Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/27/19
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
902 PM CDT Sat Oct 26 2019
Issued at 859 PM CDT Sat Oct 26 2019
Made a few adjustments this evening. Updated PoPs, and added a bit
to QPF progs given latest HRRR runs. This resulted in just a bit
more snow vs previous package. Next round of pcpn is forming over
the High Plains, and is headed toward the southwest CWA. Temperature
forecast looks to be on track.
Issued at 235 PM CDT Sat Oct 26 2019
A cold front continues to traverse the region and will be through
the CWA over the next few hours. As expected, post frontal winds
have become quite gusty with areas in the western CWA with observed
gusts up to 40 mph. Winds will decrease a bit from west to east
tonight, although will still remain breezy overall through Sunday. A
few light showers (potentially with some snow mixed in) this
afternoon will cross over north central South Dakota. These
showers won`t produce much in the way of precipitation. More
significantly is the potential for snow tonight in central South
Dakota as shortwave energy passes through the area. One to two
inches of snow is possible in central South Dakota with the
highest amounts likely confined to along and south of the I90
corridor. Still, a few tenths to half an inch of snow are
certainly possible in portions of northeastern South Dakota as
well, especially on the Coteau.
Beyond tonight, an upper level longwave trough sets up over the
southwest to central CONUS and doesn`t really move much through the
workweek. This will lead to colder than average and mostly dry
conditions through the forecast period. By the weekend, models
indicate the longwave trough will finally kick off to the east and a
change to northwest flow will ensue. As mentioned, temperatures
take a dive with high temperatures struggling to even make it out
of the 30s through Thursday, while lows drop into the teens and
20s. The coldest period as of now looks to be Tuesday through
Wednesday night following a fropa Monday night. Highs Tuesday and
Wednesday will be in the upper 20s to low 30s with lows in the
teens over most, if not all, of the CWA.
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 614 PM CDT Sat Oct 26 2019
A mix of VFR/MVFR cigs will move from west to east across the CWA
overnight. Light rain/snow is also possible, and may occasionally
limit vsbys to less than 3 statute miles, especially at KPIR
Area Forecast Discussion
National Weather Service State College PA
1143 PM EDT Sat Oct 26 2019
Low pressure will track north through the Great Lakes tonight,
with the trailing cold front coming through Pennsylvania Sunday.
High pressure will build into the region early next week, then
another low pressure system is likely to track west of
Pennsylvania late in the week.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Radar trends and model data showing best fgen forcing lifting
north of Pa late this evening support lowering POPS from south
to north between 02Z-06Z. The latest HRRR and 12Z HREFV3
support this scenario, with only scattered showers/patchy
drizzle across the central mountains and Allegheny Plateau by
The focus still remains on approach of cold front and heavier
rain late tonight. Strong forcing ahead of approaching
shortwave, combined with a plume of tropical moisture, will
support a period of moderate to heavy rain moving into the
western half of the forecast area by dawn.
Low level stability fields indicate the surface warm front will
surge into the southern and western counties toward dawn,
causing temperatures to rise before sunrise. Evening lows are
expected to range from the upper 40s to low 50s, but readings by
dawn are likely to be well into the 50s.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
Latest guidance indicates band moderate to heavy rain will
sweep east of the region with cold front by around 15Z. HREFV3
EAS probability fields indicate rainfall totals of around 2
inches are possible across the Poconos, where orographic forcing
will play a role. Elsewhere, totals of 1 to 1.5 inches appear
likely. These amounts fall short of FFG/FFH numbers, so flooding
does not appear to be a significant threat.
Strong subsidence behind front should result in breaking clouds
across parts of the area during late morning and early
afternoon. However, low level instability associated with
arrival of cooler air around 850mb should result in plenty of
stratocu during the PM hours, especially over the Allegheny
Temperatures are expected to surge during the morning hours, as
chilly air at low levels mixes out. 850mb temps support
readings getting into the low 70s across the Lower Susq Valley
around midday before increasing clouds and cold advection
develop during the afternoon. Elsewhere, expect max temps to
range from the upper 50s over the NW Mtns, to the 60s east of
the Allegheny Plateau.
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
* Dry weather and slightly above normal temperatures for
Sunday through early Wednesday
* May be a stormy Halloween followed by colder weather with the
first mix of snow across the higher elevations Nov. 1
The storm system affecting the near and short term will clear
out by early Sunday afternoon (west) and by Sunday evening
(east) night, with not much cooling expected behind it and the
flow remains out of the southwest aloft. Surface high pressure
builds across Monday and moves off the coast Tuesday with a mild
southerly flow through PA.
