Weather Service Report

FXUS65 KCYS 302118

Area Forecast Discussion
National Weather Service Cheyenne WY
318 PM MDT THU JUN 30 2016

.SHORT TERM...(This evening through Saturday)
Issued at 300 PM MDT Thu Jun 30 2016

.Short term...

Tonight...At mid afternoon, we currently have isolated to scattered
showers and thunderstorms across our counties. Precipitable water
values this morning ranged from 120 to 170 percent of normal.

NAM depicts a slow moving shortwave moving east across southern
Wyoming overnight with deep moist low and mid level upslope
southeast winds advecting deep moisture into southeast Wyoming and
western Nebraska. Meanwhile, looking at the mid levels around 700
mb, we are seeing moderate to strong warm air advection looking at
the winds blowing perpendicular to the impressive 700 mb theta-e
ridge axis. With this in mind, expect scattered to numerous showers
to develop overnight, with best areal coverage over southern Albany
and Laramie counties of Wyoming and over the southern Nebraska
panhandle. Based on slow movement of storms, some storms may produce
locally heavy rain and possible flooding. Also, please see Mesoscale
Precipitation Discussion 399 issued at 158 pm MDT from the Weather
Prediction Center discussing the possibility of flash flooding.
Where rain is less prevalent, patchy areas of fog will form. 

Thank you to NWS Denver/Boulder for their coordination on
expected rainfall event tonight and Friday.

Since we have not yet had widespread heavy rain the past few days,
have decided to hold off for now on a flash flood watch, and have
briefed our evening shift team who can see if and where showers and
thunderstorms develop to assess the best location for a possible
flash flood watch.

Friday...Slow moving shortwave moves east across eastern Wyoming,
and with a nearly saturated airmass in place over our eastern
counties, expect numerous showers and scattered thunderstorms
producing locally heavy rain due to slow movement of storms. Lesser
POPS further west where the atmosphere is less moist and lift will
be less prevalent. Lowered maximum temperatures from Laramie to
Cheyenne to Kimball and Sidney, under guidance, where low clouds and
rain will hamper warming significantly.

Friday night...With the shortwave moving further east of our
counties, lift will gradually wane with decreasing low and mid level
moisture, thus most rain chances ending from west to east.

Saturday...Shortwave ridging develops over western Wyoming. With a
more stable airmass in place, much of our eastern counties should be
shower and thunderstorm free in the afternoon. However, looks like
enough low and mid level moisture along a theta-e ridge over our
western counties for a chance of afternoon showers and thunderstorms.

.LONG TERM...(Saturday night through Thursday)
Issued at 300 PM MDT Thu Jun 30 2016

A warmer and drier weather pattern expected to set up over the CWA
this period as the upper high over the southern Rocky Mtns weakens
and drifts a little southeast. The stronger westerlies currently
along the US/Canadian border will sink a bit to the south turning
the flow over the CWA more westerly. This will shunt the monsoonal
moisture south of the CWA by early next week while the surface
flow becomes more westerly as well. This will bring warmer weather
for next week and keep convection more isolated in nature...and
primarily early in the period.


.AVIATION...(For the 18Z TAFS through 18Z Friday morning)
Issued at 1125 AM MDT Thu Jun 30 2016

VFR over all terminals through the early part of this evening
outside of sctd tstms which will bring periods of MVFR vsbys.  More
widespread MVFR/IFR cigs with areas of fog later this evening and
overnight as moist upslope flow occurs. 


Issued at 300 PM MDT Thu Jun 30 2016

Minimal concerns through the weekend due to expected
widespread rain, relatively high humidities and light winds.
Concerns increasing again for the July 4th through Thursday period
as temperatures warm, humidities fall and winds increase somewhat.


.CYS Watches/Warnings/Advisories...



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