Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 200620
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1220 AM MDT Sat Apr 20 2019

.UPDATE...
Issued at 1216 AM MDT Sat Apr 20 2019


...Please see latest 06Z aviation discussion...

&&

.SHORT TERM...(This evening through Saturday Night)
Issued at 226 PM MDT Fri Apr 19 2019

Beautiful day across southeastern Wyoming and Western Nebraska
with clear skies and well above average temperatures. We have
upper level ridging to thank for the quiet weather through the
first part of the weekend. This ridging will continue through
Saturday with temperatures a touch warmer than today. This will
put daily highs 10 to 15 degrees above average in some spots. The
panhandle and far eastern Wyoming will likely breach the 80 degree
mark by mid afternoon.

Saturday afternoon and evening also look quiet with cloud cover
beginning to increase late. This cloud cover will develop in
response to approaching broad scale lift from a west coast trough.
A cold front will slowly meander down across Converse and
Niobrara counties late Saturday night. Gusty north winds will
develop and move south overnight. Some scattered showers may
develop along the front overnight saturday but the main brunt of
precip is not expected until Sunday afternoon and Monday morning.

.LONG TERM...(Sunday through Friday)
Issued at 226 PM MDT Fri Apr 19 2019

Models continue to be rather bullish on the chance for widespread
precipitation Sunday through early Tuesday. Large broad scale
lift from a west coast trough is expected to overspreads the
region early Sunday. A lee low and cold front will develop across
northern Colorado Sunday afternoon before ejecting onto the
plains Sunday night and Monday morning. Behind the front, a
subarctic high will drift to the southeast across the Dakotas.
This will drive initial isallobaric flow from north to south
across southeastern Wyoming. Gradual veering of the low level
trajectories is expected as the low shift further south and east.
This will drive a more orthogonal upslope component early Monday
morning. This low level lift will coincide with mid level ascent
and be the most likely time frame for moderate and potentially
heavy precipitation across southern Wyoming.

Ensembles GEFS EPS CMCE as well as deterministic guidance
continue to show a swath of 0.50 to 0.75 inches of QPF along the
front range of Colorado and Wyoming through Tuesday morning. The
broad nature of the upslope flow and the overall forcing does
support widespread precipitation but suggests that models may be
overdoing the QPF slightly. For this afternoon`s forecast
package, amounts were reduced slightly but will still be
significant enough to warrant attention over the next few runs.
Given the approaching spring snow melt and the warm temperatures,
rain on snow may be possible as temperatures look to remain warm
through the event. light snow is possible but with the warm
weather increasing, heavy snow accumulations are not anticipated.
This could stress stream and rivers which are already running
above normal thanks to a healthy snow pack. See Hydro section for
more details.

A brief return to Zonal flow is expected late Tuesday through the
end of the week. More active troughing will return again for the
weekend bringing additional chances for rain and snow. CPC
continues to call fr an above average wet period over the next 4
to 8 weeks. This could continue to cause some issues with
streamflows and snowmelt with snowpacks still remaining over 100%
in most places.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1216 AM MDT Sat Apr 20 2019

A quiet period overnight as winds have diminished. VFR conditions
expected to persist through the next six hours. Some elevated
showers may be possible across the far northern reaches of the
forecast area with little impact expected as of this forecast for
the terminals.

&&

.FIRE WEATHER...
Issued at 226 PM MDT Fri Apr 19 2019

Elevated fire conditions are possible this afternoon and
tomorrow. A warm and dry start to the period is expected with
temperatures well above average Today and Saturday. West winds
will bring drying in the afternoon along with some stronger gusts
which may lead to elevated fire conditions. Humidity values should
remain above critical values along with fuels remaining non
critical. A cold front will bring cooler and wetter weather
through the end of the week and into early next week.

&&

.HYDROLOGY...
Issued at 226 PM MDT Fri Apr 19 2019

Elevated precipitation chances are still on track with the latest
guidance suite. Sunday Monday and Tuesday will see the chance for
widespread precipitation with the potential for heavy
precipitation at times. While flooding is not anticipated, rain on
snow and additional runoff will likely cause streams and rivers to
run high for the next few days.

...PREV DISCUSSION

The threat for above average precipitation will continue through
the forecast cycle with the chance for moderate precipitation
early next week. Streamflows will likely remain elevated with low
potential for small stream flooding over the next 5 to 10 days. If
we see an increase in the precipitation amounts forecasted over
the next few days then streamflows will likely be higher as snow
melt begins to peak in the next few weeks.

&&

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

$$

UPDATE...WM
SHORT TERM...AL
LONG TERM...AL
AVIATION...WM
FIRE WEATHER...AL
HYDROLOGY...AL


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