Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 191756 AAA

Area Forecast Discussion...Update
National Weather Service Riverton WY
1156 AM MDT Sun Mar 19 2017

.SHORT TERM...Sunday through Tuesday night

Things look like they will become a bit more active over the next
few days. Radar shows some showers moving into the west in
association with a shortwave moving through and a bit of jet energy.
There could be some brief bouts of heavier precipitaion but nothing
really prolonged. With 700 millibar temperatures not dropping below
minus 2.5 Celsius, snow should be confined to the mountains for the
most part. The heaviest precipitation in the west should end this
morning. As for east of the divide, it will be another mild day with
a mix of sun and clouds. The models have shifted further north with
the best upper level support and moisture as well. Therefore, we
have removed or lowered POPS across much of the area and limited any
showers to the northern border. We also maintained the chance of
thunder as well, although nothing widespread. Temperatures will be a
few degrees cooler as well. Although it will remain breezy in the
usual areas, with somewhat higher relative humidity fire weather
concerns should ease today. With the mild temperatures and possible
showers, flooding concerns will remain so we will continue the flood

Another wave will move into the west tonight. This one is similar to
Saturday night`s in that it has some upper level support but not a
lot of moisture. This one appears also appears warm as well with
snow with again mainly rain falling in the western Valleys. There is
more uncertainty further east however. The models continue to
struggle with how far south a frontal boundary will sink before
washing out. We share the concern with the day shift with conditions
in the north. We kept temperatures across the north below MOS
guidance. As for the chance of showers, both models show the best
chance across the north close to the dying front. Another piece of
energy could bring some showers to the south as well. Both the
models zero in on the afternoon and evening for the best chance of
showers, some of which could be of the snow variety. This has a bit
more moisture but nothing huge. Temperatures elsewhere will be a bit
cooler but still above normal for this time of year, mainly due to
cloud cover.

Short wave ridging will then move in for Tuesday with quieter
weather although there will still be enough instability for some
higher elevations showers West of the Divide. Mainly dry weather
should dominate East of the Divide however. A Pacific system, this
one with more moisture to work with will move into the west Tuesday
night. After starting as rain in the Valleys, cooler air will move
in and likely drop snow levels down to the valleys floors. Dry
conditions should hold through Tuesday night East of the Divide.

.LONG TERM...Wednesday through Sunday

A spitting trough will push across the Rockies Wednesday night and
Thursday. The associated cold front is expected to push across the
forecast area late Wednesday night/Thursday with some model
solutions showing a 700mb mid-level circulation developing/pushing
east/northeast across the forecast area. Precipitation looks to be
mountain snow/valley rain. The rain in the lower elevations west
of the Divide will change to snow with frontal passage, and even
some low-elevations east of the Divide could as well, as 700mb
temps dip to around -5C. The best shot of precipitation appears to
be across the south and east, but will continue to have chance
PoPs in most areas late Wednesday night/Thursday to respect the
trough and any deviations (e.g., track) it might take.

Shortwave ridging with mainly dry conditions are expected late
Thursday night and Friday.

This again will be short-lived with another trough taking aim at
the Cowboy State Saturday and Sunday. Based on current timing, the
west would see increasing precipitation Friday night into Saturday
with some precip spilling east of the Divide Saturday night and
Sunday with the cold front.

Elevated fire weather conditions could occur in some areas east of
the Divide on Wednesday, and then again Saturday ahead of
troughs/associated cold fronts.

Low-elevations snowmelt causing localized flooding will continue
on/off through the extended.




VFR conditions will prevail at the terminal sites through tonight.
Rain showers and high elevation snow showers will redevelop after
21Z this afternoon in northwest WY and continue through tonight.
Local MVFR conditions will occur in NW WY at this time with some
mountain obscuration. These showers will dissipate by 14z Monday
morning but will continue in Northwest Wyoming.


VFR conditions will prevail through the period. A gusty wind will
occur today into this evening at some of the terminal sites. A
cold front slides into Northern WY after 01Z with a wind shift to
the north. This front will push south to a KRIW to KCPR line by 12Z



Rain and higher elevations snow showers will continue in the west,
especially further north today with the heaviest falling this
morning. Valleys will remain mainly rain with snow in the higher
elevations. Most areas East of the Divide will remain dry today
except in the far north where a few showers and possibly an
afternoon thunderstorm may fire. With temperatures a bit lower and
somewhat higher relative humidity, fire concerns should ease
somewhat today. A gusty southwest wind will continue from Rock
Springs through Casper however. Smoke dispersal and mixing should be
generally good to excellent East of the Divide and fair to poor in
the west.&&

Flood Watch through late tonight for WYZ013-023-027.



SHORT TERM...Hattings
LONG TERM...Murrell
FIRE WEATHER...Hattings is the U.S. government's official web portal to all federal, state and local government web resources and services.