641  
FNUS22 KWNS 060719  
FWDDY2  
 
DAY 2 FIRE WEATHER OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0118 AM CST WED DEC 06 2017  
 
VALID 071200Z - 081200Z  
 
...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN  
CALIFORNIA...   
..CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA
 
 
   
..SYNOPSIS
 
 
DANGEROUS AND EXTREMELY CRITICAL FIRE WEATHER CONDITIONS ARE  
EXPECTED ACROSS A GREATER PORTION OF SOUTHERN CA ON DAY 2/THURSDAY  
COMPARED TO DAY 1/WEDNESDAY.  
 
WITHIN LARGE-SCALE UPPER TROUGHING OVER MUCH OF THE CENTRAL/EASTERN  
CONUS, AN EMBEDDED POSITIVELY TILTED UPPER TROUGH WILL DEVELOP  
SOUTH-SOUTHEASTWARD OVER THE ROCKIES/PLAINS BY 12Z THURSDAY.  
ENHANCED NORTH/NORTHEASTERLY LOW- AND MID-LEVEL FLOW AROUND 30-40 KT  
ON THE WESTERN PERIPHERY OF THIS UPPER TROUGH WILL OVERSPREAD THE  
SOUTHWEST AND SOUTHERN CA THURSDAY MORNING AND EARLY AFTERNOON.  
HIGHLY AMPLIFIED UPPER RIDGING WILL REMAIN OVER THE EASTERN PACIFIC  
AND WEST COAST.  
 
AT THE SURFACE, A BROAD AREA OF HIGH PRESSURE OVER THE NORTHERN  
ROCKIES AND GREAT BASIN WILL RESTRENGTHEN LATE FROM WEDNESDAY NIGHT  
INTO THURSDAY MORNING. A CORRESPONDING INCREASE IN OFFSHORE WINDS  
WILL OCCUR ACROSS MUCH OF COASTAL SOUTHERN CA THROUGH THURSDAY  
EVENING, SUPPORTING HIGH-END CRITICAL TO EXTREMELY CRITICAL FIRE  
WEATHER CONDITIONS.  
   
..PORTIONS OF SOUTHERN CA
 
 
GIVEN THE STRENGTHENING SURFACE PRESSURE GRADIENT PLUS THE ENHANCED  
LOW- AND MID-LEVEL FLOW MENTIONED ABOVE, SUSTAINED NORTHEASTERLY TO  
EASTERLY WINDS OF 30-40 MPH WILL LIKELY OCCUR ACROSS MUCH OF THE  
HIGHER TERRAIN OF SOUTHERN CA FROM THURSDAY MORNING THROUGH AT LEAST  
THE EVENING HOURS. THIS INCLUDES THE MOUNTAINS/FOOTHILLS AND  
ADJACENT AREAS OF VENTURA, LOS ANGELES, ORANGE, SOUTHWESTERN SAN  
BERNARDINO, WESTERN RIVERSIDE, AND CENTRAL/EASTERN SAN DIEGO  
COUNTIES. STRONGER GUSTS OF 50-70 MPH WILL LIKELY OCCUR IN FAVORED  
HIGHER TERRAIN AND PASSES WHERE FLOW CHANNELING WILL BE MAXIMIZED.  
RH VALUES WILL EASILY FALL/REMAIN IN THE 5-10% RANGE DUE TO DIURNAL  
HEATING AND LOW-LEVEL DOWNSLOPE WARMING/DRYING EFFECTS. COUPLED WITH  
VERY DRY/RECEPTIVE FUELS, THESE EXPECTED METEOROLOGICAL CONDITIONS  
SUPPORT AN EXTREMELY CRITICAL FIRE WEATHER AREA. LARGE FIRE SPREAD  
AND EXTREME FIRE BEHAVIOR WILL OCCUR WITH ANY NEW/ONGOING FIRES.  
 
SURROUNDING THE EXTREMELY CRITICAL DESIGNATION, CRITICAL FIRE  
WEATHER CONDITIONS ARE ANTICIPATED. HERE, SUSTAINED WINDS OF 20-30  
MPH, WITH GUSTS TO 40-50 MPH, AND RH VALUES OF 5-15% WILL BE COMMON.  
BOTH DOWNTOWN LOS ANGELES AND THE LA BASIN ALONG WITH SAN DIEGO HAVE  
BEEN INCLUDED IN A CRITICAL DELINEATION. THESE DANGEROUS FIRE  
WEATHER CONDITIONS ARE FORECAST TO CONTINUE THROUGH THE ENTIRE DAY  
2/THURSDAY PERIOD, ALTHOUGH THE SURFACE PRESSURE GRADIENT SHOULD  
RELAX SLIGHTLY FROM LATE THURSDAY NIGHT INTO FRIDAY MORNING. THIS  
SHOULD ACT TO LESSEN WINDS SOMEWHAT ACROSS SOUTHERN CA LATE IN THE  
PERIOD.  
 
..GLEASON.. 12/06/2017  
   
..PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT
 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab SPC Page Main Text Page