FXUS65 KRIW 262309
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
509 PM MDT Fri Apr 26 2024

.KEY MESSAGES...

- More widely scattered rain showers and isolated thunderstorms
  this afternoon and evening. 

- Main system pushes through late this evening and overnight 
  and into the weekend with ample mountain snow and low valley 
  rain.
  

- Warming trend and mainly dry next work week with another
  system late week and into the following weekend.

&&

.DISCUSSION...
Issued at 1232 PM MDT Fri Apr 26 2024

IR currently depicts amply moisture across the CWA with a mainly
southerly flow. Cloud tops mainly maintaining temperatures with
the deep trough through the Great Plains and also to the west
through the Great Basin region. Radar shows ongoing spotty rain
showers and a few isolated lightning strikes across the Greens,
but otherwise, not as much coverage as previous expected at this
time. However, this should pick up in the coming hours through
the afternoon and early evening. Anything of more significance 
in terms of stronger storms are really low at this time with the
cooler air entranced through the entire CWA.

These aforementioned showery activity will diminish by this
evening as a more stratiform rain and snow pushes in from the
west and southwest towards sunset and especially through the
overnight hours. With a more upslope east to northeasterly flow
for much of the CWA, lower basins have trended downward in
overall precipitation for the weekend. This is especially true
for the Bighorn and Wind River Basins, as well as the I-25
corridor. The main divergent part of the upper level flow
coupled with a more enhanced PVA signature looks to be over the
the Absarokas and Winds as previously expected where more
significant precipitation will occur in the form of snow for
higher elevations over 9-10kft, and rain in lower areas for the
upper Wind River Basin along with points south along the I-80
corridor to Colorado. Up to a foot and a half to 2 feet can be
expected for the Winds and up to a foot for the Absarokas from
this evening into Sunday morning. The highest rates will be over
Friday night into much of Saturday morning and early afternoon
before tapering some into the evening and especially overnight
into Sunday morning. Probabilistic data shows these higher
percentages for the greater amounts over 90 percent. Other
ranges to include Yellowstone, Tetons, Salts, and Wyomings, will
see significantly less snow with the highest PROB of over 90 
percent for over 2 inches in accumulations.

Otherwise, liquid precipitation amounts have continued to be on
the downward trend as expected with the shift of the main trough
further south and not as potent as well. Temperatures will
remain on the cooler side more seasonable for this time of year
over the weekend. Late Sunday, an upper level ridge will start 
to build in from the west being more entrenched by Monday and 
Tuesday that will bring a warming and mainly dry trend 
throughout much of the work week. Some minor chances for 
precipitation for northern parts of the CWA with some passing 
shortwaves but with the main finger of the PFJ to the north, no 
impacts are expected at this time. Winds will be elevated for 
the first half of the week with the more convergent flow aloft 
and a strongly built surface high to the west that will keep a 
fairly strong gradient through the CWA. Otherwise, a lackluster 
end to the work week with the next system to keep an eye on for 
late Friday and into the following weekend with details unknown 
at this time this far out in the game.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 508 PM MDT Fri Apr 26 2024

Showers and thunderstorms continue through this evening and 
into Saturday morning for some locations. The best chances for 
rain will be west of the Divide (KRKS, KBPI, KPNA, and KJAC) as 
well as KLND due to favored flow direction. Most of these 
showers are a hit-or-miss in timing, with the greatest chances 
for rain highlighted in individual TAFs. A relatively weak cold 
front this evening will bring a notable wind shift to 
northeasterly winds for many sites.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 3 PM MDT Saturday for WYZ002.

Winter Storm Warning until 9 PM MDT Saturday for WYZ015.

&&

$$

DISCUSSION...Lowe
AVIATION...VandenBoogart/Wittmann