Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 271723
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1123 AM MDT Wed Mar 27 2024

.KEY MESSAGES...

- Mainly dry and mild weather today, with only a few snow
  showers in western Wyoming.

- A Pacific system brings moderate snow to western Wyoming
  Thursday, with strong wind likely East of the Divide.

- An impactful storm is likely Saturday and Sunday, but exact
  details for impacts remain uncertain.

&&

.DISCUSSION...
Issued at 136 AM MDT Wed Mar 27 2024

Northwest flow aloft continues over the area today and there
are still a few snow showers across the far west this morning.
Coverage is much less than last night and with a transitory
ridging moving over the area, this should be the day with the
least active weather across the area with only isolated to
widely scattered showers and mainly in the western mountains.
Most areas will be dry,as a result. Temperatures will continue
the warming trend with highs close to seasonal averages. It will
become breezy though, especially in the favored southwest flow
areas like Casper.

Things will turn active again on Thursday, as a Pacific system
moves towards the area. Some light precipitation will break out
late tonight, but the bulk of the precipitation should hold off
until after sunrise. The steadiest snow looks to be during
Thursday afternoon when the best jet energy moves through the
area and the trough axis moves through. With this, we have
hoisted Winter Weather Advisories for Yellowstone, the Tetons
and the Wind River Mountains, with a greater than 1 in 2 chance
of exceeding 6 inches of snow, the cut off for advisory level
amounts. Elsewhere, amounts look too low for highlights.
Meanwhile, in areas east of the Divide, the main impact will be
windy conditions developing ahead of the front. As for potential
wind highlights, the 700 millibar wind looks too low for High
Wind Watches at this time, peaking at 40 knots rather than the
50 knots I would prefer to see. There could be gusts to 50 mph
though. We did lower PoPs somewhat and basically removed them in
the morning as southwest flow is not favorable for rain in this
area. We maintained them in the afternoon though with the
passage of the trough axis. Amounts look light east of the
Divide though as the trough is expected to split as it crosses
the area. Sweetwater County could be interesting in the evening
though as there could be a brief period of snow and possibly
snow squalls. Stay tuned.

Friday at this point looks like a lull in the precipitation with
weak ridging over the area. There may be just enough upper level
divergence for a few showers on Friday, but most of the time
should be dry with near normal temperatures.

Things turn more active again for the weekend as an upper level
low slides southward along the West Coast and moves onshore on
Sunday. Deeper moisture will spread into the area as a result.
There is a bit, emphasis on bit, more agreement with the models
with moisture overspreading the area on Saturday and continuing
into Sunday. However, details as to placement of the heaviest
precipitation and timing of the waves moving through the flow
remains highly uncertain. Ending times are also uncertain with a
24 to 36 hour spread depending on guidance. So to sum things
up, confidence remains high for an impactful system for the
weekend. Confidence in the details remains low though. Drier
weather should then return for the middle of next week as
ridging folds over the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1123 AM MDT Wed Mar 27 2024

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

Deformation axis and the leading edge of moisture approaching from
the west has continued to generate intermittent snow showers at KJAC
Wednesday morning. Enough instability exists for continued VCSH at
KJAC through sunset with wide variability from MVFR to VFR within 10-
20 minute periods. VFR and less shower coverage at KJAC between 01Z-
09Z/Thursday before more robust moisture arrives from the west.
Conditions deteriorate between 09Z-12Z/Thursday at KJAC with
prevailing IFR by 15Z. All other terminals remain VFR through at
least 12Z/Thursday. Moisture arriving from the west may spread light
snow to KPNA/KBPI late in the period. Surface wind 12-25kts will be
common through 01Z/Thursday. Mountain tops frequently obscured.

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

All terminals to be VFR through the forecast period. Gusty westerly
surface wind 12-25kts continues at KCPR and KCOD and eventually
develops between 20Z-22Z/Wednesday at KRIW and KLND. Speeds
generally diminish around 01Z-02Z/Thursday. KCPR sees southwest
wind substantially increase between 14Z-17Z/Thursday ahead of an
approaching weather system. Mountain tops occasionally obscured
along the Continental Divide.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 AM to 11 PM MDT Thursday for
WYZ001-012-014-015.

&&

$$

DISCUSSION...Hattings
AVIATION...CNJ


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