Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 301145
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
545 AM MDT THU JUN 30 2016

.SHORT TERM...(Today through Saturday)
Issued at 400 AM MDT Thu Jun 30 2016

Main forecast concerns late this week and into the weekend will be
the potential for heavy rainfall through Friday night and strong
to marginally severe thunderstorms today. Had a cold front move
across the High Plains last night. This cold front has stalled
near the Laramie Range early this morning and seems to be located
just east of the city of Laramie at this hour. Believe the
position of this initial front will not change much today as a
backdoor front will move south and west across the area and stall
near the Nebraska/Wyoming border this evening. This will provide
very good LLVL convergence with high moisture content east of the
Laramie Range. Meanwhile...models show a weak disturbance aloft
slowly moving east across the area while PW`s remain between 1.00
to 1.50 inches. These features will combine to produce a fairly
widespread moderate to heavy rain event today through Friday. The
best chance of strong to severe thunderstorms will be today since
more sunshine is expected resulting in more LLVL instability. The
primary hazards will be hail and strong winds...but heavy rainfall
and flash flooding is starting to become more of a
concern...especially near the Colorado border this afternoon and
this evening. It will be cooler today with highs in the 70`s to
low 80`s. Showers and isolated thunderstorms may continue through
midnight tonight. If the rainfall ends with clearing skies towards
sunrise Friday morning...may see some patchy fog before showers
and thunderstorms quickly redevelop on Friday.

Similar conditions are expected Friday afternoon with high
temperatures struggling to reach 70 degrees across most of the
forecast area...although some locations along and near the Pine
Ridge and Cheyenne Ridge may struggle to reach 65 during the day
due to persistent low clouds and fog. Given the time of the
year...decided not to lower temperatures any further since even a
few peaks of sunshine will push temperatures into the 70`s.
Although it will be cooler...PW`s will be even higher on Friday
with plenty of instability as a stronger upper level disturbance
slowly moves over the area. May see some moderate to heavy
rainfall amounts out of these two events through Friday night...so
will have to closely monitor the potential for flash flooding.
Increased POP between 50 to 65 percent across most of the area
with the exception of the lower elevations across Albany and
Carbon county.

Saturday will be a slight improvement as the upper level
disturbance will push over the area and eventually east. Some
drier air aloft will move into the area but there will still be
plenty of moisture and instability south of the North Platte River
valley. Expect another round of scattered showers and
thunderstorms along and south of the I80 corridor.

.LONG TERM...(Sunday through Wednesday)
Issued at 330 AM MDT Thu Jun 30 2016

Hot and dry conditions return to the region for the end of the
holiday weekend and into the middle of next week. Weak
west/southwest flow aloft will prevail as main belt of westerlies
is shunted north of the area. Medium range models are consistent
with diurnally driven convective chances in and around the
southeast Wyoming mountains both Sunday and Monday. Do not expect
much coverage given weak progd instability params, but should at a
minimum see afternoon build-ups each day. Otherwise, heights will
be on the rise early next week as four corners high becomes re-
established amplifying the llvl thermal ridge amplifies. These
warmer mid-level temps should keep a lid on convective chances
ovr the plains. H7 temperature progs soar to 16-18C by the middle
of next week. This will easily yield mid/upper 90s ovr lower
elevations of SE Wyoming and the western Nebraska Panhandle. Would
not be at all surprised to see triple digit heat ovr parts of the
western Nebraska Panhandle and North Platte River Valley Tue-Wed.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 538 AM MDT Thu Jun 30 2016

An active upcoming period at most southeast Wyoming and western
Nebraska terminals as thunderstorms develop 16-20z. Thunderstorm
coverage will be greater compared to recent days so felt confident
in adding -TSRA as the predominating condition for a time this
afternoon. The exception will be at KRWL, where coverage will
likely be a bit less, thus greater uncertainty exists. Although a
few storms may become strong, do not anticipate widepsread severe
activity. Very heavy rain is anticipated with these thunderstorms
especially at KLAR, KCYS, KBFF and KSNY. Convection will gradually
dissipate this evening, with the potential of fog developing. So,
VFR conditions initially will give way to MVFR in thunderstorms.
May see some localized IFR in fog later tonight.

&&

.FIRE WEATHER...
Issued at 301 AM MDT Thu Jun 30 2016

Fire weather concerns will be minimal through early next week as
a wet and cool weather pattern will prevail through this weekend.
There is a good chance for widespread wetting rainfall today
through Friday night across the area. Drier and warmer weather
is expected by early next week and possibly as early as Sunday as
an upper level ridge builds over the central Rockys.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.

&&

$$

SHORT TERM...TJT
LONG TERM...CAH
AVIATION...CAH
FIRE WEATHER...TJT



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