Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/18/20
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
827 PM EDT Sat Oct 17 2020
Cool and dry conditions will prevail through tonight as high
pressure builds in from the west and settles across the area.
The high becomes centered from Atlantic Canada to the local area
from Sunday through Tuesday, bringing dry weather with gradually
warming temperatures to the local area.
.NEAR TERM /THROUGH SUNDAY/...
As of 815 PM EDT Saturday...
Latest RAP analysis shows surface high pressure over the MD
lower eastern shore early this evening. Overnight that surface
high will shift up to New England, while another surface high
from the west settles over the area. Skies are mainly clear this
evening, with calm winds over the interior and 5-10 mph near the
coast. Ideal radiational cooling conditions tonight over inland
portions of the area will allow temps to fall steadily. Will
continue to go lower than guidance for low temps, with mid to
upper 30s inland, and lower 40s to low 50s closer to the coast
where the light onshore wind will keep temps up a bit.
Frost Advisory continues for the far W/NW sections of the CWA
where confidence is highest for overnight lows into the mid 30s
(with a few of the coldest spots potentially near freezing).
Patchy frost is also expected in far western and northern
Richmond suburbs, along with the Salisbury to Dorchester areas,
although coverage is not expected to be widespread enough to
On Sunday, a weak sfc trough moves into ern NC and SE VA and
will increase clouds such that skies avg out partly sunny (and
possibly mostly cloudy for a few hrs). Not enough deep moisture
to include any PoPs. Highs will be a little warmer, mainly from
around 70F SE to the mid 60s NW.
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 345 PM EDT Saturday...
The center of the high will be well to our NE by Sun night.
With weak return flow, lows won`t be quite as cold with mid 40s
inland and 50s near the immediate coast.
The latest 12z/17 model guidance continues to show a cold front
approaching the eastern states from the west on Monday but
parent low pressure becomes increasingly removed from the
boundary well to the north into Canada. As such, the boundary is
forecast to assume an east-west orientation across the Ohio
Valley with little to nothing to push the boundary toward our
area. Upper ridging builds toward the region from the SW
Atlantic on Monday resulting in continued dry weather and
afternoon highs in the low-mid 70s. Similar conditions for Tue,
with highs trending up another degree or two with some upper 70s
possible under partly/mostly sunny skies. Given the gradual
increase in low level moisture, some patchy fog/low clouds will
be possible early Tue AM.
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 345 PM EDT Saturday...
Latest models remain in decent agreement that a fairly strong
upper level ridge will remain anchored along the SE US coast
through the mid to late week timeframe, with sfc high pressure
over the local area and all systems staying off to our NW (with
a potential tropical system also staying well offshore to our
E). Temperatures will be above normal with highs mainly from 75 to
80F Wed-Fri with lows in the 50s to lower 60s. The ridge
gradually breaks down late Fri into next weekend, with the
typical differences in the models by that point. For now, will
have the forecast partly to mostly sunny/dry through Fri, with
more clouds and a low chance for showers by Fri night/Sat.
Cooler Sat with highs in the mid 60s to mid 70s.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 700 PM EDT Saturday...
VFR conditions to start the 00Z TAF period. Mostly clear skies
overnight. A light onshore flow at ORF/ECG around 5 kts,
with calm winds at RIC/SBY/PHF. Low level moisture increases
Sunday morning. This will result in clouds developing first
over the SE and then spreading N/NW throughout the morning. MVFR
ceilings are possibly by Sunday afternoon at ORF/ECG, while
remaining terminals are more likely to remain VFR. Winds after
15Z Sunday will be E/SE 5-10 kts.
OUTLOOK...Mainly VFR conditions with little to no chance for
rain Sun night through Thu. With the onshore flow, some flight
restrictions will be possible in low clouds/patchy fog early
each morning from Mon-Thu however.
As of 305 PM EDT Saturday...
