Fire Weather Outlook Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000
FNUS21 KWNS 021549
FWDDY1

DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1048 AM CDT THU OCT 02 2014

VALID 021700Z - 031200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CNTRL/WRN LOS ANGELES
COUNTY AND CNTRL/SRN/ERN VENTURA COUNTY IN SOUTHERN CALIFORNIA...

...COASTAL RANGES AND ADJACENT FOOTHILLS OF SOUTHERN CALIFORNIA...

THE PREVIOUS FORECAST REMAINS ON TRACK...NO CHANGES NEEDED.

MESOWEST OBSERVATIONS INDICATED LIGHT TO MODERATE OFFSHORE WINDS
THIS MORNING ACROSS THE LOS ANGELES AND VENTURA COUNTY
MOUNTAINS/FOOTHILLS WITH WIDESPREAD GUSTS IN THE 30-40 MPH RANGE.
RELATIVE HUMIDITY VALUES RANGED FROM AROUND 10-20 PERCENT /EXCEPT
NEAR THE IMMEDIATE COAST WHERE HIGHER VALUES WERE NOTED/ AND WILL
CONTINUE TO FALL THROUGH THE DAY AS SFC HIGH TEMPERATURES WARM INTO
THE 90S TO NEAR 100 DEGREES. BREEZY CONDITIONS ARE EXPECTED THROUGH
AT LEAST MIDDAY. WINDS MAY WEAKEN BY LATE AFTERNOON/EVENING BEFORE
INCREASING SOME AGAIN OVERNIGHT.

FURTHER SOUTH TOWARD ORANGE...RIVERSIDE AND SAN DIEGO
COUNTIES...STRONGER WINDS WILL REMAIN MORE ISOLATED...LIMITED TO
GENERALLY WIND-PRONE AREAS WHERE TERRAIN ENHANCED CHANNELING OCCURS.
LATEST OBSERVATIONS SHOW A FEW LOCATIONS HAVE GUSTED INTO THE 40-45
MPH RANGE BUT MORE WIDESPREAD 20-30 MPH WINDS WERE NOTED. GIVEN HOT
AND DRY CONDITIONS THOUGH...ELEVATED TO BORDERLINE CRITICAL
CONDITIONS WILL PERSIST FOR SEVERAL MORE HOURS...BEFORE INCREASING
SOME AGAIN OVERNIGHT.

..LEITMAN.. 10/02/2014

.PREV DISCUSSION... /ISSUED 0227 AM CDT THU OCT 02 2014/

...SYNOPSIS...
MID-LEVEL CYCLONIC FLOW WILL COVER THE CNTRL UNITED STATES...AS AN
EMBEDDED IMPULSE TRACKS FROM THE NRN ROCKIES TO THE CNTRL
PLAINS...AND A LOWER-LATITUDE SHORTWAVE TROUGH ADVANCES FROM THE SRN
ROCKIES TO THE MID-MS VALLEY. MEANWHILE...A MID-LEVEL RIDGE WILL
SLOWLY SHIFT EWD ACROSS THE W COAST VICINITY. IN RESPONSE TO THESE
DEVELOPMENTS...SFC RIDGING WILL BE MAINTAINED/ENHANCED ACROSS THE
CNTRL GREAT BASIN...BENEATH SUBSIDENT NWLY FLOW IN THE MID LEVELS.
THIS PATTERN WILL ALSO ENCOURAGE THE MAINTENANCE OF DEEP DRY AIR
ACROSS PORTIONS OF THE WRN CONUS...WITH EARLY-MORNING GPS DATA
INDICATING PW VALUES AROUND ONE-QUARTER INCH ACROSS MUCH OF THE
CNTRL GREAT BASIN.

