Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 240924

Area Forecast Discussion
National Weather Service Riverton WY
324 AM MDT Tue Oct 24 2017

.SHORT TERM...(Today through Thursday night)
Issued at 300 AM MDT Tue Oct 24 2017

Imagery shows an amplified ridge across the wrn CONUS and a large
trof across the ern half of the CONUS. The next upper lvl SW trof
that will eventually affect WY currently lays at about 160W lon ovr
the PAC. H5 heights currently around 580dm +/- 8dm across the FA.
The SFC is post frontal across WY with the CONUS basically following
the upper levels with high pressure entrenched across the west and
low pressure over the east and a long cold front dividing the two
areas. No precip falling anywhere over/near WY.

Today through Wednesday: Warming and drying trend in place as
heights rise with the ridge. No significant weather expected today
or tonight...just a seasonal and rather nice. Wednesday, good above
seasonal warming warming expected (warmest day of the week.
However, it will come at a price in the form of elevated to
extreme fire weather conditions for many locations across central
and southern WY. ATTM, it appears that portions of Natrona and
Fremont county will stand the best chance for extreme (Red Flag)
conditions of RH<=15 percent and winds sustained/gusting >= 25
mph. Will issue a Fire Weather Watch for forecast zones 19, 20 and
11 (Fire Weather zones 289, 280 and 281 respectively) to support
this possibility Wednesday afternoon and early evening.

Wednesday night through Thursday: the upstream SW trof mentioned
above will cruise into/through the ridge, bringing much colder temps
and modest moisture along with with a rather vigorous cold front
through WY. The most brutal activity with this system will be the
sharp decreases in temperatures as the wind shifts out of the north
at and behind the cold front. Precip, both liquid or frozen, will be
modest with this very quick moving system with snow amounts < 6
inches in the high mountains of the north (both Absarokas and
Bighorns) with less than 2 inches across the lowlands east of the
Divide...those higher amounts either south of Casper going up the
mountain or perhaps in the Rattlesnake mountains through the day
Thursday. It`s a quick hitter...then out. Thursday
night...clear/clearing and cold with lows in the teens and 20s for
most locations in the CWA.

.LONG TERM...(Friday through Tuesday)
Issued at 300 AM MDT Tue Oct 24 2017

Friday through Sunday will be dry across the area. High
temperatures will be cool Friday, then gradual warming through
Sunday. Breezy areas Saturday and Sunday in the wind prone
locations of central WY. GFS model brings a cold front and some
precipitation into Northern WY Sunday night, spreading into
Central WY by sunrise Monday. Then the precip moves into southern
WY during the day Monday. Brisk north wind will accompany this
cold front. Precip ends Monday night from north to south with
decreasing clouds and wind. Next Tuesday could see another
weather system move into the north in the afternoon, spreading
south Tue night. Plenty of time watch the Mon and Tue unsettled
weather pattern and make adjustments as needed. High temps would
be colder next Mon and Tue in this weather pattern.


.AVIATION...(For the 12Z TAFS 12Z Tuesday through 12Z Wednesday)
Issued at 300 AM MDT Tue Oct 24 2017

VFR conditions are expected through the forecast period with mainly
clear skies and relatively light winds.


Issued AT 300 AM MDT Tue Oct 24 2017

Fuels remain at critical levels across over Fremont, Johnson and
Natrona Counties. (Please see the Fire Weather Forecast product
for more information).

...Elevated Fire Conditions east of the Divide and across southern
Wyoming this Wednesday afternoon...

...Fire Weather Watch for Zones 280, 281 and 289 Wednesday

Today will have seasonal temperatures dry with modest minimum RH
values ranging from the upper teens to 30 percent across the lower
elevations east of the Divide and over southern WY. Winds across
most of central Wyoming will relatively light today with generally
less 15 mph expected for most locations and gusts less than 25 mph.
Wednesday will be above seasonal as far as temperatures and quite
dry with RH values dropping into the lower and mid teens with winds
gusting ahead of the next Fall weather system greater than 30 mph
from eastern Sweetwater through Natrona and into southern Jonson
Counties. This will in effect raise Fire Weather conditions to
elevated for most of the low land areas east of the Divide and
possibly into the extreme category over fire zones 280, 281, and 289.


Fire Weather Watch from Wednesday afternoon through Wednesday
evening for WYZ280-281-289.



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