Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 040912
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
312 AM MDT TUE AUG 4 2015

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

WV IMAGERY SHOWING LARGE CLOSED LOW + TROF OVR PAC NW COAST AND
BC...RIDGE INTERMOUNTAIN WEST WITH EMBEDDED SMALL/DEEP SW ROTATING
THROUGH THE W SIDE OF THE RIDGE OVR WY. UPSTREAM AND OFFSHORE NRN
CALIFORNIA...OPENING/WEAKENING WAVE JUST NOW HEADED INLAND. WIDE
AREA OF SHOWERS ACROSS THE FA W/ A FEW EMBEDDED STORMS OVR SRN
FREMONT/NATRONA COUNTIES. HIGH P WRN/SWRN WY...LOWERING P N/NERN WY
WITH STATIONARY FRONT DIVIDING THE TWO SIDES FROM NCNTRL TO SERN WY.

TODAY...A DEVELOPING SFC TROF/LEE CYCLONE OVR NERN/ERN WY WILL BE
SPURRED ON BY THE SW...KEEPING GOOD MOISTURE TUCKED INTO THE ERN
ZONES. THE ERN ZONES...AND ESPECIALLY THE FOOTHILLS OF THE ERN SIDE
OF THE BIGHORN MOUNTAINS...WILL BE THE MOST SUSCEPTIBLE TO HEAVIER
RAINFALL AMOUNTS THIS AFTERNOON WITH PWS REMAINING AOA 1 INCH.
ACCORDINGLY THERE WILL SOME POSSIBILITY FOR ISOLATED AREAS OF FLASH
FLOODING THIS AFTERNOON/EARLY EVENING. ELSEWHERE...SHOWERS AND
ISOLATED STORMS ENDING ACROSS THE NORTHERN FA FROM W TO E.

WED/WED NIGHT...THE BC/PAC NW LOW/SW TROF WILL COMBINE WITH WHAT`S
LEFT FROM THE NRN CA DISTURBANCE...ADVECTING MOISTURE AND LIFT OVR
THE FA...ADDING TO LOCAL TERRAIN CONVERGENCE AS THEY FURTHER
DESTABILIZE THE ATMOSPHERE...ALLOWING FOR INCREASED CHANCES FOR
PRECIPITATION ACROSS THE FA...ALTHOUGH ON MORE OF A WIDELY SCATTERED
BASIS...EXCEPT FOR THE NWRN CWA WHICH MAY SEE MORE SCATTERED
PRECIPITATION. SW WINDS WILL INCREASE TO 20+ MPH IN THE AFTERNOON
ACROSS THE SRN/SWRN ZONES...WITH GUSTS 30+ MPH.

THURSDAY...INCREASING DRY ZONAL FLOW ALOFT...WITH GUSTY DRYING WRLY
WIND AT THE SFC WILL BEGIN TO INCREASE FIRE DANGER ACROSS THE SRN
FA. THIS AREA WILL HAVE TO BE MONITORED OVER THE NEXT COUPLE OF DAYS
FOR THE POSSIBILITY OF A RED FLAG WATCH/WARNING TO BE POSTED.
ATTM...IT APPEARS THAT WHILE WINDS MAY BE JUST HIGH ENOUGH...MIN RH
VALUES WILL REMAIN MORE IN THE UPPER TEENS TO NEAR 20 PERCENT
RANGE...REMAINING JUST BELOW CRITICAL LEVELS.


.LONG TERM...FRIDAY THROUGH TUESDAY

MEDIUM RANGE MODELS ARE IN PRETTY GOOD AGREEMENT AGAIN TONIGHT.
UPPER HIGH WILL HOLD IN THE NRN TX/OK THROUGH THE PERIOD. A COUPLE
UPPER LEVEL LOWS MAY COME INTO PLAY DURING THIS PERIOD. ONE LATE
SATURDAY AND ANOTHER AT THE END OF THIS PERIOD. THE FIRST UPPER LOW
CURRENTLY NEAR 36N/138W IS FORECAST TO GRADUALLY MOVE ONSHORE AND
LIFT NE INTO WRN WYO LATE SAT AFTN OR EVE. AHEAD OF IT...THE FLOW
BACKS WITH MODEST SURGE OF MONSOONAL MOISTURE. AS OF NOW...IT
DOESN`T LOOK TOO DEEP BUT ENOUGH TO CREATE SOME GUSTY TSTMS ACROSS
MUCH OF THE AREA WITH LIGHTNING CONCERNS. THE SURGE OF MOISTURE WILL
LIKELY KEEP SOME SHOWERS/TSTMS GOING FRIDAY NIGHT AND SATURDAY
MORNING. THE AFOREMENTIONED UPPER LOW AND ASSOCIATED JET STREAK THEN
MOVES INTO THE W OR NW WITH POTENTIAL FOR SOME STRONGER STORMS SAT
AND A CHANCE OF SHOWERS/TSTMS ACROSS MOST OF THE AREA WITH THE
CONTINUED MODEST MONSOONAL SURGE. RIDGE THEN TAKES OVER AGAIN SUNDAY
THROUGH AT LEAST MONDAY AND POSSIBLY THROUGH TUESDAY WITH DRY AND
VERY WARM CONDS. WE COULD START TO SEE ANOTHER LITTLE SURGE OF
MONSOONAL MOISTURE WITH AN EMBEDDED DISTURBANCE LATE TUESDAY BUT
WE`LL JUST HAVE TO WATCH THIS WITH TIME.

