Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 252253
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
453 PM MDT SAT JUN 25 2016

.SHORT TERM...(Tonight - Monday Night)
Issued at 326 PM MDT Sat Jun 25 2016

The latest KCYS radar loop shows numerous surface outflow boundaries
across Laramie county. This has already triggered a few showers and/
or weak thunderstorms along and south of I-80, so this forcing could
yield additional activity through early evening. Weak instability is
expected to limit storm coverage/intensity with maximum CAPES around
500 J/kg. Quasi-zonal flow aloft continues on Sunday with a few weak
disturbances traversing the flow. Upslope flow along and east of the
Laramie Range should bring dew points back into the mid/upper 40s on
the high plains before afternoon mixing yields some low-level drying
after 18z. Convective coverage should be higher tomorrow, but expect
another day of modest instability with very little risk for stronger
storms. Inverted-v sounding profiles with cloud bases between 10-15k
feet suggests gusty winds as the primary hazard, so can not rule out
a couple of 50 knot gusts. Better chances for more widespread severe
storms arrive on Monday with a stronger wave riding the edge of deep
upper-level ridging centered over the 4 corners. GFS and NAM suggest
dew points in the 50s to near 60 over the plains with good low-level
veering and MUCAPES around 2000 J/kg and 0-6 km shear vectors of 40-
50 knots. The combination of cooling temperatures aloft, convergence
in the low-levels, and surface upslope should support the initiation
of thunderstorms, some of which may rapidly become supercells. Day 3
SPC outlook has a SLIGHT Risk over the I-80 corridor, but should see
this expanded farther north and west in the future if model guidance
comes into better agreement. Overall temperatures should be near our
climatological normals with west to northwest flow in the mid-levels
over the CWA.

.LONG TERM...(Tuesday through Saturday)
Issued at 326 PM MDT Sat Jun 25 2016

The summer pattern will persist through much of next week as fairly
weak ridge axis remains centered ovr the four corners. Mid-level
moisture along with a series of disturbances will ride the top of
the ridge producing nearly daily mainly afternoon/evening shower and
thunderstorm chances. Instability and shear will be sufficient on
Tuesday and Wednesday for severe thunderstorm potential mainly in
areas along and east of the Laramie Range. Can`t completely rule out
strong-severe potential the other days either, but chances will be
less given limited progd shear parameters. Temperatures will be
right at seasonal normals next week as well with highs reaching
around 80F for locations above 5000 feet and 80s to near 90 for
elevations below.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 451 PM MDT Sat Jun 25 2016

Isolated thunderstorms in Laramie County should continue to move
east and not impact KCYS. Will continue to monitor though and
update as needed. All convection to end towards sunset...so kept
convection out of TAF sites for now. VFR conditions expected.

&&

.FIRE WEATHER...
Issued at 326 PM MDT Sat Jun 25 2016

Critical or near-critical fire weather conditions will continue this
afternoon and early evening for FWZ 301 with warm temperatures, very
dry air and gusty winds. Winds will be lower on Sunday and Monday w/
increasing chances for showers and thunderstorms especially over the
high plains.

&&

.CYS Watches/Warnings/Advisories...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ301.

NE...None.
&&

$$

SHORT TERM...CLH
LONG TERM...CAH
AVIATION...GCC
FIRE WEATHER...CLH



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