Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/15/19
Area Forecast Discussion
National Weather Service Billings MT
717 PM MST Thu Nov 14 2019
Occasional high clouds and dry weather are expected tonight, as we
remain under the influence of high pressure aloft. Dew point
depressions are 3F and 7F at Baker and Miles City, respectively,
and there is a risk of localized valley fog in our east tonight.
Latest HRRR continues to keep fog out of southeast MT, but there
is no denying the moist boundary layer and another night of
relatively light S-SE winds. To the west, we will see winds along
the foothills increase through the night, but Livingston has seen
W-NW winds linger into the evening. Have made some minor wind, sky
and temp adjustments...but overall forecast is in good shape. JKL
.SHORT TERM...valid for tonight and Fri...
High pressure building over the region will bring mainly dry
conditions to the area through Friday. Tightening pressure
gradients and strengthening winds aloft will increase the winds
along the western foothills this evening and overnight, but
advisory level winds are not expected. Patchy fog is possible from
Miles City south to Broadus and areas east tonight. The next
system moves into the region Friday night in the form of a
shortwave and associated cold front bringing showers to the area.
Temperatures look warm enough that any snow will be confined to
the mountains. High temperatures on Friday will range from the 40s
over far eastern areas to the 50s elsewhere. Low temperatures
tonight and Friday night will range from the 20s to 30s. STP
.LONG TERM...valid for Sat...Sun...Mon...Tue...Wed...Thu...
Saturday still on track for a shortwave drop through the area.
Still looks that south and east of Billings will see some rain,
with the high elevations see some light snow. Behind the
shortwave, the surface pressure gradient will increase Sunday.
Guidance, both ensemble guidance and local probabilistic, is
showing a fair strong signal for a Wind Advisory around Livingston
and Nye. Winds should still decreasing by Monday morning.
Tuesday onward the models are still showing significant spread in
the ensemble members as a splitting trough moves into the western
US. The general tread is for cooling temperatures, and snowfall.
Much of the details on this are too uncertain say how cold or how
much precip will fall. Reimer
Localized valley fog is expected from KMLS to K00F eastward late
tonight into early Friday. MVFR or lower is possible where fog
develops, but it will not be as widespread as Wednesday night.
Otherwise, VFR under scattered to broken high clouds will prevail
through tomorrow. SW-W winds will become gusty along the western
foothills, with gusts to 35 kts at KLVM overnight. JKL
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
BIL 036/058 039/051 034/058 043/059 035/051 032/041 022/038
00/B 31/B 02/W 11/N 34/R 54/O 31/B
LVM 035/060 037/048 034/054 040/055 036/052 031/041 021/040
00/N 51/N 02/W 21/N 35/R 53/O 21/B
HDN 028/056 034/050 029/057 039/058 032/051 029/041 018/038
00/B 43/W 02/W 21/U 24/O 44/O 31/B
MLS 027/050 033/045 028/053 038/053 030/046 027/038 019/035
00/B 32/W 02/W 21/B 33/O 33/O 21/B
4BQ 027/055 032/046 028/054 038/055 030/049 027/038 018/036
00/B 35/W 02/W 21/B 23/O 43/O 31/B
BHK 025/048 030/042 025/047 035/049 027/042 025/036 017/033
00/B 12/W 01/E 21/N 13/O 33/S 21/B
SHR 025/056 031/046 024/054 035/056 028/051 027/041 016/038
00/B 46/W 02/W 21/U 23/O 44/O 31/B
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
902 PM EST Thu Nov 14 2019
A weak cold front will continue to shift through the Great Lakes
while high pressure builds in behind. Temperatures will remain
below normal into the weekend as cold air is reinforced a little
behind the front, and additional weak backdoor cold front
slipping through on Friday night. Dry weather is anticipated
through the weekend, although clouds will likely remain
.NEAR TERM /THROUGH FRIDAY/...
The SCT/BKN 4-5kft clouds that had developed earlier in the
evening have since dissipated as expected. However, focus has
been on the fairly extensive area of low clouds centered over
IL/IN that has been ever-so-slightly shifting southeast through
the late afternoon/evening hours. Despite the increasingly deep
inversion and relatively weak low level flow, the cloud deck
continues to erode somewhat on its southeastern fringe per
latest GOES-East imagery. This lends itself to a bit more
uncertainty than would ideally be expected for the overnight
period in terms of just how much this cloud deck will overspread
the area and how it will evolve past daybreak Friday morning.
There are several hi-res models that continue to show low level
moisture becoming better entrenched across the area past about 2
AM or so through mid-morning. However, the 15.00 KILN RAOB
showed quite a bit of dry air in the low levels so the exact
evolution of the cloud cover through tonight still remains a bit
Will maintain a cloudier solution in the official fcst for the
late overnight/early morning period than perhaps is being
depicted by some of the guidance. This will ultimately have an
impact on temp traces as well. Moreover, should expansive cloud
cover develop/advect into the ILN CWA, it`ll likely stick around
longer than some models have suggested owing to weak low level
flow and a fairly deep inversion set to persist through the day.
Low temps tonight will bottom out in the low to mid 20s.
PREVIOUS DISCUSSION -->
Focus on the overnight will be on the cloud/sky trends.
