Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/23/22

Area Forecast Discussion

National Weather Service North Platte NE

 540 PM CDT Mon Aug 22 2022


.SHORT TERM...(This evening through Tuesday night)
Issued at 337 PM CDT Mon Aug 22 2022

The main forecast challenges through midweek revolve around
thunderstorm chances and continued summertime temperatures. A couple
surface boundaries and a mid-level wave passage present isolated to
scattered thunderstorm chances this evening and again tomorrow.
Somewhat stronger systems toward the end of the week present more
widespread precipitation potential, along with slightly cooler
temperatures.

This evening and tonight... A subtle surface boundary stretches
across the panhandle, which may be a focus for isolated
thunderstorms. Dry air has resulted in very steep lapse rates near
the surface and fairly steep (7-8 C/km) in the mid levels. Some CAMS
solutions, including the HRRR, suggests a few cells initiating
before 00z and dissipating by 03z. Conditions don`t appear overly
great for activity as surface dew points have been dropping through
the afternoon. However, a couple storms managed to develop yesterday
under the same conditions. Introduced schc (20%) PoP in the
panhandle and western Sandhills near the boundary. Otherwise, partly
to mostly clear conditions are expected overnight with fairly mild
lows in the mid/upper 50s southwest and lower/mid 60s north central.

Tuesday...  The heart of the main upper ridge that covers much of
the Western US retreats slightly toward the Desert Southwest.
Nebraska has enough influence from the ridge to keep summertime
conditions around, especially with persistent south/southwest flow
at H85. Weak WAA is in play with temps approaching or surpassing
25C. A weak shortwave brushes north central Neb during the morning,
which may provide enough forcing to support a few brief rain showers
or embedded thunder. Later in the day, a surface low slides across
South Dakota, which presents a greater chance for precipitation for
the northern half of the CWA. The low and attendant surface trough
will take advantage of steep low and mid level lapse rates and
slightly better moisture than today. Severe parameters are low
however, as MUCAPE maxes out around 500 j/kg and deep layer shear of
only 15 to 20 kts. Used a blend of HREF and HRRR for general precip
coverage and timing. Expect most (if not, all) activity to wane by
midnight as forcing and instability decrease.  For max temps, the
guidance envelope is fairly small and centered around the lower/mid
90s. Felt no need to push temps any higher given increasing
cloudiness and precip chances during the afternoon and peak heating
period. There`s also the chance for the far northern CWA to
transition to northerly flow in the vicinity of the surface low.
Tuesday night lows should be similar to tonight`s, perhaps a degree
or two cooler in the wake of thunderstorms.

.LONG TERM...(Wednesday through Monday)
Issued at 337 PM CDT Mon Aug 22 2022

Wednesday and beyond... The upper ridge breaks down and is replaced
by a progressive trough over the northern Plains, partially driven
by a closed low riding the international border. Closer to the
surface, a series of boundaries cross the forecast area, including a
cool front late Wednesday and a warm front late Friday. Each of
these will promote additional shower and thunderstorm development.
An early look at severe potential appears mixed with bouts of decent
instability and shear, but the best ingredients are somewhat
localized. Temperature-wise, seasonably warm highs near 90F continue
Wednesday, then dip into the 80s to round out the week with a little
rebound later in the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 540 PM CDT Mon Aug 22 2022

Expecting VFR conditions to prevail across central and western
Nebraska through this valid period.

Current scattered field of cumulus may result in an isolated,
brief shower/thunderstorm early this evening but do not expect any
impacts in the vicinity of either KLBF or KVTN. Toward the end of
the valid period expect some scattered showers/thunderstorms will
develop along the NE/SD border and sink southward, but not make
much progress past highway 2. Will include VCTS at KVTN with a
VFR CIG toward the end of the valid period, but maintain dry
conditions at KLBF.

The low level wind field will amplify early tonight and there are
indications that the boundary layer will remain mixed enough to
support an occasional wind gust at KVTN. Will indicate this in the
TAF but expect any gusts will be quite sporadic. There may be a
few gusts Tuesday morning once better mixing becomes established
after sunrise but overall do not expect winds to have a
significant impact to aircraft operations through Tuesday evening.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Snively
LONG TERM...Snively
AVIATION...MBS



Area Forecast Discussion

National Weather Service Phoenix AZ

 453 PM MST Mon Aug 22 2022

.UPDATE...Updated 00z Aviation Discussion...

&&

.SYNOPSIS...
Storm chances are low for the lower deserts this afternoon and
evening, but with better chances Tuesday and Wednesday. A gradual
downtrend in storm chances takes place during the latter half of
the week and over the weekend. Highs today will be below normal
most places. Over the coming days, near normal highs can be
expected near and west of the Lower Colorado River Valley with
somewhat below normal highs east of there. Anticipate day to day
fluctuation depending upon thunderstorm activity.

