Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/31/20
Area Forecast Discussion
National Weather Service Aberdeen SD
934 PM CDT Fri Oct 30 2020
Issued at 934 PM CDT Fri Oct 30 2020
Increased lows overnight. Otherwise, the rest of the forecast
UPDATE Issued at 657 PM CDT Fri Oct 30 2020
00z aviation discussion updated below.
.SHORT TERM...(This Evening through Saturday Night)
Issued at 229 PM CDT Fri Oct 30 2020
Stratus and fog remain entrenched over central SD this afternoon. A
slow erosion from the south of the stratus field is expected to
continue into this evening. The clouds have markedly affected
temperatures today and are posing a headache for hourly temp
guidance this evening. Went with HREF for both sky cover and hourly
temps, though even it may be a little high until winds kick in.
A front will sweep through the Dakotas tonight. South to southwest
winds ahead of the front will be breezy with some enhancement
expected along the Sisseton Hills and Coteau as the H85 winds shift
to the southwest. Drier air with steeper lapse rates will push in
behind the front. However, an upper trough with shortwave energy
will, too, and may bring some increased mid level cloud cover for
the morning. Any clouds will limit mixing and gustiness.
As winds shift to the northwest behind the front, the pressure
gradient be a difference of about 10 mb across the state which is
not as strong as models indicated yesterday. Lapse rates remain
steep at 7-9 with inverted V soundings. 6z model runs were weaker,
overall, than 12z runs. The GFS still maintains 70kts at 700 mb and
a 50 kt corridor at H85 at 21z which is similar to yesterday`s model
guidance. Only the 12z RAP BUFKIT soundings showed Lemmon, Mobridge,
or Pierre briefly gusting to 50 kts between 21 and 23z. It would
require mixing to 3500 to 4000 ft, which is unlikely in the valleys.
Cannot completely rule out an isolated gust on one of the ridges
during the late afternoon, though. Decided with neighbors to go with
an area-wide wind advisory and message the potential for isolated
higher wind gusts. It does look like a slam-dunk for a high end wind
advisory provided the clouds clear out as models indicate in the
afternoon. High pressure then builds in at the sfc Saturday night.
.LONG TERM...(Sunday through Friday)
Issued at 229 PM CDT Fri Oct 30 2020
A surface ridge axis will move east across the area on Sunday while
a warm air advection pattern begins to take shape. This will be the
onset of rather mild air that will stream across the region through
Thursday of next week. Given the 850mb temps in the mid teens
combined with favorable west to southwest mixing winds, decided to
lean towards the warmer end of guidance for high temperatures. This
ended up being a few degrees warmer than inherited NBM guidance
after blending in warmer solutions. Only thing to worry about would
be any residual snow cover across central/north central SD into the
Glacial Lakes region come Monday or even into Tuesday. Hard to say
how much will be left by that time, given the expected highs during
the short term period. May need to make some adjustments in the
coming days, but expect most of the snow to be gone or close to it
by the start of next week. As for precipitation chances, the pattern
looks rather dry for the upcoming week and do not see anything
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 657 PM CDT Fri Oct 30 2020
A surface cool front will sweep quickly across the region tonight
into Saturday morning bringing very strong northwest winds on
Saturday. Strong llws is expected this evening into Saturday morning
until the mixing layer deepens and the strong winds mix down. The
llws will be from the southwest tonight and from the northwest early
Saturday with wind speeds up to 50 knots to 2000 feet. Otherwise,
VFR conditions are expected through Saturday.
***Construction to improve taxiways at both KABR/KPIR terminals
may cause an occasional temporary visibility reduction due
to blowing dust (bldu), mainly during daytime hours UFN.
SD...Wind Advisory from 1 PM CDT /noon MDT/ to 8 PM CDT /7 PM MDT/
Saturday for SDZ003>011-015>023-033>037-045-048-051.
MN...Wind Advisory from 1 PM to 8 PM CDT Saturday for MNZ039-046.
Area Forecast Discussion
National Weather Service Bismarck ND
1019 PM CDT Fri Oct 30 2020
Issued at 1012 PM CDT Fri Oct 30 2020
Several SPS`s have been issued for wind gusts up to 55 mph that
have accompanied some light rain making it into western North
Dakota. Focus for strong winds is shifting southward as the cold
front pushes southeast. The trend this past hour has been for the
max wind gusts to diminish slightly, with upstream wind gusts in
the 30 to 40 mph range behind the frontal trough. With the bulk of
the current pressure rises forecast to remain to the west of the
state, we`ll refrain from making any headline changes at this time
with overall winds expected to stay sub-advisory criteria for now.