...COASTAL RANGES AND ADJACENT FOOTHILLS OF SOUTHERN CALIFORNIA...
AS SFC RIDGING IS MAINTAINED/ENHANCED ACROSS THE CNTRL GREAT
BASIN...THE LATEST MULTI-MODEL CONSENSUS CONTINUES TO INDICATE A
RELATIVELY TIGHT SFC PRESSURE GRADIENT BECOMING ESTABLISHED TODAY.
MEAN SEA-LEVEL PRESSURE DIFFERENCES BETWEEN THE SRN CA COAST AND
CNTRL NV ARE PROJECTED TO REACH NEAR 8-10 MB.

A MORE SUBSTANTIAL SURGE OF MODIFIED COOL AIR/HIGHER SFC PRESSURE
INTO THE WRN MOJAVE DESERT/ANTELOPE VALLEY IS EXPECTED TO FOCUS AN
AREA OF STRONG ENELY TO ELY SFC WINDS ACROSS PORTIONS OF CNTRL/WRN
LOS ANGELES COUNTY AND CNTRL/SRN/ERN VENTURA COUNTY.
TERRAIN-CHANNELED FLOW IN THIS REGIME IS EXPECTED TO SUPPORT
SUSTAINED WINDS OF 20-25 MPH WITH GUSTS REACHING 35-40 MPH --
LOCALLY STRONGER THROUGH FAVORED PASSES/CANYONS. THIS EXPECTATION IS
BACKED BY THE LATEST 4-KM AND 1.33-KM NAM OUTPUT ALONG WITH 4-KM
AFWA ENSEMBLE AND SSEO OUTPUT...WHICH CAN ENHANCE THE RESOLUTION OF
TERRAIN VARIABILITY AND BETTER DEPICT ITS EFFECT ON THE MESOSCALE
FLOW PATTERN. THESE STRONG WINDS WILL BE MOST LIKELY FROM 12Z THIS
MORNING TO 20Z LATER TODAY...WITH WINDS WEAKENING THEREAFTER AS THE
SFC PRESSURE GRADIENT RELAXES. AND...WITH DEEP DRY AIR COUPLED WITH
BOUNDARY-LAYER WARMING/DRYING OWING TO DOWNSLOPE FLOW...RH VALUES
WILL LIKELY RANGE FROM 4 TO 15 PERCENT FOR TODAY INTO TONIGHT...WITH
LITTLE TO NO RH RECOVERY EXPECTED TONIGHT. FURTHERMORE...
TEMPERATURES WILL LIKELY SOAR INTO THE 80S AND 90S THIS
AFTERNOON...ENCOURAGING DIURNAL RH REDUCTIONS. FOR THESE REASONS...A
CRITICAL AREA IS IN EFFECT FOR PORTIONS OF CNTRL/WRN LOS ANGELES
COUNTY AND CNTRL/SRN/ERN VENTURA COUNTY IN SOUTHERN CALIFORNIA.

ELSEWHERE ACROSS THE COASTAL RANGES AND ADJACENT FOOTHILLS OF SRN
CA...AN ELEVATED FIRE-WEATHER AREA IS IN EFFECT. RH VALUES ARE
EXPECTED TO RANGE FROM THE MIDDLE SINGLE DIGITS TO THE MIDDLE TEENS
IN THESE AREAS. NELY TO ELY SFC WINDS OF GENERALLY 15-20 MPH WITH
LOCALLY HIGHER GUSTS -- STRONGEST THROUGH FAVORED PASSES/CANYONS --
ARE EXPECTED TO COMBINE WITH THE AFOREMENTIONED RH VALUES TO SUPPORT
ELEVATED TO BORDERLINE CRITICAL FIRE WEATHER CONDITIONS.
HOWEVER...THE ABSENCE OF A TIGHTER SFC PRESSURE GRADIENT IN THESE
LOCATIONS THAT SURROUND THE AFOREMENTIONED CRITICAL AREA IS EXPECTED
TO PREVENT CRITICALLY STRONG SUSTAINED WIND SPEEDS FROM OCCURRING ON
ANY MORE THAN A BRIEF/SPOTTY/MARGINAL BASIS.

...PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT...



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.