Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 290553 AAA
AFDRIW

Area Forecast Discussion...UPDATED
National Weather Service Riverton WY
1153 PM MDT THU JUL 28 2016

.UPDATE...Updated to add 06z aviation discussion.

&&

.AVIATION.../06Z ISSUANCE/

West of the Continental Divide...KJAC/KBPI/KPNA/KRKS

Smoke from the Cliff Creek Fire near Bondurant may bring MFVR vsbys
to vcnty KBPI-KPNA until 17z Friday, and areas of smoke from the
Lava Mountain Fire will partially obscure terrain over Togwotee
Pass through Friday morning.

With the exception of obscurations from smoke, VFR conditions will
prevail through 12z Saturday with afternoon and evening thunderstorm
activity developing along and east of the Continental Divide Friday
afternoon and evening.  Surface west to northwest wind at 15-25 kts
will develop across the southern wind corridor, KEVW-KRKS-KRWL,
Friday afternoon through early evening.  A wind shift from the NE
will attempt to push south into VCNTY KRKS Friday evening, but is
not expected to push much further south than Interstate 80.

East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL

Areas should be free of shower or thunderstorm activity through
Friday morning.  Smoke from the larger Cliff Creek and Lava Mountain
will result in some reductions in visibility across the Wind River
Basin, but vsbys are expected to remain 6sm or greater.  A slightly
unstable northwest flow will result in isolated thunderstorms across
the area Friday afternoon and early evening, with most of this
activity expected remain over the near the mountains.  KCOD and KWRL
stand the best chance of seeing TS in their vicinity.  This activity
should dissipate after 03z Saturday.

&&

.PREV DISCUSSION... /issued 226 PM MDT THU JUL 28 2016/

SHORT TERM...TONIGHT THROUGH SUNDAY

Earlier convection today has now moved off to the east with that
thunderstorm activity from the previous shortwave now over the
Nebraska state line. Looks like a relatively late show today with
any activity associated with the next upstream shortwave. This shortwave
now appears to be over southern Montana. Convection is getting a
slow start with some cells forming over the spine of the northern
Big Horn Mountains and also over Washakie Needles over the Owl
Creek Mountains. There are pockets where the capes are almost1400J/KG
east of the divide. The morning cap took a while to
break...especially over Natrona/Johnson Counties where a deck of
stratocu was in place earlier this morning, but mixing out has
occurred. We expect the rest of the day today and tonight to be
the second episode of the most active period of convection for the
week. SPC had our CWA in "marginal risk" east of a line roughly
from Cody through Riverton for this round of convection. Again,
not much activity is expected west of the divide, although a few
storms may glance areas to the west near the divide. The
associated cold front will penetrate farther to the southwest
Friday morning then any of the other surface intrusions from the
northeast did this week. Some area fires east and west of the
divide will likely see 60 to 80 percent recovery once again Friday
morning as the BL moisture will likely be able to circumvent its
way west of the divide. Then by Friday afternoon after we mix out,
we will likely see another weaker round of late day convection.

Then on Saturday, the high over the southwest United States will
build east toward New Mexico as a closed low approaches the
Pacific Northwest. This will back our flow from west northwest to
more of a difluent flow from the due west, enabling monsoon
moisture to approach western Wyoming Saturday from the southwest
and west. So Saturday we will shift our attention from convection
north and east of the divide to west where the far west could see
some evening thunderstorms Saturday evening. On sunday, as the
closed stacked low moves east across southern Alberta, the risk of
t storms will spread east to the rest of the CWA. By Saturday,
with the expanding high, hotter temperatures will likely spread
north again with the Big Horn basin likely witnessing highs in the
mid to upper 90s once again. temperatures west of the divide,
however, will be left relatively unchanged. similar temperatures
are expected Sunday.

LONG TERM...SUNDAY NIGHT THROUGH THURSDAY

Significant changes in the longwave pattern during the next week. We
start out briefly with the upper high over the TX region and then it
gets suppressed swd as a long wave trough develops and extends swd
into the northwest part of the country through the middle of next
week. It looks like the ridge will build back in at the end of this
period and beyond again. End result for our area will be potential
for limited mainly mid and high level moisture to move across the
area at times early in the week with probably nothing more than
isold coverage and mainly srn/sern/mtn areas. We could see a little
more mid level moisture drawn nwd ahead of what could be a
significant cold front late Tuesday for at least the west and north
as upper low passes across Srn Canada. Any monsoonal moisture will
likely be shunted south again on Wednesday behind this front in the
more wly flow. Secondary shortwave behind this first strong wave
will likely usher in cooler but still dry area on Thursday. Cold
front will hover around east of the divide through the middle of
next week while the sw remains quite warm to hot. Tuesday will
likely be the hottest day east of the divide ahead of the front with
temps well up into the 90s with some hopeful cooling of at least 5
to 10 degrees on Wednesday. Temps by Thursday morning could actually
be somewhat cool with temps near freezing in YNP and 5-10 degrees
cooler east of the divide.

AVIATION.../00Z ISSUANCE/

West of the Continental Divide...KJAC/KBPI/KPNA/KRKS

VFR conditions will prevail through Friday with any thunderstorms
confined to the northern part of the area. It will continue breezy
at times with west to northwest winds in the afternoon. A dry
cold front will result in a wind shift from the NE along the
Interstate 80 corridor, vcnty KRKS, this evening.

East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL

Widely scattered to scattered showers and thunderstorms will
develop across most areas this afternoon and early evening some
storms may produce hail, strong wind gusts and frequent lightning.
Most of this activity will move out of the area by 03z Friday.
A similar afternoon is expected Friday.

FIRE WEATHER...

Scattered showers and thunderstorms are expected for much of the
area east of the Continental Divide for the rest of this afternoon
and evening. Gusty wind to 50 mph may occur with some storms, and
some higher gusts are not out of the question. Additionally, hail
and brief periods of heavy rain may round out storm activity
today along with small hail. Another round of afternoon showers
and thunderstorms possible on Friday under slightly warmer
temperatures. Further warming is anticipated on Saturday, when
storm coverage will mostly move to areas west of the Continental
Divide.

&&

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

$$

SHORT TERM...Lipson
LONG TERM...Skrbac
AVIATION...AEM
FIRE WEATHER...Lipson



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