Public Information Statement
Issued by NWS Riverton, WY

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NOUS45 KRIW 191007
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WYZ001>020-022>030-191800-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
406 AM MDT FRI APR 19 2013

...THIS IS SEVERE WEATHER AWARENESS WEEK IN WYOMING...

THE WEEK OF APRIL 15 TO APRIL 19 HAS BEEN DESIGNATED SEVERE WEATHER
AWARENESS WEEK IN WYOMING. TODAY WE WILL DISCUSS FIRE WEATHER.

WHAT IS FIRE WEATHER AND WHY WOULD IT BE INCLUDED IN SEVERE WEATHER
AWARENESS WEEK?

FIRE WEATHER IS A BROAD TERM USED TO DESCRIBE WEATHER VARIABLES THAT
INFLUENCE FIRE POTENTIAL...BEHAVIOR...AND SUPPRESSION. THE NATIONAL
WEATHER SERVICE ISSUES WATCHES AND WARNINGS WHEN CERTAIN WEATHER
VARIABLES ENCOURAGE EXTREME FIRE BEHAVIOR...JUST LIKE WE DO FOR
EXTREME WINTER WEATHER CONDITIONS OR FOR SEVERE THUNDERSTORMS.

LAST YEAR ALONE...OVER 600K ACRES WERE BURNED AND IT COST OVER 100
MILLION DOLLARS TO FIGHT FIRES ACROSS THE STATE. AS PEOPLE MOVE OUT
OF URBAN AREAS AND CLOSER TO NATURE AND THE FORESTS OF WYOMING...AN
INCREASING NUMBER OF PEOPLE ARE BECOMING MORE VULNERABLE TO WILDFIRE.
WHICH BECAME A STARK LESSON LAST YEAR AS TWO OF OUR MAJOR WILDLAND
URBAN INTERFACES BURNED DURING THE LITTLE HORSETHIEF CANYON FIRE NEAR
JACKSON AND THE SHEEP HERDER HILL FIRE ON CASPER MOUNTAIN...SEVERAL
THOUSAND PEOPLE WERE IMPACTED AS THEY WERE PUT ON NOTICE FOR POSSIBLE
EVACUATION...SEVERAL HUNDRED DID EVACUATE...OVER 50 STRUCTURES WERE
LOST INCLUDING FULL TIME RESIDENCES. BOTH OF THESE FIRES WERE STARTED
BY HUMAN ACTIVITY.

HOW CAN YOU USE FIRE WEATHER TO HELP PREVENT A TRAGEDY LIKE THIS IN
THE FUTURE? YOU CAN START BY KNOWING WHICH WEATHER CONDITIONS CAN
ENCOURAGE A FIRE TO GROW INTO A WILDFIRE...AND WHICH PRODUCTS TO
LOOK FOR FROM THE NATIONAL WEATHER SERVICE TO WARN YOU OF THESE
CONDITIONS. THERE ARE TWO PRODUCTS ISSUED TO WARN OF EXTREME FIRE
BEHAVIOR...THE FIRST IS A FIRE WEATHER WATCH WHICH IS ISSUED WHEN
THE WEATHER IS EXPECTED TO ENCOURAGE EXTREME FIRE BEHAVIOR A COUPLE
OF DAYS FROM NOW...IT IS OFTEN UPGRADED TO WHAT IS KNOWN AS A RED
FLAG WARNING ONCE THE TIME OF THE ANTICIPATED CONDITIONS DRAWS NEAR.

FOR WHICH WEATHER VARIABLES IS A RED FLAG WARNING ISSUED?

ONE OF THE VARIABLES THAT ENCOURAGES FIRES TO GROW OUT OF CONTROL IS
LOW RELATIVE HUMIDITY...STUDIES HAVE SHOWN THAT WHEN THE RELATIVE
HUMIDITY DROPS BELOW FIFTEEN PERCENT...FIRE BEHAVIOR BECOMES
EXTREME. IN ADDITION...LONG PERIODS OF LOW HUMIDITY CAUSES GRASSES
AND TIMBER TO BECOME VERY DRY...MAKING THEM RECEPTIVE TO EVEN THE
SMALLEST SPARK.

ANOTHER VARIABLE IMPORTANT TO FIRE BEHAVIOR IS THE WIND SPEED. THIS
VARIABLE PERHAPS HAS THE GREATEST INFLUENCE ON FIRE BEHAVIOR AND
SPREAD AND WHEN IT IS COMBINED WITH LOW HUMIDITY...A RED FLAG
WARNING IS ISSUED.

