SPC Day 2 Fire Weather Outlook

DAY 2 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0438 AM CDT TUE AUG 28 2012

VALID 291200Z - 301200Z

...CRITICAL FIRE WEATHER AREA FOR A LARGE PART OF MT...A SMALL PART
OF ERN ID...WRN AND PARTS OF CNTRL ND...NWRN SD...
...CRITICAL FIRE WEATHER AREA FOR MUCH OF NEB...A SMALL PART OF ERN
CO...NWRN KS...FAR SERN SD...FAR WRN IA...

...SYNOPSIS...
A CYCLONE...CURRENTLY OFF THE COAST OF WA AND ORE...WILL EVOLVE INTO
AN OPEN WAVE AS IT MOVES FROM THE PACIFIC NW ACROSS THE NRN GREAT
BASIN AND NRN ROCKIES BEFORE EVENTUALLY REACHING THE NRN PLAINS.
THIS EVOLVING FEATURE WILL AID IN THE BREAKDOWN OF A RIDGE EXTENDING
NORTH OF A BROAD WRN-CONUS ANTICYCLONE...WHILE A ZONE OF STRONG FLOW
ALOFT OVERLAYS PARTS OF THE NWRN/N-CNTRL CONUS. IN ADDITION TO A SFC
COLD FRONT ACCOMPANYING THE WAVE...A FRONT/TROUGH WILL ALSO EXTEND
OVER PARTS OF THE NRN/CNTRL PLAINS TO THE SOUTH/SOUTHEAST OF WHICH
THE SFC PRESSURE GRADIENT WILL BE ENHANCED.

...A LARGE PART OF MT...A SMALL PART OF ERN ID...WRN AND PARTS OF
CNTRL ND...NWRN SD...
MODEL PREFERENCES: AS DISCUSSED IN THE DAY-1 FIRE WEATHER
OUTLOOK...THE NAM MODEL AND NAM-BASED MODEL SOLUTIONS -- E.G.
NEMS-NMMB MEMBERS OF THE SREF AND 4-KM NAM OUTPUT -- REPRESENT THE
PREFERRED GUIDANCE SUITE FOR THIS OUTLOOK CYCLE. SUBSTANTIATION
INCLUDES MARKEDLY REDUCED DISCREPANCIES IN THE THERMODYNAMIC
STRUCTURE WITHIN THE LOWER TROPOSPHERE BETWEEN NAM-RELATED MODEL
OUTPUT AND OBSERVATIONS COMPARED TO GFS/ARW-KF SOLUTIONS...AND
BACKING FROM ECMWF OUTPUT. ACCORDINGLY...THIS FORECAST CLOSELY
FOLLOWS THE NAM MODEL AND NAM-BASED MODEL SOLUTIONS.

WINDS: SWLY TO WLY SFC WINDS FROM 20 TO 25 MPH WITH HIGHER GUSTS ARE
EXPECTED ACROSS MUCH OF THE AREA AS STRONGER MIXING DEEPENS INTO THE
AFOREMENTIONED ZONE OF STRONGER FLOW ALOFT. WIND DIRECTIONS WILL BE
MORE SLY ACROSS PARTS OF WRN/CNTRL ND AND NWRN SD BEFORE VEERING AND
ATTAINING MORE OF A WLY COMPONENT DURING THE DAY. THESE WINDS IN ND
WILL BE LOCALLY ENHANCED BY THE RELATIVELY TIGHTER PRESSURE GRADIENT
ACCOMPANYING A SFC LOW MOVING EWD ACROSS THE SRN CANADIAN PRAIRIES
AND A PERSISTENT LOW-LEVEL JET MAX. WINDS ACROSS THE ENTIRE AREA ARE
EXPECTED TO BECOME NWLY FOLLOWING THE PASSAGE OF A COLD FRONT THAT
IS FORECAST TO CROSS THE AREA DURING THE LATE AFTERNOON INTO THE
OVERNIGHT HOURS. THIS WIND SHIFT COULD HAVE AN IMPACT ON ANY FIRES.

