Fire Weather Outlook Discussion
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000
FNUS21 KWNS 300831
FWDDY1

DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0330 AM CDT SUN AUG 30 2015

VALID 301200Z - 311200Z

...SYNOPSIS...
A LARGE-SCALE UPPER TROUGH OVER THE PACIFIC NORTHWEST AND WRN
CANADIAN PROVINCES EVIDENT ON WATER VAPOR SATELLITE IMAGERY EARLY
THIS MORNING WILL CONTINUE EWD TODAY...REACHING THE NRN HIGH PLAINS
AND SASKATCHEWAN/MANITOBA BY EARLY MON MORNING. DOWNSTREAM RIDGING
WILL ALSO MOVE EWD FROM THE NRN PLAINS TO THE GREAT LAKES
REGION/ONTARIO THROUGH THE PERIOD...WHILE ANOTHER AREA OF UPPER
RIDGING OVER THE DESERT SOUTHWEST BECOMES SUPPRESSED WITH THE TROUGH
PASSING TO THE N. AT THE SFC...AN AREA OF LOW PRESSURE WITH TRAILING
COLD FRONT ASSOCIATED WITH THE UPPER TROUGH DESCRIBED ABOVE WILL
ALSO MOVE EWD OVER THE NRN GREAT BASIN...PORTIONS OF THE NRN/CNTRL
ROCKIES AND ADJACENT HIGH PLAINS.

...PORTIONS OF THE NRN/CNTRL ROCKIES...NRN/CNTRL HIGH PLAINS...AND
GREAT BASIN...
BEHIND THE SFC COLD FRONT MENTIONED ABOVE...STRONG/GUSTY DOWNSLOPE
WINDS WILL LIKELY OCCUR THIS AFTERNOON ACROSS PORTIONS OF THE NRN
ROCKIES AND ADJACENT NRN HIGH PLAINS IN ASSOCIATION WITH ENHANCED
SWLY MID-LEVEL FLOW MOVING OVER THE REGION. WHILE SFC TEMPERATURES
WILL LIKELY BE COOL THIS MORNING WITH FRONTAL PASSAGE...DOWNSLOPE
WARMING/DRYING OF THE BOUNDARY LAYER SHOULD LOWER RH VALUES TO 20-25
PERCENT FOR SEVERAL HOURS IN THE AFTERNOON ACROSS PORTIONS OF THIS
AREA. ALTHOUGH ISOLATED...GENERALLY WET THUNDERSTORMS MAY OCCUR FOR
N-CNTRL/CNTRL MT THIS AFTERNOON...THE EXPECTED COMBINATION OF
WIND/RH VALUES SUPPORTS THE ELEVATED DESIGNATION FOR MUCH OF
CNTRL/SWRN MT...ERN ID...AND FAR NWRN WY...WITH LOCALLY CRITICAL
CONDITIONS POSSIBLE...PARTICULARLY IN ERN ID AND S-CNTRL MT.

FURTHER S ACROSS PORTIONS OF THE GREAT BASIN AND MUCH OF
WY...MID-LEVEL FLOW SHOULD BE GENERALLY WEAKER TODAY...AROUND 20-40
KT. REGARDLESS...AS DIURNAL MIXING OF THE BOUNDARY LAYER COMBINES
WITH DAYTIME HEATING...SOME OF THESE WINDS ALOFT MAY BE PROMOTED TO
THE SFC...AND AREAS OF STRONG/GUSTY WINDS MAY ALIGN WITH RH VALUES
APPROACHING CRITICAL LEVELS FOR SEVERAL HOURS THIS AFTERNOON. HAVE
ADJUSTED THE SRN ELEVATED AREA TO REMOVE A PORTION OF UT AND NWRN
CO...WHERE GREATER CONVECTIVE COVERAGE IS EXPECTED...AND FORECAST
WINDS/RH NO LONGER SUPPORT ELEVATED FIRE WEATHER CONDITIONS.

SIMILAR TO THE NRN ELEVATED AREA...ISOLATED TO WIDELY SCATTERED
CONVECTION MAY DEVELOP THIS AFTERNOON ACROSS PORTIONS OF THE GREAT
BASIN INTO WY...WITH SOME POTENTIAL FOR A MIX OF WET/DRY
THUNDERSTORMS GIVEN FORECAST AND OBSERVED PWAT VALUES. AN ISOLATED
DRY THUNDERSTORM AREA HAS THEREFORE BEEN INTRODUCED ACROSS PORTIONS
OF WY...WHERE A WELL-MIXED/DRY SUB-CLOUD LAYER...FAST STORM
MOTIONS...AND DRY FUELS COULD SUPPORT NEW FIRE STARTS FROM LIGHTNING
STRIKES.

ACROSS PORTIONS OF THE NRN/CNTRL PLAINS...SLY LOW-LEVEL FLOW SHOULD
INCREASE AHEAD OF THE SFC LOW AND COLD FRONT APPROACHING FROM THE W.
LOWERED RH VALUES NEAR/BELOW CRITICAL LEVELS COMBINED WITH THE
STRONG FORECAST WINDS WOULD NORMALLY SUPPORT AN ELEVATED FIRE
WEATHER AREA...BUT GENERALLY UNRECEPTIVE FUELS ACROSS THIS REGION
SHOULD GREATLY LIMIT THE FIRE WEATHER THREAT...AND THEREFORE NO
ELEVATED AREA IS WARRANTED.

..GLEASON.. 08/30/2015

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



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