAS PRIMARILY DERIVED FROM A COMPOSITE BLEND OF THE 12 UTC  
GEFS/ECMWF ENSEMBLES, THE NBM AND WPC CONTINUITY.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
SPECIFICS ARE UNCERTAIN, BUT THERE ARE SEVERAL STRONG SIGNALS  
SUPPORTING A LARGER SCALE HAZARD THAT WAVY/SLOW MOVING FRONTAL  
SYSTEMS WILL COMBINE WITH THETA-E ADVECTION/POOLED MOISTURE AND  
INSTABILITY TO FUEL PERIODS OF HEAVY CONVECTION/MCS ACTIVITY. THE  
MOST ORGANIZED THREAT SHOULD FOCUS ACROSS THE CENTRAL PLAINS AND  
MID/UPPER MISSISSIPPI VALLEY INTO THE GREAT LAKES. MEANWHILE,  
PACIFIC ENERGIES WORKING INLAND IN SEPARATED SOUTHERN STREAM FLOW  
ARE EXPECTED TO RENEW SOME MONSOONAL CONNECTIONS/CONVECTION FOR  
THE SOUTHWEST AND SOUTH-CENTRAL GREAT BASIN/ROCKIES IN A BOUT OF  
LATER SUMMER ACTIVITY. ALSO, THE PASSAGE OF POTENTIAL TROPICAL  
WAVES/DISTURBANCES WILL SET THE STAGE FOR CLUSTERD HEAVY RAINFALL  
OVER FL AND THE GULF COAST.  
 
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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