Afternoon surface analysis shows 1028mb high pressure centered over
north-central VA with north and NNE winds continuing across the
waters. Waves are 2-3 ft in the bay with seas generally 4-6 ft
Despite a weakening pressure gradient as high pressure nears the
region, winds over the waters have been quite stubborn to subside
across the Ches bay this afternoon. Dry and cool air contacting the
still relatively warm bay/ocean waters has led to efficient mixing
of higher momentum winds aloft. Winds will slowly subside from west
to east through the remainder of the afternoon so have allowed most
bay headlines to expire on schedule but have extended SCA flags for
the mouth of the bay and the Currituck Sound until 7pm. Buoy 44009
off Ocean City continues show seas 5-6 ft so will extend this area a
few more hours as well. Seas will be slowest to subside across the
southern coastal waters south of the VA/NC border where SCA
headlines remain in effect through 4am.
High pressure moves away to the NE on Sunday but an elongated ridge
remains across the area with onshore winds 10-15 knots expected to
continue into the late afternoon before falling to 5-10 knots. Much
of the same is expected for the mid-week period with sub-sca onshore
flow and seas 3-4 ft.
As of 305 PM Saturday...
Large amplitude astronomical tides will continue this weekend
into early next week along with light to moderate onshore winds.
This combination will result in periods of mostly nuisance to
minor tidal flooding. Tonight`s high tide is lower than the one
earlier today so not expecting many coastal flood issues other
than some potentially low-end nuisance flooding. The next high
tide cycle on Sunday could be more problematic with minor and
potentially moderate tidal flooding in a few spots.
As of 115 AM EDT Saturday...
KDOX radar will be down until 10/21 for a scheduled generator
replacement. See FTMDOX for details.
VA...Frost Advisory from 2 AM to 9 AM EDT Sunday for VAZ048-060>062-
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ656.
Small Craft Advisory until 4 AM EDT Sunday for ANZ658.
Area Forecast Discussion
National Weather Service La Crosse WI
1042 PM CDT Sat Oct 17 2020
.SHORT TERM...(Tonight through Monday)
Issued at 200 PM CDT Sat Oct 17 2020
Cold front sweeping in from the northwest this afternoon with RAP
pointing to fairly decent frontogenetic forcing along it. The bulk
of the associated saturation is mostly in the mid/upper levels, but
ample to support shower production. Rather dry sub cloud layer but
warmer wet bulb temps per bufkit soundings would suggest rain will
be the the pcpn type at the outset. Can`t rule out a brief swing to
more of a wintry mix (or just snow) later into the night...although
sfc temps and soundings suggest is a small chance at this time.
Meanwhile, that dry layer will enhance already gusty winds around
Speaking of those winds, pressure gradient gets a little baggy as
the cold front moves in, but tightens later in the evening as the
front exits east. Will continue Wind Adv for small portion of south
west Wisconsin into the evening, but anticipation is that the rest
of the local area (while blustery) will stay below criteria.
A blast of cold air follows in the wake of the front and Sunday and
Monday are looking rather chilly as a result. 850 mb temps as cool
as -7 C while NAEFS 850 mb temp anomalies near -2. Highs in the 40s
will be the result while some locations in the north could struggle
to even reach that.
Weak high pressure builds in Monday, but models also point to a
ripple in the upper level flow sliding west-east across the region.
Some frontogenetic forcing with the shortwave, with models
generally favoring along/south of I-90 for the better lift.
Time/height x-sections point to enough saturation to fuel some pcpn
chances. Mostly just rain, light with minor accumulations (where it
falls). Some snow potential early and/or late...depending on how the
timing of the shortwave shakes out.
.LONG TERM...(Tuesday through Saturday)
Issued at 205 PM CDT Sat Oct 17 2020
Swift northwest to zonal flow a loft will slide various shortwave
troughs across the region, resulting in periodic precipitation
chances. Some differences between the GFS and EC on placement and
timing, especially in the smaller scale features, but latest runs do
agree on a couple periods: Tue and Thu. Temperatures look to be cold
enough that snow will be possible, moreso north of I-90...and
dependent on timing of the systems. Way too early to sketch out
possible/if any accumulations...but both models suggest minor snow
accums (mainly cold, grassy surfaces) are in play for the local area
north of I-94 later in the day Tue. Tis the season...
