Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
000
FXUS65 KRIW 272243
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
443 PM MDT Sun May 27 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 304 PM MDT Sun May 27 2018

Plenty of atmospheric moisture available across the forecast area
this afternoon. Morning precipitable water values were around 150
percent of normal. Strong thunderstorms developed during the late
morning over the Wind River Mountains accompanied by heavy rain
and pea-sized hail. Convection has continued to increase in
coverage early this afternoon. Mid-level circulation will track
north across the area before setting up over northeast Wyoming
later Sunday evening and early Monday. Central sections of the
forecast area, primarily Fremont and Natrona counties, will
receive the heaviest rain this afternoon. The convection then
shifts to the northern reaches of the area Sunday evening and
night. Good upper-level divergence coupled with the increasing
easterly upslope flow could set the stage for flash flooding along
the east slopes of the Bighorn Mountains. Soil moisture has
increased in the northern portion of the county the past week, so
it may not take as much rain to get creeks and streams to respond.
Have extended the flash flood watch for this region through
12Z/Mon to account for the continued moisture feed into the
Bighorns. After a relatively lull Monday morning, scattered
showers and thunderstorms will again develop late Monday morning
and afternoon. The pesky upper-low hanging out to our southwest
will finally begin to eject and move northeast. This will nudge
the best moisture and instability just to our east. The low will
continue to eject northeast through Tuesday with gradual drying
west of the Continental Divide. Cyclonic flow and northwest flow
aloft will lead to the best chance for showers and storms over the
northern Wyoming. Shortwave ridging will build in behind this low
leading to a warmer and drier Wednesday.

.LONG TERM...(Wednesday night through Sunday)
Issued at 304 PM MDT Sun May 27 2018

Southwest flow aloft Wednesday night through Thursday night.
Scattered showers and storms mainly western WY Wed night and again
Thursday afternoon into the evening. Mostly dry elsewhere. Next
weather system moves through the area Thursday night and Friday
bringing more showers and storms across the region at that time.
Conditions improve Friday night with decreasing showers and
storms. Saturday looks mostly dry with only isolated showers or
storms. Next Sunday will see isolated showers and storms.
As for temps, Warm on Thursday and Friday, then a little cooler
Saturday and slightly warmer next Sunday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday)
Issued at 304 PM MDT Sun May 27 2018

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

Scattered showers and thunderstorms will occur northwest WY
through 15Z. Heavy rain, small hail and wind gusts to 30 knots
will be common with storms. KJAC airport will be impacted by this
activity. VFR to MVFR conditions will occur in this area through
15Z with reduced visibility at times. Mountains will be obscured
at times. Isolated showers and storms will occur after 15Z in NW
WY.

In SW WY, isolated showers and storms will occur tonight and
then again Monday afternoon after 18Z. VFR conditions will prevail
through the period in SW WY. Wind gusts to 30 knots will occur
with some of the storms.

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

Scattered showers and thunderstorms will occur most of the area
through 06Z. Then the main area of rain and thunderstorms will
occur over northern WY after 06Z through 15Z Monday. Heavy rain,
hail and wind gusts to 30 knots will be common with the stronger
storms. MVFR conditions will occur at times through 15Z with local
IFR conditions. Showers and storms will be decreasing over
northern WY after 15Z with only isolated activity through 00Z Tue.
In central WY after 06Z, showers and storms will be isolated late
tonight through 18Z Monday. Then after 18Z Mon, more thunderstorms
will develop through 00Z Tue.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC
for the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 304 PM MDT Sun May 27 2018

The slow-moving area of low pressure over southwest Wyoming will
gradually drift across the state later Monday and Monday night. The
best chance for showers and thunderstorms will be in central and
northern Wyoming through tonight. Heavy rain will be the primary
hazard. Another round of less numerous and intense showers and
storms is anticipated Monday afternoon. Mountain areas, especially
over the north, could get an inch or more of rain through Monday
night. Therefore, temperatures will be slightly below normal Monday
with a wetting rain falling in most areas. Conditions may begin to
dry late Tuesday west of the Continental Divide as the low tracks
northeast and away from Wyoming. Wednesday will find much drier and
warmer conditions returning to the entire area.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

Flood Watch through Monday afternoon for WYZ002>004-006-008-009-
012-015>017.

Flash Flood Watch through late tonight for WYZ010-011-020-022.

&&

$$

SHORT TERM...Jones
LONG TERM...AR
AVIATION...AR
FIRE WEATHER...Jones



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.