Area forecast discussion
National Weather Service Cheyenne Wyoming
745 PM MDT Thursday may 23 2013
Update...
issued at 745 PM MDT Thursday may 23 2013
The few showers over the west part of the County Warning Area have ended as of
0030z. Main issues for the rest of tonight will continue to be
the strong winds over much of the County Warning Area as well as the possibility
of fog and drizzle. Southerly winds hgave been gusting as high as
55 miles per hour from klar to kdgw. The tight surface pressure gradient
should gradually shift east tonight. That should allow for the
winds to slowly taper off in the west and increase over and
near the Panhandle. The previously issued Wind Advisory starting
soon and running through 12z over the Panhandle looks good.
Cloud bases should lower over the East Part of the County Warning Area tonight.
Fog will likely be kept to a minimum due to the tight southerly
surface pressure gradient. The same can be said for drizzle as
there is less of a cloud depth than Wednesday night. Fog has been
developing early this evening over the southern Laramie range.
The fog may be dense at times early tonight before the winds turn
more southwesterly.
In a recent update removed the mention of showers and made minor
adjustments to the first period of the forecast.
&&
Short term...(this evening through Saturday night)
issued at 300 PM MDT Thursday may 23 2013
Fog took much of the day to erode along the southern Laramie range
but most of it is finally gone. At this time The Summit webcam
showing some lingering fog but it is no longer dense and is
expected to mix out completely over the next few hours. The
question is if...or maybe when will the fog set back in. Models do
show moisture hugging the Laramie range through much of tonight
although the upslope flow will weaken through the night as the low
level jet slide east into the Nebraska Panhandle. Winds should
turn to the southwest around sunrise with dry air quickly eroding
any low clouds and fog. Mainly looking at low stratus east of the
Laramie range but some patchy fog possible tonight.
Large temperature and pressure difference currently driving winds
across Converse County and Albany counties. Sustained winds of 40
miles per hour with gusts over 50 miles per hour occurring at Laramie and Douglas. These
winds will continue through the afternoon into possibly into early
evening as the strong gradient relaxes and the main core of the
low level jet shifts east. Will be close to High Wind Warning
criteria until winds do relax. The other wind concern is over the
Nebraska Panhandle tonight. Models showing 50 to 60 knots winds below
a strong low level inversion. Strongest winds will be over
northern portions of the Panhandle where 50 miles per hour wind gusts should
reach the surface. Main concern is with such strong winds below
the inversion that these winds could be directed to the surface.
Should this occur...a High Wind Warning would be needed and may
need to add an advisory to southern portions of the Panhandle.
Turning to Friday...skies will clear from west to east through the
day with much warmer temperatures across the forecast area. Will
see some 80s over eastern portions of the area...although it
depends how fast the clearing occurs over the Panhandle. There is
a chance for thunderstorms in the Panhandle Friday afternoon. Not
the best set up but could see thunderstorms develop along a
surface moisture discontinuity. Models still showing 2000 plus
j/kg surface based cape and the NAM and GFS both model sounding
now showing the cap breaking...which is different from previous
run. Model soundings showing 0-6 km bulk shear values 40-50 kts...
supportive of supercell thunderstorms capable of producing large
hail. With a boundary in place isolated tornadoes not out of the
question. Still looking like the moisture boundary will retreat to
the west...similar to a retreating dry line like occur in West
Texas this time of year. Although the cap will strengthen during
the evening hours...thunderstorm could actually develop westward
Friday evening. Not likely...but something to watch. Another
chance for thunderstorms Saturday afternoon in the Nebraska
Panhandle.
Long term...(sunday through thursday)
issued at 300 PM MDT Thursday may 23 2013
Upper trough will hold over the Pacific northwest Sunday through Tuesday
keeping the County Warning Area under a generally SW flow aloft. Weak impulses
emanating from the base of this trough will move across the County Warning Area and
likely help to set off some afternoon and evening convection
mainly over the plains. Sunday looking mainly dry for now then
some uptick Monday and Tuesday. Upper trough will then move east and
across the region Wednesday. GFS brings it more bodily across the
region and more quantitative precipitation forecast while European model (ecmwf) splits the energy...cutting off an
upper low over northern Mexico thus having less quantitative precipitation forecast over the County Warning Area.
Either way at least widely scattered showers and a few storms look a
decent bet Wednesday before drying on Thursday. Temperatures warm
through the weekend into Monday then trending down a bit Tuesday
and Wednesday.
&&
Aviation...(for the 00z tafs through 00z Friday afternoon)
issued at 745 PM MDT Thursday may 23 2013
Through 15z...widespread IFR in low clouds and fog along and east of
the Laramie range...then becoming VFR. VFR elsewhere. Gusty south to
southeast winds.
&&
Fire weather...
issued at 300 PM MDT Thursday may 23 2013
Conditions will vary across the forecast area the next few day
with mostly dry and breezy conditions west with less wind east
and higher chances for thunderstorms. Humidity values will
drop below 20 percent in the afternoon through this weekend for
lower elevations west of the Laramie range and as low as 10 percent
in the Rawlins area. There will be small chances for afternoon
thunderstorms mainly over the Nebraska Panhandle through the
weekend.
&&
Cys watches/warnings/advisories...
Wyoming...none.
NE...Wind Advisory until 6 am MDT Friday for nez002-003-095-096.
&&
$$
Update...Weiland
short term...liebl
long term...re
aviation...Rubin
fire weather...liebl
