Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/19/20
Area Forecast Discussion
National Weather Service Great Falls MT
746 PM MDT Mon May 18 2020
.UPDATE...
With mean SBCAPE ranging from 500 to 1000 J/kg, LI`s ranging from
-3 to -1, and other stability indices indicating thunderstorm
activity, convective weather has developed, and thunderstorms are
moving through the area from the SSW to the NNE. Timing and
intensity of storms is occurring as forecast; therefore, no changes
to the forecast will be made at this time.
- Fogleman
&&
.SYNOPSIS...
A rather unsettled and stormy weather pattern will over the region
this week. Expect periods of rain and thunderstorms, with some
storms containing brief heavy rain, gusty winds and hail.
Afternoon temperatures will be several degrees above normal
through Tuesday, but gradually cool to below normal by mid week.
&&
.DISCUSSION...
Tonight through Tuesday...Upper level trough with embedded closed
low centered off the northern CA coast as of this afternoon
gradually pushes east into the Great Basin Tuesday. Next in a
series of disturbances rotating around the upper low will lift
north through western MT later this evening, and expect showers
and storms to develop over the next few hrs across central and SW
MT in the increasingly unstable environment and track north
through central and north central MT late this afternoon and
evening. A few organized strong to severe cells still appears
likely through this evening thanks to moderate instability and
strong shear with strong winds being the primary threat but also
localized heavy rain and at least some potential for marginally
severe hail. We start Tuesday in a similar situation however upper
level jet support and axis of greatest instability will have
shifted a bit further east. A greater degree of instability and a
more favorable diffluent flow aloft will support a more widespread
coverage of thunderstorms with focus for severe thunderstorm
potential looking especially favorable across eastern portions of
north-central MT Tuesday afternoon and evening. Hoenisch
Wednesday through Thursday...The main upper level low will start to
exit into eastern MT by Wednesday. The main difference from models
is how fast does it exit the region. Some models linger the low over
eastern MT, resulting in rain back over our region, with other
models quickly move it off to the northeast, resulting in drier
conditions over our region. Overall the blend of the NBM has the
best handle, resulting in some rain over the Rocky Mountain Front
and thunderstorms further east/south. At this time though,
confidence is a bit lower in the forecast for Wed into Thursday,
with some areas possibly being bit drier than currently forecasted.
Overall, below normal temperatures look on track.
Friday through Monday...An upper level trof will be over the region
on Friday, but how this upper level trof exits the region varies
from model to model. Thus confidence is low at this time in terms of
precipitation for next weekend and into the Memorial Day holiday.
Some models are rather wet, while some are dry. Thus the NBM blend
with low pops seems to have a handle on the trend.
Afternoon temperatures will likely slowly rise towards normal
readings by late in the weekend. Brusda
&&
.AVIATION...
Updated 626 PM MDT Mon May 18 2020 (19/00Z TAF Period)
Showers and thunderstorms continue through the area from SSW to NNE,
this evening. Some of these thunderstorms may become severe with
winds that may gusty to 50KTS. Additionally, there is a potential
for some of these storms to produce hail. Lingering showers will
continue even after thunderstorm activity ends. Expect periods of
MVFR conditons, as well as mountain obscuration. Hazard forecast
valid times range from 19/00Z to 19/11Z. During this time, upper
level icing is forecast. Low level winds shear is forecast for KWYS.
Expect the associated turbulence. Outside of thunderstorm, some
breezy winds up to 25KTS from KGTF to Southwest Montana will impact
light aircraft near mountains and in passes. For detailed
information on icing and turbulence and more, please go to:
aviationweather.gov/icing
aviationweather.gov/turbulence
- Fogleman
NOTE: Amendments not scheduled for Ennis (KEKS) due to ongoing
runway closure.
&&
.HYDROLOGY...
Periods of rain, heavy at times, will affect portions of Central
and North Central MT for the next several days. The rainfall will
be convective at times, resulting in some areas receiving heavy
rainfall and locations just a few miles away receiving much less
precipitation. Overall, the Rocky Mountain Front continues to
favor the highest precipitation amounts. Thus a marginal risk for
flash flooding is possible in that area today, which will expand a
bit for Tue/Wed out over the northern Plains.
No flood watches will be issued with the 4 AM morning package, but
it is possible later today or tomorrow, that an areal/river flood
watch might be needed for portions of the region. It is possible
that because of the breaks in the periods of precipitation, that
any flooding issues that develop over the next few days might not
be widespread/severe enough for an areal flood warning, but a
flood advisory might be able to handle the situation. Brusda
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 48 70 49 67 / 70 70 90 70
CTB 47 64 46 63 / 80 60 90 80
HLN 47 73 48 68 / 60 80 90 80
BZN 45 76 44 67 / 30 60 70 70
WYS 38 68 34 55 / 20 50 40 70
DLN 43 69 42 61 / 40 50 70 80
HVR 51 78 52 74 / 70 30 80 70
LWT 47 72 48 68 / 30 70 70 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls
Area Forecast Discussion
National Weather Service Las Vegas NV
903 PM PDT Mon May 18 2020
.SYNOPSIS...
