Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 241700
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1100 AM MDT FRI JUL 24 2015

UPDATE...ADDED 18Z AVIATION DISCUSSION

.SHORT TERM...FRIDAY THROUGH SUNDAY NIGHT

OVERALL...MORE OF THE SAME THIS EVENING AS RADAR SHOWS A FEW MAINLY
LIGHT SHOWERS RIDING ALONG A BOUNDARY AND A BIT OF JET ENERGY
STRETCHING FROM SOUTHERN IDAHO INTO NORTHERN AND NORTHWESTERN
WYOMING. A FEW OF THESE WILL LINGER INTO THE MORNING HOURS BUT LIKE
YESTERDAY...MOST OF THE ACTIVITY WILL BE ACROSS NORTHWESTERN AND
NORTHERN WYOMING WITH THERE IS NOT A TON OF CAPE TO WORK WITH AND
PRECIPITABLE WATER VALUES CONTINUE TO LOWER SO AT THIS TIME COVERAGE
OF STORMS STILL LOOKS TO BE FAIRLY SPARSE. WITH RELATIVELY HIGH
CLOUD BASES THE MAIN THREAT FROM ANY STORMS LOOKS TO BE GUSTY WINDS
FROM ANY DOWNBURSTS. TEMPERATURES SHOULD BE FAIRLY SIMILAR TO
YESTERDAY. ACROSS SOUTHERN AREAS...MAINLY DRY WEATHER WILL BE THE
RULE. WITH SOMEWHAT LIGHTER 700 MILLIBAR WINDS AND LESS OF A
PRESSURE GRADIENT...WINDS WILL BE A BIT LIGHTER THAN YESTERDAY.

THE GRADUAL DRYING AND WARMING TREND WILL CONTINUE INTO THE WEEKEND
AS RIDGING GRADUALLY BUILDS ACROSS THE AREA. THERE WILL STILL BE
ENOUGH INSTABILITY ACROSS NORTHWESTERN MOUNTAINS FOR A COUPLE OF
SPOTTER THUNDERSTORMS BUT COVERAGE OF STORMS WILL CONTINUE TO WANE.
THE DRYING TREND REALLY PICKS UP STEAM FOR SUNDAY AS PRECIPITABLE
WATER VALUES OF UNDER 0.50 INCHES BUILD IN FROM THE SOUTH AND WEST
AS A DRY SLOT DEVELOPS WITH LOW PRESSURE DEVELOPING ACROSS IDAHO AND
MONTANA. THE GFS IS DRY EVERYWHERE WHILE THE NAM STILL MAINTAINS
SOME CONVECTION IN THE NORTHWEST. FOR NOW WE LEFT SOME POPS IN THE
NORTHWEST BUT LIMITED THEM TO SLIGHT CHANCES. ELSEWHERE...EXPECT
WARM TO HOT WEATHER WITH SOME BREEZY CONDITIONS ACROSS THE FAVORED
AREAS LIKE THE WIND CORRIDOR FROM ROCK SPRINGS TO CASPER.

.LONG TERM...MONDAY THROUGH FRIDAY

...EXTREME FIRE WEATHER CONDITIONS MONDAY EAST OF THE DIVIDE AND
SOUTH WHERE FUELS ARE CRITICAL...