As for temperatures, after the cold Sun/Mon the flex in the upper
level flow will promote a bump up in temps, although still likely 5
to 10 degrees below the mid October normals. No significant warmup in
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1040 PM CDT Sat Oct 17 2020
The band of showers has diminished quite a bit, and dry conditions
are expected through this period. MVFR ceilings will linger for
awhile early this morning with the low clouds expected to erode
before daybreak. Lingering mid clouds through the morning give way
to nearly SKC in the afternoon, followed by increasing high
clouds in the evening. Northwest winds will lighten a bit late
tonight before turning breezy again in the afternoon. Winds then
become light and westerly in the evening.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
954 PM CDT Sat Oct 17 2020
...Short Term Update...
Issued at 953 PM CDT Sat Oct 17 2020
After "playing around" with various short term model data sets
(including latest HRRR/RAP/NAM), ended up making fairly minimal
change to the inherited forecast for overnight. If nothing else,
am feeling a bit more confident that any narrow frontogenetic snow
band that could potentially "zing" us with perhaps greater-than-
expected snow amounts in the 1-2" range would focus pretty
solidly north of the I-80 corridor, and would be most favored
within our far northern few counties (Valley/Greeley/Nance). South
of there, odds are that most places between Highway 92 and I-80
will see little to no snow (mainly just a dusting), while areas
south of I-80 and especially down into KS stand almost ZERO
chance of accumulating snow overnight. Have updated our Hazardous
Weather Outlook (HWOGID) to tweak this latest thinking a bit, but
again, the overall message from the earlier day shift forecast
package remains largely unchanged. This is not a major snow event
by any means, but especially our far north could easily see its
first accumulation of the season by sunrise.
.DISCUSSION...(This evening through Saturday)
Issued at 344 PM CDT Sat Oct 17 2020
The primary forecast concerns centered around the chance for
accumulating snow tonight, and then another chance for light snow
tomorrow tonight along with possible subfreezing temperatures for
areas that have yet to have a freeze.
Tonight...We will see strong cold air advection tonight along with
a decent frontogenetic precipitation band. Forecast models are
pretty consistent in showing banded precipitation stretching from
west to east across Nebraska tonight. However, there are subtle
model differences regarding the exact location of this narrow
precipitation band as well as differences in how quickly the rain
will change over to snow. Our higher resolution models such as
the HRRR and RAP tend to be the furthest south with this
precipitation band, with recent 18Z runs placing some of the
heaviest rain and snow centered over the Grand Island area. We`ll
see if that pans out or if it moves a bit one way or the other.
The overall 00Z and 12Z model consensus is for the heavier
rain/snow band to be just north of the Grand Island area. My
feeling is that this may end up trending just a bit further south
and I`m leaning towards the more southern solution with the
heavier snow running from northern Dawson County to around Grand
Island to York County. This is the kind of set up where the snow
band could be very narrow, only 25 to 50 miles in width. We are
officially calling for around one inch or less within this snow
band due to marginal temperatures right around or just above
freezing. Most of any snow accumulation will be on grassy
surfaces. However, given the nature of this band, and favorable
diurnally cool time of the morning, can not rule out a 10 to 20
mile wide 1-3 inches of snow on grassy surfaces in a few spots. I
could see this snow band shifting one way or the other by perhaps up
to 25 miles.
Temperatures tonight should only bottom out right around freezing
in areas that see the change over to snow, while areas along and
south of the Neb/Kansas border should remain just a bit above
It will be a raw/cold day with breezy north winds and highs only
in the 40s. Any snow should end by around mid morning.