UPDATE Issued at 849 PM CDT Fri Oct 30 2020
A line of showers have developed along strong 850mb frontogenesis
over northeast Montana. These showers have a recent history of
producing several 50 to 60 mph wind gust reports as well as 75 mph
at the Glasgow MT airport. The GGW 00Z observed sounding features
an inverted V signature with dry adiabatic lapse rates up to near
500mb atop a shallow boundary layer inversion. RAP forecast
soundings in NW North Dakota show a similar dry sub-cloud layer
developing, though with a more substantial inversion given colder
As 850mb winds rapidly increase over the next hour or so atop
northwest North Dakota, there is the increasing potential for
strong gusty winds to be associated with the aforementioned
showers. Though this may be tempered by cooler surface
temperatures, the inversion on the forecast soundings is shallow
and may not fully prevent the momentum transfer of stronger winds
aloft. The northwest portions of North Dakota from McKenzie county
northward should watch for strong gusty winds in the next one to
two hours, with increasing uncertainty further east.
UPDATE Issued at 712 PM CDT Fri Oct 30 2020
00Z surface analysis places upcoming cold front from northeast
through south central Montana, currently past Malta and Lewistown.
Pressure falls ahead of the frontal trough have maintained breezy
southerly/southeasterly winds across much of North Dakota. Warm
air advection overrunning the cool surface layer has also
maintained a very shallow surface inversion, responsible for
lingering stratus and fog over south central North Dakota.
Guidance is not in great agreement about when this near-surface
layer finally drys out, with RAP drying by 03Z, GFS by 05Z, and
NAM not until almost 12Z. Based on the 00Z observed BIS sounding,
the stratus layer is not terribly deep at just over 1000 feet. But
with the RAP continuing 850mb WAA until 08Z, this stratus/fog may
stick around this evening. We issued a short-term SPS for areas
of dense fog based on road cameras and surface obs, but this may
need to be re-issued based on how trends play out.
No need for changes to messaging for tomorrow`s winds. We`ll see
how upstream observations and 00Z guidance comes in but current
forecast and headlines look good.
.SHORT TERM...(This evening through Saturday)
Issued at 140 PM CDT Fri Oct 30 2020
Two strong cold fronts and associated gusty winds are the
highlight of the short-term.
Ahead of an approaching low pressure system strong warm air
advection will kick in. Breezy southerly winds will keep
temperatures from falling too far tonight with readings generally
in the 30s. The first cold front will sweep through around
midnight tonight. This will shift winds out of the west, but only
increase them marginally. The stronger cold front (and main
pressure rises) will arrive Saturday morning.
Although a few cold advection showers can not be ruled out near
the Canadian border, it is likely most areas will stay dry
Saturday. A downsloping wind component, strong Cold air advection
behind the cold front, isallobaric forcing and afternoon mixing
all have the potential to come together and produce sustained
winds around 35 mph and gusts to 55. There are some indications
that winds could be even stronger, however, there are some
factors that could limit the higher end potential of this event.
Thus, a Wind Advisory has been issued as confidence is high in
widespread Wind Advisory level winds, but not great enough for
the higher end potential to warrant a High Wind Warning at this
Timing, mixing and cloud cover are factors that could limit the
higher end potential of winds.
With the surface low tracking to our north, the strongest
pressure rises will be noticed across northern North Dakota,
however,cloud cover could limit mixing. Additionally, the 12 UTC
guidance suite has the cold front and pressure rises moving
through a bit earlier than previous runs. This could also limit
the highest potential as the strongest cold air advection could be
east of the area by the time peak heating/mixing kicks in.
With that said...if these factors don`t contribute then wind gusts
over 60 mph will be possible.
.LONG TERM...(Saturday night through Friday)
Issued at 140 PM CDT Fri Oct 30 2020
A dry, warming trend highlights the long term. Highs in the 60s
will be common across much of the forecast area Monday through
Wednesday, with a 70s not out of the question over the southwest.
The broad upper level ridge responsible for this nice weather,
begins to flatten by the middle of the week with more seasonable
temperatures and perhaps a hit or miss shower by next weekend.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 712 PM CDT Fri Oct 30 2020
LIFR stratus continues at KBIS through part of the evening. Not a
lot of confidence in when this stratus should improve to VFR,
though an upcoming cold front and wind shift early Saturday
morning should do the trick. The question will be is if this
stratus can dissipate before then. The TAF may need to be amended
if trends show the stratus continuing after 03Z.
