SPC Day 2 Fire Weather Outlook

DAY 2 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0245 AM CDT MON APR 29 2013

VALID 301200Z - 011200Z

...CRITICAL FIRE WEATHER AREA FOR NERN AZ...NWRN NM...FAR SERN
UT...FAR SWRN CO...

...SYNOPSIS...
A CYCLONICALLY CURVED BAND OF STRONG TROPOSPHERIC FLOW ACCOMPANYING
AN AMPLIFYING DEEP TROUGH WILL IMPACT PORTIONS OF THE CNTRL/WRN
CONUS. A SW/NE-ORIENTED ZONE OF ENHANCED MID-LEVEL FLOW WILL PRECEDE
THE TROUGH AND EXTEND FROM PORTIONS OF THE SW STATES AND CNTRL GREAT
BASIN INTO THE UPPER MS VALLEY AND WRN GREAT LAKES REGION. AT THE
SFC...AN EXTENSIVE COLD FRONT WILL ADVANCE EWD/SWD ACROSS PORTIONS
OF THE CNTRL/WRN CONUS. LEE TROUGH DEVELOPMENT WILL OCCUR S OF THE
FRONT AND ALIGN WITH A N/S-ORIENTED DRYLINE OVER PARTS OF THE
CNTRL/SRN HIGH PLAINS. MEANWHILE...A ZONE OF SUBSIDENT NLY/NWLY
MID-LEVEL FLOW ON THE BACKSIDE OF THE TROUGH WILL IMPACT PORTIONS OF
THE NWRN CONUS AND SUPPORT A BUILDING SFC ANTICYCLONE OVER PARTS OF
THE NRN GREAT BASIN.

...NERN AZ...NWRN NM...FAR SERN UT...FAR SWRN CO...
WITHIN THE SW/NE-ORIENTED ZONE OF ENHANCED MID-LEVEL FLOW PRECEDING
THE AMPLIFYING DEEP TROUGH...AN EMBEDDED 700-MB WIND SPEED MAXIMUM
IS FORECAST TO OVERLIE THE FOUR-CORNERS REGION DURING PEAK HEATING.
WIND SPEEDS OF 30-40 MPH AT THE 700-MB LEVEL ARE FORECAST TO YIELD
WSWLY TO WLY SFC WINDS AROUND 25 MPH WITH HIGHER GUSTS...AS
DIURNALLY STRENGTHENING VERTICAL MIXING ALLOWS THE STRONGER FLOW
ALOFT TO BE MANIFESTED AT THE SFC. MEANWHILE...A DRY AIR MASS --
CHARACTERIZED BY PW VALUES OF AROUND 0.2-0.3 INCH -- WILL SUPPORT
MINIMUM RH VALUES FROM THE UPPER SINGLE DIGITS TO THE MIDDLE
TEENS...AS TEMPERATURES INCREASE INTO THE 70S AND 80S. AND...WITH
BELOW-NORMAL PRECIPITATION DURING THE PAST MONTH ACROSS MUCH OF THE
REGION...CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED.

...SURROUNDING THE CRITICAL AREA FROM CNTRL-SRN NV/FAR SERN CA/WRN
AZ EASTWARD TO SERN CO/FAR SWRN KS/THE OK PANHANDLE/FAR W TX...
ELEVATED TO BORDERLINE CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED
TO OCCUR WITHIN THE BROAD REGION SURROUNDING THE CRITICAL AREA.
HOWEVER...IN GENERAL...THESE LOCATIONS WILL BE REMOVED FROM THE ZONE
OF STRONGER LOW/MID-LEVEL FLOW DESPITE THE PRESENCE OF CRITICALLY
LOW RH...ALLOWING ANY INSTANCES OF CRITICALLY STRONG SUSTAINED SFC
WIND SPEEDS TO BE SHORT-DURATION AND/OR SPOTTY IN NATURE. EXCEPTIONS
ARE AS FOLLOWS:

/1/ W OF THE CRITICAL AREA ACROSS PORTIONS OF NRN AZ AND SRN UT --
CRITICALLY STRONG WINDS AND LOW RH ARE ANTICIPATED...THOUGH THE
LIMITED SUPPLY OF DRY FUELS THAT WOULD FAVOR LARGE FIRE DEVELOPMENT
PRECLUDES CRITICAL DESIGNATION.

/2/ N/NE OF THE CRITICAL AREA ACROSS PORTIONS OF CNTRL UT AND
CNTRL/S-CNTRL CO -- STRONG WINDS WILL BE POSSIBLE...THOUGH COOLER
BOUNDARY-LAYER CONDITIONS WILL LIKELY BE ASSOCIATED WITH NO MORE
THAN SPOTTY/BRIEF INSTANCES OF CRITICALLY LOW RH VALUES.

/3/ WELL E OF THE CRITICAL AREA ACROSS PORTIONS OF THE ERN TX
PANHANDLE AND ERN OK PANHANDLE -- SLY WINDS MAY REACH AROUND 20 MPH
IN ASSOCIATION WITH AN ENHANCED PRESSURE GRADIENT E OF THE LEE
TROUGH/DRYLINE...THOUGH RELATIVELY HIGHER DEWPOINTS ARE EXPECTED TO
PREVENT RH VALUES FROM BECOMING CRITICALLY LOW ON ANY MORE THAN A
BRIEF/SPOTTY BASIS.

...SACRAMENTO VALLEY OF CA...
A TIGHTENING PRESSURE GRADIENT TO THE S OF THE SFC ANTICYCLONE
BUILDING OVER THE NRN GREAT BASIN IS FORECAST TO SUPPORT NLY WINDS
OF 15-20 MPH WITH HIGHER GUSTS. AS TEMPERATURES INCREASE INTO THE
80S...RH VALUES ARE FORECAST TO FALL TO 15 TO 20 PERCENT DURING THE
AFTERNOON. THESE FACTORS COULD YIELD AN ELEVATED FIRE WEATHER
THREAT. HOWEVER...CONFIDENCE IS FAIRLY LIMITED IN CRITICALLY STRONG
WINDS OCCURRING ON ANY MORE THAN A BRIEF/SPOTTY BASIS WITHOUT AN
EVEN TIGHTER SFC PRESSURE GRADIENT. FURTHERMORE...CONFIDENCE IS
RELATIVELY LIMITED IN CRITICALLY LOW RH VALUES OCCURRING ON ANY MORE
THAN A BRIEF/SPOTTY BASIS IN THE ABSENCE OF A WARMER AIR MASS.
ACCORDINGLY...A CRITICAL AREA HAS NOT BEEN OUTLINED AT THIS TIME.

..COHEN.. 04/29/2013

...PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT...
via SPC Forecast Products http://www.spc.noaa.gov/products/fire_wx/fwdy2.html