Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 290052

Area Forecast Discussion
National Weather Service Cheyenne WY
652 PM MDT THU JUL 28 2016

Issued at 644 PM MDT Thu Jul 28 2016

Latest radar loop was showing the convection continuing to fester
in Laramie county. These storms are having a hard time pushing
east due to limited instability and more subsidence. As a result,
we are not expecting much in the way of widespread convection
tonight. In fact, we went ahead lowered precipitation chances in
the northern areas.


.SHORT TERM...(This evening through Saturday night)
Issued at 245 PM MDT Thu Jul 28 2016

It is still rather stable for areas to the east of the Laramie
Range.  The SPC mesoanalysis shows quite a bit of CIN (100-150 J/kg)
across Laramie county and extending eastward into the southern
Panhandle.  The svr storm threat this aftn/evening is looking more
and more uncertain as the strong outflow from this mornings
convective complex have stabilized things quite a bit. Cumulus is
father flat on visible imagery. Latest runs the RAP have backed
off on instability along the Colorado Border and HRRR shows only
isolated convection over Laramie county by 00z. Deep layer shear
of around 50 kts is more than sufficient to get rotating updrafts
should convective initiation occur in areas near the southern
Laramie Range. Being less confident about the svr storm potential,
went ahead and removed large hail and damaging winds from the
grids and reduced pops overall through the evening. Light
southerly winds may cause areas of fog to develop by late tonight
in areas along Interstate 80.

Northwesterly flow aloft will continue through Saturday across
the region as the midlvl ridge center is located near northern
Arizona. Southeasterly winds across the plains will keep llvl
moisture high. Cannot rule out a strong to svr storm during the
aftn/evening with good bulk shear and instability. Better warming
will promote higher CAPE values on Saturday with the GFS showing
2000 J/kg over the Nebraska Panhandle. Overall storm coverage will
remain mostly isolated however through the weekend. The warmest
day will be Sunday with highs in the upper 80s to mid 90s.

.LONG TERM...(Sunday through Thursday)
Issued at 245 PM MDT Thu Jul 28 2016

Broad area of high pressure will slowly propagate east towards the
southern plains from the four corners through the period. This
will keep the main storm track and more organized precipitation
chances north of the area. As the high shifts east, mid/upper-
level flow will ever so gradually turn southwesterly which will
allow monsoonal moisture to begin to advect back towards the area
by the middle of next week, especially in the higher elevations.
Medium range guidance hints at another weak frontal passage
sometime on Tuesday or Wednesday of next week, which when combined
with increases in monsoonal moisture, should produce increases in
convective chances. Steering flow will remain fairly weak for the
first half of the period, which would limit convective strength.
These begin to increase towards the middle of the week, which may
add to afternoon thunderstorm organization and strength. Monday-
Tuesday will be the warmest days next week as afternoon highs
climb into the upper 80s and 90s across lower elevations. Minor
cooling is expected behind the cold front Wednesday-Thursday.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1214 AM MDT Thu Jul 28 2016

Initial thunderstorm complex that passed through western Nebraska
Panhandle sites has cleared the area. Cloud cover has been quick
to dissipate north of the North Platte River Valley...less so to
the south. Still think that the main concern to aviation ops will
be the expected redevelopment of thunderstorm activity later this
afternoon. Thunderstorm development and location will be heavily
dependent upon how quickly clouds break-up in the vicinity of the
higher elevations along with lingering outflow boundaries from the
morning convection. Confidence is not high enough to include
anything more than VCTS at this time. After thunderstorm threat
diminishes around 03z...will see low cigs/fog develop again late
tonight at KCYS...KSNY...KBFF...and KLAR.


Issued at 219 PM MDT Thu Jul 28 2016

No fire weather concerns through the weekend.  Minimum relative
humidity values will fall to 15-20 percent each afternoon across
Carbon county.  However, wind gusts will stay mostly below 20 mph.
Isolated to scattered thunderstorms will be possible most days,
mainly to the east of the Laramie Range.


.CYS Watches/Warnings/Advisories...


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