Fire Weather Outlook Discussion
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000
FNUS21 KWNS 251631
FWDDY1

DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT SUN SEP 25 2016

VALID 251700Z - 261200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...

...PORTIONS OF SOUTHERN CALIFORNIA...
RECENT SURFACE OBSERVATIONS SAMPLED -11 MB LAX-TPH...-5 MB
LAX-DAG...AND -7 SAN-LAS GRADIENTS. WIND SPEEDS HAVE BEEN GRADUALLY
INCREASING OVER THE PAST FEW HOURS WITH MULTIPLE HIGH ELEVATIONS
SITES NOW REPORTING NELY SUSTAINED WINDS AROUND 30 MPH. INTERIOR
SITE AT ONT HAS ALSO REPORTED INCREASING WIND SPEEDS OVER THE PAST
HOUR WITH THE LATEST OBSERVATION REPORTING SUSTAINED WINDS OF 20 MPH
AND GUSTS OF 35 MPH. INCREASING TREND IS EXPECTED TO CONTINUE WITH
WIDESPREAD GUSTY CONDITIONS ANTICIPATED THIS AFTERNOON. THESE STRONG
WINDS COUPLED WITH TEMPERATURES IN THE UPPER 90S/LOW 100S AND MIN RH
VALUES IN THE LOWER TEENS/SINGLE DIGITS WILL SUPPORT A WIDESPREAD
CRITICAL FIRE THREAT TODAY. CRITICAL THREAT WILL EXTEND INTO THE
EVENING AND OVERNIGHT AS POOR OVERNIGHT RECOVERY KEEP RH VALUES LOW
AND WINDS REMAIN STRONG. THIS SCENARIO MATCHES WELL WITH THE
PREVIOUS FORECAST AND NO CHANGES ARE NEEDED.

...PORTIONS OF NORTHERN CALIFORNIA...
RECENT SURFACE OBSERVATIONS REVEAL MOSTLY ELEVATED FIRE WEATHER
CONDITIONS AT THE HIGHER ELEVATION SITES ACROSS THE REGION. SIMILAR
CONDITIONS ARE EXPECTED ACROSS THESE AREAS THROUGHOUT THE DAY.
ELEVATED CONDITIONS ARE EXPECTED ACROSS THE VALLEY DURING THE
AFTERNOON AS TEMPERATURES CLIMB INTO THE UPPER 90S/LOW 100S AND RH
VALUES DROP INTO THE SINGLE DIGITS. NO CHANGES ARE NEEDED TO THE
PREVIOUS FORECAST.

...PORTIONS OF THE NORTHERN/CENTRAL PLAINS...
MINOR CHANGES WERE MADE TO THE PREVIOUS ELEVATED DELINEATION BUT THE
OVERALL SCENARIO DESCRIBED IN THE PREVIOUS OUTLOOK /BELOW/ REMAINS
VALID.

..MOSIER.. 09/25/2016

.PREV DISCUSSION... /ISSUED 0315 AM CDT SUN SEP 25 2016/

...SYNOPSIS...
A MID/UPPER-LEVEL TROUGH EXTENDING FROM NORTHERN MEXICO TO THE
NORTHERN PLAINS WILL SHEAR INTO TWO DISTINCT AREAS TODAY -- A CLOSED
CYCLONE DRIFTING SOUTHWEST TOWARDS THE GULF OF CALIFORNIA...AND THE
REMAINDER OF THE ORIGINAL TROUGH OVER THE NORTHERN PLAINS AND UPPER
MIDWEST. TO THE WEST OF THIS TROUGH...RIDGING WILL BUILD OVER PARTS
OF THE PACIFIC NORTHWEST AND GREAT BASIN.

...PORTIONS OF SOUTHERN CALIFORNIA...
WIDESPREAD CRITICAL FIRE-WEATHER CONCERNS ARE EXPECTED ACROSS PARTS
OF SOUTHERN CA TODAY...WITH VERY DRY FUELS AND GUSTY WINDS FAVORING
RAPID FIRE SPREAD. 07Z OBSERVATIONS DEPICT SOME ELEVATED CONDITIONS
ONGOING ACROSS HIGHER TERRAIN...AND WINDS SHOULD FURTHER INCREASE
TOWARD SUNRISE -- WITH SUSTAINED VALUES UPWARDS OF 20-30 MPH AND
GUSTS TO 40-55 MPH -- AS THE SFC PRESSURE GRADIENT FURTHER
STRENGTHENS. RH VALUES WILL FALL RAPIDLY AFTER SUNRISE...GENERALLY
INTO THE 5-15 PERCENT RANGE ACROSS MUCH OF THE REGION...AS TEMPS
CLIMB INTO THE 90S/LOWER 100S TODAY. DUE TO THE OFFSHORE ORIENTATION
OF FLOW ALOFT...WINDS SHOULD NOT EXPERIENCE AS MUCH OF A DIURNAL
WEAKENING AS IS TYPICAL. THUS...GUSTY OFFSHORE FLOW SHOULD PERSIST
AS RH VALUES PLUMMET...SUPPORTING WIDESPREAD CRITICAL FIRE-WEATHER
CONCERNS. TODAY SHOULD BE THE PEAK OF THE ONGOING OFFSHORE FLOW
EVENT...WITH THE POTENTIAL FOR EXTREME FIRE BEHAVIOR FOLLOWING ANY
IGNITIONS. MOREOVER...AS THE SFC PRESSURE GRADIENT STRENGTHENS AGAIN
TONIGHT...CRITICAL CONDITIONS SHOULD CONTINUE THROUGH THE OVERNIGHT
HOURS.

...PORTIONS OF NORTHERN CALIFORNIA...
ELEVATED/LOCALLY CRITICAL FIRE-WEATHER CONCERNS ARE ANTICIPATED THIS
MORNING THROUGH AT LEAST EARLY AFTERNOON ACROSS THE SACRAMENTO
VALLEY AND SURROUNDING TERRAIN. AN ENHANCED SFC PRESSURE GRADIENT
WILL SUPPORT BREEZY NORTHERLY FLOW ACROSS THE VALLEY...AND EASTERLY
DOWNSLOPE WINDS OVER HIGHER TERRAIN. SUSTAINED WINDS AROUND 15-25
MPH AND RH VALUES BELOW 15-20 PERCENT WILL RESULT IN
ELEVATED/LOCALLY CRITICAL CONDITIONS TODAY...BEFORE WINDS WEAKEN
SOME LATE THIS AFTERNOON INTO THE EVENING. SOME ENHANCEMENT OF
EASTERLY WINDS ACROSS THE SIERRA NEVADA RANGE TONIGHT SHOULD THEN
RESULT IN A RETURN OF ELEVATED CONCERNS LATE IN THE PERIOD.

...PORTIONS OF THE NORTHERN/CENTRAL PLAINS...
WITHIN A DRY POST-FRONTAL AIR MASS...BREEZY NORTHWESTERLY WINDS
SHOULD FOSTER ELEVATED CONDITIONS TODAY. SUSTAINED WINDS AROUND
15-25 MPH THIS AFTERNOON WILL COMBINE WITH MIN RH VALUES AROUND
18-25 PERCENT AND SUFFICIENTLY DRY FUELS TO ENHANCE FIRE-WEATHER
CONCERNS.

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

$$



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