399  
FNUS21 KWNS 041531  
FWDDY1  
 
DAY 1 FIRE WEATHER OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0930 AM CST MON DEC 04 2017  
 
VALID 041700Z - 051200Z  
 
...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PARTS OF VENTURA AND LOS  
ANGELES COUNTIES IN SOUTHERN CALIFORNIA...   
..CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA
 
 
   
..PORTIONS OF SOUTHERN CA
 
 
ONGOING FORECAST IS ON TRACK, NO CHANGES NEEDED. WIND SPEEDS WERE  
ALREADY GUSTING TO 40-50 MPH IN SOME LOCATIONS WITH LIGHTER WINDS IN  
LOWER ELEVATIONS. EXPECT WIND SPEEDS TO INCREASE LATER TODAY INTO  
TONIGHT WITH CRITICAL TO EXTREMELY CRITICAL CONDITIONS DEVELOPING BY  
THIS EVENING. SEE PREVIOUS DISCUSSION BELOW FOR FURTHER DETAILS.  
   
..PORTIONS OF THE CENTRAL/SOUTHERN PLAINS
 
 
NO CHANGES NEEDED, SEE PREVIOUS DISCUSSION FOR DETAILS.  
 
..LEITMAN.. 12/04/2017  
   
PREV DISCUSSION
 
/ISSUED 0150 AM CST MON DEC 04 2017/  
   
..SYNOPSIS
 
 
THE PRIMARY UPPER TROUGH OVER THE NORTHERN ROCKIES/HIGH PLAINS EARLY  
THIS MORNING WILL MOVE EAST-NORTHEASTWARD ACROSS THE NORTHERN PLAINS  
INTO THE UPPER MIDWEST/GREAT LAKES REGION TODAY. A POSITIVELY TILTED  
TRAILING PORTION OF THIS UPPER TROUGH WILL REMAIN OVER PORTIONS OF  
THE GREAT BASIN AND SOUTHWEST THROUGH THE PERIOD. AT THE SURFACE, A  
COLD FRONT WILL SWEEP SOUTHEASTWARD ACROSS MUCH OF THE  
CENTRAL/SOUTHERN PLAINS AS A LOW DEVELOPS NORTHEASTWARD ACROSS THE  
UPPER MIDWEST. LARGE-SCALE SUBSIDENCE IN THE WAKE OF THE UPPER  
TROUGH WILL SUPPORT A BROAD AND STRONG SURFACE HIGH ACROSS THE  
NORTHERN ROCKIES AND GREAT BASIN. THE SURFACE PRESSURE GRADIENT  
ACROSS SOUTHERN CA WILL STRENGTHEN THIS EVENING INTO EARLY TUESDAY  
MORNING, AND HIGH-END CRITICAL TO EXTREMELY CRITICAL FIRE WEATHER  
CONDITIONS ARE EXPECTED ACROSS PARTS OF THIS REGION.  
   
..PORTIONS OF SOUTHERN CA
 
 
EXTREMELY CRITICAL AREA: A VERY STRONG SURFACE PRESSURE GRADIENT  
(EVIDENCED BY A LAX-DAG DIFFERENCE OF -8 TO -10 MB AND LAX-TPH  
DIFFERENCE OF -15 TO -20 MB) COUPLED WITH STRONG LOW-LEVEL  
NORTHEASTERLY FLOW WILL EASILY SUPPORT SUSTAINED OFFSHORE WINDS OF  
30-40 MPH ACROSS PARTS OF VENTURA INTO LOS ANGELES COUNTIES  
BEGINNING LATER THIS EVENING AND CONTINUING THROUGH EARLY TUESDAY  
MORNING. WIND GUSTS OF 60-80 MPH WILL BE POSSIBLE ACROSS THE  
MOUNTAINS/FOOTHILLS OF THESE COUNTIES WHERE CHANNELING AND TERRAIN  
EFFECTS CAN LOCALLY ENHANCE THE ALREADY STRONG FLOW, WITH GUSTS OF  
45-60 MPH LIKELY AT LOWER ELEVATIONS. RH VALUES WILL QUICKLY PLUMMET  
BELOW 10% LATER TODAY, AND WILL LIKELY REMAIN BELOW 10% THROUGH THE  
END OF THE PERIOD OWING TO NO OVERNIGHT RH RECOVERY GIVEN THE  
STRENGTH OF THE WINDS. COUPLED WITH VERY DRY AND RECEPTIVE FUELS,  
THESE EXPECTED METEOROLOGICAL CONDITIONS SUPPORT THE CONTINUATION  
AND EASTWARD EXPANSION OF THE EXTREMELY CRITICAL FIRE WEATHER  
DELINEATION.  
 
