Fire Weather Outlook Discussion
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FNUS21 KWNS 041556
FWDDY1

DAY 1 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1055 AM CDT SAT JUL 04 2015

VALID 041700Z - 051200Z

NO CHANGES TO PREVIOUS FORECAST.  A FEW LOCATIONS IN THE LEE OF THE
CASCADES WILL HAVE SUSTAINED WINDS APPROACHING 20 MPH FOR BRIEF
PERIODS...YIELDING LOCALLY CRITICAL FIRE WEATHER CONDITIONS AT TIMES
DURING THE AFTERNOON.  FOR MORE INFORMATION...SEE PREVIOUS
DISCUSSION BELOW.

..COOK.. 07/04/2015

.PREV DISCUSSION... /ISSUED 0357 AM CDT SAT JUL 04 2015/

...SYNOPSIS...
DEVELOPMENT OF MID-/UPPER-LEVEL HIGH-OVER-LOW BLOCK ACROSS THE
EASTERN PACIFIC OCEAN WILL CONTINUE THROUGH THE FORECAST
PERIOD...WITH A TROUGH-OVER-RIDGE PATTERN EVOLVING DOWNSTREAM ACROSS
WESTERN NORTH AMERICA. THIS MID-/UPPER-LEVEL CONFIGURATION WILL
FAVOR HOT/DRY CONDITIONS ACROSS THE WESTERN UNITED STATES /WITH
UNSEASONABLY WARM TEMPERATURES ACROSS THE PACIFIC NORTHWEST/ AND AN
INCREASE IN MID-LEVEL MOISTURE /DRAWN NORTHWARD FROM THE TROPICAL
EASTERN PACIFIC/. FARTHER EAST...MEAN TROUGHING WILL PERSIST ACROSS
EASTERN NORTH AMERICA.

AT THE SURFACE...A REMNANT FRONT ACROSS THE SOUTHERN/EASTERN UNITED
STATES WILL ONCE AGAIN SUPPORT SHOWER/THUNDERSTORM DEVELOPMENT.

...CENTRAL OREGON NORTHWARD INTO CENTRAL AND EASTERN WASHINGTON...
A SHORT-WAVE TROUGH MOVING THROUGH THE LARGER WESTERN CANADA TROUGH
WILL ACT TO STRENGTHEN THE WESTERLY COMPONENT OF THE MID-LEVEL FLOW
ACROSS THIS REGION. THE RESULTANT DOWNSLOPE FLOW WILL SUPPORT AN
INCREASING SURFACE-PRESSURE GRADIENT AS A LEE TROUGH DEVELOPS EAST
OF THE CASCADES. THIS WILL ALLOW FOR SURFACE WINDS TO INCREASE TO
BETWEEN 10-20 MPH WITH STRONGER GUSTS POSSIBLE.
ADDITIONALLY...HOT/DRY ANTECEDENT CONDITIONS...COUPLED WITH
DOWNSLOPE FLOW...WILL ALLOW FOR SURFACE AND NEAR-SURFACE
RELATIVE-HUMIDITY VALUES TO FALL QUICKLY INTO THE TEENS AND LOWER
20S PERCENT RANGE DURING THE AFTERNOON. THE COMBINATION OF STRONGER
WINDS AND LOWER RELATIVE-HUMIDITY VALUES WILL YIELD
ELEVATED-T0-LOCALLY CRITICAL FIRE-WEATHER CONDITIONS.

...GREAT BASIN...SIERRA MOUNTAINS...NORTHERN CALIFORNIA...AND FAR
SOUTHERN OREGON...
MID-/UPPER-LEVEL MOISTURE WILL CONTINUE TO INCREASE ACROSS THE AREA
AS MOISTURE IS DRAWN NORTHWARD ON THE WESTERN PERIPHERY OF THE
SUB-TROPICAL RIDGE CENTERED OVER THE ROCKY MOUNTAINS. COINCIDENT
WITH THIS INCREASE IN MOISTURE...CONVECTIVELY-INDUCED VORTICITY
MAXIMA FROM PREVIOUS DAYS CONVECTION ARE EMBEDDED WITHIN THE
MID-LEVEL FLOW AROUND THE SUB-TROPICAL RIDGE. ASCENT ASSOCIATED WITH
THESE SUBTLE VORTICITY MAXIMA...ALONG WITH OROGRAPHIC EFFECTS...WILL
YIELD ISOLATED-TO-SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS.
FORECAST SOUNDINGS SUGGEST PRECIPITABLE-WATER VALUES WILL BE HIGH
ENOUGH TO SUPPORT WETTING RAINS WITHIN THUNDERSTORM CORES.
HOWEVER...PERSISTENT DROUGHT ACROSS THE AREA HAS LEFT FUELS VERY DRY
AND RECEPTIVE TO LIGHTNING INDUCED FIRES...ESPECIALLY FROM LIGHTNING
STRIKES REMOVED FROM THUNDERSTORM CORES. ADDITIONALLY...VERY DRY
SUB-CLOUD LAYERS WILL SUPPORT A DOWNBURST POTENTIAL WITH STRONGER
THUNDERSTORMS. THIS WILL LEAD TO STRONG/GUSTY THUNDERSTORM OUTFLOW
WINDS. PLEASE SEE THE LATEST SPC DAY-1 CONVECTIVE OUTLOOK FOR
ADDITIONAL INFORMATION REGARDING THUNDERSTORM WIND POTENTIAL.

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



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