Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 251922
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
122 PM MDT Tue Jul 25 2017

.SHORT TERM...(This evening through Friday)
Issued at 122 PM MDT Tue Jul 25 2017

Moist mid level surge began last night with low level moisture
following behind. Morning dew points in the southwest were running
about 17 degrees above the same time yesterday. These higher surface
dew points and overall higher pw air will overspread the rest of the
area through the afternoon and evening setting the stage for a
better coverage of showers and thunderstorms the next couple days.
Thick cloud cover today keeping temps down and with only gradually
increase low level moisture, capes are rather non-existent to skimpy
today. Multiple circulations/disturbances in the flow, especially
Upper Green to Fremont County (RIW VWP is showing se flow up to
15K) will still have the chance of focusing a few heavier
showers/embedded thunder into this evening. Frontal boundary
pushing south into Central Wyo will also be a potential focusing
mechanism. As better moisture, continued mid level shortwaves and
favorable jet axis comes into play Wednesday into Thursday, along
with some forecast warmer temps all lead to a better chance of
thunderstorms and heavier rain Wednesday through Thursday. Not
enough to put out any flash flood watches but enough to continue
the heavy rain wording in the forecast. Later shifts will have to
watch this potential and see if any areas need a flash flood watch
or just the continued wording. No doubt the overall soundings
look better Wed and Thu for stronger, wetter storms. SPC has the
western two- thirds of the area in marginal risk Wednesday and
almost the entire area Thursday as NorCal upper low opens up and
moves toward nwrn Wyoming late Thursday/Thursday evening. Frontal
boundary/upslope will remain east of the divide into Thursday
morning before lifting north as a warm front Thursday. The remnant
CA upper low moves across the north Friday with best focus for
storms up there. The south looks the driest with only a few over
the mtns and off the Uintas.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 122 PM MDT Tue Jul 25 2017

The mean ridge stays over the central and southern Rockies for the
weekend into early next week.  The center of the upper level high is
forecast to migrate from the southern Rockies into the Intermountain
West through by Tuesday.  A familiar pattern appears to continue
over WY for the extended period with enough mid-level moisture and
weak instability for afternoon and evening showers and
thunderstorms, primarily over the western mountains and northern
part of the state. The only day that looks like it has more forcing
is Monday, as a disturbance rides over the top of the ridge axis and
down the WY Front Range.  The GFS is much stronger than the ECMWF
with this feature though as the ECMWF build the high much stronger.
Consensus has both max and min temperatures near normal through the
period, with generally light winds.  East of the divide should see
mostly northerly or easterly flow; and the southwest part of the
state could see breezy southwest wind at times.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday afternoon)
Issued at 122 PM MDT Tue Jul 25 2017

Moisture continues to stream over the area from the south and
southwest along with weak instability due to the upper level high
over the Southern Plains and disturbances over northern California
and SW Canada. General VFR conditions are expected throughout the
period, although localized MVFR conditions may occur under and
around more intense showers and any isolated thunderstorms.  The
unsettled activity is expected to continue through 03-06Z/Wed, with
mid-level clouds lingering into the next day.  Wind speeds are only
expected to be elevated this afternoon around any showers and
storms, though gusts should be in the 20-25 kt range.  Convective
activity looks to be more pronounced on Wednesday afternoon,
especially across the northwest quarter of the state, as a
disturbance moves from eastern ID into southern MT.

&&

.FIRE WEATHER...
Issued AT 122 PM MDT Tue Jul 25 2017

Monsoonal moisture will overspread the area from the south into
tonight increasing the chance of wetting rain across the area the
next couple days, especially in the mountains and foothills. Min
rh`s will be much higher the next couple days decreasing the fire
threat also. Temperatures will also be down through Wednesday before
slowly rebounding Thursday into Friday.

&&

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

&&

$$

SHORT TERM...Skrbac
LONG TERM...McDonald
AVIATION...McDonald
FIRE WEATHER...Skrbac


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