CRITICAL AREA: SURROUNDING THE EXTREMELY CRITICAL AREA, CRITICAL  
FIRE WEATHER CONDITIONS WILL OCCUR ACROSS A BROADER PART OF COASTAL  
SOUTHERN CA TODAY INTO TONIGHT. RH VALUES WILL RAPIDLY FALL TO 5-15%  
LATER THIS MORNING AS DIURNAL HEATING AND DOWNSLOPE WARMING/DRYING  
ACT ON AN ALREADY DRY AIRMASS. SUSTAINED WINDS OF 20-30 MPH WILL BE  
COMMON ACROSS THE CRITICAL DELINEATION, WITH HIGHER GUSTS OF 40-60  
MPH LIKELY, ESPECIALLY IN HIGHER TERRAIN. SIMILAR TO THE EXTREMELY  
CRITICAL AREA, THE PRESSURE GRADIENT ACROSS THIS REGION WILL BE  
STRONGEST FROM LATE THIS EVENING THROUGH THE END OF THE DAY 1/MONDAY  
PERIOD, AND OVERNIGHT RH RECOVERY WILL BE VERY POOR.  
 
ELEVATED AREA: LOWER CONFIDENCE IN SUSTAINED WINDS IN EXCESS OF 20  
MPH AND/OR SUB-15% RH VALUES EXIST ACROSS THE ELEVATED DELINEATION  
SURROUNDING THE CRITICAL AREA. HOWEVER, WINDS WILL RAPIDLY  
STRENGTHEN ACROSS THE MOUNTAINS/FOOTHILLS OF SOUTHERN CA, RESULTING  
IN A RELATIVELY TIGHT GRADIENT BETWEEN ELEVATED AND CRITICAL FIRE  
WEATHER CONDITIONS.  
   
..PORTIONS OF THE CENTRAL/SOUTHERN PLAINS
 
 
IN THE WAKE OF THE COLD FRONT MENTIONED ABOVE, STRONG/GUSTY  
NORTHWESTERLY WINDS OF 20-30 MPH WILL OCCUR ACROSS MUCH OF KS INTO  
OK, THE TX/OK PANHANDLES, AND EASTERN NM THIS AFTERNOON AND EARLY  
EVENING. HIGHER GUSTS UP TO 40 MPH WILL BE POSSIBLE GIVEN THE  
STRENGTH OF THE MID-LEVEL FLOW THAT WILL LIKELY BE DIURNALLY MIXED  
TO THE SURFACE. WITH A DRY AIRMASS ALREADY IN PLACE ACROSS THE  
CENTRAL/SOUTHERN HIGH PLAINS, RH VALUES WILL LIKELY BECOME LOWERED  
INTO THE 15-25% RANGE FOR AT LEAST A FEW HOURS BEHIND THE COLD FRONT  
PASSAGE.  
 
SOME LOCALLY CRITICAL CONDITIONS MAY BRIEFLY OCCUR ACROSS PORTIONS  
OF SOUTHERN/CENTRAL KS INTO WESTERN OK AND THE TX/OK PANHANDLES  
IMMEDIATELY BEHIND THE FRONT, WHERE RH VALUES MAY BECOME CRITICALLY  
REDUCED. STILL, LATEST GUIDANCE CONTINUES TO SUGGEST THAT THESE  
CONDITIONS SHOULD OCCUR FOR JUST AN HOUR OR TWO. HAVE THEREFORE NOT  
INCLUDED A CRITICAL AREA AT THIS TIME. REGARDLESS, WIDESPREAD  
ELEVATED CONDITIONS ARE ANTICIPATED ACROSS PARTS OF THE  
CENTRAL/SOUTHERN PLAINS WHERE GENERALLY DRY/DORMANT FUELS SHOULD  
SUPPORT LARGE FIRE SPREAD GIVEN THE EXPECTED METEOROLOGICAL  
CONDITIONS.  
   
..PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT
 
 

 
 
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