Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/25/20
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
542 PM CST Fri Jan 24 2020
.UPDATE...
Issued at 539 PM CST Fri Jan 24 2020
Extended and expanded the dense fog advisory for north central SD
into Saturday morning. However, based on DOT cameras, all but the
highest points of the Coteau appear to have improved visibilities
so cancelled that portion of the advisory for now. It may need to
be reissued and expanded as well if fog redevelops and the
affected area broadens overnight.
Raised overnight temperatures from the James Valley east to be
more in line with the most recent HRRR and last night`s lows.
&&
.SHORT TERM...(This Evening through Saturday Night)
Issued at 347 PM CST Fri Jan 24 2020
Forecast challenges surround fog/low clouds potential tonight into
Saturday morning, along with some possible freezing rain p-type by
Saturday afternoon into Saturday night.
Currently, the CWA has surface high pressure over it; sandwiched
between lee-of-the-Rockies surface low pressure troffing and
large/broad surface low pressure off to the southeast. It is cloudy
over the forecast area, and there are even still at this hour a few
areas west river and on/in the lee of the Prairie Coteau
experiencing dense fog. A dense fog advisory continues for this
until 6 PM CST. Temperatures are holding in the teens and 20s on
light and variable winds.
This area of surface high pressure won`t be going anywhere quickly
tonight, as it remains locked in place between these two
aforementioned surface low pressure features. Therefore, the current
set-up (the set up that promotes fog and low stratus) will persist
overnight while the next low pressure system to influence the region
begins to approach on Saturday. It`s entirely possible that within
the next 3 to 6 hours, all the remaining fog (and some of the low
clouds) will dissipate, and radiational cooling/light winds/clear
skies will be able to make more fog later tonight. But, it`s also
possible that the current fog/low clouds condition persists into
tonight and the light winds/high moisture content air near the
surface works to re-produce/re-spread areas of fog over the CWA
through sunrise Saturday morning.
On the warm air advection arm of this approaching system for
Saturday, there may be enough forcing/lift to produce a small window
of (likely liquid) precipitation reaching the ground. Surface
temperatures are currently forecast to be below freezing when this
might occur, so the forecast does include some light freezing
precip/sprinkles mention from late morning through late Saturday
evening. QPF guidance is barely measurable for a few spots over
north central over into northeast South Dakota and west central MN.
Models do suggest that low level lapse rates can steepen some once
this system`s surface cold front passes through the region late
Saturday afternoon through Saturday night, resulting in the
potential for a few snow showers around the region.
There is not all that much in the way of low level thermal advection
over this CWA over the next 36 hours. There will be a warming trend
developing by Saturday morning, starting out west river, that will
work its way over toward the MN/SoDak border by Saturday evening.
Low temperatures tonight are a low confidence forecast, given how
much they are tied to whether or not clouds dissipate. Don`t expect
the needle to move all that much at all from current temperatures,
if the fog/low clouds stick around all night. Saturday and Saturday
night look like warmer than climo normal forecast periods given the
meager low level warm advection pattern forecast to set up.
.LONG TERM...(Sunday through Friday)
Issued at 347 PM CST Fri Jan 24 2020
Relatively dry and mild conditions are expected through most of the
long term. The upper ridge sits over the rockies Sunday shifting
slowly as the week progresses and should keep our temps near or above
normal for most of next week. The one chance we may see some
precipitation will be next Thursday/Friday as we transition to split
flow aloft and a shortwave trough is expected to move through the
plains. Have some slight pops in the forecast for this but as of now
little to no accumulations are expected.
High temps hover around freezing to start the week and by Wednesday
may reach into the upper 30s. Lows are expected in the low 20s or
upper teens through next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 539 PM CST Fri Jan 24 2020
IFR conditions are expected to prevail in stratus and fog through
Saturday morning. There may be some improvement toward the end of
the period.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 9 AM CST /8 AM MST/ Saturday for
SDZ003>005-009-010-015.
MN...None.
&&
$$
UPDATE...Wise
SHORT TERM...Dorn
LONG TERM...Dye
AVIATION...Wise
Area Forecast Discussion
National Weather Service Boston/Norton MA
915 PM EST Fri Jan 24 2020
.SYNOPSIS...
