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000
FNUS21 KWNS 251650
FWDDY1

DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1150 AM CDT SAT MAY 25 2013

VALID 251700Z - 261200Z

...CRITICAL FIRE WEATHER AREA FOR NRN AZ...NWRN NM...EXTREME SRN
NV...

...NRN AZ...NWRN NM...EXTREME SRN NV...
NO CHANGES HAVE BEEN MADE TO THE ONGOING CRITICAL AREA...AS LOW-END
CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED. WITH THE 12Z
FLAGSTAFF RAOB AND RECENT VWP DATA INDICATING SWLY FLOW EXCEEDING 25
MPH AOA 1500 FT AGL...DIURNALLY STRENGTHENING VERTICAL MIXING SHOULD
SUPPORT SSWLY TO SWLY SFC WINDS AROUND 20 MPH WITH GUSTS REACHING
AROUND 25 MPH. AND...WITH PW VALUES AROUND 0.15-0.20 INCH PER THE
12Z FLAGSTAFF RAOB AND GPS DATA...RH VALUES ARE EXPECTED TO FALL TO
AROUND 8-12 PERCENT THIS AFTERNOON. THE ANTICIPATION OF CRITICAL
FIRE WEATHER CONDITIONS IS AFFIRMED BY EXPERIMENTAL SPC SSEO
GUIDANCE. FURTHERMORE...PRECIPITATION HAS BEEN BELOW NORMAL DURING
THE PAST FEW MONTHS IN MANY LOCATIONS. AS SUCH...THE CRITICAL AREA
IS BEING MAINTAINED FOR A LOW-END CRITICAL FIRE WEATHER RISK.

...LOCATIONS THAT SURROUND THE CRITICAL AREA ACROSS PORTIONS OF
AZ...SERN CA...SRN NV...SRN UT...SWRN CO...WRN NM...
ELEVATED FIRE WEATHER CONDITIONS ARE ANTICIPATED AS RH VALUES BECOME
CRITICALLY LOW. HOWEVER...CONFIDENCE IN CRITICALLY STRONG WINDS
OCCURRING ON ANY MORE THAN A BRIEF/SPOTTY BASIS IS TOO LIMITED FOR
CRITICAL DESIGNATION IN THE ABSENCE OF STRONGER LOW/MID-LEVEL FLOW.

...MOUNTAINS OF CNTRL NM...
NO CHANGES HAVE BEEN MADE TO THE ONGOING FORECAST. ISOLATED TO
WIDELY SCATTERED DRY THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON.
HOWEVER...THE ABSENCE OF STRONGER DEEP FORCING FOR ASCENT IN AREAS
WHERE LOW/MID-LEVEL MOISTURE/THERMAL PROFILES WOULD SUPPORT A
DRY-THUNDERSTORM MODE WITH PW VALUES OF 0.50-0.75 INCH SHOULD
PREVENT THE COVERAGE OF DRY THUNDERSTORMS FROM EXCEEDING WIDELY
SCATTERED. THIS IS AFFIRMED BY THE CONSENSUS AMONGST THE LATEST
CONVECTION-ALLOWING MODEL GUIDANCE. AS SUCH...A DRY-THUNDERSTORM
CRITICAL AREA HAS NOT BEEN INCLUDED.

...CNTRL PA SWD INTO CNTRL VA...
AN ENHANCED SFC PRESSURE GRADIENT WILL SUPPORT WNWLY TO NWLY SFC
WINDS OF 15-20 MPH WITH GUSTS REACHING 25-30 MPH. THE STRONGEST OF
THESE WINDS ARE EXPECTED ACROSS CNTRL PA. AND...WITH STRENGTHENING
VERTICAL MIXING AMIDST DEEP DRY AIR CHARACTERIZED BY PW VALUES
AROUND 0.25 INCH...MINIMUM RH VALUES FROM THE MIDDLE 20S TO THE
MIDDLE 30S ARE EXPECTED AS TEMPERATURES CLIMB INTO THE 60S AND 70S.
THE LOWEST OF THESE RH VALUES ARE EXPECTED ACROSS CNTRL VA WHERE THE
WARMEST AIR MASS IS EXPECTED TO BE PRESENT. THESE FACTORS MAY
SUPPORT MARGINALLY ELEVATED FIRE WEATHER CONDITIONS.

HOWEVER...IN THE ABSENCE OF AN EVEN WARMER AIR MASS...CRITICALLY LOW
RH VALUES ARE NOT EXPECTED TO OCCUR ON ANY MORE THAN A BRIEF/SPOTTY
BASIS. FURTHERMORE...THE ABSENCE OF STRONGER LOW-LEVEL FLOW MAY
PREVENT CRITICALLY STRONG WINDS FROM OCCURRING ON ANY MORE THAN A
LOCALIZED/SHORT-DURATION BASIS. ALSO...ANY FIRE WEATHER THREAT MAY
BE MITIGATED BY THE STRONGER WINDS BEING DISPLACED TO THE NORTH OF
LOWER RH/HIGHER TEMPERATURES ACROSS THE REGION. ADDITIONALLY...FUEL
CONDITIONS MAY ONLY BE MARGINALLY RECEPTIVE FOR THE SPREAD OF FIRES
IN MANY LOCATIONS. AS SUCH...FIRE WEATHER HIGHLIGHTS HAVE NOT BEEN
INCLUDED.

