Fire Weather Outlook Discussion
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000
FNUS22 KWNS 011744
FWDDY2

DAY 2 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1243 PM CDT TUE SEP 01 2015

VALID 021200Z - 031200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SRN MT...ERN ID...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CNTRL NV...

WITHIN THE BROADER ELEVATED AREA DETAILED IN THE PREVIOUS
FORECAST...TWO CRITICAL AREAS HAVE BEEN ADDED THIS FORECAST UPDATE:

/1/ ACROSS PORTIONS OF SRN MT AND ERN ID...AND
/2/ ACROSS PORTIONS OF CNTRL NV.

THE LATEST MULTI-DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE PROVIDE
INCREASED CONFIDENCE THAT THESE TWO AREAS WILL BE THE FOCUS OF
RELATIVE MAXIMA IN SFC WIND SPEEDS WITHIN THE BROADER ELEVATED AREA.
ACROSS THE NRN CRITICAL AREA...THE INFLUENCE OF STRENGTHENING
MID-LEVEL FLOW IN ADVANCE OF AN AMPLIFYING TROUGH IS FORECAST TO
YIELD SWLY SFC WINDS OF 20-25 MPH AND HIGHER GUSTS AS VERTICAL
MIXING DIURNALLY STRENGTHENS. THIS MIXING...COMBINED WITH AREAS OF
DOWNSLOPE-FLOW-ENHANCED WARMING/DRYING...IS FORECAST TO SUPPORT
MINIMUM RH OF 13-20 PERCENT AMIDST DRY TO VERY DRY FUELS. THESE
FACTORS WARRANT UPGRADE TO CRITICAL DESIGNATION IN PARTS OF SRN MT
AND ERN ID. FARTHER S...IN PORTIONS OF CNTRL NV...SIMILAR CRITICALLY
STRONG WINDS ARE ALSO ANTICIPATED -- THOUGH ENHANCED BY A TIGHTER
LOW-LEVEL PRESSURE GRADIENT ON THE SRN PERIPHERY OF AN EVOLVING SFC
TROUGH ACROSS PARTS OF THE GREAT BASIN. RH VALUES ACROSS THE SRN
CRITICAL AREA WILL BE RELATIVELY LOWER -- IN THE 10-14 PERCENT
RANGE -- AMIDST A WARMER AIR MASS AND DRY/VERY DRY FUELS. THESE
FACTORS WARRANT CRITICAL DESIGNATION ACROSS PORTIONS OF CNTRL NV.

ASIDE FROM MINOR ADJUSTMENTS TO THE NRN BOUND OF THE ELEVATED
DELINEATION IN MT/ID AND VICINITY -- I.E. SLIGHT NWD EXTENSION BASED
ON THE LATEST MODEL GUIDANCE -- THE REMAINDER OF THE ONGOING
FORECAST IS ON TRACK AND NO ADDITIONAL CHANGES HAVE BEEN MADE.

..COHEN.. 09/01/2015

.PREV DISCUSSION... /ISSUED 0300 AM CDT TUE SEP 01 2015/

...SYNOPSIS...
AN UPPER TROUGH OVER THE BRITISH COLUMBIA/PACIFIC NORTHWEST REGION
SHOULD UNDERGO AMPLIFICATION THROUGH THE D2/WED PERIOD. ENHANCED
SWLY MID-LEVEL WINDS WILL CONTINUE OVER PORTIONS OF THE GREAT BASIN
AND NRN ROCKIES WED AFTERNOON AND EVENING. AT THE SFC...AN AREA OF
LOW PRESSURE SHOULD DEEPEN FROM LATE D1/TUE INTO THE D2/WED PERIOD
ACROSS SRN ID/NERN NV/NWRN UT WITH THE APPROACH OF THE UPPER TROUGH.
THE RESULTING SFC PRESSURE GRADIENT BETWEEN THIS LOW AND HIGH
PRESSURE CENTERED OVER THE CNTRL ROCKIES SHOULD INCREASE BY WED
EVENING. STRONG/GUSTY WINDS OWING TO THIS INCREASED PRESSURE
GRADIENT AND THE PROMOTION OF STRONGER WINDS ALOFT TO THE SFC SHOULD
ELEVATE FIRE WEATHER CONCERNS ACROSS PORTIONS OF THE GREAT BASIN AND
NRN/CNTRL ROCKIES ON D2/WED AHEAD OF A EWD/SEWD MOVING COLD FRONT
THAT WILL BE ADVANCING OVER THE PACIFIC NORTHWEST AND NRN ROCKIES.

...PORTIONS OF THE GREAT BASIN AND NRN/CNTRL ROCKIES...
AN ELEVATED FIRE WEATHER AREA HAS BEEN DELINEATED FOR MUCH OF THE
GREAT BASIN...INCLUDING MOST OF NV AND UT...AND EXTENDING NEWD INTO
SRN ID/MT...MUCH OF WY...AND NWRN CO. WITHIN THIS BROAD REGION...
SUSTAINED SLY/SWLY WINDS OF 15-25 MPH SHOULD BE FAIRLY COMMON...
WITH SOME HIGHER GUSTS POSSIBLE...PARTICULARLY ACROSS NRN PORTIONS
OF THE ELEVATED AREA. DAYTIME HEATING OF THE BOUNDARY LAYER SHOULD
ENCOURAGE A WELL-MIXED PROFILE BY AFTERNOON...AND RH VALUES SHOULD
GENERALLY LOWER INTO THE 10-20 PERCENT RANGE FOR THREE OR MORE HOURS
ACROSS MUCH OF THIS REGION. WHILE LOCALLY CRITICAL CONDITIONS APPEAR
PROBABLE FOR ONE OR MORE PORTIONS OF THE ELEVATED AREA WED AFTERNOON
AND EVENING...THE COMBINATION OF STRONG WINDS WITH CRITICALLY
LOWERED RH VALUES AMONGST VARIOUS MODEL SOLUTIONS REMAINS TOO
LIMITED IN TIME AND SPACE TO WARRANT A CRITICAL DESIGNATION AT THIS
TIME. HOWEVER...IT IS POSSIBLE THAT ONE OR MORE CRITICAL AREAS MAY
BE INTRODUCED IN LATER OUTLOOKS IF CONFIDENCE IN A SUFFICIENT
OVERLAP OF STRONG WINDS/LOWERED RH INCREASES.

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



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