Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cheyenne Wyoming
1220 PM MDT sun Jul 5 2015
Short term...(today through tuesday)
issued at 402 am MDT sun Jul 5 2015
One more very warm day for far southeast Wyoming and much of the
Nebraska Panhandle...but it will be cooler into far northern and
western portions of the forecast area as increased cloud cover and
showers will hold temperatures down. By early afternoon and cold
front will being to move into northern portions of the forecast
area and should reach the Colorado border by this evening.
Widespread showers and scattered thunderstorms will develop this
afternoon as an upper disturbance moves into southeast Wyoming.
The main question is what is the potential for severe
thunderstorms today. Based on the latest BUFKIT soundings...robust
cape profiles this morning will quickly fizzle this afternoon as
the surface cold front stabilizes the lower levels of the
atmosphere. At the same time increasing Pacific middle level
moisture will serve to saturate the middle levels...further
decreasing the overall instability. Therefore thinking the severe
thunderstorm threat will be low today...especially with very
little shear through early afternoon. Expecting gusty winds and
small hail with the stronger thunderstorms with a few marginal
severe thunderstorms possible. Heavy rain is likely with some
storms but storms should move fast enough such that the flash
flood threat will be minimal in relative terms.
Monday will be cloudy and cool with most shower and thunderstorm
activity west of the Laramie range. A rain cooled boundary layer
will remain following Wednesday/Wednesday night precipitation.
Depending an how much cool air remains...forecast temperatures may
be a bit optimistic Monday. One change in the models Monday night
is they are hinting at a weak disturbance moving across southeast
Wyoming Monday night. Did not add probability of precipitation into the plains Monday
night but may need to eventually. A stronger disturbance will hold
off until late Tuesday but could bring the next shot of widespread
Long term...(tuesday night through saturday)
issued at 236 am MDT sun Jul 5 2015
Medium to long range models show a continuation of the unsettled
weather pattern into the middle part of next week...and are now
showing this wet unsettled pattern persisting into late in the
week as well...due to the absence of the upper level high. The
GFS and Gem were indicating anticyclonic flow developing across
New Mexico and Texas 24 hours ago...but now show the upper level
low around central California slowly drifting eastward across the
Great Basin and eventually towards the Continental Divide. There
is some potential of conditions to dry a bit by late this week and
next weekend...but given recent model trends of under estimating
bl moisture...not very confident with this solution at this time.
Currently...the European model (ecmwf) is closest to a "drier" solution...but even
the European model (ecmwf) shows some subtropical moisture advecting northward
across Colorado and Wyoming on Friday and Saturday.
Models show another cold front moving southward and stalling
along the Front Range. There is a decent chance of strong to
severe storms due to a combination of cool air aloft pushing into
the area...upper level divergence...and favorable 0-6km shear
profiles across the High Plains. Kept pop between 40 to 60
percent Wednesday afternoon and evening with a good chance of
moderate to high rainfall amounts over portions of southeast
Wyoming. Expect these conditions to continue into Thursday although
it will be considerably warmer compared to earlier in the week.
Going into next weekend...low confidence for this portion of the
forecast as models are showing completely different solutions
compared to 24 hours ago. Previously...all models were showing an
upper level high building south of the forecast area similar to
what the current 00z European model (ecmwf) run is doing this morning.
However...the GFS and most ensemble runs show the Pacific upper
level low stalling across Montana and Wyoming as more upper level
jet energy pushes across the Pacific northwest. The GFS shows the
upper level high much further south...centered along the Mexico
border. Kept pop between 10 to 20 percent with temperatures near
normal for this time of the year for now.
Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1220 PM MDT sun Jul 5 2015
Showers and thunderstorms are developing along the Colorado/Wyoming border at
18z and will move to the northeast over the next few hours. The
cold front is steadily moving south across central Wyoming and
South Dakota...and will initiate showers and storms as it moves
south across our forecast area through the afternoon. MVFR
conditions are likely in the heavier storms late this afternoon
and evening...with stratus developing overnight bringing the
possibility of IFR conditions along the Cheyenne Ridge. Rain will
continue at times overnight as well as a weather disturbance moves
overhead. Conditions should improve middle morning Monday.
issued at 236 am MDT sun Jul 5 2015
One more warm day across the plains ahead of a cold front which will
move across the area today. A bit cooler into south central Wyoming
as cloud cover increases along with developing showers and
thunderstorms. Showers and thunderstorms will become widespread by
late this afternoon and continue into the overnight hours as an
upper level trough and surface cold front move across the northern
rockies and into the plains. Mostly cloudy and much cooler for Monday
with a few showers and thunderstorms possible into south central
Wyoming and dry across the plains.
Unsettled weather will continue through next week with showers
and thunderstorms possible every day and likely into the overnight
hours many nights.