Weak disturbance moves across Great Lakes Tuesday night just
bringing a slight chance shower to the northwest. Still
uncertainty with the timing of the next high amplitude system
which is looking to impact Halloween. Increasing chances of rain
from slight to chance Wednesday due to the uncertainty of the
timing with the next storm system. It may hold until Thursday
morning. Another pretty good rain expected as the storm system
moves by. Strong cold front with temperatures and thickness
dropping behind it. Brought a mixture of rain and snow showers
in over the higher elevation areas overnight Thursday and
Post frontal westerly flow will continue into Saturday with dry
weather and near to below normal temps for the early part of
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Rain more spotty as of 11 PM. Minor updates to the TAFS.
Earlier discussion below.
00Z TAFS sent.
Much of the rain has stayed well to the west of the area, but
conditions starting to head down.
LLWS will be of concern as well overnight.
Expect rain to become more widespread to the southeast later
tonight and Sunday morning.
Hints since late last evening when I was getting done with
the fcst that the system is moving slightly faster now, than
what the models showed the other day. Thus improving conditions
from west to east during the afternoon Sunday.
After Sunday, several real nice days for late October, as high
pressure builds eastward into the area.
Mon-Tue...Dry with mainly VFR conditions.
Wed...Increasing clouds with a chc of rain late.
Thu...Widespread showers with restrictions.
Area Forecast Discussion
National Weather Service Cheyenne WY
706 PM MDT Sat Oct 26 2019
Issued at 654 PM MDT Sat Oct 26 2019
Despite the quicker than anticipated frontal passage over the
region, light snow has not occurred as far south as anticipated
by 01Z. Temperatures are not dipping down to dew point readings
and the atmosphere isn`t moistening down to the surface toward the
WY/CO border. Due to this observation, snow totals have been
decreased a bit to reflect the current situation. It should not
take much longer to have light snow in Cheyenne as observations
show Wheatland having snow falling as of 01Z.
.SHORT TERM...(This evening through Monday)
Issued at 330 PM MDT Sat Oct 26 2019
At 3 pm, the leading edge of much colder air was situated from
north of Rawlins and Laramie through Cheyenne and the southern NE
Panhandle. The front was 2-3 hours ahead of schedule, and will
continue its southward trek into northern CO through late this
afternoon and early evening. There was a north to south temperature
gradient, ranging from 31 at Casper WY to 71 at Sidney NE. An
increasing northeast-southwest band of post-frontal snow from
western through northeast WY will settle south across the CWA
through this evening.
Most high-resolution models and model ensemble blends are
consistent with the development of widespread accumulating snow
tonight and Sunday. Very deep dendritic growth zone below 0C (up
to 10000 ft), significant upward vertical motion in left front
quadrant of 140-kt 250mb jet, slow moving 700mb front over
southeast WY and moist upslope low-level northeasterly flow
are the ingredients coming together for periods of moderate to
heavy snowfall. Winter weather headlines were adjusted to account
for storm total snowfall, with no changes to the timing of the
event (tonight through Sunday night). In addition to Dawes County
NE, Winter Weather Advisories were issued for Box Butte, Banner,
Scotts Bluff, and Kimball counties. A Winter Storm Warning was
issued for South Sioux County NE, as well as the Sierra MAdre
Range in southeast WY. Both the Pine and Cheyenne Ridges will
measure locally higher totals, with widespread 2 to 8 inches for
the NE Panhandle, and 8 to 18 inches for southeast WY. Model
ensembles have been trending higher the last few model cycles,
while outliers like the NAM are trending lower. Gusty north to
northeast winds around 25 mph wil create patchy blowing snow. the
combination of falling and blowing snow, slick/snow-covered
roads and poor visibility will create dangerous winter driving
conditions tonight and Sunday. Snowfall will begin to taper off
Sunday night and Monday morning.
.LONG TERM...(Monday night through Friday)
Issued at 422 AM MDT Sat Oct 26 2019
The active winter weather will persist through the upcoming week,
with the next round of snow expected as early as Monday night and
Tuesday morning. A reinforcing shot of very cold air and accompanying
upper level trough will produce periods of light to moderate snow.
At this time, advisory snow amounts will be possible, with 2 to 6
inches for much of southeast WY and the southern half of the NE
Panhandle. After this system departs and snow ends Tuesday night,
expect bitter cold temperatures with fresh snow cover (lows 5 to
-5 degrees and wind chills as low as -20). A slow moderation of
temperatures commences Wednesday through the end of the week, but
remaining well below normal. An increasing northwest flow aloft
and 700-850mb gradients may produce strong winds Wednesday night
and Thursday morning for the southeast WY wind corridors.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 519 PM MDT Sat Oct 26 2019
Front has made its way through southeast Wyoming this afternoon
and is currently in northeast Colorado. Winds have shifted
northeast for locations east of the Laramie Range...so upsloping
conditions have started. Generally followed HRRR guidance for the
00Z TAFs which shows lower ceilings developing after 03/04Z and
continuing overnight. Snow should begin in earnest after 06Z for
many locations and continue through much of the day Sunday. LIFR
conditions looking likely...especially for KCYS.
