159  
FXUS01 KWBC 172013  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
412 PM EDT TUE OCT 17 2017  
 
VALID 00Z WED OCT 18 2017 - 00Z FRI OCT 20 2017  
   
..HEAVY RAIN POSSIBLE OVER PARTS OF THE PACIFIC NORTHWEST
 
 
...HEAVY RAIN POSSIBLE OVER THE CENTRAL-NORTHEASTERN FLORIDA  
COAST...  
 
A FRONT EXTENDING FROM THE NORTHERN ROCKIES SOUTHWESTWARD INTO THE  
PACIFIC NORTHWEST WILL MOVE EASTWARD TO THE GREAT LAKES/MIDDLE  
MISSISSIPPI VALLEY INTO THE CENTRAL PLAINS BY THURSDAY. MOISTURE  
WILL BE LACKING WITH THE BOUNDARY SO THERE WILL BE A DRY FRONTAL  
PASSAGE ALONG THE LENGTH OF THE FRONT FROM THE NORTHERN HIGH  
PLAINS TO THE GREAT LAKES/CENTRAL PLAINS THROUGH THURSDAY.  
 
IN THE MEANTIME BEHIND THE FRONT, ONSHORE FLOW WILL STREAM  
MOISTURE INTO THE PACIFIC NORTHWEST ON STRONG LOW-LEVEL WIND  
THROUGH THURSDAY MORNING WHEN THE STRONG LOW-LEVEL WIND DECREASES.  
THE FLOW WILL AID IN PRODUCING RAIN OVER PARTS OF THE PACIFIC  
NORTHWEST INTO PARTS OF THE NORTHERN ROCKIES ENDING OVERNIGHT  
TUESDAY WHEN UPPER-LEVEL RIDGING MOVES OVER THE PACIFIC  
NORTHWEST/NORTHERN ROCKIES.  
 
MEANWHILE, A STRONGER FRONT OVER THE EASTERN PACIFIC MOVES CLOSE  
TO THE NORTHWEST COAST BY THURSDAY MORNING. A DEEP UPPER-LEVEL  
TROUGH ASSOCIATED WITH THE BOUNDARY WILL BEGIN TO MOVE OVER THE  
PACIFIC NORTHWEST ON WEDNESDAY AFTERNOON AND BECOMING STRONGER AS  
THE FRONT APPROACHES. THE APPROACHING UPPER-LEVEL TROUGH AND  
ONSHORE FLOW WILL AID IN PRODUCING RAIN OVER PARTS OF THE  
NORTHWEST COAST ON WEDNESDAY. THE RAIN WILL BECOME HEAVY BY  
WEDNESDAY EVENING OVER THE NORTHWEST AS THE RAIN MOVES FARTHER  
INLAND INTO THE NORTHERN INTERMOUNTAIN REGION BY WEDNESDAY  
EVENING. OVERNIGHT WEDNESDAY, THE HEAVY RAIN WILL MOVE SOUTHWARD  
ALONG THE PACIFIC NORTHWEST COAST APPROACHING NORTHERN CALIFORNIA  
BY THURSDAY. ADDITIONALLY, THE SNOW LEVELS WILL LOWER OVER THE  
REGION WITH SNOW DEVELOPING OVER THE NORTHERN CASCADES OVERNIGHT  
WEDNESDAY INTO THURSDAY MORNING.  
 
A PERSISTENT FRONT OVER SOUTHERN FLORIDA WILL REMAIN  
QUASI-STATIONARY THROUGH THURSDAY. IN ADDITION, UPPER-LEVEL  
ENERGY OVER NORTHEASTERN FLORIDA WILL SLOWLY MOVE EASTWARD OUT  
OVER THE ATLANTIC BY LATE WEDNESDAY NIGHT WHILE TROPICAL MOISTURE  
OVER SOUTHERN FLORIDA SLOWLY RETREATS SOUTHWARD SOUTH OF THE  
FLORIDA KEYS BY THURSDAY. SHOWERS AND THUNDERSTORMS WILL DEVELOP  
OVER SOUTHERN FLORIDA INTO NORTHEAST FLORIDA THAT WILL BEGIN TO  
WANE EARLY THURSDAY MORNING OVER THE NORTHEAST COAST. SHOWERS AND  
THUNDERSTORMS WILL CONTINUE OVER THE SOUTHERN TIP OF FLORIDA  
THROUGH THURSDAY MORNING.  
   
..MORE TO FOLLOW
 
 
ZIEGENFELDER  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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