Area Forecast Discussion
Issued by NWS Riverton, WY

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434
FXUS65 KRIW 160825
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
225 AM MDT Mon Oct 16 2017

.SHORT TERM...Monday through Wednesday night

One thing we will not have to worry about for the next three days is
precipitation as a ridge controls the weather and brings mild to
warm and dry conditions with sunshine mixing with high clouds at
times. However, we do have a couple of concerns to look at.

The first is for the potential for critical fire weather. With 700
millibar winds increasing and a tightening pressure gradient, it
will become quite breezy across the southwestern wind corridor from
Rock Springs to Casper. In addition, we have a very dry atmosphere
in place with relative humidity expected to fall below 15 percent at
times. The windiest day would be Tuesday, so this looks to be the
most critical day. Today is more borderline though. However, it
appears we will have enough time for critical fire conditions to
issue a Red Flag Warning through Tuesday for Natrona County, with an
obvious break on Monday night. Conditions should improve for
Wednesday with slightly less wind but may remain near critical.
However, most zones do not have critical fuels anymore.

The other concern is for potential high wind across the Cody
Foothills, mainly in the vicinity of Clark late Tuesday into Tuesday
night. The NAM, which usually does a decent job, showers 700
millibar winds up to 60 knots across that area. In addition, a
shortwave passing by to the north should provide enough mixing to
bring some of those winds to the surface. Still a bit out to issue
any highlights however.

.LONG TERM...Thursday through Monday

Ahead of an approaching trough, elevated to possibly critical
fire weather conditions could occur Thursday in the wind corridor
along and east of the Divide.

A trough and associated cold front will sweep across the area late
Friday into Friday night. This will bring a good shot of some
precipitation across the west Friday afternoon/evening with some
precip possibly spreading east of the Divide Friday night.
Precipitation is expected to quickly end from west to east late
Friday night/Saturday morning. Precipitation amounts are expected
to be mainly light. Ahead of the cold front, windy conditions are
expected, but an increase in surface moisture should keep RHs
from reaching critical values. Also models are keeping winds
below high wind thresholds.

In wake of this tough, flat ridging to strong zonal flow will be
impacting the area with little or no chance of precipitation with
temps seasonal to above average. The main concern would be high
wind potential across the Cody Foothills with northern Wyoming
possibly under the influence of the right exit region of a 140+ kt
250 mb jet Saturday/Sunday.

&&

.AVIATION...12Z Issuance

VFR conditions will occur over the region through tonight. A gusty
wind will occur from KRKS airport to KCPR airport today through
about 00Z, then decrease. A gusty wind at the KCOD airport will
decrease toward 18Z this morning.

&&

.FIRE WEATHER...

...RED FLAG WARNING FOR NATRONA COUNTY FROM THIS AFTERNOON THROUGH
TUESDAY...

A combination of a strengthening mid level winds and good mixing
will bring a gusty wind to the wind corridor from Rock Springs
through Casper from this afternoon through Tuesday. With relative
humidity falling below 15 percent, critical fire weather looks
likely this afternoon and especially on Tuesday afternoon. Mixing
and smoke dispersal will range from fair to poor across most of
the area but good across the southwestern wind corridor.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 7 PM MDT Tuesday for WYZ280.

&&

$$

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



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