Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 210510 AAA
AFDRIW

Area Forecast Discussion...UPDATED
National Weather Service Riverton WY
1110 PM MDT TUE SEP 20 2016


.AVIATION.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

The main concern will be MVFR ceilings and mountain obscurations
developing Wednesday evening in wake of a cold front pushing
south Wednesday afternoon and evening. The best chance of low
clouds will be across the Cody Foothills, and Johnson County with
less certainty farther south. Also some convection is possible
late this afternoon into the overnight hours, but only brief restrictions
are expected with this activity. Breezy northerly winds of 15-25kt
will occur across northern Wyoming late Wednesday afternoon through
late evening in wake of the front, but are expected to weaken in
most areas by around midnight.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

Marginal LLWS form the south is expected at the KJAC terminal
through Wednesday morning. Attention then turns to increasing
chances of convection Wednesday afternoon into the overnight
hours ahead of a slow moving upper low that will impact the area
for a few days. Instability is limited with a gradient across the
far west. Thus will only have VCTS at KJAC terminal, but only VCSH
at other terminals. Brief MFVR/IFR restrictions could occur
Wednesday afternoon and evening with convection. After 03-06Z
Thursday there is better shot at persistent rain showers with
MVFR or low VFR ceilings and mountain obscurations. KJAC terminal
has the best shot at seeing persistent MVFR ceilings with rainfall
after 06Z Thursday.

&&

.PREV DISCUSSION... /issued 219 PM MDT TUE SEP 20 2016/

Short Term...tonight Through Wednesday

Breezy to windy conditions will increase tonight and Wednesday
as a large Pacific low pressure trough moves inland.  Moisture
will increase in the flow Wednesday with scattered showers and
isolated thunderstorms developing over the west by the afternoon.
Temperatures will fall in the west and north through the day.

Long Term...Wednesday Night Through Tuesday

Showers will become widespread with embedded thunderstorms
Wednesday night through Thursday as temperatures fall rapidly.
A colder wetter period will continue through Friday. Snowfall is
expected to be limited to the mountains above 9500 feet. Friday
night the closed upper level low is expected to move northeast
from southwest Wyoming into central Wyoming which is not the most
favorable location for much of the area. Precipitation is shifted
north and east with decreasing precipitation central and south.
Precipitation will be spottier on Saturday with the cold pool
centered over the area. North flow will develop Saturday night and
Sunday with drying. Cold high pressure will be over the area
Sunday night and Monday then a warming trend will occur through
Tuesday.

Fire Weather...

Breezy to windy conditions will increase tonight and Wednesday
as a large Pacific low pressure trough moves inland.  Moisture
will increase in the flow Wednesday with scattered showers and
isolated thunderstorms developing over the west by the
afternoon. Showers will become widespread with embedded
thunderstorms through Thursday as temperatures fall rapidly. A
colder wetter period will continue through Friday.

&&

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

&&

$$

SHORT TERM...C.Baker
LONG TERM...C.Baker
AVIATION...WM
FIRE WEATHER...C.Baker



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