Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 210931
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
331 AM MDT MON JUL 21 2014

.SHORT TERM...MONDAY THROUGH WEDNESDAY NIGHT

FORECAST IS WORKING OUT FAIRLY WELL AS AN AREA OF MONSOONAL MOISTURE
AND ASSOCIATED SHORTWAVE ARE NOW LIFTING NORTHWARD ACROSS THE COUNTY
WARNING AREA. THE BEST MOISTURE AS OF AROUND MIDNIGHT WAS STILL
ACROSS IDAHO. WE EXPECT THE DEEPEST MOISTURE TO STAY WEST OF THE
AREA. HOWEVER...THERE WILL BE ENOUGH MOISTURE AND INSTABILITY FOR A
DECENT AMOUNT OF CONVECTION ACROSS THE NORTHWESTERN MOUNTAINS TODAY.
MEANWHILE...WE EXPECT A DRYING TREND ACROSS SOUTHERN WYOMING AS SOME
DRIER AIR ROTATES INTO THE AREA FROM UTAH AND COLORADO. WITH THIS
VERY DRY AIR MOVING IN ALONG WITH CONTINUED WARM TEMPERATURES AND A
GUSTY WIND FROM A DECENT TIGHT GRADIENT...CRITICAL FIRE WEATHER IS
ONCE AGAIN POSSIBLE ACROSS SOME AREAS THAT ARE CRITICAL. AS A RESULT
WE WILL CONTINUE THE RED FLAG WARNING FOR SWEETWATER AND NATRONA
COUNTIES FOR THIS AFTERNOON. CONVECTION SHOULD END THIS EVENING AS
THE BEST FORCING MOVES AWAY TO THE NORTH. TEMPERATURES WILL CONTINUE
TO BE HOT EXCEPT IN THE WESTERN MOUNTAINS WHERE CLOUD COVER SHOULD
BRING A COOLER CONDITIONS THEN RECENT DAYS.

THUNDERSTORM ACTIVITY WILL ONCE AGAIN WANE JUST A BIT FOR TUESDAY AS
HEIGHTS BUILD SOMEWHAT. AT THE SAME TIME...THE MODELS...ESPECIALLY
THE GFS SHOW SOME DRY AIR MOVING IN FROM THE SOUTH WITH PRECIPITABLE
WATER VALUES DROPPING TO UNDER 0.50 INCHES ACROSS APPROXIMATELY THE
SOUTHERN TWO THIRDS OF THE COUNTY WARNING AREA. THE NAM ALSO HAS
SOME DRYING ALTHOUGH NOT TO THE SAME EXTENT. CONTINUITY HAD ANY
SHOWERS AND THUNDERSTORMS CONFINED TO THE NORTHERN MOUNTAINS AND
THIS SEEMS REASONABLE SO FEW CHANGES WERE MADE. TEMPERATURES WILL BE
SLIGHTLY COOLER...EMPHASIS ON SLIGHT...EAST OF THE DIVIDE BUT STILL
NEAR TO ABOVE NORMAL. ONE BIGGER CHANGE IS THAT LIGHTER WINDS ARE
EXPECTED SO FIRE DANGER SHOULD LESSEN.

BY WEDNESDAY THE RIDGE WILL BUILD MORE ALONG WITH INCREASING
THICKNESSES. THIS WILL RAISE TEMPERATURES ONCE AGAIN WITH SOME OF
THE WARMER AREAS LIKE THE EASTERN BIG HORN BASIN SEEING HIGH
TEMPERATURES APPROACHING TRIPLE DIGITS. COVERAGE OF ANY SHOWERS OR
THUNDERSTORMS IS A LITTLE MORE UNCERTAIN THOUGH. THERE WILL BE A
BIT MORE MOISTURE AROUND. HOWEVER...WITH HIGHER HEIGHTS IT WILL BE
HARDER TO BREAK ANY CAPPING. AT THIS POINT...WE LEFT CONTINUITY
ALONE WITH CHANCES IN THE NORTH AND EAST. HOWEVER...CHANCES WERE
KEPT AT SLIGHT AND A VAST MAJORITY OF THE DAY AND EVENING STILL
LOOKS TO BE RAIN FREE.

