Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 230450
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1050 PM MDT WED APR 22 2015

.SHORT TERM...TONIGHT THROUGH THURSDAY (ISSUED AT 138 PM MDT)

CLOUDS BUILDING OVER THE MOUNTAINS AGAIN WITH MORE ISOLATED SHOWERS
AND PERHAPS A FEW LIGHTNING STRIKES SIMILAR TO YESTERDAY INTO THE
EARLY EVENING. EVEN HAVE A FEW ALONG THE CODY FOOTHILLS...GREEN/
RATTLESNAKES...NEAR THE HIGHER TERRAIN IN NATRONA AND ERN
SWEETWATER. NOT MUCH INSTABILITY...SHEAR OR MOISTURE TO WORK WITH
THOUGH. ON THURSDAY...DISTURBANCE/DEFORMATION AXIS OVER SRN UT
WILL SPREAD NWD INTO THE SW WHILE AT THE SAME TIME...A WEAKENING
TROUGH CURRENTLY MOVING INTO ID AND WRN MT WILL MOVE INTO OUR NWRN
CORNER. MOISTURE WILL BE FUNNELED NORTH IN THIS PATTERN. HOWEVER...
IT LOOKS TO BE MARGINAL MID LEVEL MOISTURE WITH LIMITED LOW LEVEL
MOISTURE TO WORK WITH IN ANY DIRECTION. THE MOVEMENT OF THESE
SYSTEMS WILL LIKELY RESULT IN THE DEVELOPMENT OF A SURFACE LOW
OVER OUR FAR ERN ZONES OR ERN WYOMING WITH A WEAK FRONTAL BOUNDARY
HANGING AROUND THE CENTRAL ZONES TO AID IN SOME FOCUS. MODIFIED
SOUNDINGS INDICATE SOME BETTER CAPE...300-500 J/KG IF SFC DEW
POINTS CAN HOLD OR BE IN THE LOWER TO MID 30S WITH TEMPS IN THE
MID 60S FOR OUR ERN ZONES. A LITTLE LESS IN THE WEST BUT STILL
BETTER THAN TODAY. SHEAR OVERALL IS STILL WEAK OR NOT FAVORABLE
BUT COULD BE ENHANCED ALONG THE BOUNDARY SOMEWHERE AROUND NATRONA
COUNTY UP INTO SRN JOHNSON. WE`LL JUST HAVE TO WATCH HOW THE
MOISTURE...BOUNDARY AND SFC LOW DEVELOPMENT PLAY OUT. EITHER
WAY...MORE SHOWERS AND ISOLATED THUNDERSTORMS THURSDAY AFTERNOON
AND MORE EAST OF THE DIVIDE. THE SW WILL LIKELY EVEN HAVE SHOWERS
MOVING IN DURING THU MORNING.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

BEGINNING OF FCST THRU FRI NIGHT...FLAT RIDGING AND WEAK FLOW ALOFT
CONTINUES. UNSTABLE THOUGH...ESPECIALLY AFTERNOONS AND EVENINGS...WITH
MODERATE TO DRY LAPSE RATES RANGING BETWEEN 8.5 AND 10.5 AND CAPE
VALUES MAXING OUT BETWEEN 100 AND 600 J/JG EAST TO WEST. DEVELOPING
LOW OVR CNTRL WY THEN LEE SIDE ERN WY BY THURSDAY AFTERNOON WITH
MOUNTAIN SHOWER AND THUNDER ONCE AGAIN...AND ALSO ALONG/NEAR WEAKLY
DEVELOPING FRONT/BOUNDARY STRETCHING FROM SOUTH PASS...E INTO
NATRONA COUNTY LIFTING N AND WRAPPED INTO/AROUND LOW STRETCHING N
THRU JOHNSON COUNTY. THIS BOUNDARY WILL BE WORTH WATCHING AS IT WILL
BE THE AREA WITH THE MOST CAPE AND SHEAR. ALTHOUGH RELATIVELY LITTLE
WILL BE EXPECTED OVERALL...ELEVATED STORMS SOUTH OF THE FRONT COULD
PROVIDE GUSTY WINDS...WHILE ALONG AND JUST NORTH OF THE
FRONT...UNDER BACKING WINDS...COULD SEE LEFT MOVERS WITH VERY SMALL
HAIL AND SOME LOW LEVEL CIRCULATIONS...WITH POSSIBLY A SHORT-LIVED
LANDSPOUT POSSIBLE. LATER...A LITTLE BETTER MOISTURE BEGINS TO MAKE
ITS WAY INTO SWRN/WRN FA THU EVENING THRU FRI MORNING...WITH BETTER
MOUNTAIN WRN MOUNTAIN SHOWERS IN ADDITION TO LL FORCING ALONG NEAR
STATIONARY FRONT OVR SWRN/SCNTRL WY. THE CONVECTIVE NATURE OF THIS
PRECIPITATION WILL ALLOW FOR LOCALIZED ISOLATED AREAS TO RECEIVE A
FEW TENTHS OF AN INCH LIQUID...1 TO 2 INCHES OF SNOW (HIGH
MOUNTAINS/OVERNIGHT) IN SHORT ORDER. RATHER HARD IN PINNING DOWN
JUST ONE LOCATION. THE SALTS/WYOMING AND WIND RIVER RANGES WOULD
CERTAINLY BE FAVORED IN THIS SCENARIO.

