593  
FXUS02 KWBC 170701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT TUE OCT 17 2017  
 
VALID 12Z FRI OCT 20 2017 - 12Z TUE OCT 24 2017  
 
...GUIDANCE/UNCERTAINTY ASSESSMENT AND SENSIBLE WEATHER  
HIGHLIGHTS/THREATS...  
 
MODELS AND ENSEMBLES REMAIN IN REASONABLE AGREEMENT INTO THE  
WEEKEND AND FORECAST CONFIDENCE IS ABOVE NORMAL DURING THIS PERIOD  
WITH GOOD RUN TO RUN GUIDANCE CONTINUITY.  
 
IN THIS PERIOD THE MAIN FORECAST FOCUS WILL BE ACROSS THE WRN US.  
DEEP PACIFIC TROUGH RELATED HEIGHT FALLS SLAM INTO THE WEST COAST  
FRI THAT WORK INLAND ACROSS MUCH OF THE WRN US AND ROCKIES INTO  
SAT. EXPECT HEAVY PCPN OVER THE NWRN US INTO CA WITH INITIAL  
MOISTURE FEED THAT COULD PRODUCE SOME RUNOFF ISSUES. DYNAMICALLY  
DRIVEN/TERRAIN ENHANCED AMOUNTS THEN PROGRESS ACROSS THE N-CENTRAL  
INTERMOUNTAIN WEST/ROCKIES. COOLING TEMPS WITH FRONTAL PASSAGE AND  
HIGH PRESSURE SURGE WILL SUPPORT SOME HEAVY TERRAIN ENHANCED SNOWS  
IN A PERIOD WITH LOWERING SNOW LEVELS. ADDITIONAL UPSTREAM PACIFIC  
ENERGIES PUNCHING INTO THE NWRN US SHOULD ADD ANOTHER SHOT OF  
MODERATE PCPN INTO THE REGION OVER THE WEEKEND. MID-UPPER LEVEL  
RIDGE BUILDING SHOULD THEN USHER IN A DRY PATTERN WITH MODIFYING  
TEMPS NEXT WEEK.  
 
FORECAST SPREAD AND UNCERTAINTY INCREASES SIGNIFICANTLY NEXT WEEK  
DOWNSTREAM ACROSS THE CENTRAL AND ERN US. GUIDANCE HAS NOT OFFERED  
STELLAR RUN TO RUN CONSISTENCY WITH THE FORECAST OF SUBSEQUENT  
STREAM SEPARATION AS AFOREMENTIONED WRN US TROUGH ENERGIES  
PROGRESS INTO THE CENTRAL US AND LATER THE ERN US. RECENT RUNS OF  
THE ECMWF HAS BEEN SHOWING DEEP CLOSED LOW DEVELOPMENT THAT HAS  
SHIFTED OVER THE PAST FEW DAYS FROM AS FAR WEST AS THE SRN ROCKIES  
TO THE SRN PLAINS THEN LOWER MS VALLEY. ENSEMBLE SUPPORT FOR THIS  
HAS BEEN MARGINAL...AND THE LATEST 00 UTC ECMWF RUN CONTINUES THIS  
TREND WITH A MUCH WEAKER LOW SHIFTED PROGRESIVELY EASTWARD.  
ACCORDINGLY...THE NOTION THAT THE HIGHER RESOLUTION ECMWF MIGHT BE  
CATCHING ONTO A THREAT NOT SHOWN WELL IN OTHER GUIDANCE HAS PRETTY  
MUCH DWINDLED. ACCORDINGLY...EXPECT THERE MAY WELL BE SOME STREAM  
SEPARATION TO SOME DEGREE...BUT OVERALL EXPECT A POTENT AND WAVY  
COLD FRONT AND EMERGING DEEP INFLOW FROM THE GULF OF MEXICO INLAND  
AND NORTHWARD TO FUEL A PROGRESSIVE AND WIDESPREAD SWATH OF  
MODERATE TO HEAVY RAINS ACROSS THE CENTRAL THEN ERN US NEXT WEEK.  
MOST GUIDANCE NOW SUPPORTS THIS SCENARIO.  
 
SCHICHTEL  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page