Issued at 139 PM MDT Sat Oct 26 2019
Warm, breezy and dry conditions early this afternoon will be
short-lived as a strong cold front advances south across the
districts through late the afternoon and early evening. Sharply
colder temperatures will cause rain to quickly change to snow.
Widespread snowfall, moderate to heavy at times, is likely tonight
and Sunday before decreasing Sunday night. Bitter cold wind
chills are expected Sunday night through Tuesday night. Another
strong cold front and upper level weather disturbance will bring a
continuation of very cold temperatures and additional light to
WY...Winter Storm Warning until 6 AM MDT Monday for WYZ101>110-
NE...Winter Storm Warning until 6 AM MDT Monday for NEZ095-096.
Winter Weather Advisory until 6 AM MDT Monday for NEZ002-003-019-
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
939 PM CDT Sat Oct 26 2019
939 PM CDT
Heavy rainfall has impacted much or northeast IL during the late
afternoon and evening hours, with many reports of 2" to 3" amounts
as of mid-evening. Getting several reports of street/viaduct
flooding around and near the Chicago metro area. Have issued an
areal flood warning for much of northeast IL which runs through
845 am Sunday morning. Plan to maintain other headlines (Lakeshore
Flood Advisory, etc.) as they are at this time.
Vigorous autumn storm system was tracking northeast across the
region as of 9 pm, with surface low pressure near 995 mb located
near Kankakee. Large deformation zone area of moderate to heavy
rain extends from east of St Louis northeast across northern IL
into southeast WI, with some decrease in reflectivity intensity
noted across the forecast area recently. Radar rainfall
estimation has generally been significantly underdone compared to
measured reports received this evening, with many spotter reports
of rainfall in excess of 2 inches received. Based on this, and
many reports of various street and low lying area flooding, have
issued aforementioned areal flood warning in effect through the
overnight hours and early Sunday morning. Rain will eventually
taper off from southwest to northeast during the pre-dawn hours.
Otherwise, not much change in thinking or to headlines from the
previous shift. Have maintained a special weather statement for
gusty 40-50 mph winds across our far southeastern cwa associated
with strong isallobaric gradient, as well as lakeshore flood
advisory for large waves impinging on the Illinois section of our
Lake Michigan shore.
303 PM CDT
Through Sunday night...
A very potent Autumn storm system will impact the area though
tonight. As a result of this storm system there continue to be
several concerns, most notably:
-Several hours of moderate rain this afternoon and evening, with
some concern for some areal and river flooding.
-Lake shore flooding this afternoon and tonight due to strong
-A period of strong, potentially damaging westerly winds tonight.
Water vapor imagery early this afternoon shows the main mid/upper
level storm system now in the beginning stages of transitioning
to a negative tilt (northwest to southeast orientation) over the
Ozarks. Meanwhile, the associated surface low is now moving
northward into far southern IL. As the system continues to take
on a negative tilt through the afternoon, expect rain rates to
increase some across the area as dynamic forcing for ascent begins
to really ramp up over IL. The heaviest rain is likely to occur
over northern IL early this evening. This is the time when the
strong upper level dynamics will coincide with strong mesoscale
forced ascent within a developing deformation zone over the area.
While instability is expected to remain lackluster over the area
into this evening, negative EPV within this zone of strongly
forced ascent could support a few embedded rumbles of thunder into
this evening and this could support some locally heavier rainfall
Total rainfall amounts through later this evening should end up
around 2", with the highest amounts again expected to be centered
right across northern IL, in and near the Chicago metro area.
This is the area in which a band of strong mid-level frontogenesis
will develop within a strengthening deformation zone. The
enhanced lift, generated from a ageostrophic response, in this
zone will likely drive some locally enhanced rainfall rates this
evening. Expect the rain to abate over the area overnight as the
storm system quickly shifts to the northeast.
The other concern tonight is with the magnitude of the winds.
With a surface low this deep, winds are certainly gusty tonight.
