000
FNUS22 KWNS 201821
FWDDY2
DAY 2 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0121 PM CDT SUN MAY 20 2012
VALID 211200Z - 221200Z
...CRITICAL FIRE WEATHER AREA FOR W-CNTRL NV...
...W-CNTRL NV...SMALL PART OF MONO COUNTY CA...
THE LATEST MODEL GUIDANCE SUGGESTS THAT AN UPGRADE TO CRITICAL IS
WARRANTED ACROSS PORTIONS OF W-CNTRL NV AND THE FOOTHILLS OF THE
SIERRAS IN MONO COUNTY CA. WHILE THE STRONGEST MIDLEVEL SWLY FLOW
WILL REMAIN ALONG THE PAC NW COAST THROUGH 00Z AS PREVIOUSLY
MENTIONED...A BRANCH OF 30-40 KT WINDS IS FORECAST TO NOSE INTO FAR
WRN NV BY 21-00Z. POINT FORECAST SOUNDINGS INDICATE A DEEPLY MIXED
BOUNDARY LAYER AS TEMPERATURES WARM INTO THE 70S AND 80S AND COUPLED
WITH DOWNSLOPE EFFECTS IN THE LEE OF THE SIERRAS...GUSTY WINDS AND
DRYING POTENTIAL WILL BE GREAT. EXPECT RH VALUES FROM 10-14 PERCENT
/LOCALLY LOWER WHERE DRYING IS ENHANCED DUE TO DOWNSLOPE/ AND SWLY
WINDS NEAR 20 MPH GUSTING TO 35 MPH BY LATE AFTERNOON. RH RECOVERY
WILL BE POOR OVERNIGHT AS DOWNSLOPE WINDS CONTINUE OVER THE SIERRAS
AND WINDS MAY REMAIN BREEZY NEAR HIGHER TERRAIN. FURTHER REMOVED
FROM THE MOUNTAINS...RH VALUES WILL REBOUND SLIGHTLY OVERNIGHT AND A
NOCTURNAL INVERSION WILL LEAD TO LIGHTER WINDS AFTER SUNSET.
...ERN NV/LOWER ELEVATIONS OF WRN UT/FAR NWRN AZ...
NO CHANGES FROM PREVIOUS FORECAST. WIND SPEEDS WILL BE LIGHTER HERE
DESPITE LOW RH VALUES AND WARM TEMPERATURES...LEADING TO
SUB-CRITICAL CONDITIONS.
..LEITMAN.. 05/20/2012
.PREV DISCUSSION... /ISSUED 0219 AM CDT SUN MAY 20 2012/
...SYNOPSIS...
IN THE MID/UPPER LEVELS...A PROGRESSIVE WAVE PATTERN WILL EXIST
ACROSS A LARGE PART OF THE NRN HALF OF THE UNITED STATES. ONE
SHORTWAVE TROUGH WILL SHIFT EWD FROM THE UPPER MISSISSIPPI VALLEY
TOWARD THE GREAT LAKES REGION...WHILE AN UPSTREAM RIDGE MOVES EWD
FROM THE NRN/CNTRL ROCKIES TOWARD THE NRN/CNTRL PLAINS. A RELATIVELY
STRONGER SHORTWAVE TROUGH WILL ADVANCE EWD FROM PARTS OF THE FAR
EAST PACIFIC OCEAN ACROSS THE PACIFIC NW AND THE NRN GREAT BASIN. A
BELT OF STRONG MID-LEVEL FLOW WILL ACCOMPANY THIS FEATURE AS IT
MOVES ONSHORE.
...MUCH OF NV/LOWER ELEVATIONS OF WRN UT/FAR NWRN AZ...
WITH A DRY AIR MASS IN PLACE OVER THE REGION...RH VALUES ARE
FORECAST TO FALL TO 6-15 PERCENT ACROSS MOST OF THE AREA...WITH THE
LOWEST OF THESE VALUES ANTICIPATED ACROSS SRN/ERN NV...WRN UT...AND
FAR NWRN AZ. THIS WILL OCCUR AS TEMPERATURES WARM INTO THE 80S AND
90S ACROSS MUCH OF THE REGION...SUPPORTING DEEP VERTICAL MIXING
DURING THE AFTERNOON. THIS VERTICAL MIXING INTO THE RELATIVELY
STRONGER FLOW ALOFT SHOULD SUPPORT SSWLY TO SWLY WINDS OF 10 TO
LOCALLY/BRIEFLY 20 MPH WITH GUSTS REACHING 25 MPH DURING THE
AFTERNOON...YIELDING ELEVATED FIRE WEATHER CONDITIONS.
HOWEVER...THE MORE SUBSTANTIAL STRENGTHENING OF MID-LEVEL FLOW IN
ASSOCIATION WITH THE AFOREMENTIONED RELATIVELY STRONGER SHORTWAVE
TROUGH IS NOT FORECAST TO COMMENCE UNTIL AFTER PEAK HEATING...WHEN
/1/ VERTICAL MIXING DECREASES AND /2/ THE POTENTIAL FOR STRONGER
FLOW ALOFT TO BE MANIFESTED AT THE SFC AS CRITICALLY STRONG
SUSTAINED WIND SPEEDS ALSO DECREASES. THERE IS SOME CONCERN THAT
PORTIONS OF CNTRL/NRN NV MAY EXPERIENCE A BRIEF PERIOD OF CRITICALLY
STRONG WINDS DURING THE LATE AFTERNOON. REGARDLESS...WITH THE
ARRIVAL OF THE STRONGER FLOW ALOFT EXPECTED TO TAKE PLACE AFTER THE
PEAK OF THE DIURNAL HEATING CYCLE...THE CONFIDENCE IN CRITICALLY
STRONG SUSTAINED WIND SPEEDS OCCURRING IN CONJUNCTION WITH LOW RH ON
ANY MORE THAN A BRIEF BASIS IS TOO LIMITED FOR THE DESIGNATION OF A
CRITICAL AREA AT THIS TIME.
...PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT...
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