Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 290545 CCA

Area Forecast Discussion...CORRECTED
National Weather Service Cheyenne WY
1135 PM MDT THU JUL 28 2016

Issued at 921 PM MDT Thu Jul 28 2016

Shower and thunderstorm chances are looking fairly minimal tonight
due to the influence of surface high pressure providing good
subsidence over the region tonight. Still looking at some fog along
the Cheyenne Ridge and portions of the Nebraska Panhandle.

UPDATE 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 06Z TAFS through 06Z Friday night)
Issued at 1129 PM MDT Thu Jul 28 2016

Moist boundary layer and light winds will promote the development of
low clouds and fog with MVFR to IFR conditions especially from the
south Laramie Range east along the Cheyenne Ridge including Cheyenne
and Sidney between 09Z and 16Z. Patchy MIFG possible elsewhere
across the plains overnight. Afternoon tstorm coverage will be
isolated to widely scattered, mainly along and east of the Laramie
Range Friday. Included VCTS except Rawlins after 20Z. Gusty/erratic
winds and small hail will be possible with some of the tstorms.


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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