&&

.DISCUSSION...
Following yesterday and last night`s complexes of strong to
severe storms that moved north to south through Arizona, the
environment is notably drier and more stable. The 12Z soundings
from Phoenix and Yuma and the recent aircraft soundings from
Phoenix all show the greatest drying has been within the boundary
layer and they also all show a pretty strong capping layer on the
boundary layer. The mid-level lapse rates are better than they
were this time yesterday, supportive of robust updrafts, but the
dryer and capped boundary layer will make it very difficult to
see any convective activity over the lower deserts this afternoon.
Storms will mainly favor the high terrain, including southern
Gila County. Mid- level steering flow is still lightly from the
north, so storms may creep into the northern Maricopa foothills
before dissipating as advertised by the majority of hi- res
models. These storms will be capable of producing brief heavy
rainfall and could push an outflow(s) into the lower deserts later
this afternoon and evening.

Tuesday, conditions become more favorable for thunderstorms
spreading to the lower deserts again with a Rim-to-Valley setup as
northerly steering flow persists, even becoming more
northeasterly. A PV anomaly from the southwest Tuesday afternoon
may also aid upper level ascent. The capping inversion in the
Phoenix area will still have to be overcome tomorrow afternoon to
see storms through the metro. So, there is no guarantee, but BUFR
soundings do suggest a gradual erosion of the the inversion
through the afternoon and evening. With mid- level lapse rates
still forecast around 7 C/km and afternoon MLCAPE reaching 1000
J/kg will support strong updrafts tomorrow and with the boundary
layer still relatively dry (PWATs around 1.6") DCAPE will be high
tomorrow. Strong to severe winds will be a primary threat
tomorrow afternoon and evening under these parameters. The 12Z
HREF shows the highest probability for strong storms tomorrow
coming together in Pinal county, with 50-70% probabilities for
wind speeds greater than 35 mph across Pinal and Maricopa counties
and a 10% probability for severe winds (>58 mph). The winds may
also generate areas of blowing dust through the prone areas. Flash
flooding will still be possible, but the storms will likely be
less efficient than they were late last week and over the weekend.

A mid-level sub-tropical low moving north along the Sierra Madre
Occidentals tomorrow may help keep our region in an active monsoon
regime through at least Wednesday, helping increase the moisture
once again across the area. GEFS and EPS PWAT forecasts show
magnitudes generally climbing back to near 2.0" by Thursday before
beginning a gradual, but more significant drying through the rest
of the week and this weekend. Global ensemble clusters suggest the
flow across the Desert Southwest may become somewhat quasi-zonal
for a time period, with increased and deeper westerlies that
likely explains the drying trend.

With the dryer conditions the next couple of days across the
western deserts it is expected to heat up. Moderate HeatRisk is
forecast across Southeast California with highs reaching 105-109F.
Slightly cooler temperatures will follow to round out the week. Below
normal temperatures are expected to continue further east in
South-Central AZ. Afternoon highs in the Phoenix area are
forecast to be around the 100 degree mark each day through this
weekend.

&&

.AVIATION...Updated 2350Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Mainly tranquil weather conditions are expected to continue
through at least early Tuesday afternoon. Isolated to scattered
thunderstorm activity currently over the higher terrain is not
expected to make its way into the Phoenix area, with only a slight
chance (<20%) of any outflow winds affecting the terminals.
Westerly winds with speeds aob 8 kts will continue through mid-
evening, becoming easterly afterwards and prevailing through
Tuesday morning. A westerly wind shift is then anticipated late
morning into the early afternoon hours on Tuesday with speeds
remaining below 10 kts. A better potential for thunderstorm
activity is anticipated by late Tuesday afternoon/early evening,
with a 50-70% chance of winds exceeding 30 kts.


Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns expected through the period. Winds
will generally follow a southerly component at KBLH and a
southeasterly component at KIPL through the period. Mostly clear
skies are anticipated through the period.


&&

.FIRE WEATHER...
A substantial downtrend in storm coverage is expected today
followed by an uptrend Tuesday expanding to southeast California
Wednesday. A gradual decline in storm chances takes place from
west to east beginning Thursday. MinRH values peak on Wednesday
with values ranging from 30-40% lower elevations and 40-50% higher
terrain. The lowest values will be on Sunday with MinRH ranging
from 20-30% lower elevations and 30-40% higher terrain. Apart from
thunderstorms, winds will follow familiar diurnal patterns.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Benedict
AVIATION...Lojero
FIRE WEATHER...AJ