High pressure over the Maritimes brings dry weather to New
England tonight and Saturday morning. Low pressure over the
Midwest redevelops over the Mid Atlantic states. This will
bring a period of heavy rain and gusty coastal winds late
Saturday and Saturday night as it tracks across interior
southern New England. It may be preceded by some light freezing
drizzle over the Berkshires. Mainly dry and mild conditions
return Sunday then dry and seasonable for much of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
915 PM update...
Ocean stratus has overspread much of eastern and central MA into
northern RI. With continued easterly flow expect the low clouds
to fill in across western MA and northern CT overnight per HREF
solution which indicates high probs of low cigs overnight. Some
patchy fog will also develop. Still a low risk for patchy
drizzle/freezing drizzle late tonight over upslope areas, but
most areas will remain dry. Temps not expected to fall much
from current readings and some locations may see temp increases.
Lows generally upper 20s to mid 30s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Closed upper low over the Great Lakes with a 100-kt southern jet
feeding in. This will generate a secondary low during the night
that moves up over our area late Saturday and Saturday night.
Low level wind forecasts show a 50-60 kt low level jet moving
up over New York City early afternoon and along the South Coast
of New England late afternoon and early night.
The combination of these two jets will generate strong lift
over Southern New England during the late afternoon and early
night. This will generate rain from mid afternoon through
around midnight. PW values of 0.75 to 1.0 inches suggest some
heavy showers. The PW values are above normal for January, but
the system is moving fast enough to limit any flooding threat to
urban/poor drainage concerns. The rain tapers off a little
before midnight in the west and a little after midnight in the
east.
That low level jet moves over the region early Saturday night.
The low level inversion will limit the amount of wind to reach
the surface, but gusts of 25-35 kt should be possible especially
along the South Coast and Islands. Winds will diminish after
midnight as the system moves past.
A 1 to 2 ft surge is expected along the south coast around the high
tide Sat evening as the low level jet is moving through.
Astronomical tides are rather low and no coastal flooding is
expected.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...
* Temperatures slowly trending downward through the extended.
* Dry and quiet through the extended. The only exception is across
the eastern slopes of the Berkshires Sunday into late on Monday
where light scattered rain and snow showers are possible.
Details...
Sunday AM through Tuesday AM...
Initially a cutoff low will be situated over the eastern Great
Lakes. The cutoff will gradually rotate northeastward into northern
New England by Sunday evening. Expect -5 to -8 degree Celsius
westerly cold air to advect in. Will see a mixture of sunshine and
clouds across the region on Sunday. There are chances of light rain
and snow showers across the eastern slopes of the Berkshires. Little
to no snowfall accumulation is anticipated. Temperatures will be
slightly warmer when compared to Saturday. Readings range from the
mid 30s across the Berkshires to the mid to upper 40s along
the coast.
The cutoff low will rotate across northern New England on Monday. A
shortwave will rotate from the eastern Great Lakes late on Sunday
through southern New England on Monday. Winds will shift to the
northwest and continue advecting cold air into the region. Increased
cloud cover a bit compared to the previous forecast. There will be
chances of snow showers across the eastern slopes of the Berkshires.
Suspect that these chances could linger further east as suggested by
several GEFS members, especially during the day time. The
combination of the shortwave sliding through, cold air advection and
diurnal heating could bring scattered shower activity. Confidence is
low to moderate at this point in time, so have kept things dry at
this point in time. Temperatures on Monday range from the low 30s
across the Berkshires to the low to mid 40s along the coast.
Tuesday through Friday...
Confidence in the forecast significantly lowers Tuesday until the
end of the long term. Model guidance is all over the place with
several shortwaves sliding through with large differences between
individual models and run to run differences. At this point in time
it appears that we will remain dry, but under cyclonic flow aloft.
Temperatures should continue trending downward as colder air advects
in.
Next shot for precipitation is late in the week and heading into the
weekend. High temperatures cool to the 30s by the end of the
extended. Low temperatures cool to the teens and 20s above zero.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday Night/...
Tonight...Moderate confidence. MVFR ceilings continue to spread
in from the ocean and NH due to increasing easterly flow. This
primarily impact BOS, BED and ORH over the next 6 hours. Will
see ceilings lower to IFR at ORH along with fog development, but
am not confident on visibilities at this point in time. BOS will
particularly be tricky as the HRRR and GLAMP keep the terminal
on the edge of MVFR/VFR. Leaned toward VFR from roughly 06Z
until 14Z based on the latest HRRR. Other terminals will see
ceilings lower to MVFR closer to 12Z.