RH: RH VALUES ARE EXPECTED TO FALL TO 7 TO 14 PERCENT...AIDED BY
DOWNSLOPE EFFECTS IN SOME AREAS. SLIGHTLY HIGHER RH VALUES -- INTO
THE UPPER TEENS -- ARE FORECAST ACROSS N-CNTRL/CNTRL ND.
HOWEVER...THESE READINGS ARE STILL EXPECTED TO BE CRITICALLY LOW --
IN COMBINATION WITH STRONG WINDS -- FOR THAT PARTICULAR AREA.

...MUCH OF NEB...A SMALL PART OF ERN CO...NWRN KS...FAR SERN
SD...FAR WRN IA...
AN UPGRADE TO CRITICAL DESIGNATION HAS BEEN MADE IN COORDINATION
WITH THE BOULDER...GOODLAND...HASTINGS...NORTH PLATTE...OMAHA...AND
SIOUX FALLS WEATHER FORECAST OFFICES. THE NAM MODEL AND NAM-BASED
MODEL SOLUTIONS -- E.G. NEMS-NMMB MEMBERS OF THE SREF AND 4-KM NAM
OUTPUT -- ARE HEAVILY FOLLOWED IN THIS FORECAST CYCLE AS ADDRESSED
IN THE PREVIOUS SUBSECTION AND THE DAY-1 FIRE WEATHER OUTLOOK.

A BROADER AREA OF STRONG SFC WINDS IS EXPECTED TO IMPACT THE CNTRL
PLAINS ON D2/WED COMPARED TO D1/TUE...OWING TO A MORE EXPANSIVE
TIGHT SFC PRESSURE GRADIENT/LOW-LEVEL JET MAX. SSWLY TO SWLY SFC
WINDS OF 20-25 MPH WITH OCCASIONALLY HIGHER GUSTS ARE EXPECTED TO
COMBINE WITH CRITICALLY LOW RH VALUES OF 8-17 PERCENT -- LOWEST WEST
AND HIGHEST EAST. THIS WILL OCCUR AS VERTICAL MIXING INCREASES OWING
TO SFC TEMPERATURES BECOMING HOT -- I.E. FROM 94 TO 103 DEGREES.
AND...WITH DRY FUELS ACROSS THE AREA PER THE AFOREMENTIONED
COORDINATION...A CRITICAL FIRE WEATHER AREA HAS BEEN ISSUED.

...SURROUNDING THE CRITICAL AREAS ACROSS PORTIONS OF THE NRN/CNTRL
PLAINS...UPPER/MIDDLE MS VALLEY...NRN/CNTRL ROCKIES...NRN/CNTRL
GREAT BASIN...
IN ADVANCE OF A COLD FRONT THAT WILL CROSS PORTIONS OF THE AREA FROM
THE LATE AFTERNOON INTO THE OVERNIGHT HOURS...THE COMBINATION OF
MINIMUM RH VALUES OF 10 PERCENT TO THE LOWER 20S AND WIND SPEEDS OF
10 TO LOCALLY/BRIEFLY 20 MPH WILL YIELD AN ELEVATED FIRE WEATHER
THREAT. HOWEVER...IN THE ABSENCE OF STRONGER DEEP-LAYER FLOW AND/OR
A TIGHTER SFC PRESSURE GRADIENT...CRITICALLY STRONG SUSTAINED WINDS
ARE GENERALLY NOT EXPECTED TO OCCUR ON ANY MORE THAN A BRIEF/SPOTTY
BASIS OUTSIDE OF THE CRITICAL AREAS. ONE EXCEPTION MAY BE ACROSS NRN
ND TO THE EAST OF THE NWRN CRITICAL AREA...WHERE WINDS SHOULD BE
LOCALLY ENHANCED BY A RELATIVELY TIGHTER SFC PRESSURE GRADIENT.
HOWEVER...LOW-LEVEL TRAJECTORIES ACROSS THIS REGION ARE EXPECTED TO
SUPPORT SLIGHTER GREATER MOISTURE TRANSPORT AND RH VALUES ABOVE
CRITICAL THRESHOLDS. OF NOTE...WINDS ARE FORECAST TO SHIFT TO NWLY
FOLLOWING THE PASSAGE OF THE AFOREMENTIONED COLD FRONT WHICH COULD
HAVE AN IMPACT ON ANY FIRES.

..COHEN.. 08/28/2012

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