Area Forecast Discussion
Issued by NWS Cheyenne, WY

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297
FXUS65 KCYS 200000
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
600 PM MDT Fri May 19 2017

.SHORT TERM...(This evening through Saturday)
Issued at 325 PM MDT Fri May 19 2017

Record-breaking spring storm is finally easing across the area as
a broad upper level low is drifting eastward across northern
Colorado this afternoon. Still getting bands of rain or rain/snow
mix over the high plains, mainly due to some llvl convergence and
jet dynamics, but do not expect this activity to amount to much
over the next 6 to 12 hours into tonight with mainly bands of
light rain. Can not rule out some snow above 5500 feet, but
accumulations should be less than one inch through tonight.
Temperatures will be quite cold tonight across the area with lows
in the mid 20`s to mid 30`s. A few locations across southeast
Wyoming may see record low temperatures if skies clear out a bit
due to the deep surface snowpack. Added patchy fog in the Laramie
Valley towards Elk Mountain and along/just east of the Laramie
Range due to saturated conditions and relatively light winds.

For Saturday, other than a few showers around Sidney and Alliance
early in the morning, the major storm should continue to weaken as
it moves into the central plains. Skies will become partly to
mostly cloudy with some sunshine and cool temperatures. Highs will
remain below normal, but should still be 10 to 15 degrees warmer
compared to the last few days. A fast moving clipper system is
then expected to dig southeast late on Saturday across Idaho and
Montana, resulting in showers and isolated thunderstorms late in
the day, mainly west of I-25.

.LONG TERM...(Saturday night through Friday)
Issued at 300 PM MDT Fri May 19 2017

The upper low will drift northeast across Minnesota Sunday then
over the Great Lakes region early next week.  Several shortwaves
will rotate around this low clipping the CWA so rather unsettled
weather will persist through Tuesday with temperatures remaining
below average. Strongest system looks to pass across late Monday
with scattered showers and some higher mtn snow showers. Looking
rather breezy Monday as decent mid-level northwesterly flow mixes
down.  Upper ridging then moves by Tuesday through Weds bringing
dry and warmer conditions. The upper flow then flattens and
becomes more westerly by Friday maintaining mild to warm
conditions with some isolated showers possible Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 554 PM MDT Fri May 19 2017

The upper level low in northeast Colorado will continue to
to slowly spin its way east-northeast into Nebraska tonight into
Saturday. Latest radar loop was showing the back edge of the rain
covering much of the Nebraska Panhandle. This rain will slowly
come to an end as the evening progresses, but it will leave behind
IFR ceilings and even some fog at CYS and LAR. We will need to
keep an eye on these two sites for lower visibilities through at
least 06z or so. The rest of the panhandle may remain under IFR
ceilings through much of the night, before slowly clearing
Saturday morning.
&&

.FIRE WEATHER...
Issued at 240 PM MDT Fri May 19 2017

No Fire Weather concerns through next week due to recent heavy
precipitation and high humidities.

&&

.HYDROLOGY...
Issued at 240 PM MDT Fri May 19 2017

Concern this weekend will be mainly focused on the influx of
water into area creeks, streams, and rivers as a result of
yesterday and todays heavy precipitation event. Expect high
plains locations east of the Laramie Range to see these rises
first through the upcoming weekend as snow begins to melt.
Although flooding is not anticipated at this time, many of these
streams and creeks will be bankfull by early next week.
Fortunately, cool conditions will continue for the next week,
which should help slow the mountain snow melt and resultant flows
into the mainstem rivers. Will continue to watch these levels very
closely over the next few weeks.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...TJT
LONG TERM...RE
AVIATION...REC
FIRE WEATHER...TJT
HYDROLOGY...TJT



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