Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 261718

Area Forecast Discussion
National Weather Service Riverton WY
1118 AM MDT MON SEP 26 2016

.SHORT TERM...Today through Wednesday night

Imagery shows deep amplified upper trof located from south central
Canada, through the upper midwest, and on south through the
Central/Southern Plains. Upper ridging building across the western
CONUS over a modest subtropical cut-off low over the Baja region of
Mexico. Surface has large occluded cyclone over southern Canada and
high pressure continuing to build over WY. No precipitation.

Through the forecast period: Relatively ridging and high pressure at
the surface continues over WY through most of the forecast period
with no significant weather to speak of. Increasing small chances
for precipitation will come Wednesday night as a slowly approaching
trough from the west spreads westerlies over the aforementioned cut-
off low and then draws it towards the FA...with PV advecting towards
the FA and both of these systems inducing low level low pressure
across the west and subsequent easterly flow back into the forecast
area. Low end POPs will then increase from the Four Corners area to
the north and across western WY Wednesday night. Otherwise, the
pattern through the period will keep the lower levels warming and
drying slowly with winds relatively light and fire danger low.

.LONG TERM...Thursday Through Monday

Medium range models are changing with each run recently as we
transition back to a mean trough over the west towards the end of
this week and into next week. Confidence in the details will
likely be low for a few days until the models start to pick up on
this change a little better. At the beginning of this period, we
may see some moisture/energy picked up from the desert sw (a
little piece of energy that came down the back side of our wet
storm system from late last week actually) resulting in a few
showers/isold tstms Thursday, especially near and west of the
divide. Our first of two likely shortwave troughs will swing east
across the area from the Pacific Northwest later Saturday/Saturday
night with a decent shot of showers/few storms in the west with a
few making it east of the divide, especially north. A few mountain
showers may linger in between these first two systems on Friday. A
rather troughy pattern will then persist the remainder of the
period with the best chance of showers and some higher elevation
snow will continue in the west. It`s quite possible that one of
these systems will be much stronger than the models are showing
now so stay tuned as we watch the changing pattern once again
towards next weekend and beyond.



VFR conditions with unlimited ceilings will prevail through 18z
Tuesday. However, patchy fog or isolated lower IFR-LIFR ceiling may
partially obscure valleys from around 08z to 16z Tuesday. Winds
will be generally light at 10 knots or less.



Fire danger low all areas today...lasting through the rest of work
week. Upper level ridging and surface high pressure will combine to
provide very stable conditions over the forecast area for the next
several days...with no rainfall, mostly sunny/clear skies and
relatively light winds. The next chance for isolated to widely
scattered precipitation will not arrive until late Wednesday
night...with small chances continuing mainly west of the
Divide through Friday.


.RIW Watches/Warnings/Advisories...None.



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