Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 230503
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1103 PM MDT Sun Oct 22 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 201 PM MDT Sun Oct 22 2017

A Pacific low pressure trough and cold front will bring widespread
snow to the western mountains this evening tapering off through the
night.  Strong winds will accompany the snow.  The strongest
winds will be over and near the east slopes of the mountains and
through the wind corridor from Northern Sweetwater county through
Natrona county this evening. Behind the cold front strong north
winds will blow on Monday across northern Johnson county.
Temperatures will cool on Monday behind a cold front with
decreasing winds.  Dry and warmer conditions are then expected
through mid week with lighter winds as a large high pressure
ridge builds over the western U.S.

.LONG TERM...(Wednesday night through Sunday)
Issued at 201 PM MDT Sun Oct 22 2017

After a warm day Wednesday, many areas are going to be in for a slap
in the face as we head into Thursday. A strong Canadian cold front
will drop into northern portions of the state Wednesday night and
continue to sweep southward through the night and into Thursday. As
for precipitation, it should move into the north before midnight and
move across most areas East of the Divide by Thursday morning. With
the Canadian origin of the system, there is not a tremendous amount
of moisture associated with it. However, there will be some decent
upper level forcing in the form of a 110 knot jet streak moving in
behind the front. The precipitation would likely start out as rain
but then change to snow quickly as the front passes through. And the
timing of the snow could have some concerns for the morning commute
on Thursday if the snow is heaviest at that time. It is too early to
talk about amounts however. In addition, it will be windy behind the
front. This pattern is a good one for strong and possibly high winds
in areas favored by strong cold advection with north to northwest
flow, mainly the northern Bighorn Basin as well as northern Johnson
County. With the quick movement of the system, most steady
precipitation should end by Thursday afternoon and all by Thursday
night. We kept temperatures below what forecaster builder loaded in
since the models usually do not capture this very well. Out west,
other than the north, most areas should remain dry from this system.

Quieter weather should be the rule after that. At this point, Friday
looks to be dry but cool day. Both the GFS and European have come
into better agreement as well for Saturday with keeping the area dry
and shifting another system further to the east. We maintained some
slight POPs in the north and east put nothing more. The area should
continue to see a warming trend with near to possibly above normal
temperatures by Sunday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1055 PM MDT Sun Oct 22 2017

Isolated valley rain/mountain snow showers ongoing across northern
Wyoming will gradually sag south/southeastward with time tonight.
A cold front continues to slide southward and should push across
the Casper terminal between 08Z and 10Z. Strong northwest wind
will be observed over the northern Big Horn Basin and N. Johnson
County before weakening somewhat during the predawn hours.

Any shower activity will come to an end from north to south
between 09Z and 14Z. Otherwise dry conditions are expected with
decreasing cloudiness today with VFR conditions. Winds will be
breezy from the west/northwest in most locations today with the
exception of middle of the central basins where lighter winds are
expected. Winds are expected to subside around sunset with light
winds tonight.

&&

.FIRE WEATHER...
Issued AT 201 PM MDT Sun Oct 22 2017

A Pacific low pressure trough and cold front will bring widespread
snow to the western mountains this evening tapering off through the
night.  Strong winds will accompany the snow.  The strongest
winds will be over and near the east slopes of the mountains and
through the wind corridor from Northern Sweetwater county through
Natrona county this evening. Behind the cold front strong north
winds will blow on Monday across northern Johnson county.
Temperatures will cool on Monday behind a cold front with
decreasing winds.  Dry and warmer conditions are then expected
through mid week with lighter winds as a large high pressure
ridge builds over the western U.S.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 6 AM MDT Monday for WYZ010.

&&

$$

SHORT TERM...Baker
LONG TERM...Hattings
AVIATION...Murrell
FIRE WEATHER...Baker



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