&&

.AVIATION.../12Z ISSUANCE/

UPPER LOW CONTINUES TO DRIFT SLOWLY EAST EARLY THIS MORNING. BEST
CONVECTION CONTINUES TO BE IN THE VICINITY OF THE TIGHTLY PACKED
LOW WITH BRIEF HEAVY RAIN THE MAIN HAZARD. CONDITIONS LOOK TO BE
VFR THROUGH THE FORECAST PERIOD AS THE LOW TRUDGES EAST AND DRIER
AIR SURFACES FROM THE WEST LATER THIS MORNING AND AFTERNOON. GUSTY
NORTHWEST SURFACE WIND OF 12-25KTS WILL BE COMMON BY 18Z/TUE AT
TERMINALS IN SOUTHWEST WYO AND THE WIND RIVER BASIN. DRIER
NORTHWEST FLOW WILL WAIT UNTIL 18Z-22Z/TUE TO REACH KWRL AND KCPR.
FAVORABLE MOISTURE PROFILE AND BEST INSTABILITY WILL LINGER FROM
KCPR NORTH ALONG THE BIGHORNS TO VICINITY OF KBYG LATER THIS
AFTERNOON. EXPECT ALL TERMINALS TO BE VFR AND DRY BY 00Z/WED AS
SHORTWAVE RIDGING BEGINS TO PUSH ACROSS THE STATE FROM THE WEST.
ONLY INCREASING MID-HIGH CLOUDS EXPECTED...MAINLY ACROSS NORTHWEST
WYO AFTER 06Z/WED IN ADVANCE OF THE NEXT SHORTWAVE TROUGH. AS FOR
MOUNTAIN OBSCURATIONS...ANTICIPATE FREQUENT OBSCURATIONS IN THE WIND
RIVER RANGE AND FAR WESTERN WYO MOUNTAINS UNTIL 15Z/TUE. CONDITIONS
WILL GRADUALLY IMPROVE BY 18Z/TUE WITH ONLY OCCASIONAL MOUNTAIN TOP
OBSCURATIONS AFTER THAT TIME...MAINLY WITH CONVECTION IN THE
EASTERN PORTIONS OF THE FORECAST AREA.

&&

.FIRE WEATHER...

FIRE DANGER RELATIVELY LOW TODAY...REMAINING SO THROUGH
WEDNESDAY...AS INCREASED MOISTURE ACCOMPANYING AN UPPER LEVEL
DISTURBANCE CONTINUES ACROSS THE FORECAST AREA TODAY...EXITING LATER
TONIGHT. NORTHERN...THEN EASTERN/NORTHEASTERN WYOMING WILL SEE THE
BEST CHANCES FOR RAINFALL...SOME ON THE HEAVY SIDE THIS AFTERNOON AND
EARLY EVENING ACROSS THE EASTERN ZONES. LATER ON WEDNESDAY WILL SEE
A RENEWED CHANCE FOR MORE RAINFALL ACROSS THE REGION...ALTHOUGH ON A
MORE ISOLATED TO WIDELY SCATTERED BASIS. WINDS WILL ALSO INCREASE
OUT OF THE SOUTHWEST ACROSS THE SOUTHERN AND SOUTHWESTERN ZONES. DRY
WEATHER RETURNS THURSDAY...WITH GUSTY WEST WIND ACROSS THE SOUTHERN
ZONES ALLOWING FOR ENHANCED FIRE DANGER.

&&

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

&&

$$

SHORT TERM...BRAUN
LONG TERM...PS
AVIATION...CNJ
FIRE WEATHER...BRAUN


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