...W-CNTRL FL PENINSULA...
SFC OBSERVATIONS AROUND 16Z INDICATE ELY WINDS AROUND 10-13 MPH WITH
LOCALLY HIGHER GUSTS. THESE WINDS WILL CONTINUE THROUGH THE DAY
WITHIN AN OFFSHORE FLOW REGIME OVER THE W-CNTRL FL PENINSULA COAST
WHILE A MODESTLY ENHANCED SFC PRESSURE GRADIENT PERSISTS.
STRENGTHENING DIURNAL HEATING/VERTICAL MIXING AMIDST PW VALUES FROM
0.75 TO 1.00 INCH WILL SUPPORT RH VALUES FALLING INTO THE
MIDDLE/UPPER 30S. MARGINALLY ELEVATED FIRE WEATHER CONDITIONS MAY
OCCUR IN AREAS WHERE PRECIPITATION DURING THE PAST COUPLE OF WEEKS
HAS BEEN BELOW NORMAL. HOWEVER...IN THE ABSENCE OF A DRIER AIR
MASS...CRITICALLY LOW RH VALUES ARE NOT EXPECTED TO OCCUR ON ANY
MORE THAN A BRIEF/SPOTTY BASIS. FURTHERMORE...IN THE ABSENCE OF
STRONGER LOW-LEVEL FLOW/A TIGHTER SFC PRESSURE GRADIENT...CRITICALLY
STRONG SUSTAINED WIND SPEEDS ARE NOT EXPECTED. AS SUCH...FIRE
WEATHER HIGHLIGHTS HAVE NOT BEEN INCLUDED.

..COHEN.. 05/25/2013

.PREV DISCUSSION... /ISSUED 0405 AM CDT SAT MAY 25 2013/

...SYNOPSIS...
ANOTHER IN A SERIES OF SHORTWAVE TROUGHS IS FORECAST TO ROTATE
THROUGH THE FLOW SURROUNDING THE LARGE...STATIONARY PACIFIC
NORTHWEST UPPER LOW. TO THE EAST OF THIS UPPER LOW...SHORTWAVE
RIDGING SHOULD PERSIST ACROSS THE CENTRAL UNITED STATES.

...NORTHERN ARIZONA...NORTHWESTERN NEW MEXICO...EXTREME SOUTHERN
UTAH...AND EXTREME SOUTHEASTERN NEVADA...
STRONG DIURNAL HEATING...COUPLED WITH A DRY ATMOSPHERE /PW VALUES AT
OR BELOW 0.25 INCHES/...WILL ONCE AGAIN RESULT IN RH VALUES DROPPING
INTO THE SINGLE DIGITS ACROSS MUCH OF THE AREA. MODEST LOW-TO-MID
LEVEL FLOW /AROUND 700 MB/ AND DEEPLY MIXED BOUNDARY LAYERS WILL
RESULT IN SURFACE WINDS NEAR OR SLIGHTLY ABOVE 20 MPH YIELDING AT
LEAST LOW-END CRITICAL FIRE WEATHER CONDITIONS. HOWEVER...GIVEN
MODEL/OBSERVATIONAL TRENDS OF DECREASING THE LOW-TO-MID LEVEL
FLOW...SURFACE WINDS MAY END UP BEING SLIGHTLY LESS THAN FORECAST.
IF OBSERVATIONS LATER TODAY SUPPORT THIS DECREASED SURFACE WIND
SCENARIO..THE CRITICAL RISK MAY NEED TO BE DOWNGRADED IN THE DAY 1
UPDATE.

...AREAS OF SOUTHERN ARIZONA AND SOUTHERN UTAH...SURROUNDING THE
CRITICAL AREA...
ELEVATED FIRE WEATHER CONDITIONS ARE EXPECTED IN THE AREAS
SURROUNDING THE CRITICAL RISK. RELATIVE HUMIDITY VALUES ARE ONCE
AGAIN EXPECTED TO BE CRITICALLY LOW DURING THE AFTERNOON
HOURS...WITH THE DRIEST CONDITIONS EXPECTED ACROSS SOUTHERN ARIZONA
/RH VALUES IN THE SINGLE DIGITS/...AND SLIGHTLY MORE MOIST
CONDITIONS ACROSS SOUTHERN UTAH /RH IN THE TEENS/. WIND SPEEDS ARE
EXPECTED TO FLIRT WITH EXCEEDING CRITICAL THRESHOLD /20 MPH/ AT
TIMES DURING THE AFTERNOON...WITH THE HIGHEST POTENTIAL FOR
EXCEEDING 20 MPH ACROSS SOUTHERN UTAH. HOWEVER...AT THIS TIME IS
APPEARS THAT JOINT OCCURRENCE OF CRITICALLY LOW RH AND CRITICALLY
HIGH WIND SPEEDS OCCURRING FOR THE REQUISITE 3 HRS APPEARS
SUFFICIENTLY LOW THAT A CRITICAL DELINEATION IS NOT WARRANTED.

...MOUNTAINS OF CENTRAL NEW MEXICO...
WIDELY SCATTERED AFTERNOON THUNDERSTORMS ARE EXPECTED TO DEVELOP IN
FAVORED OROGRAPHIC ASCENT AREAS. PW VALUES HERE ARE EXPECTED TO
REMAIN BELOW 0.75 INCHES. THIS...COUPLED WITH DEEP INVERTED-VEE
SOUNDINGS WILL TEND TO PREVENT MOST PRECIPITATION FROM REACHING THE
GROUND WITH ANY CONVECTION THAT DOES DEVELOP. GIVEN THE WIDELY
SCATTERED NATURE OF ANY CONVECTION...A CRITICAL IS NOT FELT TO BE
NECESSARY. SHOULD LATER FORECASTS INDICATE MORE CONVECTION THAN
CURRENTLY EXPECTED...A DRY THUNDERSTORM CRITICAL MAY BE NEEDED.

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