SAT THRU THE END OF THE FCST...MAIN DIFFERENCE OVER THE LAST 24 HRS
IS THE SLOW DOWN OF THE TROF AS IT SEEMS THAT A SWRN CONUS COL WILL
HAVE MORE INFLUENCE OVR THE NRN TROF THAN PREVIOUSLY THOUGHT.
OTHERWISE...THIS UPSTREAM TROF...CURRENTLY ASSOCIATED WITH DEEP GULF
OF ALASKA LOW...WILL MOVE INTO AND THRU THE FA BETWEEN SAT AND SUN
NIGHT...WITH WITH A SOMEWHAT STRONGER AND MORE ELONGATED LEE TROF
BUILDING FROM ERN CO INTO ERN WY. TRACK AND BETTER MOISTURE
ASSOCIATED WITH THIS FEATURE SHOULD BRING A WIDE AREA OF SHOWERS/ISO
THUNDER TO THE REGION FROM SAT AFTERNOON...NOW LASTING THRU THE DAY
SUN...POSSIBLY DRAGGING INTO SUN EVENING OR MONDAY MORNING BEFORE
ALL IS SAID AND DONE. FOR MONDAY AND TUE...POST UPR TROF/SFC FRONTAL
AND MODEST RIDGING RETURNING WILL KEEP THE FA MOSTLY DRY...EXCEPT
FOR SOME SMALL CHCS FOR SHRA MONDAY AFTERNOON/EVE FOR NATRONA COUNTY
AND POINTS SOUTH. THE REST OF THE FCST WILL BE MAINLY DRY...AS THE
STORM/MOISTURE TRACK PUSHES NWD TOWARDS AND INTO SRN
CANADA.

&&

.AVIATION.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL OCCUR OVER AND
NEAR THE MOUNTAINS AFTER 19Z. SOME OF THIS ACTIVITY WILL MOVE EAST
OVER THE LOWER ELEVATIONS THROUGH 03Z. TERMINAL SITES MAY BE
IMPACTED BY SHOWERS AND OUTFLOW WIND GUSTS AROUND 30 KNOTS.
ISOLATED SHOWERS WILL OCCUR THROUGH 10Z FRIDAY. VFR CONDITIONS WILL
PREVAIL TODAY AND TONIGHT WITH LOCAL MVFR CONDITIONS ASSOCIATED WITH
HEAVIER SHOWERS OR STORMS. EXPECT OCCASIONAL MOUNTAIN OBSCURATION
DURING THE AFTERNOON AND EVENING HOURS.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

ISOLATED SHOWERS ARE POSSIBLE THROUGH 18Z THIS MORNING. THEN
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER AND NEAR THE
MOUNTAINS AFTER 19Z. SOME OF THIS ACTIVITY WILL MOVE EAST OVER THE
LOWER ELEVATIONS THROUGH 03Z. TERMINAL SITES MAY BE IMPACTED BY
SHOWERS OR STORMS ALONG WITH OUTFLOW WIND GUSTS AROUND 30 KNOTS.
ISOLATED SHOWERS WILL OCCUR THROUGH 10Z FRIDAY. EXPECT OCCASIONAL
MOUNTAIN OBSCURATION THIS AFTERNOON AND EVENING. VFR CONDITIONS WILL
PREVAIL AT THE TERMINAL SITES THROUGH THE PERIOD. THERE MAY BE LOCAL
MVFR CONDITIONS OVER AND NEAR THE MOUNTAINS DURING THE AFTERNOON AND
EVENING HOURS.

&&

.FIRE WEATHER...

TODAY LOOKS LIKE THE DRIEST AND MOST STABLE DAY OF THE NEXT THREE
WITH ISOLATED TO SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS IN
THE MOUNTAINS WITH THE LOWER ELEVATIONS REMAINING LARGELY DRY. THE
CHANCE OF SHOWERS AND THUNDERSTORMS WILL INCREASE THURSDAY AND
FRIDAY BUT WIDESPREAD ACTIVITY IS NOT EXPECTED AND WIDESPREAD
WETTING RAIN IS NOT EXPECTED THROUGH THE REST OF THE WORKWEEK.

&&

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

&&

$$

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





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