SPC Day 1 Fire Weather Outlook
DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1151 AM CDT FRI SEP 03 2010
VALID 031700Z - 041200Z
...NO CRITICAL AREAS...
...N-CNTRL/NERN ORE...SERN WA...
NO CHANGES MADE TO THE PREVIOUS FORECAST.
...PIEDMONT OF THE CAROLINAS INTO CNTRL VA...
MODIFIED 12Z RAOBS ACROSS THE REGION AS WELL AS GPS TPW GUIDANCE
CONFIRM THE PRESENCE OF DRY AIR W-SW OF TC EARL SUPPORTIVE OF LOW
AFTERNOON RH VALUES /AOB 25 PERCENT/ ACROSS THE PIEDMONT OF THE
CAROLINAS INTO CNTRL VA. HOWEVER...AS MENTIONED IN PREVIOUS D1
FORECAST...MODEL GUIDANCE CONTINUES TO INDICATE WLY SUSTAINED WIND
SPEEDS AOB 15 MPH DURING MUCH OF THE AFTERNOON...MITIGATING A MORE
SUBSTANTIAL FIRE WEATHER THREAT.
...NRN FL AND THE PANHANDLE...
AS SURFACE TEMPERATURES WARM TO AROUND 90 F DURING THE
AFTERNOON...AND DEWPOINTS MIX DOWN TO NEAR 60 F...MIN RH VALUES WILL
FALL TO 35 PERCENT. HOWEVER...ALL MODEL GUIDANCE SHOWS SUSTAINED
WIND SPEEDS AOB 5 MPH...WHICH WILL PRECLUDE CRITICAL FIRE WEATHER
CONDITIONS FROM DEVELOPING.
...PORTIONS OF CNTRL AND SRN AZ...
MODEL FORECAST SOUNDINGS AS WELL AS MODIFIED 12Z TUS RAOB INDICATE
DEEP INVERTED-V THERMODYNAMIC PROFILES WILL BE POSSIBLE FOR
LOCATIONS OVER CNTRL AND SRN AZ THAT CAN APPROACH 100 F DURING THE
AFTERNOON...SUGGESTING SOME POTENTIAL EXISTS FOR DRY THUNDERSTORMS.
HOWEVER...COMBINATION OF INCREASING PWAT VALUES /RANGING FROM 0.60
INCHES OVER CNTRL AZ TO NEAR 1 INCH OVER SRN AZ/ AND SLOW FORECAST
STORM MOTIONS MAY MITIGATE THAT THREAT SOMEWHAT...RESULTING IN A
MIXTURE OF WET AND DRY STORMS.
..GARNER.. 09/03/2010
.PREV DISCUSSION... /ISSUED 0322 AM CDT FRI SEP 03 2010/
...SYNOPSIS...
A LARGE-SCALE UPPER-LEVEL TROUGH WILL PROGRESS EWD ACROSS THE GREAT
LAKES/MIDWEST...WHILE AN UPSTREAM RIDGE SHIFTS FROM THE PACIFIC NW
TO THE NRN ROCKIES. AN UPPER-LEVEL SHORT WAVE TROUGH WILL REACH THE
SRN BRITISH COLUMBIA COAST BY EARLY SAT.
...N-CNTRL/NERN ORE...SERN WA...
WEAK MID-LEVEL INSTABILITY MAY DEVELOP DURING THE LATE
AFTERNOON/EVENING AS MODEST HEIGHT FALLS AND DIFFLUENT UPPER-LEVEL
FLOW OVERSPREAD THE REGION DOWNSTREAM OF THE SHORT WAVE TROUGH
APPROACHING SRN BRITISH COLUMBIA. LATEST MODEL FORECASTS DIFFER WITH
THE DEGREE OF DESTABILIZATION WITH THE NAM AND ITS COMPANION HI-RES
WRF-NMM MORE AGGRESSIVE THAN OTHER DETERMINISTIC AND ENSEMBLE
GUIDANCE. GIVEN THE EXPECTATION OF RELATIVELY WEAK
FORCING/MOISTENING...OVERALL TSTM PROBABILITIES SHOULD REMAIN LOW
/AROUND 10 PERCENT/. HOWEVER...SHOULD ANY TSTMS DEVELOP THEY OUGHT
TO BE MAINLY DRY WITH THE PRESENCE OF DEEP INVERTED-V THERMODYNAMIC
PROFILES AND FAST STORM MOTIONS. NEVERTHELESS...FUEL DRYNESS LEVELS
IN THE MOIST CATEGORY /PER LATEST NWCC OUTLOOK/ WITH RECENT
ABOVE-NORMAL RAINFALL OVER PORTIONS OF THE AREA WILL MITIGATE THE
THREAT.
...PIEDMONT OF THE CAROLINAS INTO S-CNTRL VA...
A CORRIDOR OF RELATIVELY LOWER PW VALUES WAS SAMPLED IN 06Z
PIT/RNK/FFC RAOBS...BETWEEN AREAS OF RICHER MOISTURE ASSOCIATED WITH
TC EARL AND A WRN GREAT LAKES UPPER-LEVEL TROUGH. THIS DRY AIR
CORRIDOR WILL SHIFT EWD AND BE CENTERED ACROSS THE PIEDMONT BY EARLY
AFTERNOON. WELL ABOVE-NORMAL TEMPERATURES IN THE MIDDLE TO UPPER 90S
SHOULD LEAD TO LOW RH VALUES /FROM 18 TO 25 PERCENT/. HOWEVER...WLY
SURFACE WINDS WILL REMAIN MODERATE /AROUND 8 TO 15 MPH/ AND LIMIT A
MORE SUBSTANTIAL THREAT.
...PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT...
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