There is some uncertainty here, but we could see another round of
light rain/snow across southern Nebraska, although it would likely
be lighter than tonight. There will be a good deal of clouds, but
temperatures do not have to fall off much for some folks to catch
their first freeze. We are currently forecasting lows to be right
around freezing, but clouds could play into which side of freezing
we end up on. With the forecast uncertainty Sunday night and the
snow to worry about tonight, decided to hold off on any Sunday
night frost/freeze headlines for now.
Monday through Saturday...
Did not make many changes from the overall forecast blend of
models during this outer forecast period, which continues to
indicate cool and mainly dry conditions. The big story will be the
below normal temperatures with highs in the 50s to lower 60s and
lows a few degrees either side of the freezing mark most every
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 721 PM CDT Sat Oct 17 2020
High confidence in VFR ceiling/visibility both right away this
evening and then through much of the latter half of the period
Sunday daytime. That leaves the late-evening through early-AM
hours (particularly 06-11Z) as the main time frame of concern, as
much of this time is expected to feature MVFR ceiling and at least
an off-and-on rain possibly transitioning to outright-snow for a
time. Wind-wise, the overall-strongest winds of the period are
right away this evening (sustained northerly 15-20KT/gusts to
around 25KT), with a gradual decrease in speeds then occurring
late tonight into the daytime Sunday as direction gradually starts
turning more easterly especially late Sunday afternoon. Read on
for more details regarding ceiling/visibility and precipitation
Ceiling/visibility and precipitation details:
Confidence is medium-high that much of especially the 06-11Z time
frame will feature quite a bit of MVFR ceiling, but the "exact
details" are still a bit murky, as probably cannot rule out a
brief period of IFR at some point, and at least high-end MVFR
could move in slightly before 06Z and perhaps linger until around
14Z. As for precipitation/visibility, confidence is fairly high
that a period of light rain will affect both sites overnight,
which could mix with some wet/slushy snow at some point. Have
indicated -RASN as the main prevailing type overnight, as expect
rain to be the predominant type overall. That being said, there is
an outside chance that a light coating of slushy snow could
materialize (slightly favoring KGRI versus KEAR). Once any light
precipitation moves out Sunday morning expect a return to VFR
especially beyond 14Z, although a considerable amount of mid-high
cloud cover will likely persist through the day.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1025 PM EDT Sat Oct 17 2020
Issued at 1025 PM EDT SAT OCT 17 2020
The valleys continue to drop off quick this evening so have taken
their lows and hourly T grids down into Sunday morning. Also
beefed up the frost in the weather grids as a result. Finally,
adjusted the near term T and Td grids per the latest obs and
trends. These updates have been sent to the NDFD and web servers
along with a forthcoming ZFP and SAF update.
UPDATE Issued at 740 PM EDT SAT OCT 17 2020
23z sfc analysis shows high pressure off to the east of Kentucky
and the light winds are starting to respond in its wake -
swinging around to the southeast. Skies remain mostly clear and
dewpoints are rather dry which should allow for another night of
good radiational cooling and a moderate ridge to valley
temperature split. This is already underway with the sheltered
spots already in the mid 40s while low to mid 50s are noted on the
hilltops. Dewpoints are generally in the low to upper 30s with
most of the variance found in the valleys. We are looking at some
of those valleys falling into the mid 30s by early morning with
patchy frost a good possibility for those locations. This
potential is featured in the grids, zones, and HWO. With this
update have mainly fine tuned the sky cover, T, and Td grids per
the latest obs and trends but also tweaked the fog potential.
These updated grids have been sent to the NDFD and web servers.
.SHORT TERM...(This evening through Sunday night)
Issued at 347 PM EDT SAT OCT 17 2020
The afternoon surface analysis reveals an area of surface high
pressure is parked to our east along the Central Apps. The flow
around the high is weak out of the south to southeast. The upper
levels we are seeing zonal pattern as yesterdays shortwave is now
in Maine. The zonal flow is bringing in a little smoke aloft from
the western states this afternoon based on the satellite and HRRR
smoke product. This is leading to a quiet forecast for tonight
under mostly clear and calm conditions. Despite the return flow,
a few of the cooler eastern valleys will see some patchy frost
tonight and perhaps a few locations see some valley fog.