That said, there is not enough confidence in any one area for a
wind headline (regular 45+ mph gusts). Two areas though that winds
could briefly top criteria are near the lakefront and then the
southeast forecast area overnight. As the low approaches,
northeasterly winds will sharply strengthen within the pressure
falls this evening. This component will be fully onshore into
northeast Illinois thus lowering any frictional aspect and
allowing for potential 40+ gusts. For the southeast forecast area,
in the immediate wraparound cold advection, there is a surge of
pressure rises collocated with mixing (albeit shallow), that
potentially supports a brief period of 50 mph gusts. The HRRR has
been showing wind gusts of this high, and most models have near or
up to 50 kt flow at 925 mb. For now have handled this with a
Special Weather Statement, but a short-lived Wind Advisory is
Regarding the strong onshore winds in northeast Illinois, this
will build waves considerably this evening as more of the fetch is
realized with the backing wind direction. Waves of 8-11 ft are
likely with some occasional higher. With the high to near-record
lake levels, this nears our criteria for a warning, but the
somewhat short duration of a great onshore component lowers
confidence a bit. Will maintain a strongly worded advisory for
now. For northwest Indiana, the waves will take a noteworthy jump
in the northwest flow overnight, but that is even short lived, so
no advisory needed for now but still some brief high wave action
predicted overnight especially for Porter County.
After tonight, conditions will improve nicely for Sunday. Lighter
winds and clearing skies should set up a nice end to the weekend,
with highs likely in the upper 50s to around 60.
305 PM CDT
Monday through Friday...
Not much has changed with the forecast thinking in the extended.
Please see the previous discussion below for more info.
Next week looks to remain active with several periods of precip
chances. Highly amplified pattern and a large upper level trough
in place across the CONUS will support periodic precip chances
through mid week. An upper level low/trough then expected to swing
through the region late in the work week and provide additional
precip chances. Guidance still varying to the overall evolution to
the pattern and systems next week, including the extent and
timing of any colder air moving through the region. This will be
something to keep an eye on, as this colder air could bring a
chance of more wintry type weather.
For the 00Z TAFs...
704 PM...Forecast concerns include...
Strong gusty northeast winds shifting northwest tonight.
Rain with lifr/ifr cigs this evening.
Low pressure over east central IL will continue lifting northeast
this evening. Strong/gusty northeast winds will slowly turn
northerly and then northwesterly and some tweaks to this timing
are possible. Wind speeds/gusts may diminish some as the low
passes just to the east of the Chicago terminals. Winds will then
shift northwest and a period of gusts to 30kts is possible
overnight. Winds will turn more west/northwest Sunday morning with
speeds/gusts slowly diminishing by midday.
Moderate rain is likely to continue through mid evening with light
rain tapering to showers overnight. Prevailing vis likely to
remain 1.5sm to 3sm for next few hours and will then slowly trend
up as rain tapers off. As the low approaches...cigs may trend
lower with prevailing lifr expected. As winds shift northwest...
cigs will slowly lift through ifr and eventually become vfr Sunday
349 PM CDT
This is the prime time for Great Lakes strong wind and high wave
systems, and one certainly is impacting southern Lake Michigan
through early Sunday. Northeast winds will increase through mid
evening across the southern part of the lake, with this direction
maximizing the fetch into northeast Illinois, where waves will peak
to occasionally over 10 ft. Confidence is a little lower in
northwest Indiana, which will realize its best onshore potential
overnight and very early Sunday morning. Have expanded the Gale
Warning to include northwest Indiana overnight. Winds will be
sharply coming down in speed after daybreak Sunday and waves
should slowly subside, most quickly along the Illinois shore.
ILZ021-ILZ022 until 3 AM Sunday.
Lakeshore Flood Advisory...ILZ006-ILZ014 until 5 AM Sunday.
Flood Watch...ILZ023-ILZ032-ILZ033-ILZ039 until midnight Sunday.
LM...Gale Warning...IL nearshore waters until 7 AM Sunday.
Small Craft Advisory...LMZ740-LMZ741-LMZ742...7 AM Sunday to 10
Gale Warning...LMZ743-LMZ744-LMZ745...3 AM Sunday to 9 AM Sunday.
Small Craft Advisory...IN nearshore waters until 3 AM Sunday.
Small Craft Advisory...LMZ743-LMZ744-LMZ745...9 AM Sunday to 1
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
Area Forecast Discussion
National Weather Service Pueblo CO
329 PM MDT Sat Oct 26 2019
.SHORT TERM...(This evening through Sunday)
Issued at 254 PM MDT Sat Oct 26 2019
Southern Colorado enjoying one last mild autumn day as temperatures
have soared into the 60s/70s across the plains with 50s/60s over the
mountains and high valleys. The end of the warmth is in sight as
strong cold front was racing south through WY this afternoon, driven
southward by deepening upper trough over the nrn Rockies. Stuck with
the HRRR forecast bringing the boundary through Colorado Springs
around 04z, then reaching the CO/NM border by 09z. North winds will
become strong for several hours behind the front, gusting to around
40 kts along and east of I-25, before speeds diminish and direction
turns more easterly after sunrise. Precip chances overnight look
fairly low, with perhaps some flurries or freezing drizzle
developing over the Palmer Divide/eastern mt slopes and high terrain
south of the Arkansas River as low levels gradually saturate.