.LONG TERM...THURSDAY THROUGH MONDAY

A WEATHER SYSTEM MOVES EAST THROUGH SOUTHERN CANADA THURSDAY AND
THURSDAY NIGHT AND ENDS UP IN CENTRAL SASKATCHEWAN FRIDAY. A COLD
FRONT MOVES THROUGH NORTHWEST WY THURS PM AND PUSHES EAST AND SOUTH
THURSDAY NIGHT. ISOLATED SHOWERS OR STORMS FOR THE FAR NORTH STILL
LOOKS OK FOR THURS PM AND EVE WITH DRY WEATHER ELSEWHERE. A WEST
FLOW ALOFT IS FORECAST FOR FRIDAY. BREEZY CONDITIONS TO OCCUR FRIDAY
IN THE SOUTH HALF IN THE AFTERNOON AS MIXING OCCURS. THE COLD FRONT
BOUNDARY LOOKS TO STAY OVER THE NORTH AND NORTHEAST ZONES WHERE IT
APPEARS THAT THE WIND WILL NOT MIX DOWN. DRY WEATHER IS EXPECTED
FRIDAY. SATURDAY LOOKS DRY WITH A LIGHTER WIND REGIME. MID AND UPPER
LEVEL MOISTURE IS FORECAST TO RETURN SUNDAY AND MONDAY. FOR NOW WILL
HAVE ISOLATED SHOWERS/STORMS OVER AND NEAR THE MOUNTAINS. DRY FOR
THE LOWER ELEVATIONS AT THIS TIME. WILL SEE HOW THE MODELS LOOK
AGAIN TONIGHT AND ADJUST AS NEEDED.

AS FOR HIGH TEMPS...THURSDAY LOOKS TO BE VERY WARM TO HOT AHEAD OF
THE IMPENDING COLD FRONTAL PASSAGE THURS NIGHT. A LITTLE COOLER
FRIDAY FOR THE REGION AS 700MB TEMPS EASE A BIT. FOR SATURDAY
THROUGH MONDAY THE 700MB TEMPS GRADUALLY RISE OVER THE REGION...
WITH THE SOUTH AND SOUTHWEST HAVING HIGHER 700MB TEMPS THAN THE FAR
NORTH AND NORTHEAST. BOTTOM LINE A GRADUAL WARMING SATURDAY THROUGH
MONDAY. ADDED CLOUDS ON MONDAY WERE ALSO FACTORED INTO THE HIGH
TEMP FORECAST ON THAT DAY.

&&

.AVIATION.../12Z ISSUANCE/

HERE COULD BE ONGOING VERY ISOLATED CONVECTION /SHRA/ OVER THE
WEST/NORTHWEST WYOMING EARLY THIS MORNING. HOWEVER WITH DAYTIME
HEATING ISOLATED TO SCATTERED CONVECTION /SHRA AND TSRA/ WILL
DEVELOP LATE MORNING/EARLY AFTERNOON AND LAST THROUGH THE EARLY
EVENING...MAINLY ALONG AND NORTHWEST OF A KBPI-KDUB-KTHP-KBYG LINE.
THE TERMINALS MOST IMPACTED BY CONVECTION SHOULD BE KJAC AND KCOD.
VFR CONDITIONS ARE EXPECTED...EXCEPT BRIEF IFR/MVFR CONDITIONS
ASSOCIATED WITH ANY CONVECTION. BREEZY WEST TO SOUTHWEST WINDS WILL
BE OBSERVED IN MOST LOCATIONS THIS AFTERNOON. MUCH OF THE CONVECTION
WILL WANE BY AROUND 03Z TUESDAY...BUT ISOLATED CONVECTION COULD
CONTINUE WELL INTO THE NIGHT...MAINLY OVER THE NORTHWEST.

&&

.FIRE WEATHER...

THE COMBINATION OF WARM TEMPERATURES...GUSTY WINDS AND RELATIVE
HUMIDITY IN THE LOW TEENS WITH BRING CRITICAL FIRE WEATHER TO THE
SWEETWATER COUNTY AND LOWER ELEVATIONS OF NATRONA COUNTY AGAIN THIS
AFTERNOON AND EVENING. MOISTURE MOVING NORTH WILL BRING SOME SHOWERS
AND THUNDERSTORMS...SOME WETTING...TO THE WESTERN MOUNTAINS AND THE
BIG HORN BASIN. ELSEWHERE...EXPECT ELEVATED FIRE DANGER THIS
AFTERNOON WITH GUSTY WINDS. FIRE CONDITIONS SHOULD IMPROVE ON
TUESDAY AS WINDS WILL SUBSIDE. VERY WARM TEMPERATURES AND A GUSTY
BREEZE DEVELOPING MAY BRING MORE ELEVATED FIRE DANGER FOR WEDNESDAY
AS RIDGING STRENGTHENS ACROSS THE AREA.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING
WYZ279-280.

&&

$$

SHORT TERM...HATTINGS
LONG TERM...AR
AVIATION...WM
FIRE WEATHER...HATTINGS



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