Saturday and Saturday night...Moderate to high confidence.
Widespread MVFR with IFR conditions. Still expect patchy fog
with drizzle or higher elevation freezing drizzle in the
morning. Best opportunity for IFR/LIFR is when the heavier
precipitation moves in. Heaviest precipitation timeframe looks
like 21Z to 06Z at this point. East winds gust 25 to 35 knots
over Cape Cod and the Islands during the afternoon and into the
evening. Rain tapering off close to midnight in the CT River
Valley and eastern coastal MA after midnight. Precipitation
becoming lighter after midnight.
KBOS Terminal...Low to moderate confidence until 12Z. On the
fence between MVFR/VFR conditions due to ocean stratus. Moderate
confidence after 12Z with MVFR/IFR ceilings expected.
KBDL Terminal...Moderate to high confidence until 12Z. Moderate
confidence after 12Z. MVFR/IFR conditions spreading in.
Potential for LIFR as heavier precipitation moves in late in the
afternoon.
Outlook
/Sunday through Monday/ ...
Sunday through Monday: Mainly VFR, with local MVFR possible.
Breezy.
Monday Night through Tuesday: VFR. Breezy.
&&
.MARINE...
Short Term /through Saturday Night/...High confidence.
Northeast wind around 10 kt tonight will increase to 20-25 kt by
late Saturday and early Saturday night. Wind gusts will be 30-40
kt at that time. Strongest gusts will be on the eastern MA
waters. Winds then diminish after midnight as the weather system
moves past. Winds at that time will shift out of the southwest.
Gale Watch continues on the waters east of Massachusetts for
Saturday and Saturday night. Small Craft Advisory continues on
all other waters through Sunday.
Outlook /Sunday through Wednesday/...
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 11 ft.
Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 9 ft.
Monday: Winds less than 25 kt. Areas of rough seas.
Monday Night: Winds less than 25 kt. Seas up to 5 ft.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from noon Saturday to 7 PM EST Sunday for
ANZ232.
Small Craft Advisory from noon Saturday to 1 AM EST Sunday for
ANZ233-234.
Small Craft Advisory from 3 PM Saturday to 5 AM EST Sunday for
ANZ230.
Gale Watch from Saturday evening through late Saturday night
for ANZ231-251.
Small Craft Advisory from noon Saturday to 11 AM EST Sunday
for ANZ236.
Small Craft Advisory from 7 AM Saturday to 7 PM EST Sunday for
ANZ235-237.
Gale Watch from Saturday evening through late Saturday night
for ANZ250-254.
Small Craft Advisory from 4 AM Saturday to 7 PM EST Sunday for
ANZ255-256.
&&
$$
SYNOPSIS...WTB
NEAR TERM...KJC
SHORT TERM...WTB
LONG TERM...BL
AVIATION...WTB/BL
MARINE...WTB/BL
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
558 PM CST Fri Jan 24 2020
.SHORT TERM...(This evening through Saturday)
Issued at 146 PM CST Fri Jan 24 2020
Concerns in the near term revolve around cloud cover and the
potential for fog development tonight.
Currently, the majority of the area remains stuck under a stratus
deck on the the back side of a stacked upper level low moving
over Illinois. These clouds have been very slow to clear, and
models have all been clearing them out too quickly. Nevertheless,
there is still a window late this afternoon and evening where we
may see some sun, especially west of Highway 281.
Tonight, winds will become light and variable as the surface
ridge moves through. With these light winds and abundant low-level
moisture from recent snow/rain, it would be a favorable night for
fog and low stratus. As a result, the HRRR and RAP are indicating
a good swath of reduced visibility across northern and central
Nebraska tonight through Saturday morning. Therefore, areas of fog
were introduced in this forecast package.
Lingering cloud cover on Saturday may put a bit of a damper on
temperatures, but we should still end up 5 to 10 degrees warmer
than today with highs ranging from the low 30s to upper 40s from
northeast to southwest.
