Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

000
FXUS65 KCYS 280238 AAB
AFDCYS

Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
838 PM MDT Sat May 27 2017

.UPDATE...
Issued at 838 PM MDT Sat May 27 2017

Mid evening update package sent which removed PoPs for the rest of
tonight. Currently watching some showers that have developed along
a weak shortwave moving down through the Black Hills area, with
concern that we might need some PoPs across the northern Nebraska
Panhandle late tonight. However NAM and HRRR both have a decent
handle on the past and near term evolution of that activity, and
they both dissipate it as it moves south of the Black Hills with
further loss of instability. Will continue to monitor that, but
for now will continue with no showers late tonight in the
northeast.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 237 PM MDT Sat May 27 2017

With weak instability in place, will continue to see scattered
showers and isolated tstms over the next few hours, before
activity decreases around 00Z with the loss of daytime heating.
Cannot rule out pea sized hail with the heavier showers with the
low freezing levels. The shortwave wave trough axis that is
currently overhead will move southeastward into Kansas by tonight.
Northwesterly flow aloft will dominate the pattern through early
next week. Highs will rise around 10 degrees on Sunday, back into
the 60s to low 70s for areas to the east of the Laramie Range.
There will be enough aftn instability (CAPE values of 100-200
J/kg) for at least isolated to scattered showers/tstms to develop,
although the activity looks less than today across the plains. A
weak front will push across the region on Sunday night, with llvl
winds becoming more easterly/upslope along the southern Laramie
Range. All models show more storm activity in Albany/Laramie
counties by Monday aftn in an area of enhanced sfc convergence.
Thus, will show higher PoPs 30-40 percent for Monday. Outside of
some breezy northerly winds through the remainder of the aftn,
winds will be rather light in the short term period.

.LONG TERM...(Tuesday through Saturday)
Issued at 237 PM MDT Sat May 27 2017

Upper ridge over the western US at the start of the period will
migrate very slowly eastward and be positioned roughly over the
central and northern Rockies by Thursday. Temps will be gradually
warming each afternoon through Thursday with Thursday likely being
the warmest day. Chance for afternoon showers and thunderstorms
will return by Wednesday mainly over the mountains and possibly
over the plains as some mositure return gets going in S`ly to
SE`ly boundary layer flow. GFS might be a little over aggressive
with the amount of precip generated in this environment especially
in the evening/overnight hours with only weak forcing from minor
shortwaves traveling through the mean ridge and weak flow aloft.
Should be a fairly robust cap in place with 700 mb temps progged
at 10-12 C on the GFS and EC. Trimmed POPs back to slight chance
Wednesday and Thursday over much of the area outside of the
mountains. Model difference become much larger after Thursday with
the EC maintaining significant ridging aloft and warm conditions
through Sat with only slight chances for afternoon convection. GFS
allows stronger shortwave energy to flatten the ridge with much
higher chances for storms along the front range.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 631 PM MDT Sat May 27 2017

Isolated showers & t-storms persist mainly in the vcnty Laramie
Range and west-central portions of Nebraska Panhandle. Expect this
activity to continue through sunset before diminishing. Gusty
north to northwest winds will ease with sunset as well. Sunday
will see a similar pattern as today, except shower activity should
hold off until after 18Z.


&&

.FIRE WEATHER...
Issued at 237 PM MDT Sat May 27 2017

No fire weather concerns through early next week.  Temperatures will
warm to back around normal over the next few days.  However, minimum
afternoon humidity values will mostly remain above 25-30 percent.

&&

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

$$

UPDATE...JG
SHORT TERM...ZF
LONG TERM...DEL
AVIATION...RJM
FIRE WEATHER...ZF



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.