Fire Weather Outlook Discussion
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FNUS21 KWNS 271557
FWDDY1

DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1057 AM CDT THU AUG 27 2015

VALID 271700Z - 281200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE CENTRAL ID
MOUNTAINS THROUGH SOUTHERN MT...

...PARTS OF NV/UT...ID...MT/WY FOR DRY THUNDERSTORMS...

THE SCATTERED DRY THUNDERSTORM AREA HAS BEEN REMOVED FROM NV AND
TRIMMED BACK TO ENCOMPASS PORTIONS OF THE CENTRAL ID MOUNTAINS INTO
SOUTHWEST AND SOUTH-CENTRAL MT WHERE HIGH RESOLUTION FORECAST
GUIDANCE SUGGESTS THE GREATEST COVERAGE OF THUNDERSTORMS WILL OCCUR
FROM THIS AFTERNOON THROUGH LATE EVENING. THE ISOLATED DRY
THUNDERSTORM AREA ALSO HAS BEEN MODIFIED TO BETTER REFLECT WHERE
ISOLATED DRY THUNDERSTORMS ARE EXPECTED TODAY. ACROSS PARTS OF NV/UT
AND WY...A MIX OF WET AND DRY THUNDERSTORMS WILL BE POSSIBLE.

...EASTERN WA INTO NORTH-CENTRAL MT...

NO CHANGES WERE MADE TO THE PREVIOUS FORECAST. SEE PREVIOUS
DISCUSSION BELOW FOR MORE DETAILS.

..LEITMAN.. 08/27/2015

.PREV DISCUSSION... /ISSUED 0218 AM CDT THU AUG 27 2015/

...SYNOPSIS...
THE LARGE-SCALE PATTERN OVER THE CONUS WILL BE DOMINATED BY UPPER
RIDGING OVER THE SOUTHWESTERN CONUS AND A LARGE...SLOW-MOVING UPPER
LOW OVER THE NORTHEASTERN PACIFIC.  THIS UPPER LOW WILL SPREAD
ENHANCED SOUTHWESTERLY MID-LEVEL FLOW ACROSS INTERIOR PARTS OF THE
NORTHWEST THROUGHOUT THE DAY.  A SHORTWAVE TROUGH WILL MAKE SLOW
EASTWARD PROGRESS ACROSS THE CENTRAL PLAINS TODAY...WHILE A
BROAD/DIFFUSE AREA OF WEAKNESS IN THE GEOPOTENTIAL HEIGHT FIELD WILL
REMAIN ACROSS THE SOUTHEASTERN STATES...ALONG THE EASTERN PERIPHERY
OF THE SOUTHWESTERN UPPER RIDGE.

...PARTS OF IDAHO/MONTANA AND FAR NORTHEASTERN NEVADA/FAR
NORTHWESTERN UTAH FOR DRY THUNDERSTORMS...
THIS REGION WILL REMAIN ON THE NORTHERN AND WESTERN PERIPHERY OF
DEEPER LOW- AND MID-LEVEL MOISTURE/EXTENSIVE CLOUDINESS THAT HAS
PERSISTED IN PARTS OF UTAH/COLORADO AND SURROUNDING AREAS OVER THE
PAST 2-3 DAYS.  AS SURFACE HEATING COMMENCES...WEAK MID-LEVEL
INSTABILITY AND WEAK MID-LEVEL STEERING FLOW SHOULD CONTRIBUTE TO
POCKETS OF ISOLATED TO SCATTERED THUNDERSTORMS...PERHAPS MOST
CONCENTRATED ACROSS CENTRAL IDAHO INTO SOUTHWESTERN MONTANA.  MUCH
OF THE REGION REMAINED RELATIVELY RAIN-FREE WEDNESDAY
AFTERNOON/EVENING...AND FUELS ARE MOSTLY EXPECTED TO REMAIN VERY DRY
AND SUPPORTIVE OF RAPID FIRE GROWTH.  THE CURRENT CRITICAL/SCATTERED
DRY THUNDERSTORM DELINEATION REPRESENTS GREATEST CONFIDENCE AND
CONCENTRATION OF LIGHTNING STRIKES OCCURRING IN AREAS OF VERY DRY
FUELS.  FARTHER WEST /IN THE LEE OF THE CASCADES/...RECENT MODEL
GUIDANCE SUGGESTS THAT COVERAGE OF THUNDERSTORMS SHOULD REMAIN TOO
SPARSE TO CONTINUE AN ISOLATED DRY-THUNDER AREA.

...EASTERN WASHINGTON EASTWARD TO NORTH-CENTRAL MONTANA...
ELEVATED MID-LEVEL FLOW WILL PERSIST ACROSS THIS REGION TODAY IN
ADVANCE OF THE VIGOROUS SYSTEM OVER THE NORTHEASTERN PACIFIC.  A DRY
AIRMASS WILL REMAIN IN PLACE ACROSS THIS REGION...WITH
INSOLATION/VERTICAL MIXING AND A DEEPENING BOUNDARY LAYER
CONTRIBUTING TO 10-15 MPH WEST-SOUTHWESTERLY SURFACE FLOW /WITH
HIGHER GUSTS/ AND 13-20 PERCENT SURFACE RH VALUES DURING THE
AFTERNOON AND EARLY EVENING.  ELEVATED TO LOCALLY CRITICAL FIRE
WEATHER CONDITIONS WILL EXIST ACROSS THIS AREA FOR MUCH OF THE
AFTERNOON AND EARLY EVENING.

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




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