Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 161931
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
131 PM MDT Mon Oct 16 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 130 PM MDT Mon Oct 16 2017

A mild/warm short term period with large diurnal (~40 degrees in
many areas) swings due to the dry atmosphere and warm mid level
temperatures. Breezy to windy at times in the wind corridor and
along the Cody Foothills and along the east slope of many mountain
ranges. The Cody Foothills are a challenge the next couple days with
strong to high wind potential. Mesoscale cross sections are showing
some mountain wave potential mainly in the 10-16z period Tuesday
morning and then possibly again Tuesday evening and night. The flow
into the barrier is initially too weak this evening (around 25kts)
but increases to 30kts around 10-11z. ARW/WRF are showing the
developing mountain wave early in the evening with winds peaking
after 10-11z for several hours. Upward propagating wave is also
shown in the cross section. Upwind soundings do show a increasing
near mtn top inversion strengthening in the same time frame. Tough
call with some conflicting signals but it`s worth watching very
closely this evening. Will issue an SPS for now with local high wind
in the favored areas tonight late and again Tuesday night.
Otherwise, our main `weather` will be the mild/warm days and chilly
nights with rapid drops at sunset each day as dew points are very
low and will remain so. Thursday still looks like the warmest day
due to potential best mixing in a large areas with better H8-H7 wind
and potential lee side trough/low. Either way, still quite warm each
day, especially for late October. 60s and some 70s east of the
divide with 50s and some 60s west. The mountains will vary from the
40s and 50s with even a few lower 60s in the foothills.

.LONG TERM...(Tuesday night through Monday)
Issued at 130 PM MDT Mon Oct 16 2017

The small circulation now seen at the tail end of the Aleutian
Island Chain will arrive next weekend as an open trough. Ahead of
this approaching trough, the pressure gradient will increase and
winds Thursday night and Friday will increase from the southwest
ushering in a continuation of the influx of mild air. By Friday, we
may have fire weather concerns as winds continue out ahead of the
approaching trough and dew points drop. Then on Friday night and
Saturday morning, this trough will come through in much the same
fashion as it did last Friday night and Saturday morning, except for
at least one thing. The air may not be as cold as the last system in
spite of the fact that -10.5c temps are progged at 700mb with this
system since earlier runs were advertising warmer temps and the
origin if this air is from a more southern latitude. Rain and snow
showers will accompany the trough/cool front Friday night/Saturday
morning. Spotty precip is progged for the NW mtns Saturday night due
to isentropic lift ahead of the next weak shortwave progged to track
across the Northern Rockies. Then the GFS depicts this weak wave to
track across the area Sunday for additional spotty precip in the NW
mtns. We will see a period of cooling this weekend and into Monday
but temps will still be close to normal. Just like last Saturday,
this coming Saturday will be the coolest day of the week with highs
in the 40s in the far west valleys and mid to upper 50s in the
basins east of the divide.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday afternoon)
Issued at 130 PM MDT Mon Oct 16 2017

Strong and gusty winds will blow along the Cody Foothills at times
through Tuesday night. The wind corridor from northeast of KRKS to
KCPR will also see periods of gusty southwest wind. Otherwise, it
will be a dry period with VFR conds everywhere.

&&

.FIRE WEATHER...
Issued AT 130 PM MDT Mon Oct 16 2017

...RED FLAG WARNING FOR NATRONA COUNTY THROUGH TUESDAY...

A very dry atmosphere the next several days combined with warm
daytime temperatures and areas of breezy to windy conds will create
elevated fire weather conditions across the lower elevations. A Red
Flag Warning will continue for fire zone 280 through early
Tuesday evening as fuels remain critical there along with breezy
to windy conds and min rh`s of 10 to 15 percent during the day.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT Tuesday for WYZ280.

&&

$$

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



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