621  
FNUS21 KWNS 141547  
FWDDY1  
 
DAY 1 FIRE WEATHER OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0946 AM CST THU DEC 14 2017  
 
VALID 141700Z - 151200Z  
   
..CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA
 
 
THE ONGOING FORECAST IS ON TRACK AND RATIONALE IS UNCHANGED FROM THE  
PREVIOUS FORECAST. AREAS OF ELEVATED TO CRITICAL FIRE WEATHER  
CONDITIONS ARE EXPECTED IN PORTIONS OF SOUTHERN CALIFORNIA AS AN  
OFFSHORE GRADIENT PERSISTS. EASTERLY WINDS IN TERRAIN-FAVORED AREAS  
ARE ALREADY EXCEEDING 20 MPH (WITH GUSTS IN EXCESS OF 45 MPH) AND RH  
VALUES ARE BELOW 10% AT MANY OBSERVATION SITES. THESE CONDITIONS  
WILL PERSIST FOR AT LEAST A FEW MORE HOURS, WITH POOR OVERNIGHT  
RECOVERY RESULTING IN ELEVATED TO CRITICAL CONDITIONS PERSISTING  
WELL AFTER DARK.  
 
NEAR-CRITICAL CONDITIONS ARE ALSO EXPECTED IN PORTIONS OF THE LOWER  
COLORADO RIVER VALLEY AS DRY NORTHERLY FLOW AND LOW RH PERSISTS.  
 
SEE THE PREVIOUS DISCUSSION BELOW FOR MORE INFORMATION.  
 
..COOK.. 12/14/2017  
   
PREV DISCUSSION
 
/ISSUED 0133 AM CST THU DEC 14 2017/  
   
..SYNOPSIS
 
 
A SHORTWAVE TROUGH EMBEDDED IN LARGER-SCALE FLOW WILL DIG SOUTHWARD  
ACROSS THE SOUTHWESTERN U.S. INTO NORTHWEST MEXICO TODAY. THIS WILL  
RESULT IN A STRONG MID/UPPER LEVEL NORTH/NORTHEASTERLY JET STREAK  
OVERSPREADING PORTIONS OF THE GREAT BASIN AND THE LOWER CO RIVER  
VALLEY AND ADJACENT SOUTHERN CA. AT THE SURFACE, STRONG HIGH  
PRESSURE WILL REMAIN OVER THE INTERMOUNTAIN WEST. THIS WILL RESULT  
IN CONTINUED FIRE WEATHER CONCERNS ACROSS PARTS OF SOUTHERN CA AS  
WELL AS THE LOWER CO RIVER VALLEY.  
   
..SOUTHERN CA
 
 
CRITICAL FIRE WEATHER CONDITIONS WILL PERSIST TODAY. VERY DRY  
CONDITIONS CONTINUE, WITH SINGLE-DIGIT RH VALUES EXPECTED BY EARLY  
AFTERNOON. SOME DIURNAL WEAKENING OF THE PRESSURE GRADIENT IS  
ANTICIPATED, WHICH MAY YIELD SOME LIGHTENING OF WINDS SPEEDS DURING  
THE AFTERNOON/EARLY EVENING BEFORE THE GRADIENT ONCE AGAIN INCREASES  
OVERNIGHT, WITH A CORRESPONDING INCREASE IN WIND SPEEDS ONCE AGAIN.  
WINDS OF 20-30 MPH WITH GUSTS OF 40-55 MPH ARE POSSIBLE. OVERNIGHT  
RH RECOVERY WILL REMAIN VERY POOR.  
   
..LOWER CO VALLEY
 
 
GUSTY NORTH WINDS AND LOW RH VALUES WILL BRING ELEVATED TO LOCALLY  
CRITICAL CONDITIONS TO THE REGION TODAY. HIGH TEMPERATURES WILL  
APPROACH THE LOW TO MID 70S AND BOUNDARY-LAYER MIXING WILL RESULT IN  
DOWNWARD TRANSPORT OF STRONG MIDLEVEL WINDS. SUSTAINED NORTH WINDS  
OF 15-20 MPH WITH HIGHER GUSTS ARE EXPECTED. RH VALUES WILL FALL  
INTO 10-20 PERCENT RANGE. WIND SPEEDS WILL DIMINISH OVERNIGHT AND RH  
VALUES WILL INCREASE TO THE 30-40 PERCENT RANGE.  
   
..PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT
 
 

 
 
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