786
FXUS65 KCYS 021713
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1113 AM MDT Sun Jun 2 2024

.KEY MESSAGES...

- Numerous showers and thunderstorms are expected across all of
  southeast Wyoming and the western Nebraska Panhandle today. Strong
  to locally damaging wind gusts will be the main convective
  hazard, mainly from late morning through late afternoon.

- Elevated to high winds will be possible across the Arlington wind
  prone and south Laramie Range foothills and I-80 Summit
  Tuesday and Wednesday. A High Wind watch may be needed.

- Above normal temperatures likely Tuesday through Thursday as temperatures
  climb into the mid to upper 80s across much of the region.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 415 AM MDT Sun Jun 2 2024

Convection is finally wrapping up across the area as the lift
associated with the latest vorticity maximum moves out to the
east. High clouds and moisture can be seen on satellite ejecting
across western Nebraska. The break will not be long-lived
though. The broad but low amplitude trough axis is nearing the
area and will finally push through later today and bring another
round of showers and thunderstorms. This trough has supported
the development of a modest surface cyclone in the lee of the
Bighorns in NE WY/SE MT. The low and associated surface trough
extending southward along the front range will push eastward
this morning as a cool front, pushing the dryline mostly east of
our area and ushering in west to northwest winds at the
surface. Recent guidance has trended faster with this, which
will lead to an earlier than usual max temperature today and
also inhibit the heating potential somewhat. Convection will
kick off early today, perhaps as early as 11AM with scattered to
numerous showers and storms expected to cover much of the area
by mid afternoon. While the low-levels will be fairly dry,
precipitable water is above normal for this time of year thanks
to good moisture between about 600 and 200 mb. Vertical wind is
decent, but mostly speed shear as winds will be more or less
mostly westerly through the column. These parameters and HiRes
guidance indicate the potential for upscale growth into linear
systems as the afternoon progresses. Storms will be capable of
producing isolated to scattered strong to severe wind gusts.
Isolated hail reports are certainly possible, but wind is the
primary concern today. A more favorable environment for severe
storms will be located just east of our forecast area, so we
will be watching for more diverse storm hazards in the eastern
row of counties where low-level moisture is better and there is
some directional wind shear. On the bright side, this should not
be a very long duration event, as the trough axis should pass
through between 6 and 8PM and shut off the primary lifting
mechanism behind. A few showers may linger into the evening, but
the severe threat should be concluded by then.

Again, the break won`t be very long as this next shortwave races out
to the east and another strong but low amplitude wave drops into the
Pacific northwest tonight. However, considerable warm air advection
aloft overnight into tomorrow morning will result in reduced mid-
level lapse rates on Monday and fairly minimal instability. While
synoptic lift should still be enough to kick off shower activity
along and ahead of the next front, severe convection is fairly
unlikely. However, the marginal instability should be enough to have
embedded thunderstorms. Monday will also be a fairly late show,
since it`s more related to the synoptic cold front which will arrive
in the evening. Look for activity to develop over our western zones
in the late afternoon and progress eastward through about midnight.
This trough will be more potent than the preceding ones, leading to
a return of the gusty winds across the area. Elevated to near high
winds will start as early as Monday night, but more information on
this is found in the long term section below.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 415 AM MDT Sun Jun 2 2024

The first half of the long term forecast period will be quiet in
terms of precipitation chances, but we could see a period of
elevated to high winds impacting the both the wind prone regions and
locations along and east of the Laramie Range Tuesday and Wednesday.
A strong shortwave trough will pass north of the region and at the
base of this trough axis will be a band of 50-55kt 700mb winds that
will be located across Wyoming. This flow will also be out of the
west which is typically a good vector for our region to see some
elevated wind gusts. Tight MSLP gradients located across the Laramie
Range will be the driving force for the high winds across the
Arlington wind prone and the I-80 Summit. In house model guidance
still show greater than 50 percent probabilities for high wind gusts
for Arlington and the south Laramie Range location Tuesday and
Wednesday. If trends hold, a High Wind Watch may be needed for those
areas where the confidence is highest for wind gusts greater than 58
mph will occur. Areas along and east of I-25 across SE Wyoming could
see breezy conditions through this time period, but high winds are
not anticipated at this time.

Temperatures during this period wil also trend to above normals for
much of SE Wyoming. These temperatures may also be boosted by the
warm and dry downslope winds that will be ongoing. Current forecast
shows temperatures int he mid 80s holding steady Tuesday through
Thursday across much of SE Wyoming and the Nebraska Panhandle. With
these warmer than average temperatures and gusty winds, there is
some concern for some fire weather conditions to materialize during
the afternoon hours.

Heading toward the end of next week, ridging builds aloft which will
keep the forecast predominately dry and warm but there is a chance we
could see some afternoon diurnal convection over the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1109 AM MDT Sun Jun 2 2024

Scattered rain showers and thunderstorms will sweep through the
area quickly this afternoon. VFR is expected at all terminals,
with brief fluctuations to MVFR when VCTS and TSRA bring VIS
reductions and gusty winds at times between 18z and 0z today.
Wind gusts could approach severe thresholds, so AMD may be
necessary at times this afternoon for some terminals. Please see
individual TAFs for further information.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...MN
LONG TERM...AW
AVIATION...BW