Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 250504
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1104 PM MDT FRI JUL 24 2015

.SHORT TERM...TONIGHT THROUGH SATURDAY (ISSUED AT 154 PM MDT)

WV IMAGERY SHOWING LOWER AMPLITUDE TROF RIDGE TROF PATTERN FROM W TO
E ACROSS THE CONUS...WITH A FEW EMBEDDED SMALL SWS...ONE  CURRENTLY
MOVING ACROSS NWRN WY...ANOTHER UPSTREAM MOVING FROM NERN NV INTO
SCNTRL ID...AND HEADED THIS WAY FOR THIS AFTERNOON...AND ANOTHER
BROADER WAVE OVR NRN CA/SRN OR...WHICH WILL EXTEND PRECIP CHANCES
OVERNIGHT. SFC HAS WEAK HIGH P OVR WRN WY WITH WEAK LOW P EAST AND A
WEAK TROF/FRONT DRAPED FROM N TO S OVR ERN WY...MOSTLY JUST E OF THE
CWA. A COUPLE ISOLATED SHOWERS CURRENTLY ACROSS WCNTRL WY.

AS ON THURSDAY...NEAR RED FLAG CONDITIONS WILL EXIST ACROSS FIRE WX
ZONE 280...NATRONA COUNTY. MIN RH VALUES WILL LIKELY DROP AND HOVER
AROUND THE MID TEENS PLUS/MINUS...WHILE WINDS GUST FOR A COUPLE
HOURS IN THE 20 TO 25 MPH RANGE. WILL MONITOR THROUGH THE AFTERNOON.

THIS AFTERNOON AND TONIGHT...UPR RIDGING TAKING PLACE WITH MODEST
BUT SLIGHTLY ABOVE AVG MOISTURE ACROSS THE WEST AND NORTH...DRYING
ELSEWHERE WITH A GOOD CAP IN PLACE THROUGHOUT THE REST OF THE FA.
ISOLATED TO WIDELY SCATTERED STORMS OVR THE W/NW AND NRN ZONES. RUN
OF THE MILL STORMS FOR THE MOST PART TODAY...CHARACTERIZED BY VERY
LOW CAPE BUT DECENT SHEAR. BRIEF HEAVY RAIN WITH STORMS MOVING ALONG
AT 30+ MPH. GUSTY WINDS AND SMALL HAIL WILL ALSO ACCOMPANY AN
ISOLATED STORM OR TWO. DUE TO THE TRAIN OF EMBEDDED UPR DISTURBANCES
DESCRIBED ABOVE...CHANCES FOR SHOWERS AND MAYBE AN ISOLATED
THUNDERSTORM WILL LINGER ACROSS THE NRN FA THRU THE OVERNIGHT PERIOD
AND INTO SATURDAY MORNING.

SATURDAY...A FEW SHOWERS AND ISOLATED THUNDER WILL BE ONGOING N/NE
SAT MORNING AS THE CA/OR WAVE MAKES ITS WAY ACROSS THE NRN/NERN FA.
RIDGING...DRYING AND MORE ROBUST CAPPING WILL TAKE PLACE FROM W TO E
SO THAT BY THE AFTERNOON PERIOD...ONLY ISOLATED SHOWERS OR THUNDER
WILL BE POSSIBLE OVR A FEW OF THE HIGHER PEAKS IN THE NW/NRN ZONES.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