The warming trend will continue Sunday, with partly sunny skies
and return flow leading to highs in the mid to upper 60s. The NAM
is depicting a decent low level jet kicks up in the afternoon and
provides the shot for a few showers in the Lake Cumberland and
perhaps the Bluegrass. However, most other guidance keeps it dry
and hold any precipitation until Sunday night. Did keep some
slight PoPs to account for this, but then all attention will be on
the baroclinic zone to the north. At the surface, we see a weak
boundary from a front that is disconnected from the parent low
across Canada. This will remain mostly to the northwest, as upper
level ridging to the southeast keeps this system from making much
headway east and southeast. This system will bring increasing
clouds at a minimum, but some showers will be possible mainly in
the Bluegrass regions nearer the I-64 corridor. This seems to
align well with the GEFS and EPS chances of seeing measurable
rainfall around that 24 hour period.
.LONG TERM...(Monday through Saturday)
Issued at 425 PM EDT SAT OCT 17 2020
Models are generally in better agreement today compared to
yesterday, at least in respect to frontal feature timing/location
and associated precip coverage and how it affects the state. That
being said, it will be a fairly active period, with generally S to
SW flow and temperatures moderating warmer. That part has remained
certain. The precip and fronts will continue to be the varying
To start the period Monday morning, Kentucky will find itself on the
SW flow side of a deep and large trough that will be encompassing
much of the U.S. Meanwhile, a pretty stout frontal boundary will be
progressing eastward, making its way across the Ohio Valley and
infringing on the Ohio River at 12Z. At this point the front will
stall, being partially slowed by a strong area of high pressure
across the Mid and Southern Atlantic States, and as the surface low
continues to become more occluded and wrapped up. The presence of
this stationary boundary will keep pops centered along its axis,
including increased pops across the northern portion of the CWA,
generally north of the I-64 corridor.
By Tuesday, the stalled front will begin to weaken and will
eventually dissolved upon the progression of the next frontal boundary
and upper level system. As the boundary fades, so too will the
precip chances...with both the GFS and ECMWF dissipating throughout
the afternoon. High pressure will then build in from the east for
Tuesday evening and into the day Wednesday. Meanwhile, a surface low
will develop and strengthen across the Central Plains by Tuesday
evening, as a shortwave begins to develop within the axis of the
trough. This low will continue to quickly project northeastward,
with a frontal boundary extending SW from this. This will bring
about another center of instability and precip, along with a
developing line of precip along the frontal boundary.
The ECMWF keeps this boundary and associated precip north of
Kentucky through the day Wednesday and well into Thursday, lifting
it back north as a warm front, while high pressure continues to
strengthen and dominate much of the SE. The GFS on the other hand
does bring precip associated with this front through the state
briefly WEdnesday night, before it dissipates.
Yet another, stronger system, and upper level shortwave, will
develop late in the work week. This surface low will be located over
the southern/central Plains Thursday afternoon. And will quickly
follow the height falls NE, reaching the Upper Midwest by Thursday
night, and SE Canada by Friday. Models come into much better
agreement again for this system, as it drags a potent cold front
eastward towards the MIssissippi and Ohio Valleys Thursday night and
Friday. Both models have precip overspreading the state and into
eastern Kentucky Friday afternoon and Friday night, continuing
through the day Saturday as the front slows and gradually pushes
eastward through the state. The deep SW flow in place ahead of this
system could also be enough to muster up some instability, and
soundings did show the potential of some thunder during this time.
Will note that based on the GFS and ECMWF, pops should be fairly
substantial. However, given that it is heading into Day 7, kept with
the NBM, which seems quite a bit overdone with only slight and low
end chance pops. Expect these to increase in the coming runs unless
the pattern changes for some reason.
