Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 260839
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
239 AM MDT SUN JUL 26 2015

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

HOT...DRY AND WINDY THROUGH MONDAY AFTERNOON WITH HIGH FIRE
DANGER THE PRIMARY CONCERN. A COLD FRONT WILL MOVE THROUGH MONDAY
NIGHT...COOLING THINGS OFF FOR TUESDAY BUT THE FRONT WILL BE DRY
IN MOST AREAS...KEEPING THE FIRE DANGER HIGH AS IT PASSES.

THERE WILL BE A CHANCE FOR SHOWERS AND THUNDERSTORMS ACROSS THE
NORTHWEST THIS AFTERNOON AND EVENING AS A TROUGH CURRENTLY DIGGING
ACROSS THE WEST COAST SENDS OUT A WEAK LEADING SHORT WAVE LATE
THIS AFTERNOON AND THEN MOVES INTO THE AREA ON MONDAY. THERE WILL
BE SOME MOISTURE AT THE MID LEVELS COMING ALONG WITH THIS FEATURE
TO KICK OFF SOME SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND
EVENING...BECOMING MORE LIKELY ON MONDAY WITH THE COLD
FRONT...AGAIN MOST OF THIS ACTIVITY WILL BE ACROSS THE FAR NORTH.
THE MAIN THREAT WITH THESE STORMS WILL BE STRONG WINDS.

TEMPERATURES WILL BE MUCH COOLER ON TUESDAY BUT THERE COULD BE A
PERIOD OF GUSTY WINDS IN THE AFTERNOON AS THE UPPER LOW PULLS OFF
TO THE NORTHEAST. THE AIRMASS ACROSS SOUTHERN WYOMING WILL REMAIN
DRY THROUGH THIS PERIOD AS WELL THOUGH THERE DOES NOT APPEAR TO BE
AN AREA LARGE ENOUGH WHERE THE DRY AND WINDY CONDITIONS OVERLAP
FOR LONG PERIOD OF TIME...THOUGH IT WILL BE WATCHED
CLOSELY...ESPECIALLY IF ANY FIRES ARE STARTED THIS WEEKEND.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

SYNOPSIS...UPPER RIDGE OVER THE SOUTHERN PLAINS WILL DRIFT WEST AND
STRENGTHEN OVER THE FOUR CORNERS AREA THROUGH THE PERIOD.  THIS WILL
BRING DRY WEATHER WITH A WARMING TREND WEDNESDAY THROUGH FRIDAY.  A
SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE NORTH AND FAR SOUTH RETURN
NEXT WEEKEND.

DISCUSSION...AFTER A BRIEF TASTE OF AUTUMN ON TUESDAY BEHIND THE
COLD FRONT...A MORE TYPICAL MID-SUMMER PATTERN SETS UP WITH UPPER
HIGH SETTING UP OVER THE FOUR CORNERS AREA THURSDAY AND FRIDAY WITH
BUILDING HEIGHTS ACROSS THE AREA.  A VERY DRY AND STABLE AIRMASS
WILL RESULT IN MAINLY CLEAR SKIES AND SOME BREEZY CONDITIONS ACROSS
THE SOUTHERN WIND CORRIDOR FROM ROCK SPRINGS TO CASPER IN THE
AFTERNOONS.  HIGHS ON WEDNESDAY WILL REMAIN ON THE COOL SIDE...A FEW
DEGREES BELOW NORMAL...DURING THE TRANSITION PERIOD.  TEMPERATURES
WILL THEN RETURN TO ABOVE NORMAL TERRITORY FOR MOST AREAS THURSDAY
AND FRIDAY WITH HIGHS IN THE LOWER CENTRAL BASINS PUSHING INTO THE
LOWER 90S.