On Sunday, cold air deepens over the plains and eastern mountains,
with wedge of warm/dry air holding on from the Sangres westward.
Favored upslope areas along and west of I-25 will see on/off light
snow through the day, with precip slowly becoming more widespread
toward late afternoon as dynamic lift begins to increase ahead of
the upper trough. Not expecting much if any snow accumulation during
the day Sunday, with generally a dusting most locations, while Pikes
Peak region and Palmer Divide see up to an inch. Didn`t make too
many changes to precip chances over the eastern mountains and
plains, but did lower pops somewhat farther west over the central
mountains, where most models suggest snow holds off until evening.
Max temps on the plains won`t rise much from morning lows, with
readings steady or evening falling slightly by afternoon. Relatively
warmer air holds on across the San Luis Valley and southwest
mountains, with only slight cooling from Sat readings.
.LONG TERM...(Sunday night through Saturday)
Issued at 254 PM MDT Sat Oct 26 2019
Sunday night - Monday night...
At the start of this period, the aforementioned southwest-northeast
oriented upper trough axis will extend from east-central
California through the Great Basin and and into North Dakota. The
associated southwesterly jet will be draped across Colorado. Post-
frontal surface flow will be easterly across the eastern plains,
and snowfall will be increasing in coverage and intensity across
the central mountains and Pikes Peak Region southward.
Sunday night through Monday morning, the trough axis will shift east
across the Great Basin and into Colorado, with considerable QG
forcing for ascent and height falls overspreading southern
Colorado. Strong upper forcing combined with intense southwest to
westerly upslope low to mid level flow will result in accumulating
snowfall over the Continental Divide, with greatest amounts over
the southwest mountains and central mountains. Heaviest
precipitation appears to be focused along a 700 mb
front/convergence zone, between 06Z and 15Z Monday morning.
Further east, the strong upper forcing combined with continued
easterly upslope surface flow across the plains into the eastern
mountains will yield widespread snowfall, with greatest
coverage/intensity across the I-25 corridor and Wet mountains.
Another factor promoting accumulating snowfall will be
strengthening isentropic lift during the morning within a
saturated dendritic growth zone. Finally, the strong southwesterly
upper level jet overhead will support the development of
southwest to northeast oriented snow bands, within which locally
heavy snowfall may occur. Heaviest snowfall across the I-25
corridor should occur between 12Z and 18Z. Thereafter, snow across
the forecast area will decrease in coverage and intensity as the
trough axis shifts east out of Colorado, with snowfall ending
across most areas by 00Z. Height rises and large scale descent in
the wake of the exiting trough will lead to dry weather Monday
night. There is limited uncertainty regarding the likelihood of
accumulating snowfall with this system, as deterministic runs have
shown an acceptable degree of run-run and model-model consistency
over the last several day or so. Further, ensembles show only
minor timing and QPF differences, hence a slight snow total/timing
As for snow totals, currently expecting 4-8 inches across the
southwest and central mountains, and 6-12 inches over the eastern
mountains, with the Wet Mountains on the higher end of the
threshold, and Sangres lower. For the I-25 corridor from Walsenburg
to Colorado Springs, expect anywhere from 3-8 inches of total
accumulations with this event, while northern El Paso and Teller
Counties should see more like 6-10 inches. Snow banding could result
in varying snow totals within small spatial areas, including locally
higher amounts. Locations across the eastern plains should
experience 1-3 inches of snow accumulations, while the San Luis
Valley will see snowfall up to one inch. Therefore, have upgraded
all zones within the existing watch to a Winter Weather Advisory,
with the addition of the northern Sangres. Held off on including the
eastern San Juans as models have been inconsistent here, so will
wait for the next round of runs in order to gain confidence in this
Temperatures will dip into the teens across the plains and valleys
both Sunday night and Monday night, with highs on Monday struggling
to rise above freezing anywhere except in the San Luis Valley.
Tuesday - Wednesday...
After a brief break Monday night, the next system will dig into the
Great Basin and across Colorado Tuesday through Wednesday,
sending another cold front down the eastern plains Tuesday night.
