Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 280011 CCA
AFDCYS

Area Forecast Discussion...CORRECTED UPDATE
National Weather Service Cheyenne WY
606 PM MDT SAT AUG 27 2016

.UPDATE...for the early evening aviation forecast update.

Previous UPDATE issued at 602 PM MDT Sat Aug 27 2016

We issued a quick update to introduce some patchy radiation fog in
the grids late tonight mainly along and east of an Alliance to
Sidney line. This fog not be as widespread as last night due to
limited low level moisture and more subsidence in place.
Otherwise, current forecast looks to be on track.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 243 PM MDT Sat Aug 27 2016

A drier and more subsident pattern will remain overhead the next
couple of days. For today, humidities are slowly falling early
this afternoon with many obs out west showing RH values in the
upper teens to low 20s. Wind gusts are generally in the 20-30 mph
range along and west of the Laramie Range, with a few spots
including KRWL a few mph higher. Still thinking we`ll see Red Flag
conditions over the next few hours as humidities continue to fall
and winds remain gusty. Will have to keep an eye on lower
elevations of FWZ 309 as conditions here could be close to
critical. Otherwise, invigorated cu have developed over the high
mountains as well as sw-ne across Laramie County. These are the
areas to watch for showers and t- storms later this afternoon.
Status quo for Sunday, except winds through the mixed layer should
be weaker with mid and upper level RH higher. This should help
keep fire weather concerns minimal while improving chances for
showers and perhaps a weak t-storm or two near the Colorado border
in south-southeasterly upslope flow. A stronger wave moving into
Colorado on Sunday and Monday will turn winds to the east-
northeast across the forecast area through nearly 500 mb, so a
better fetch of moisture and deeper upslope flow should bring a
broader coverage of convection over the mountains and perhaps near
the Colorado border as well. Models vary some on location and
intensity of vort max tho, so some uncertainty exists whether
upper level dynamics will aide or suppress convection. Kept low
PoPs for now which seems to be the better consensus at this time.

.LONG TERM...(Tuesday through Saturday)
Issued at 243 PM MDT Sat Aug 27 2016

An upper ridge will be over the CWA Tuesday boding for warm and
dry weather. The ridge will slip slowly eastward Weds and
Thursday. As it does so moisture should increase across the region
allowing for some increase in convection for the latter part of
the week. Best chance would appear to be late Thursday as an
upper trof swings across the northern Rockies into the northern
plains and pushes a weak front across the CWA. Drier weather
returns Friday and Saturday under westerly flow aloft with better
moisture suppressed to the south. Temperatures holding a little
above seasonal norms through the period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 606 PM MDT Sat Aug 27 2016

Main aviation concern tonight is the potential for fog formation
in the Nebraska Panhandle like what we saw early this morning. The
boundary layer has dried out quite a bit today whereas yesterday
there was quite a bit of rain activity over the Panhandle that
moistened up the boundary layer going into the overnight period
with light winds. After full-on sunshine all day today, things
have dried out and we are thinking any fog formation will be in
Sidney and Alliance and of the lighter MVFR category variety. NAM
has a predeliction for over-forecasting fog and looking at the
RAP, NAM and GFS soundings thinking is MVFR would be the more
likely result there. For the rest of the area across SE Wyoming
and the western Nebraska Panhandle we are thinking VFR category
will prevail next 24 hours with light southwest to west winds.

&&

.FIRE WEATHER...
Issued at 240 PM MDT Sat Aug 27 2016

Humidities are steadily falling this afternoon with many obs out
west showing RH values in the upper teens to low 20s. Wind gusts
are generally in the 20-30 mph range along and west of the
Laramie Range, with a few spots near the mountains a few mph
higher. Still thinking Red Flag conditions will prevail through
the afternoon for many locations along and west of the Laramie
Range, in addition to western Converse County, as humidities
continue to fall and winds remain gusty. Will have to keep an eye
on lower elevations of FWZ 309 as conditions here could be close
to critical. Conditions will improve by mid-evening. Although
temperatures are expected to be warmer and humidities less on
Sunday, winds look less as well. Winds turn east for Monday which
will suppress fire weather concerns.

&&

.CYS Watches/Warnings/Advisories...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ301>304-306-
     308.

NE...None.
&&

$$

UPDATE...REC
SHORT TERM...RJM
LONG TERM...RE
AVIATION...JG
FIRE WEATHER...RJM


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