Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Cheyenne Wyoming
1119 am MDT Friday Jul 3 2015

Short term...(today through sunday)
issued at 335 am MDT Friday Jul 3 2015

Current kcys radar loop shows convection lingering into early
this morning once again as a 75 knot jet streak aloft translates
into southeast Wyoming from the north. A pretty strong cluster is
currently located near Fort Laramie and Wheatland...moving
southeast. Believe these isolated cells will continue over the
next few hours as they move southward into Colorado. Can not rule
out more cells developing just east of the Laramie range this
morning as well due to elevated cape. Expect a brief lull in the
thunderstorm activity sometime later this morning through noon
today. High temperatures will be warm for the beginning of the
Holiday weekend...with readings in the 80s. Thunderstorms will
redevelop by this afternoon with a few becoming strong late this
afternoon. Kept pop between 20 to 25 percent outside the mountains
for isolated to widely scattered coverage into tonight. Would not be
surprised if this activity continues through the night over the
High Plains Friday night due to jet dynamics aloft.

Next potential for strong or severe thunderstorms will be
Saturday as temperatures increase into the upper 80s to middle 90s
once again. Ample moisture will remain over the High
it has since may with dewpoints likely in the 50s to middle 60s.
Kept pop between 10 to 20 percent for now due to model
differences...even though model soundings do indicate high cape
values over 2000 j/kg and lowering cin through the afternoon over
western Nebraska. However...any thunderstorms may be very isolated or
further to the northeast due to an approaching upper level ridge
axis and drier air aloft.

All models indicate an approaching Canadian cold front digging
southward on Sunday. This front is pretty strong for this time of
the year with 700mb temperatures lowering to 0c late on Sunday
just north of the forecast area. This frontal boundary will
interact with upslope flow and ample low to midlevel moisture
across the area...producing scattered to numerous showers/thunderstorms
through the day on Sunday. High temperatures will likely occur in
the late morning or around noon...and then fall into the 70s
through the day. Increased pop between 30 to 50 percent for the
high valleys and High Plains...with values near 70 percent for the

Long term...(sunday night through thursday)
issued at 400 am MDT Friday Jul 3 2015

Weak upper ridge over the southwest Continental U.S. Will flatten out Sunday
night as a rather strong northern stream wave moves across Montana
and into the northern plains. The shortwave trough will extend
southward into Wyoming and Nebraska Sunday night. This trough will
push cooler air into the area and likely produce showers and
thunderstorms across much of the area Sunday night.

Monday will be on the cooler side as rain cooled air and light
easterly upslope flow will be in place. Chances for showers and
thunderstorms east of the Laramie range will be suppressed Monday
by a stable low level air but along and west of the Laramie range
daytime heating will likely produce a few showers and

Temperatures to rebound Tuesday as westerly flow aloft develops
but low level winds will remain southerly with a surface Lee
trough along The Rockies. This means the chances for showers and
thunderstorms will continue. Could even see another shortwave
trough impact the area by Tuesday night into Wednesday with even
more showers and thunderstorms and another shot of cool air.

At this time not seeing any big chances in the over all pattern
that will lead to drier conditions. If anything late next week
could be even wetter. Models are showing the cutoff low currently
west of the California coast shifting east to northeast across the
western Continental U.S. Late next week.


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1117 am MDT Friday Jul 3 2015

VFR conditions predominantly. Used latest hrrr forecast for timing
on convection at kcys and klar this afternoon. Hrrr suggesting the
possibility of late night convection once agian that could impact
kbff and ksny overnight. For now...went with thunderstorms in the vicinity wording in their
tafs. Will try to narrow down timing as the event gets closer.


Fire weather...
issued at 246 am MDT Friday Jul 3 2015

No fire weather concerns in the foreseeable future with nearly
daily chances for afternoon and evening showers and
thunderstorms. Winds will remain generally light...though briefly
gusty around storms. A monsoon pattern may set up next week which
will keep chances for showers and storms in the forecast.


Cys watches/warnings/advisories...


Short term...tjt
long term...small
fire weather...tjt

National Weather Service Glossary of Abbreviations