A THIRD WEATHER ELEMENT CONSIDERED FOR A RED FLAG WARNING IS
ATMOSPHERIC STABILITY. WHEN THE ATMOSPHERE IS VERY UNSTABLE BUT IT IS
VERY DRY...THEN A RED FLAG WARNING MAY BE ISSUED. THESE TWO ELEMENTS
COMBINED HAVE BEEN SHOWN IN STUDIES TO PRODUCE WHAT IS KNOWN AS PLUME
DOMINATED FIRES...A CONDITION WHEN FIRES OFTEN PRODUCE THEIR OWN
WEATHER CONDITIONS WITH A CONTINUALLY VENTED FIRE THAT FEEDS ON
ITSELF. WHEN YOU HAVE A VERY UNSTABLE ATMOSPHERE BUT IT IS
MOIST...YOU END UP WITH THUNDERSTORMS THAT COULD CAUSE NEW FIRES TO
START FROM THE LIGHTNING AND ARE OFTEN ACCOMPANIED BY VERY ERRATIC
AND GUSTY WINDS...A VERY DANGEROUS COMBINATION...ESPECIALLY FOR FIRE
FIGHTERS BATTLING AN EXISTING WILDFIRE.

THOSE ARE THE THREE MAIN ELEMENTS CONSIDERED WHEN WE WARN OF RED FLAG
CONDITIONS...BUT THERE ARE ALSO SEVERAL OTHERS INCLUDING A DRY COLD
FRONTAL PASSAGE...CRITICAL LIGHTNING INCLUDING AN ANTICIPATED LARGE
NUMBER OF THUNDERSTORMS THAT PRODUCE LIGHTNING BUT VERY LITTLE
RAIN...VERY WARM TEMPERATURES CAN ALSO INCREASE FIRE BEHAVIOR AS THE
HOT SUN CURES GRASSES AND DRY TIMBER.

IF A RED FLAG WARNING IS ISSUED FOR YOUR AREA...THIS IS YOUR SIGNAL
TO BE EVEN MORE CAUTIOUS WITH FIRE. THE FIRE ON CASPER MOUNTAIN WAS
STARTED BY HUMAN ACTIVITY ON A DAY WHEN THERE WAS A RED FLAG WARNING
IN EFFECT AND OVER 400 PEOPLE HAD TO FLEE THEIR HOMES AS A GIANT WALL
OF FLAMES RACED TOWARD THEM. THE HORSETHIEF CANYON FIRE WAS ALSO
CAUSED BY HUMAN ACTIVITY WHEN A SMALL FIRE ESCAPED A BURN BARREL AND
RACED UP INTO THE WILDLANDS BEHIND A HOUSE IN A MATTER OF MINUTES. IF
YOU START A WILDFIRE YOU MAY BE HELD CIVILLY...CRIMINALLY AND
FINANCIALLY LIABLE. WILDFIRES CAN BE STARTED BY THE SLIGHTEST
SPARK...EVEN FROM SOMETHING AS PERCEPTIVELY HARMLESS AS PARKING AN
ATV IN THE GRASS...THE WARM MUFFLER MAY START A GRASS FIRE. IF THERE
ARE CURRENT BURN BANS FOR YOUR COUNTY...PLEASE TAKE THEM SERIOUSLY.
IF YOU PLAN ON DOING SOME AGRICULTURAL BURNING...PLEASE NOTIFY YOUR
LOCAL SHERIFF AND FIRE DEPARTMENT TO ENSURE THAT IT IS LEGAL AND
THAT YOU DO NOT CAUSE ANY FALSE ALARM CALLS...ALSO PLEASE CALL THE
NATIONAL WEATHER SERVICE AT 800-211-1448 FOR A FORECAST FIRST SO THAT
YOU ENSURE THAT RED FLAG CONDITIONS WILL NOT DEVELOP AND CAUSE YOUR
FIRE TO BECOME UNCONTROLLABLE.

WILDFIRES ARE JUST AS FRIGHTENING AND DESTRUCTIVE AS ANY OTHER SEVERE
WEATHER EVENT...ESPECIALLY HERE IN WYOMING. WILDFIRES CAN HAVE
LASTING IMPACT ON THE LANDSCAPE FOR YEARS TO COME. ESPECIALLY IF A
HEAVY SHOWER OR THUNDERSTORM MOVES OVER A BURN SCAR...WHICH CAN CAUSE
FLASH FLOODING AND DEBRIS FLOWS IF LESS THAN ONE HALF INCH OF RAIN
FALLS IN LESS THAN AN HOUR. GIVEN THE AMOUNT OF NEW LARGE BURN SCARS
IN 2012...NOW WOULD BE A GOOD TIME TO DETERMINE YOUR LEVEL OF RISK.

IF YOU WOULD LIKE MORE INFORMATION ON HOW TO PROTECT YOURSELF FROM
FLASH FLOODING AFTER A FIRE...OR HOW TO PREVENT WILDFIRES OR WHAT
YOU CAN DO BEFORE THE FIRE STARTS TO MAKE YOUR HOME EASIER TO
PROTECT...VISIT OUR SEVERE WEATHER AWARENESS WEEK WEBSITE AT
WWW.WEATHER.GOV/RIVERTON AND CLICK ON THE SEVERE WEATHER AWARENESS
WEEK LINK.

KELLY ALLEN
METEOROLOGIST AND FIRE WEATHER PROGRAM MANAGER
NATIONAL WEATHER SERVICE
RIVERTON WY
WEATHER.GOV/RIVERTON

$$