Otherwise the main issue will be LLWS associated with a strong
cold front tonight. Winds at 1500-2000 feet increase to around 50
kts. Wind shear diminishes as surface winds increase Saturday
morning, with strong northwest surface winds gusting to around 50
kts expected. FEW to SCT at 3k ft may develop behind the front
during the day Saturday.
Wind Advisory from 10 AM CDT /9 AM MDT/ to 7 PM CDT /6 PM MDT/
Saturday for NDZ004-005-012-013-017>023-025-031>037-040>044.
Wind Advisory from 1 PM CDT /noon MDT/ to 7 PM CDT /6 PM MDT/
Saturday for NDZ045>048-050-051.
Wind Advisory from 7 AM to 7 PM CDT Saturday for NDZ001>003-
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
814 PM MDT Fri Oct 30 2020
Issued at 805 PM MDT Fri Oct 30 2020
02z surface analysis had low over southern SK with pre-frontal
trough into central WY and cold front into central UT. Water
vapour had fast-moving shortwave trough moving across central MT.
Not a lot of moisture to work for CWA. Effect of this system main
concern for update.
Previous ensemble guidance didn`t show high wind probabilities
being that high, but latest RAP/HRRR indicate 3-5mb/3hr pressure
rises during peak heating Saturday along with modest cold air
advection, subsidence, and deep mixing. This setup should tap
into 40-50kt 850mb (60kt 700mb) winds over the northwest SD
plains from K2WX-KRAP creating high wind warning speeds. Could
also have some gusty winds with pre-frontal trough, especially
over the lee side of the Black Hills overnight, but gradient
across the Black Hills only 3-4mb with 40kt boundary layer wind,
which is usually not enough to cause troubles.
.DISCUSSION...(This Evening Through Friday)
Issued at 147 PM MDT Fri Oct 30 2020
Shortwave ridging ongoing across the region as a potent ridge
topping impulse dives into the Northern Plains. Decent mixing
coupled with terrain effects around the Black Hills has allowed
temps to rise into the 60s and lower 70s in NE WY and far western
SD. Breezy conds will continue tonight there esp in the eastern BH
foothills where near adv winds may develop for a couple hours
ahead of the sfc trough. This will hold temps up there most of the
night. Otherwise, fog and low clouds has finally mixed out over
the far NE where snow cover has limited mixing. Patchy fog may
redevelop there overnight given lingering BL moisture and snow
pack. Clipper will shift east across the region Sat, with gusty NW
winds developing behind the front esp by late morning as diurnal
mixing ensues. Fast moving nature of the system has resulted in
the core of the strongest winds aloft shifting east faster, thus
not lining up with peak heating as well as earlier progs were
indicating. Forecast models are not in consensus with wind speeds,
wit the HRRR and NAM much weaker than the RAP and GFS. Hence,
confidence in a warning is not high enough to upgrade the high
wind watch at this time and will defer to later shifts. Did switch
the watch to an adv for eastern areas with concerns on mixing per
lingering snow cover and overall less wind in progs. The
potential still remains for a period of warning level winds in far
western SD, esp from 2WK to RAP. Much cooler conds expected Sat,
with a warming trend beginning Sunday and persisting into the
middle of next week. Mean ridging then progged through much of the
following week with temps well above seasonal norms. Highs will
likely reach into the 70s a couple days, esp Tues in the lee of
the Black Hills into scentral SD where a few 80s are certainly
possible. Dry pattern will continue with no chances for precip in
the next seven days. Cold and snowy weather looks to return toward
next Sunday-Monday as a deep upper trough develops over the
western CONUS and cold air advects SE into the Northern Plains.
Sfc cyclone likely early the following week (Nov. 8-10), which
would likely support snow accums in a portion of the region, where
exactly remains unknown for now.
.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 524 PM MDT Fri Oct 30 2020
VFR conditions will dominate the weather through the period. A
sharp cold front will bring gusty southwest winds ahead it over
the higher elevations tonight and then gusty northwest winds
behind it later tonight into Saturday. Wind gusts from 30-45kts
are likely Saturday on the SD plains with locally higher values
from K2WX to KRAP.
SD...Wind Advisory from 10 AM MDT /11 AM CDT/ to 6 PM MDT /7 PM CDT/
Saturday for SDZ014-032-043-044-046-047-049.
High Wind Warning from 6 AM to 6 PM MDT Saturday for SDZ001-002-
Wind Advisory from 6 AM to 6 PM MDT Saturday for SDZ025-026-072.