The latest GFS and ECMWF runs are quite similar with the track,
closing off the low over Utah and tracking it east across
Colorado. However, the GFS is faster than the ECMWF by about 12
hours. The GFS ensemble mean shows a similar solution, but with
considerable timing differences and most members displaying a
slower evolution. There is also significant timing and total QPF
spread among members. Bottom line, it appears as though a second
storm system will bring another round of accumulating snowfall to
most of south-central and southeast Colorado sometime during the
Tuesday through Wedensday evening timeframe. However, it is still
too early to pinpoint the period of heaviest snowfall, and
Temperatures will remain cold, with daytime highs near or below
freezing. Overnight lows will be very cold, with single digits
forecast over the lower elevations, and below zero temperatures over
the mountains and some valleys.
Thursday - Friday...
Tranquil weather returns to Colorado for the end of the work week as
drier air moves into the region and a ridge begins to build over the
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 254 PM MDT Sat Oct 26 2019
At KALS, VFR the next 24 hrs with increasing s-sw winds by midday on
At KCOS and KPUB, VFR into this evening. Strong cold front then
pushes south through both sites 04z-05z, bringing north winds
gusting to 40 kts until 08z-10z. Lower clouds will fill in behind
the boundary, with MVFR cigs both terminals by 10z, and areas of
IFR/LIFR conditions over the higher terrain just north and west of
KCOS. May even see a few flurries or brief freezing drizzle as air
mass saturates. Clouds and flurries hang on all day Sunday, with
MVFR cigs occasionally lowering to IFR both sites. Snow then becomes
more widespread Sun night into Mon with MVFR/IFR cigs and vis
Winter Weather Advisory from 4 PM Sunday to 6 PM MDT Monday for
Area Forecast Discussion
National Weather Service Blacksburg VA
737 PM EDT Sat Oct 26 2019
High pressure will drift northeast and away from the region as
low pressure lifts north through the Tennessee and Ohio Valleys.
The approach of this low pressure system, and its associated
cold front, will result in plenty of clouds and a slowly
increasing threat for rain from west to east with the bulk of
the rain to fall tonight into Sunday morning before skies begin
to clear from the west following passage of the front.
.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 720 PM EDT Saturday...
Rain and drizzle has been gradually lifting northward along the
Blue Ridge into portions of the New River Valley under
increasing upslope flow, despite the radar showing little
returns, as beam overshoots the lower cloud layer squeezing out
the moisture. Showers are also approaching southeast WV early
this evening, though appears main line of showers arrives after
midnight, while southeast flow induced rain showers increases
along and either side of the Blue Ridge. Updated forecast to
account for latest radar/high-res model trends with the HRRR
handling things fairly well. Updated to include some moderate to
heavy rain at times toward dawn as convective elements are
likely. Appears just enough instability to arrive in the
southern CWA late tonight for isolated thunder chance which
includes after 12z Sunday. The Storm Prediction Center is
actually showing a marginal risk for severe storms scraping our
far eastern counties tomorrow around Halifax/Charlotte due to
wind energy with this front. However, timing of this does not
favor severe as it moves through prior to 17z, but have thunder
in the grids.
Wind advisory still looks good with gusts ramping up before
midnight, lasting through about dawn, then tapering off, as flow
turns south, then southwest.
Previous discussion from early this afternoon...
Wind Advisory in effect through 10 AM Sunday from western
Greenbrier southward to Watauga county.
A cold front will slowly move across the area tonight into
Sunday. A short wave will track along the front tonight,
bringing widespread moderate rain to the area. Low level
convergence, strong warm air advection, good moisture transport
and jet dynamics may produce isolated heavy downpours overnight.
With low level southeasterly flow going up the Blue Ridge this
afternoon and overnight, storm total rainfall amount could
approach 2 inches. Across the rest of the area, rainfall amounts
will range from a half to one inch across the mountains and
foothills, to half an inch over the Piedmont. Fortunately, no
flooding concerns are anticipated due to initially relatively
low creek and stream levels. However, urban street flooding is
possible as fallen leaves may clog storm drains.
Southeast winds along the Blue Ridge will have an opposite
effect along the western slopes from Greenbrier County WV to
Watauga County NC. Downsloping winds may gusts up to 50 mph
tonight into Sunday morning.
The front is expected to clear the mountains by sunrise, then
move east of the piedmont by early afternoon. With the early
exit of rain and no strong cold air advection behind the front,
Sunday afternoon temperatures will warm above normal with upper
60s to lower 70s across the mountains and mid to upper 70s east
of the Blue Ridge.
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 215 PM EDT Saturday...
High pressure will be building into the eastern states for the
start of the work week with mild temperatures and sunny skies.
the resilient upper level ridge over the southeast will become
strongly reestablished on Monday with heights building along the
east coast while a upper trough deepens once again over the
western CONUS. This has been a familiar pattern for much of the
last 6 to 8 weeks. Well above normal highs will be in place for
Monday with 70s possible especially east of the Blue Ridge.