GFS AND ECMWF SHOW SOME SPREAD ACROSS THE NORTHERN STREAM FRIDAY
NIGHT AND SATURDAY...WITH THE GFS BRINGING A STRONGER SHORTWAVE AND
ASSOCIATED COLD FRONT INTO THE NORTHERN PLAINS WITH SHALLOW FRONT
BACKING INTO NORTHERN WY FRIDAY NIGHT WHILE THE ECMWF IS FLATTER
WITH FLOW ACROSS THE NORTHERN TIER OF THE U.S. ...KEEPING A MOSTLY
DRY AND STABLE AIRMASS OVER WYOMING THROUGH THE WEEKEND.  FORECAST
INTRODUCES ISOLATED AFTN/EVE THUNDERSTORMS OVER THE NORTHERN MTNS ON
SATURDAY...AND THEN ACROSS MOST OF THE NORTHERN ONE-HALF OF THE AREA
ON SUNDAY AROUND PERIPHERY OF ESTABLISHED FOUR CORNERS HIGH.&&

.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL AT THE TERMINAL SITES THROUGH THE
FORECAST PERIOD. THERE ARE SMALL CHANCES FOR AN ISOLATED SHOWER OR
STORM WILL OCCUR AFTER 18Z OVER NORTHWESTERN WYOMING...AND POSSIBLY
IN VICINITY OF KCOD UNTIL AROUND 04Z MONDAY. A SOUTHWESTERLY BREEZE
WILL DEVELOP NEAR KCPR AND KRKS. NORTHWESTERLY DRAINAGE WIND WILL BE
POSSIBLE AT KRIW AFTER 03Z MONDAY.

&&

.FIRE WEATHER...

...RED FLAG WARNING IN EFFECT FOR CASPER DISPATCH THROUGH
MONDAY...

HOT...DRY...WINDY AND UNSTABLE ACROSS MUCH OF THE STATE
TODAY...WITH CONDITIONS EXPECTED TO BE MORE EXTREME ON MONDAY
AHEAD OF A DRY COLD FRONTAL PASSAGE. THEREFORE...ALL ZONES WITH
CRITICALLY DRY FUELS HAVE A RED FLAG WARNING IN EFFECT TODAY AND
TOMORROW. IT IS IMPORTANT TO NOTE THAT THE FIRE DANGER EXISTS
ACROSS MUCH OF THE STATE...EVEN IN AREAS THAT ARE NOT UNDER A RED
FLAG WARNING. IT IS NOT SAFE TO BURN OR DO ANYTHING THAT MAY EMIT
SPARKS OUTDOORS TODAY OR MONDAY.

THOUGH WIND THRESHOLDS WILL BE BORDERLINE TODAY...THE RELATIVE
HUMIDITY WILL BE VERY LOW...THE TEMPERATURES WILL BE IN THE UPPER
80S AND 90S...AND THE HAINES INDEX WILL BE A 6 ACROSS MOST OF THE
AREA AS WELL...PROMPTING THE RED FLAG ISSUANCE. ON MONDAY...JUST
ABOUT EVERY CONDITION WILL BE MET FROM VERY STRONG WINDS TO HEAT
TO HUMIDITY TO A DRY COLD FRONTAL PASSAGE.

A SMALL POTENTIAL FOR FIRE STARTS WILL EXIST DUE TO LIGHTNING
STRIKES ACROSS THOSE AREAS WHERE THUNDERSTORMS EXIST...MAINLY
ACROSS THE NORTHWEST TODAY AND TOMORROW. SOME OF THESE STORMS
COULD PRODUCE STRONG DOWNBURST WINDS THAT TRAVEL FAR FROM THE
PARENT STORM...ESPECIALLY THROUGH THE NORTHWESTERN MOUNTAINS AND
INTO THE BIGHORN BASIN AND NORTHERN JOHNSON COUNTY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM 1 PM SUNDAY TO 10 PM MDT MONDAY FOR WYZ280-
281-285-300.

&&

$$

SHORT TERM...ALLEN
LONG TERM...AEM
AVIATION...HATTINGS
FIRE WEATHER...ALLEN


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