Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 162009
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
209 PM MDT Fri Jun 16 2017

.SHORT TERM...(This evening through Monday)
Issued at 225 PM MDT Fri Jun 16 2017

Moisture in westerly flow aloft with a short wave low pressure
trough will support scattered showers with isolated thunderstorms
with strong wind gusts and hail this evening. Temperatures will
cool with a cold front behind the trough moving south and east
late tonight and Saturday morning. Showers will decease on
Saturday there will remain a threat of isolated thunderstorms
mainly over the western and northern mountains. Cooling will
continue with most areas in the 40s, mid 20s and 30s mountains,
Sunday morning. Sunday and monday look dry with temperatures
warming Sunday night and Monday with lighter wind as high pressure
builds over the area.

.LONG TERM...(Monday night through Friday)
Issued at 225 PM MDT Fri Jun 16 2017

...Summer like weather ahead...

The weather will start out hot and dry in the extended forecast
for Tuesday and Wednesday as the high over the hot desert
southwest extends a flattening ridge axis north across the rest
of the western United States with the ridge axis remaining to our
west with the ridge axis never quite making it this far east. The
overall trend over the course of next week will be for the large
closed low over Eastern Canada to dig, enhancing the trough over
the Midwest, with this long wave trough retrograding west. This
will encourage each successive shortwave riding up and over the
ridge in Canada, Montana, and the northern Dakotas to track
farther southwest, with time, with each track of each shortwave
tracking ever closer to our CWA with each troughpa to our north
and east. The first wave riding the ridge will take place Monday
night, then one on Wednesday, and then the one with the greatest
impact will be Friday. This will result in a slight gradual
cooling trend during the course of next week until finally we will
see a slight chance of thunderstorms, mainly in the Northern
Mountains Friday afternoon and evening. The high temps will start
out in the low 90s at the lower elevations east of the divide
Tue/Wed and 70s west. Then by Thu/Fri highs in the 80s east and
60s west. However, on Friday we will see upper 70s in our northern
zones east of the divide with the added clouds and isold precip.
The Euro is the slowest with this trend, the GFS the fastest, with
the Canadian not quite on board with this soln, so Will go with
the GFS/Euro blend for the timing of this trend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday afternoon)
Issued at 225 PM MDT Fri Jun 16 2017

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

Isolated to scattered showers will be found mainly over Yellowstone
National Park.  A cold front will then spread widespread rain
showers and mountain obscurations south to vicinity KJAC by 20z
this afternoon with westerly flow aloft strengthening and areas of LLWS.
Expect southwest winds of 15 to 30 knots today over much of the area except
from the south at the same speeds over the western valleys including KJAC.
MVFR conditions should prevail KJAC from around 20z this afternoon and overnight.
These rain showers are not expected to make it much further south than
KBPI-KPNA tonight.  Surface winds will gradually diminish this
evening with some areas of LLWS remaining through early Saturday morning.
Expect mainly VFR conditions Saturday. Expect northwest winds of 15 to 25
knots on the back side of the exiting trough Saturday except 25 to 35 knots
in Sweetwater County including KRKS.


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

VFR conditions will prevail through this afternoon.  Surface west
winds will increase ahead of a cold front that will push into the
north, vicinity KCOD-KBYG by 00z Saturday.  Scattered to numerous
rain showers will develop behind this cold front as it pushes
further south this evening. Expect southwest winds of 25 to 35 mph
this afternoon across much of the area ahead of the approaching cold front.
Areas of lower MVFR ceilings are expected to develop after 03z Saturday
behind the cold front.  The front will push south to a vicinity KRIW-KCPR
line by 06z Saturday and further south to near Interstate 80 by 12z Saturday.
Lower MVFR, local IFR ceilings will be most probable along the Interstate
25 corridor, KBYG-KCPR and vicinity KCOD Friday night.
After 12Z Saturday expect mainly VFR conditions. Expect northwest
winds of 15 to 25 knots on the back side of the exiting trough
Saturday except 25 to 35 knots at KBYG.


&&

.FIRE WEATHER...
Issued AT 225 PM MDT Fri Jun 16 2017

Moisture in westerly flow aloft with a short wave low pressure
trough will support scattered showers with isolated thunderstorms
with strong wind gusts and hail this evening. Temperatures will
cool with a cold front behind the trough moving south and east
late tonight and Saturday morning. Showers will decease on
Saturday there will remain a threat of isolated thunderstorms
mainly over the western and northern mountains. Cooling will
continue with most areas in the 40s, mid 20s and 30s mountains,
Sunday morning. Sunday and monday look dry with temperatures
warming Sunday night and Monday with lighter wind as high pressure
builds over the area. Sufficient wind and heating will combine
with favorable mixing for good to excellent smoke dispersal in the
afternoons Saturday through Monday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Baker
LONG TERM...Lipson
AVIATION...Lipson
FIRE WEATHER...Baker


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