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Area forecast discussion 
National Weather Service Cheyenne Wyoming
323 PM MDT Tuesday Jul 7 2015

Short term...(this evening through Thursday night)
issued at 300 PM MDT Tuesday Jul 7 2015

Showers and thunderstorms are becoming more prevalent through the
afternoon along and west of the Laramie range as the shortwave
evident on water vapor approaches from the west. AMSU-SSM/I
precipitable water plots show precipitable water values roughly 100-120% of normal
over our forecast area...with deep layer mean winds of 10-15 kts
analyzed across southeast Wyoming. Low/middle clouds thinned quite a
bit over southeast Wyoming through the late morning and early
afternoon as well...allowing some sunshine to reach the surface. As
a result...sbcapes of 500 to 1000 j/kg are currently over southeast
Wyoming from east to west...with much less over the Panhandle where
low/middle level clouds are much slower to break up. With this
combination of parameters...expect much of the convective activity
to remain over southeast Wyoming especially from the Sierra madres
eastward toward the Laramie range where orographic forcing and
combines with shortwave energy. Still thinking that some storms
could become strong over this area with instability...light
winds...and high precipitable waters in place...so small hail and heavy rainfall
are still a high possibility. Therefore...maintained the Flash Flood
Watch as is for the possibility of over an inch of new rainfall in a
short amount of time over already saturated soils in these areas. A
few showers/storms could trek eastward into the Nebraska Panhandle
as well this evening so kept a 20-40 percent chance here...although
rainfall from this activity should be much less. Low level south-
southeasterly flow across the eastern plains will likely redevelop
upslope fog and drizzle over the Laramie range...but not confident
with timing nor how low visibilities will go due to expected
intermittent convection overnight so will hold off on any fog
advisories for now.

Wednesday continues to look active with another shortwave trough
moving up from the southwest. The focus for stronger activity looks
to push further east closer to the Laramie range...although heavy
rain is still a possibility over the higher peaks of the snowies and
Sierra madres. Still thinking will need to reissue flash flood
watches for tomorrow but it will ultimately depend on todays
activity.

Thursday continues to look drier overall with shortwave ridging and
warmer temperatures moving overhead...however higher instability of 500-
2000 j/kg is prognosticated over a broader portion of the County Warning Area while a
shortwave moves overhead midday...so will still see showers and
storms develop in the late morning and continue through Thursday
evening.

Long term...(friday through monday)
issued at 300 PM MDT Tuesday Jul 7 2015

It will be a mostly warm and dry extended period as the
subtropical ridge strengthens to the south of the area.
Strong southwesterly flow aloft will be in place on Friday with a
drier airmass moving into areas west of the Laramie range. There
is some disagreement between the GFS and European model (ecmwf) over the amount of
afternoon and evening convection across the plains with the wetter
European model (ecmwf) likely overdone. Kept probability of precipitation below 30 percent for now. The Lee
trough will really become established by Sat with the best
moisture and instability pushed well east of the County Warning Area. It will be a
breezy day to the west of the Laramie range as 700mb winds of
25-30 kts mix down. Not much change for Sunday with dry westerly
boundary layer flow in place. With precipitable water values generally below 0.5
inches over the entire County Warning Area on Sat and sun...will have trouble
getting much if any convection going. Temperatures will warm back up to
around normal for middle July by this weekend. Heights aloft continue
to rise over the intermountain west into early next week with the break
in the monsoonal storms persisting.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1148 am MDT Tuesday Jul 7 2015

Mainly VFR conditions through the evening. MVFR visible in haze/smoke
will continue at cys over the next few hours. Scattered showers
and thunderstorms will develop through the afternoon across
southeast Wyoming. Brief MVFR visible will be possible in heavier rain
showers. South to southeast winds will gust to 15-25 kts through
the early evening across the plains.

&&

Fire weather...
issued at 300 PM MDT Tuesday Jul 7 2015

Widespread showers and thunderstorms will continue through the
afternoon and evening as a weather disturbance and plentiful
moisture move over the district. Some of this activity could produce
very heavy rainfall mainly over southern portions of Carbon and
Albany counties where flash flooding is possible. Wednesday will see
another round of moderate to heavy rain from showers and
thunderstorms...with some of the heavier activity possibly affecting
areas further to the east toward the Laramie range. Temperatures
will remain below normal through the end of this week but will trend
warmer over the weekend as high pressure begins to build overhead.
Conditions will trend drier as well through the weekend. As a result
of cooler and wet conditions...no fire weather concerns are
anticipated in the near term.

&&

Cys watches/warnings/advisories...
Wyoming...Flash Flood Watch until midnight MDT tonight for wyz109>116.

NE...none.
&&

$$

Short term...rjm
long term...zf
aviation...zf
fire weather...rjm

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