As mentioned, the SW flow in place across the region through much of
the period will keep a warmer airmass in place. Mondays highs will
range from the low 60s in the north (where the rain will be focused)
to the low 70s in the south. By Thursday and Friday, highs will be
in the mid and upper 70s. Temps will then cool for Saturday as the
front begins to move over, along with continued precip and clouds.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 800 PM EDT SAT OCT 17 2020
An area of high pressure to the east will provide VFR skies
through the period, with perhaps a smattering of high clouds at
times becoming more substantial late. There is the potential for
some valley fog, but overall this should be of limited extent and
will not affect the TAF sites. There could be some low level wind
shear at the SME site, owing to a low level jet skirting the Lake
Cumberland region later tonight. The surface winds will be at 5 to
10 kts or less through the period generally from the south.
Area Forecast Discussion
National Weather Service North Platte NE
640 PM CDT Sat Oct 17 2020
.SHORT TERM...(This evening through Sunday night)
Issued at 253 PM CDT Sat Oct 17 2020
A cold front is surging southward across western and north central
Nebraska this afternoon. Downslope west to northwest winds will
allowed temperatures to warm up just ahead of the front with lower
70s observed across southwest Nebraska. The front pushes south into
KS and eastern CO this evening. There will be a period of north to
northeast winds of 15-25 mph with gusts to near 30 mph for a couple
of hours this evening after the frontal passage across southwest
Nebraska. Mid-level FGEN begins to develop quickly around sunset in
an west to east band across the area. Available moisture looks
decent with mid-level Pacific moisture in place. PWATS in the NAM
rise to around 0.65" prior to any precipitation development early
this evening. This is above normal for the date in the 75th
percentile range with normal values right near 1/2 inch. Short term
models are not in good agreement on the placement of a concentrated
band of precipitation. There continue to be hints of it, but overall
confidence has decreased in the development of a narrow band of
heavier precipitation. The HRRR hints that it could set up for a few
hours after midnight just north of I-80. Meanwhile the NAM is up
north near the SD border. Other solutions keep precipitation more
scattered and no concentrated band. Due to all of this will not be
increasing snow totals any. In fact with such model spread the
totals have went down a little. The exception is across Sheridan
County where 1-2 inches still seems likely. Timing would be from
around 10p Saturday night to 10a Sunday morning. The system quickly
moves east of the area Sunday afternoon with another quick moving
system arriving Sunday night. A warm front will lift northward
Sunday night, and as lift overspreads the area some light
precipitation will again be possible. Again, lots of model spread
with this too, and confidence is low on much snow accumulation.
Right now looks to be less than 1/2 inch and primarily across
eastern portions of north central Nebraska.
.LONG TERM...(Monday through Saturday)
Issued at 253 PM CDT Sat Oct 17 2020
A Hudson Bay low pattern develops next week. A series of weak
shortwaves and cold front will cross the region. Little
precipitation is currently expected with the passage of these
fronts, but some very light precipitation could occur across
portions of north central and north west Nebraska.. Highs next
week generally look to average in the 50s to mid 60s...warmest
southwest Nebraska. The pattern next week is the result of strong
high pressure ridging across the eastern pacific and the upper low
near Hudson Bay which carves out deep troughing across the
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 639 PM CDT Sat Oct 17 2020
Lowered ceilings will create MVFR conditions across western and
north central Nebraska through the evening and into tomorrow
morning. Snow showers will continue in northern Nebraska including
KVTN through the early evening, then become sporadic through the
rest of the night. Winds in northern Nebraska will be out of the
north, shifting to the west by tomorrow afternoon. Snow is expected
to impact KLBF later in the evening around midnight. Winds near KLBF
will remain northerly into tomorrow afternoon, when they will begin
to shift to the southeast. Gusty winds across the area will decrease
during the early evening.