Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 152023
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
223 PM MDT Thu Jun 15 2017

.SHORT TERM...(This evening through Sunday)
Issued at 225 PM MDT Thu Jun 15 2017

Zonal west flow aloft will remain over the area through the weekend.
A series of Short wave low pressure troughs with Pacific moisture
will bring increased showers and thunderstorms Friday and Saturday
most numerous over the northern and western mountains. Temperatures will
be below normal with windy areas over and near the mountains. Weak
ridging will begin to buckle the zonal flow with decreasing moisture
and increased stability and warming on Sunday.  Winds will also decrease
on Sunday.

.LONG TERM...(Sunday night through Thursday)
Issued at 225 PM MDT Thu Jun 15 2017

As the ridge continues to build and amplify from the west,
temperatures will continue to warm Monday and Tuesday with h7
temps maxing out around 18c in Southern WY Tuesday. Tuesday will
be the hottest day of the week with highs in the low to mid 90s
over the lower elevations of the central basins east of the divide
with similar temperatures in both the Wind River and Big Horn
Basins in spite of the fact that the Big Horn Basin is lower in
elevation than the Wind River Basin with h7 temps warmer over
southern WY closer to the high over the desert SW where temps are
now topping 120F there. Johnson and natrona Counties will be in
the upper 80s along with low 70s in the valleys/basins out west
Tuesday afternoon. As the ridge approaches, the ridge will flatten
by Tuesday. A weak vort lobe will track east within the westerly
flow within the flattened ridge Tuesday. Then a more defined
northern stream shortwave will brush our CWA Wednesday. The
outlier is the Euro as it is slower with the timing of this
shortwave. Moisture with these two features will be scant so only
have isold afternoon and evening pops for mainly our northern
zones on Tue/Wed. As the ridge continues to flatten, Wednesday and
Thursday will become slightly cooler. Thursday will be dry.
Occasional westerly breezes can be expected for much of next week.
The minimum RH will be in the mid teens in Sweetwater County
early in the week, and then these low RH readings will spread
north to Central Wyoming by mid week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 225 PM MDT Thu Jun 15 2017

West of the Continental Divide...KBPI/KJAC/KPNA/KRKS Terminals

Conditions will be mainly VFR through 18z Friday. Lowering mid-cloud
decks along with increasing low clouds around KJAC after 00Z/Fri as
moisture moves in from the west in progressive westerly flow aloft.
Have included VCSH at KJAC late in the forecast period as orographic
showers develop over the nearby mountains. Gusty wind will continue
this afternoon with west-northwest wind 15-25kts at all terminals
except KJAC where wind will be south 12-22kts. Winds will diminish
quickly between 00Z-02Z/Fri. Scattered showers Friday morning will
transition to numerous showers and thunderstorms after 18z Friday in
the central and north with areas of MVFR and isold IFR conditions
will occur along with mtn obscn. West winds will increase to 20 to
30 knots after 18z Friday except from the south 15 to 25 knots in
the western valleys including KJAC


East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

VFR conditions will prevail as mid-and high-level clouds move across
the forecast area in progressive westerly flow aloft along with
cumulus clouds with bases around 8-10k with little vertical
development. Could be some BKN080-100 at KCOD by later this
afternoon or early this evening as best moisture remains across
northwest Wyoming. Included VCSH at KCOD from 01Z to 05Z this
evening. Wind will diminish quickly between 00Z-02Z/Fri but will
pick up at stronger speeds Friday at 20 to 35 knots with some gusts
to 40 knots after 14z in many areas. Expect isold convection in the
far north, especially in the mountains after 18z Friday.

&&

.FIRE WEATHER...
Issued AT 225 PM MDT Thu Jun 15 2017

Zonal west flow aloft will remain over the area through the weekend.
A series of Short wave low pressure troughs with Pacific moisture
will bring increased showers and thunderstorms Friday and Saturday
most numerous over the northern and western mountains. Temperatures will
be below normal with windy areas over and near the mountains. Weak
ridging will begin to buckle the zonal flow with decreasing moisture
and increased stability and warming on Sunday.  Winds will also decrease
on Sunday. Afternoons should be unstable enough with strong enough
wind and mixing for very good to excellent smoke dispersal.

&&

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

$$

SHORT TERM...Baker
LONG TERM...Lipson
AVIATION...Lipson
FIRE WEATHER...Baker



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