Surface high begins to retreat to the northeast on Tuesday as
upper ridge axis shifts slowly east as well. Highs will again
top 70 in much of the area close to 10F above late October
climatology. Lows will be upper 40s to low 50s both days. High
clouds will increase on Tuesday ahead of the next potential
weather-maker over the Midwest.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 PM EDT Saturday...
A slow-moving front will stretch from the eastern Great Lakes
down to east Texas on Wednesday as meridional flow amplifies
with the stubborn ridge off the east coast combined with a
deepening trough over the Rockies. The return flow of moisture
ahead of this boundary will result in increasing clouds and pops
during the day with high chance or likely by late afternoon.
The slow movement and abundant moisture suggests the possibility
of substantial rainfall from this mid-week system with possibly
several waves of low pressure developing along the front to
slow down the front and prolong rain chances. Early QPF
forecasts from WPC suggest another 1 to 2 inches of rain
possible before ending late Thursday or early Friday.
Temperatures look to be mild through Thursday even with the
clouds and rainfall with highs generally in the 60s and lows in
the 50s. Slowly clearing skies Friday with more seasonable
temperatures likely into the start of next weekend.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 725 PM EDT Saturday...
Expect deteriorating conditions tonight into Sunday morning as
rain showers increase in coverage. Should see sub-VFR by 05z,
then IFR to at times LIFR with moderate to heavier showers as
front moves across between 08z-13z in the west, exiting the east
by 16z-17z. Southeast winds will be gusty especially at BLF with
up to 30-35kts likely this evening into overnight, then slacking
off as flow turns southwest after 08z.
Cannot rule out some low level wind shear this evening at
BLF/BCB, but at the moment kept them out due to showers
Look for improving conditions from west to east in the 12-17z
time frame Sunday to VFR. Winds turn west, and some gusts to
20kts possible in the mountains.
.Extended Aviation Discussion...
High pressure building in from the west supports VFR weather
Sunday night through at least Tuesday. Approach of yet another
Gulf Coast system and associated area of widespread rain then
expected to bring another period of sub-VFR weather to the
region on Wednesday into Thursday.
VA...Wind Advisory until 10 AM EDT Sunday for VAZ007-009-015.
NC...Wind Advisory until 10 AM EDT Sunday for NCZ001-018.
WV...Wind Advisory until 10 AM EDT Sunday for WVZ042-043-508.
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Sunday night)
Issued at 259 PM CDT Sat Oct 26 2019
19Z water vapor imagery showed a closed upper low near the MO boot
heel lifting northeast. Another upper low was noted over Manitoba
with an upper trough stretching back to the southwest over the
northern Rockies. This upper trough was digging south. At the
surface, low pressure was moving north along the MS river valley
into the Upper Midwest and a cold front was seen moving into the NEB
For tonight, relatively dry air should remain over the forecast area
keeping skies clear ahead of the approaching cold front. With light
winds, think low temps will drop off into the mid 30s for most
areas. Can`t rule out the possibility for some localized ground fog
again, but impact looks to be too limited to include in the
forecast at this time. The cold front is expected to move through
the area through the morning hours of Sunday. A lack of deep layer
moisture and forcing is expected to keep the frontal passage
mainly dry. However the NAM and now the RAP still show some
potential for the development of drizzle by Sunday evening with
some isentropic lift within the stratus deck. The GFS forecast
soundings tend to have more dry air below the stratus than other
solutions. So am not sure what to believe as the NAM tends to over
do the boundary layer moisture. Have left the mention of precip
out of the forecast for now, but later shifts will need to monitor
trends. For now lows Sunday night are expected to be in the mid
and upper 30s across east central KS where the drizzle is more
likely. So impacts from any drizzle appear to be negligible.
Temps through the day Sunday could be a little tricky. Have
trended highs cooler across north central KS where a north wind
and mostly cloudy skies are expected to keep temps steady in the
40s to near 50. East central KS could still see a warm up to near
60 where clouds will be slow to move over.
.LONG TERM...(Monday through Saturday)
Issued at 259 PM CDT Sat Oct 26 2019
The Monday into Monday night periods see a weakening upper trough
pass from southwest to northeast across the region with the
surface front well south. There are some differences on the wave`s
track with the GFS slightly farther south with the main PV
anomaly but the lack of consistent, deep saturation with the
weakening wave bring only moderate precip chances. Southeastern
areas could again see some drizzle along the elevated boundary
especially if the wetter NAM-sourced solutions end up being more
on target with low-level moisture, and forecast high temperatures
could also be a bit warm in this scenario, but an overall 10-15
degree diurnal rise seems in order area-wide. The rapidly-exiting
wave should end anything but very light precip amounts by shortly
after midnight. Most precip should fall as liquid but some light
snow can`t be ruled out Monday morning and evening.
