636  
FXUS01 KWBC 202022  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
421 PM EDT FRI OCT 20 2017  
 
VALID 00Z SAT OCT 21 2017 - 00Z MON OCT 23 2017  
 
...HEAVY SNOW POSSIBLE OVER THE NORTHERN CASCADES INTO PARTS OF  
THE NORTHERN ROCKIES...  
   
..HEAVY RAIN POSSIBLE OVER THE PACIFIC NORTHWEST
 
 
...HEAVY RAIN POSSIBLE OVER THE SOUTHERN PLAINS/LOWER MISSISSIPPI  
VALLEY...  
 
A FRONT OVER THE NORTHERN HIGH PLAINS EXTENDS ROUGHLY  
SOUTHWESTWARD TO THE GREAT BASIN WILL SLOWLY MOVE EASTWARD TO THE  
UPPER GREAT LAKES/MIDDLE MISSISSIPPI VALLEY AND PARTS OF THE  
SOUTHERN PLAINS BY SUNDAY. OVERNIGHT FRIDAY, SHOWERS AND  
THUNDERSTORMS WILL DEVELOP ALONG AND AHEAD OF THE BOUNDARY OVER  
PARTS OF THE UPPER MISSISSIPPI VALLEY IN TO THE CENTRAL/SOUTHERN  
PLAINS THAT WILL SLOWLY MOVE EASTWARD TO THE UPPER GREAT  
LAKES/UPPER MISSISSIPPI VALLEY INTO THE MIDDLE/LOWER MISSISSIPPI  
VALLEY AND PARTS OF THE SOUTHERN PLAINS BY SUNDAY MORNING.  
 
IN ADDITION, MOISTURE FROM THE WESTERN GULF COAST WILL FLOW  
NORTHWARD OVER THE SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY THAT  
WILL PROTRUDE INTO THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES  
THROUGH SUNDAY. WEAK UPPER-LEVEL ENERGY OVER THE SOUTHERN PLAINS  
WILL AID IN PRODUCING SHOWERS AND THUNDERSTORMS OVER PARTS OF THE  
WESTERN/CENTRAL GULF COAST THROUGH SATURDAY AFTERNOON.  
 
MEANWHILE, STRONG ONSHORE LOW-LEVEL FLOW WILL STREAM MOISTURE INTO  
THE PACIFIC NORTHWEST WILL AID IN PRODUCING RAIN OVER PARTS OF THE  
PACIFIC NORTHWEST WITH SNOW OVER THE HIGHER ELEVATIONS OF THE  
CASCADES THROUGH SATURDAY MORNING. RAIN AND HIGHER ELEVATIONS  
SNOW WILL DEVELOP OVER PARTS OF NORTHERN CALIFORNIA INTO THE  
NORTHERN INTERMOUNTAIN REGION/NORTHERN ROCKIES INTO PARTS OF THE  
GREAT BASIN AND CENTRAL ROCKIES THROUGH SATURDAY AFTERNOON. ON  
SATURDAY, THE SNOW LEVELS WILL RISE OVER THE WEST AS UPPER-LEVEL  
RIDGING MOVES ONSHORE. ADDITIONALLY, MOISTURE WILL SURGE ONSHORE  
OVER THE PACIFIC NORTHWEST PRODUCING RAIN, HEAVY AT TIMES, OVER  
THE NORTHWEST INTO THE NORTHERN INTERMOUNTAIN REGION/NORTHERN  
ROCKIES SATURDAY AFTERNOON INTO SUNDAY.  
 
...MORE TO FOLLOW...  
 
ZIEGENFELDER  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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