Chances for showers and isolated storms will increase on Tuesday
across the southern Great Basin and Inyo County as a strong low
pressure system passes across the region. Noticeably cooler
temperatures are expected tomorrow before a warming trend begins
Wednesday and continues through the end of the week.
&&
.UPDATE...Wind advisories were allowed to expire at 8 PM for all
areas except the Spring Mountains and Red Rock Canyon. The Wind
Advisory for those zones was extended until 6 AM Tuesday morning.
The latest high res models indicate the potential for enhanced
downslope winds gusting up to 45 mph in Red Rock Canyon and the
lower east facing slopes. Favorable conditions for downslope will
end around sunrise Tuesday. The incoming upper low was centered over
central California this evening and the leading edge will continue
to slowly work its way across stir up breezy to windy conditions
across the Mojave Desert Region Tuesday. Scattered showers and
isolated thunderstorms Tuesday will remain confined to Inyo,
Esmeralda, central Nye and Lincoln counties. It will be noticeably
cooler with high temps dropping 10-15 degrees across the region from
today`s readings.
&&
.SHORT TERM...Today through Wednesday.
A closed low, which is currently centered near the coastal border of
CA and OR, will shift southeastward over Nevada through tomorrow.
Sfc gradients will tighten today leading to increased southwesterly
winds ahead of an approaching frontal boundary. The strongest belt
of winds will gust between 40 to 50 mph and stretch from the western
Mojave Desert across Inyo county northeastward to Nye and Lincoln
counties. Wind Advisory looks good to go through this evening for
the current areas. The only exception will be on the leeward side of
the Spring Mtns as there is potential for strong winds to last into
the early Tuesday morning as the upper level jet shifts over the
area. Elsewhere, gusts will generally be between 25 to 35 mph
through this evening. As the low nudges closer tonight, moisture and
chances for rain and isolated storms will increase into Inyo,
Esmeralda, and Nye counties. Proximity of the low along with upper
level jet dynamics will at least warrant a mention of thunder
overnight tonight in these areas as the first round of activity
develops through tomorrow morning. There should be a brief lull
in activity during the mid to late morning before diurnal heating
and increasing instability allow the second round of showers and
storms to pop during the afternoon. The best chances for showers
and storms will be across similar areas to overnight; the southern
Great Basin and Inyo County with a slight chance for the higher
elevations of Clark County. Small hail, strong winds, and
lightning will be the primary threats with convection on Tuesday.
A sfc cold front will work its way southward going into Tuesday
which will allow for some breezy, northerly winds behind it and
breezy, southwesterly winds ahead of it. Speeds should be around
25 mph or less. A significant drop in temps is expected between
today and tomorrow as heights crash with this passing system. The
low will start to lift northward over the Great Basin Tuesday
night into Wednesday limiting chances for showers and storms to
the northern reaches of Lincoln County on Wednesday.
.LONG TERM...Thursday through Sunday.
Large-scale troughing will remain situated over the Western U.S. for
the remainder of the week. Heights will rise behind the strong low
from earlier in the week and temps will rebound back up to near
normal by the end of the week. A stronger shortwave will dig across
the Great Basin on Friday and Saturday which will usher in some
breezy conditions along with isolated showers and storms for
Lincoln and Nye counties.
&&
.FIRE WEATHER...
A strong low pressure system will approach and pass across the
area through tomorrow. Strong winds across Inyo County and the
southern Great Basin have been the result with southwesterly gusts
in the 40-50 mph range. Most other areas will see gusts in the
25-35 mph range through this evening. Showers and isolated storms
will move east of the Sierra overnight tonight, spreading across
the southern Great Basin by Tuesday afternoon. RH values in these
areas will come up above critical levels tomorrow with critical
RH values present across the lower elevations of Mohave, Clark,
the eastern half of San Bernardino counties. Much cooler
temperatures are expected on Tuesday which will warm up through
the end of the weak along with drying out of the lower elevations.
Southwest winds gusting between 20 and 30 mph will be present on
Tuesday and again on Friday and Saturday.
&&
.AVIATION...For McCarran...Gusty southwest winds are expected to
continue into the evening, with sustained winds generally of 15- 20
knots. Downslope winds may strengthen overnight near the terrain of
the Spring Mountains to the west and McCullough Range to the south
but are not expected to reach the terminal. Mountain waves will
introduce minor to moderate turbulence on aircraft across LAS
airspace through Tuesday. An isolated thunderstorm is possible on
Tuesday afternoon west of the terminal over the higher terrain of
the Spring Mountains. Southwest winds will continue on Tuesday but
will be lighter around 15 kts with gusts of 20-25 kts.
For the rest of southern Nevada, northwest Arizona and southeast
California...Gusty southwest winds are expected to continue across
the region into the evening hours. The strongest winds will be
across south-central NV and portions of western Mojave Desert where
gusts to 35-45 knots are expected with some isolated higher gusts
possible. Winds are expected to decrease but remain elevated
overnight with gusts to around 20-25 knots at most TAF sites. Expect
increasing mountain wave turbulence in the lee of the southern
Sierra and Spring mountain ranges. Isolated to scattered showers and
thunderstorms are possible across Inyo, Esmeralda, Nye and Lincoln
Counties tonight through Tuesday.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Adair
SHORT TERM/LONG TERM...Guillet
AVIATION...Czyzyk
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