The main periods of concern continue to be Tuesday night to late
Thursday with the next upper trough`s progressions south over the
Rockies then northeast through the central Plains. Reinforcing cold
air behind the Monday system will keep temperatures much below
normal as this system arrives. The track and timing details of the
trough continue to be uncertain, though an overall slower trend
is apparent, with the operational GFS still on the fast end of the
spectrum. This slower trend could lend itself to a more variety
of precip types with some warm nose potential in play. The bottom
line at this range is that accumulating wintry precipitation is
possible at times for much of these periods. Continued northwest
flow keeps temps cool into next weekend.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 617 PM CDT Sat Oct 26 2019
For the 00Z TAFs, have maintained LLWS eventhough most guidance
suggests it will likely be marginal and only have a short window
to develop. Increased LLJ winds ahead of the incoming boundary do
look to be around FL 10. In very low lying areas, there could be a
short window for ground fog as well. Have not mentioned in the
TAFs with overall low potential. FROPA should take place first at
KMHK around 09Z and then by 11Z time frame for KTOP/KFOE sites.
Low stratus should lag the front into the late morning hours and
some gusts up to around 20kts could be common into the afternoon.
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
947 PM MDT Sat Oct 26 2019
Issued at 942 PM MDT Sat Oct 26 2019
Snow is decreasing over the Black Hills so have cancelled the
winter wx advisory that was in effect...with additional
accumulations around an inch or less. The main band of snow has
set up across Fall River county and extends northeast through the
Badlands. This heavier band will continue to shift south/east
tonight, and taper off by morning. Will keep the advisory in place
for Fall River, Oglala Lakota, and Bennett counties where 3 to 6
inches total accumulation are likely.
UPDATE Issued at 602 PM MDT Sat Oct 26 2019
The wind advisory has expired, and winds will gradually decrease
overnight. No adjustments made to snow amounts or the winter
weather advisory at this time.
.DISCUSSION...(This Evening Through Saturday)
Issued at 138 PM MDT Sat Oct 26 2019
Upper trough is digging into the northwest quadrant of the CONUS,
with the jet across Idaho to Wyoming into western SD. Surface obs
show gusty northwest winds across the CWA behind a cold front, with
gusts into the 50s across the plains adjacent to the eastern Black
Hills. Will let the wind advisory continue. Temperatures have
been slowly dropping behind the front. Short to medium range
models continue to show a band of rain and snow crossing the CWA
late this afternoon through tonight. This band will change to all
snow this evening, bringing snowfall to much of the CWA.
Accumulations will generally be light. The exception will be
across two areas of the CWA...southwest SD and then northern Black
Hills. Short range models and Froude plots suggest upslope flow
will developing late this afternoon and continue mainly through
the evening hours. There is consensus of 3-6 inches of snow across
the northern Black Hills. The NAM and more recent runs of the
HRRR suggest higher elevations could see localized higher amounts
up to 8 inches. Will keep the advisory going given most areas will
be in the 3-6 inch range. The bulk of accumulating snow will fall
by 06z tonight, but lingering upslope snowfall is expected
through the overnight hours. Models are also showing good
consensus with 3-6 inches across portions of Fall River County in
southwest South Dakota...and 2-4 inches through Oglala Lakota and
Bennett Counties. Less amounts of 1-3 inches will be possible
overnight across south central SD. Snow will end by mid morning
tomorrow, except some lingering light snow across southwest SD
ahead of the upper trough axis working its way through the region.
Highs tomorrow will be in the 20s to low 30s. Dry weather and
slightly warmer temperatures are expected Monday as the region
remains in cyclonic flow aloft. A strong upper wave will dig
through the northern Rockies late Monday, then cut off across the
Great Basin on Tuesday. A cold front is progged to cross the
region late Monday into Monday night. Some snowfall will be
possible with the frontal passage, but light accumulations are
expected at this time. Models show max temps in the teens and 20s
on Tuesday. Dry weather is generally expected for the second half
of the week along with warming trend.
.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 514 PM MDT Sat Oct 26 2019
A band of snow will continue to move southeast across the region
this evening and overnight. Rather widespread IFR conditions with
the snow. Conditions will improve across northeast WY and
northwest SD around midnight, with improving conditions spreading
southeast overnight. Most areas should be VFR on Sunday. Gusty
northwest winds will gradually decrease tonight.
SD...Winter Weather Advisory until 6 AM MDT Sunday for SDZ027-041-042-