Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 160431

Area Forecast Discussion
National Weather Service Cheyenne WY
1031 PM MDT Sat Jun 15 2019

.SHORT TERM...(This evening through Sunday night)
Issued at 203 PM MDT Sat Jun 15 2019

As of 2 PM MDT, showers and thunderstorms seem to be restricted
to the mountains. As predicted, some of these storms are putting
down quite a bit of precipitation with 1 hour accumulations of
about 0.5 to 1 inch; this includes the North Laramie Range, and
the east sides of both the Snowys and the Sierra Madres. Over the
next 2 hours, showers should start to shift east. HiRes models
indicate that lines of heavy showers and thunderstorms will move
off the Laramie Range and move across the High Plains by 4 PM MDT,
dissipating around 9 PM MDT. Biggest threat for today will be
heavy rain, pea sized hail and gusts to about 25 mph.

Quiet conditions expected overnight, except for a band of heavy
moisture expected across east-central Wyoming as a shortwave
pushes west to east across the High Plains. An interesting set up
in store for tomorrow. A shortwave will pass through the region
from the northwest to the southeast. As it moves through, its
associated frontal boundary will slowly move from north to south
with an upslope flow pulling dewpoints over the High PLains into
the 40s and 50s. This will provide ample moisture to the
concoction that will allow for strong to severe storms to develop
along and within the vicinity of the frontal boundary over the
course of the afternoon and evening before it heads south and east
and out of the region. CAPE values will jump to near 1000 J/kg in
the afternoon, lapse rates will become modestly steep in the
midlevels and effective shear of 25-40 kts will make for a
marginally severe atmosphere capable of producing damaging winds,
and large hail. Heavy rain will also remain an issue, especially
if more than one storm moves over the same area, one after the
other. The severe threat should be limited to an area generally
south and east of an Crawford-Fort Laramie-Buford line. To the
west, looking at isolated to scattered heavy showers, mainly east
of Carbon County, as most of the moisture and energy within the
atmosphere gets sucked to the eastern boundary. Showers and
thunderstorms will dissipate around 9 PM MDT.

.LONG TERM...(Monday through Saturday)
Issued at 203 PM MDT Sat Jun 15 2019

A stronger shortwave will pass through the region on Monday
bringing widespread heavy showers and thunderstorms to the High
Plains and it`s western mountains. As the precipitable water
anomaly climbs to about 0.75 inches above normal and dewpoints to
about 40 deg to the west and 60 deg to the east, heavy showers
will become quite common across the region. Models are indicating
that the heaviest showers will be located along the Colorado
border. For those watching the flow levels along the North PLatte
River at Saratoga, this day has the potential to be the most
impactful day in the period. Tuesday will bring another round of
heavy showers, but by Wednesday, the region begin to dry out as a
ridge of high pressure builds along the California coast and a
mostly day northwest flow aloft sets up over the region. A few
passing afternoon and evening showers are expected through the
end of the week, but nothing notable until the end of the period
when another trough pushes down into the area, bringing a
potentially strong surface front with it.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1027 PM MDT Sat Jun 15 2019

Looking at two periods of possible thunderstorm activity over the
next 24 hours. First moves through Douglas/Lusk area Sunday
morning and eventually impacting KCDR and KAIA after 16Z or so.
These storms transition east fairly quickly by 18Z or so. Next
round of thunderstorms looks to be more widespread...beginning
over southeast WYoming near KLAR and KCYS around 18Z. These storms
expected to be more widespread and will move into the Panhandle
after 20Z or so. Southeast upslope flow event Sunday evening into
Monday...which may bring lowering ceilings to airports east of the
Laramie Range.


Issued at 203 PM MDT Sat Jun 15 2019

Fire concerns remain low this week as the region remains wet under
a moist flow. A ridge will build along the California coastline
by Wednesday, allowing a drier northwest flow to set up over the
region. This will bring humidities down to about 20% across Carbon
County and to the 25-30% range along and west of the Laramie


Issued at 203 PM MDT Sat Jun 15 2019

Hydrologic concerns will prevail for the Upper North Platte and
Laramie Rivers and their tributaries with a ripe high elevation
snow pack and increasing chances for rain on snow melt this weekend
into early next week. Latest RFC forecasts maintain minor flood
potential near Saratoga and along portions of the Laramie Watershed.
Current model QPF indicates the potential for significant precipitation
above 9000 feet in the form of rain with daytime temperatures in the
50-60s and low temperatures around 37 degrees. Runoff due to
saturated soils will likely cause streams and rivers to rise this
weekend and early next week. A River Flood Warning remains in
effect for the Upper North Platte River near Saratoga. Additional
flood watches and warnings may be required with the potential for
slow moving heavier convection.




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