A STRONG UPPER LOW OVER THE NORTHERN INTERMOUNTAIN WEST MONDAY
MORNING IS EXPECTED TO PUSH RELATIVELY SLOWLY EAST ACROSS
NORTHERN MONTANA MONDAY NIGHT AND TUESDAY MORNING. THE ASSOCIATED
STRONG COLD FRONT IS EXPECTED TO PUSH EAST ACROSS THE FORECAST
AREA MONDAY. TIMING IS SLIGHTLY SLOWER THAN MODEL RUNS 24 HOURS
AGO...AND MAX TEMPS MONDAY WILL BE TRICKY ESPECIALLY OVER THE
WEST/NORTHWEST DUE TO FRONTAL TIMING. MODELS CONTINUE TO SHOW
MUCH OF THE AREA BEING DRY SLOTTED...WITH CONVECTION CHANCES
CONFINED TO THE NORTHWEST AND FAR NORTH. SOME OF THIS CONVECTION
COULD BE ON THE STRONG SIDE DUE TO THE INTENSITY OF THIS
SYSTEM...BUT INSTABILITY PARAMETERS REMAIN MEAGER OVER THE
NORTHWEST. THE MAIN STORY ON MONDAY WILL BE FIRE WEATHER
PARAMETERS EAST OF THE DIVIDE AND SWEETWATER COUNTY WITH STRONG
WIND AND MIN RH VALUES IN THE 10 TO 15 PERCENT RANGE WITH A FEW
AREAS POSSIBLY DIPPING INTO THE UPPER SINGLE DIGITS.

IN WAKE OF THE COLD FRONT...ENOUGH COLD AND DRY AIR WILL PUSH INTO
THE REGION FOR A POSSIBLE LIGHT FREEZE OVER THE FAR WESTERN
VALLEYS TUESDAY MORNING AND/OR WEDNESDAY MORNING. THE MUCH COOLER
CONDITIONS TUESDAY AND THE RELAXING SURFACE PRESSURE GRADIENT
/WEAKER WINDS/ WILL TEMPER FIRE WEATHER CONDITIONS TUESDAY.
HOWEVER WOULD NOT RULE OUT ELEVATED TO EVEN ISOLATED AREAS OF
EXTREME FIRE WEATHER CONDITIONS IN THE ROCK SPRINGS TO CASPER
CORRIDOR...BUT NOTHING LIKE WHAT COULD OCCUR MONDAY.

A DRY WESTERLY FLOW IS EXPECTED WEDNESDAY THRU FRIDAY WITH
WARMING TEMPERATURES. WINDS ARE EXPECTED TO REMAIN BELOW OR
MARGINAL FOR ANY FIRE WEATHER CONCERNS AT THE MOMENT.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD. ISOLATED TO
WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE MAINLY
NORTH OF A LINE FROM AFTON TO GILLETTE. THE SHOWERS AND OCCASIONAL
STORM WILL OCCUR THROUGH 08Z WITH LINGERING SHOWERS THROUGH 18Z NEAR
KBYG. LOCAL MVFR CONDITIONS MAY OCCUR IN STORMS THAT PRODUCE BRIEF
HEAVY RAIN REDUCING VISIBILITY. WIND GUSTS TO 35 KNOTS WILL ALSO BE
POSSIBLE WITH SHOWERS AND STORMS. THE NORTHWEST MOUNTAINS AND THE
BIGHORN MOUNTAINS WILL BE PARTIALLY OBSCURED AT TIMES DURING THE
AFTERNOON AND OVERNIGHT HOURS.

&&

.FIRE WEATHER...

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL CONTINUE TO BE
POSSIBLE ACROSS NORTHERN AND NORTHWESTERN WYOMING TODAY...ESPECIALLY
IN THE AFTERNOON. DOWNBURST WIND GUSTS AND LIGHTNING WILL BE THE
MAIN THREAT. MEANWHILE...EXPECT WARM TO HOT AND DRY WEATHER ACROSS
SOUTHERN AND EASTERN WYOMING. IN ZONES 280 AND 281...RELATIVE
HUMIDITY WILL BE LOWER THAN YESTERDAY WITH VALUES FALLING INTO THE
MIDDLE TEENS. HOWEVER...WITH WINDS EXPECTED TO BE A BIT LIGHTER RED
FLAG CONDITIONS ARE NOT EXPECTED. HOWEVER...THERE COULD BE ELEVATED
FIRE DANGER FOR A TIME LATER THIS AFTERNOON AND EVENING. EXPECT A
DRYING AND WARMING TREND THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. ELEVATED FIRE CONDITIONS MAY BE A POSSIBLITY FOR SUNDAY AND
ESPECIALLY EARLY NEXT WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

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


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