SOUTHWEST FLOW WILL DOMINATE THE WEATHER ACROSS WESTERN AND CENTRAL
WYOMING THROUGH TUESDAY AHEAD OF AN UNSEASONABLY STRONG PACIFIC
LOW PRESSURE TROUGH THAT WILL BE MOVING INTO THE PACIFIC NORTHWEST.
MOISTURE WILL BE LIMITED TO THE NORTHWEST AND FAR NORTH WHERE
SCATTERED MOUNTAIN SHOWERS AND ISOLATED THUNDERSTORMS WILL BE A
THREAT EACH AFTERNOON AND EVENING WITH A FEW SHOWERS LINGERING OVER
THE HIGHER MOUNTAINS THROUGH THE NIGHT AND INTO THE MORNING HOURS.
TEMPERATURES WILL WARM WITH WINDY CONDITIONS INCREASING ACROSS THE
SOUTH...CENTRAL AND EAST...AND ALONG AND NEAR THE EAST SLOPES OF THE
MOUNTAINS.  THE STRONG WINDS AND DEEP MIXING WILL BRING VERY DRY AIR
TO THE SURFACE WITH RELATIVE HUMIDITY DROPPING BELOW 15 PERCENT OVER
A LARGE AREA SUNDAY AND EVEN LOWER ON MONDAY.  THE PACIFIC TROUGH
WILL MOVE ACROSS SOUTHERN CANADA AND MONTANA CLIPPING NORTHERN
WYOMING MONDAY NIGHT DRIVING A COLD FRONT SOUTH MONDAY NIGHT AND
TUESDAY.  THE COLD FRONT WILL BRING COOLER TEMPERATURES AND HIGHER
HUMIDITY WITH WINDS SHIFTING TO THE NORTHEAST.  THE SOUTH WILL REMAIN
WINDY ON TUESDAY WITH LOW RELATIVE HUMIDITY BEFORE THE COLD FRONT
PUSHES SOUTH THROUGH THE AREA.  COOLER AND DRY WEATHER WILL THEN BE
IN PLACE WEDNESDAY...WITH A GRADUAL WARMING TREND THROUGH FRIDAY
WITH DRY CONDITIONS PREVAILING.  WINDS MAY PICK UP ON FRIDAY AND
VERY LOW RELATIVE HUMIDITY IN THE AFTERNOON.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL AT THE TERMINAL SITES THROUGH SATURDAY
NIGHT. SHOWERS AND STORMS OVER THE NORTHWEST AND NORTHERN WY WILL
END BY 15Z. ISOLATED SHOWERS AND STORMS WILL DEVELOP OVER THE
NORTHWEST MOUNTAINS AFTER 20Z UNTIL 02Z SUNDAY. SHOWERS AND STORMS
WILL ALSO DEVELOP OVER THE BIGHORN MOUNTAINS AFTER 18Z UNTIL 02Z
SUNDAY. SOME OF THOSE STORMS COULD PRODUCE WIND GUSTS TO 40 KNOTS
AND BRIEF HEAVY RAIN. LOCAL MVFR CONDITIONS COULD OCCUR IN STORMS
WITH HEAVY RAIN. THE REST OF THE REGION SHOULD NOT SEE ANY
THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT.

&&

.FIRE WEATHER...

FUELS ARE CRITICAL ACROSS MOST OF NATRONA AND JOHNSON COUNTIES. NEAR
RED FLAG CONDITIONS FOR A FEW HOURS AGAIN TODAY AND SATURDAY ACROSS
ZONES 280 AND 300...NATRONA COUNTY...AS BOTH WINDS AND MINIMUM RH
VALUES GET CLOSE TO CRITICAL. HOWEVER...AT THE MOMENT IT APPEAR THAT
DANGEROUS RH AND/OR WIND SPEED LEVELS...WHILE APPROACHED...WILL
EITHER NOT BE MET OR WILL BE TOO SHORT-LIVED. ELSEWHERE...FIRE
DANGER WILL BE SOMEWHAT ENHANCED AS A WARM AND RELATIVELY DRY
ATMOSPHERE CONTINUES AND WINDS BECOME GUSTY AT TIMES OUT OF THE
SOUTHWEST TO WEST...OR NEAR ISOLATED TO WIDELY SCATTERED
THUNDERSTORMS ACROSS THE WEST AND NORTH. A SMALL POTENTIAL FOR FIRE
STARTS WILL EXIST DUE TO LIGHTNING STRIKES ACROSS THOSE AREAS WHERE
THUNDERSTORMS ARE PRESENT. SATURDAY...SIMILAR CONDITIONS WILL EXIST
OVER THE SAME LOCATIONS...INCLUDING NATRONA COUNTY. HOWEVER...THERE
WILL BE EVEN FEWER CHANCES FOR THUNDER ACROSS THE NORTHERN FORECAST
AREA.

&&

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

&&

$$

SHORT TERM...BRAUN
LONG TERM...C.BAKER
AVIATION...AR
FIRE WEATHER...BRAUN



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