Weak/elongated and positively tilted shortwave trough will
continue to pull east of the area this evening. While right-
entrance region of the upper jet induces a band of dense cirrus
across the southern parts of the forecast area through this
evening, have a more concerned eye on large area of
stratus/stratocumulus over IL/IN/MN/WI in the heart of the low-
level thermal trough in the wake of the cold front shifting
through. Forecast soundings show the weak low level cold
advection as the thermal trough moves into the area tonight, but
with the large closed low shifting across Hudson Bay, heights
aloft are actually slowly rising overnight with mid/high level
warm advection. So - the net effect on soundings is a rapidly
strengthening inversion with very dry air aloft - on top of
moistening and weak cold advection. This is a recipe for the
large area of stratus to our NW to continue to move into and
across the area later in the night - and this is corroborated
with simulated cloud progs in HREF and experimental RAP sky
cover forecasts, as well as the past several NAM runs. These
models tend to handle the low stratus better than GFS/CMC, so
have definitely shifted to a cloudier forecast especially after
midnight as the large area of stratus moves in. There is some
concern that some fog may develop on the leading fringe of the
low clouds, and while this is not in the forecast right now, it
may need to be added by the oncoming shifts if visibility begins
to drop in the mid-late evening. Am banking that this will
manifest more as a low cloud event - and not any dense fog. This
makes low temp forecasts very difficult given inbound stratus.
Since much of the evening will be clear or partly cloudy, expect
temps to fall off quite rapidly. But there is bust potential on
temperatures depending on when exactly the low clouds arrive.
Have raised low temps just a smidgen...but this will need to be
watched...especially with snow cover still complicating things
across the northern portions of the CWA.
.SHORT TERM /FRIDAY NIGHT/...
Depending on how expansive the low clouds are on Friday morning,
there is concern to how quickly these could erode. Could range
from mostly sunny to mostly cloudy depending on where the
thickest low clouds form overnight, but have trended the
forecast toward more clouds. The low level flow will be weak and
turning northerly, and the thermal trough remaining over the
area, there is concern that the strong inversion could keep
things locked in far longer than what is currently forecast.
This is an area of high uncertainty - but did trend things
toward more clouds than not especially on Friday morning and
especially the west/north parts of the forecast area.
A weak backdoor cold front slips into and through the forecast
area on Friday night and there will be a reinforcing shot of
stratus in the weak cold advection behinds this feature. So will
see clouds increasing again on Friday night, and this too is an
area of high uncertainty on just how expansive the low clouds
will be or if enough holes will be there for a partly cloudy vs.
a mostly clouds forecast.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
The long term period is characterized by below average temperatures
and growing forecast uncertainty beyond Sunday night. There will be
chances for light precipitation Tuesday and more widespread
An area of high pressure centered in southeastern Canada will lead
to tranquil weather to start off the extended period this weekend.
Saturday will feature below average temperatures with highs around
the middle 30s north and middle 40s south under fair weather skies.
Lows Saturday night will be in lower 20s to the north and middle 20s
to the south.
As the area of high pressure moves east on Sunday, high- and mid-
level clouds will build in from the west ahead of an approaching
upper-level trough. Forecast confidence starts to diminish Sunday
night as details on the phasing and structure of the trough, along
with a possible shortwave disturbance rounding the base of trough,
are not certain at this time.
Currently there is ensemble support for broad troughing over the
Ohio Valley Monday through Tuesday night. Under the broad trough
highs are expected to remain below average and there are chances for
precipitation on Tuesday. Ensemble solutions are widely varied
between the European EPS and GEFS in terms of precipitation
probabilities. The GEFS offer wetter solutions than the EPS members
and cannot be discounted as a shortwave rounding the base of the
trough could lead to periods of showers Monday Night through Tuesday
By Wednesday, ensemble solutions amplify the flow and have some
ridging building in before the next chance of widespread
precipitation approaches the area toward the end of the next week.
The timing of this next cold front is still uncertain, but have
included chance for precipitation starting early Thursday
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
A somewhat complex fcst is shaping up for the TAF period,
particularly as it pertains to the expanse and coverage of
a 1200-2000ft cloud deck currently positioned across IL/IN that
is slowly shifting southeast toward the local area. Hi-res
short-term guidance is not handling these low CIGs well --
especially in comparison to observations which actually show
CIGs lowering even in the past several hours upstream of the
local TAF sites. Have decided to be a bit more aggressive with
the fcst of these low CIGs making into the area past 06z,
generally from west to east across the region toward daybreak.
There are some select fcst soundings that show a 4-6 hour window
of low level moisture thick enough to support IFR CIGs leading
up to and through daybreak -- especially for northern sites of
KDAY, KCMH, and KLCK.
And with this in mind, decided to go prevailing MVFR with TEMPO
IFR with the combo of advection of stratus and the development
of some stratus immediately overhead past 06z. Did not at this
time add any VSBY restrictions as suggested by some data as fcst
soundings show a /relatively/ dry layer immediately at/above the
sfc to about 1kft.
Although guidance is fairly quick at scattering out some CIGs
by/past 15z, do think this may be a bit too early especially
considering the overall weak flow and deeper inversion in place,
essentially creating a setup where the low level moisture does
not have anywhere to go. With this in mind, there will be some
natural mixing within the BL so did show a scattering/lifting
trend by the afternoon but this will be monitored as we progress
through the morning hours and may need to be slowed beyond
current fcst if data trends suggest so.
Additional MVFR/IFR CIGs will be possible past 00z Saturday
toward the very end of the period.
Light southwesterly winds will go variable/calm tonight before
eventually going more northwesterly and northerly by Friday
afternoon/evening. Winds will generally stay 8kts or less
through the entire period.
OUTLOOK...MVFR/IFR CIGs will be possible Friday night.