A weak perturbation will move through the area Saturday
night...probably bringing more midlevel clouds to the area. A
previous run of the ECMWF had actually produced some light QPF
with this wave, but this has gone away with the latest run and
there is little support from other models. Therefore the forecast
remains dry.
.LONG TERM...(Saturday night through Friday)
Issued at 146 PM CST Fri Jan 24 2020
Warming temperatures continue on Sunday as we should see more
sunshine. Another weak disturbance is forecast to drop through the
area Sunday night into Monday, though, likely leading to a bit
cooler temperatures again on Monday.
A deeper trough is then forecast to cross the Rockies into the
Central Plains Monday night into Tuesday. Models have come into a
bit better agreement on this in that the main upper low will pass
well to the south of the area. As a result, only a light rain/snow
mix is forecast across the local area. Portions of northern
Kansas appear to have the best likelihood to see heavier amounts,
but even that would only be 0.10-0.20" of total QPF at most.
Beyond that, there isn`t much of a coherent signal for any
precipitation through the rest of the week. There is some chance
for rain/snow as another trough moves through Thursday into
Friday, but significant differences exist between the models.
Otherwise, daily high temperatures are expected to generally be in
the upper 30s and 40s each day. This overall warmer-than-normal
pattern will likely continue into early February before a cooldown
arrives in the Feb 4th-5th timeframe.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 548 PM CST Fri Jan 24 2020
With light wind and solid stratus in place, the low-level moisture
from standing water and snow will aid the development of fog later
tonight as the stratus deck lowers. KEAR may actually dip first as
it will be nearer to the western edge of the stratus deck. Fog may
be slow to clear, especially as the sun angle is still rather low.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
938 PM CST Fri Jan 24 2020
.UPDATE...
930 PM CST
Overall forecast is in good shape. Have made some adjustments to
tighten up the PoP and QPF gradients across the area through the
rest of the overnight hours, and to add a bit more fog through the
night south of I-80. Stout upper jet divergence is helping to
support an arcing band of light to moderate precipitation across
roughly the northwestern third of the CWA at this hour as the core
of a wound up upper low is pinwheeling off to our south and east.
The entire precip shield is pivoting now that the upper low is
starting to slosh eastward a bit more, and it looks as if this
pivot point may very well occur right across the heart of central
Cook County and down towards I-80 near Ottawa. The rain/snow line
snakes from near a La Salle to Aurora to Arlington Heights to
Highland Park line (or thereabouts) based on Dual Pol data and
incoming mPing reports. Do expect that this entire shield of
precipitation will eventually build a bit farther southward
through the rest of the night, and the inherited forecast captures
this trend nicely.
Have received a few reports of 1.5 to near 2 inches of heavy wet
snow across parts of McHenry and Lake counties as of 830 to 9 PM.
Based on current radar presentation, snowfall amounts (and
inspection of webcams), wouldn`t be surprised to see some pockets
of near Warning criteria snowfall before all is said and done,
somewhere in the I-90 corridor vicinity across parts of Kane,
McHenry, Lake, and far northwest Cook County. This messaging
continues to be handled well by the ongoing Winter Weather
Advisory, however, with impacts mitigated by us heading into the
weekend. Have also sharpened up the snow gradient across east-
central Cook County (including downtown Chicago) to reduce
snowfall amounts just a bit based on the pivot point and recent
hi-res guidance trends to show more of a 1-2" amount immediately
near the lake. Will likely be a decent snowfall gradient as you
move northwest, however. Finally, debated pushing back the start
time of the Advisory for La Salle, Grundy, and Will counties by a
smidge, but with snow beginning to pivot southward now, elected to
keep things as is.
Carlaw
&&
.SHORT TERM...
315 PM CST
Through Saturday night...
The forecast expectations for the evolution of the moderate to at
times heavy snow tonight into Saturday remain largely unchanged.
Despite the close proximity in time to now, there remains fairly
large uncertainty on the precise placement of the most sustained
snow and thus the highest values which could be pushing to over
six inches in isolated locations by Saturday morning. Confidence
is highest in the center to western parts of the current Advisory
to start the earliest in snow and maintain the longest into
Saturday morning with efficient rates. The eastern parts certainly
will have Advisory criteria impacts, it`s just uncertain how
quick they will onset. We expect the poorest conditions to be the
most expansive later this evening through overnight and into
early-mid Saturday morning. With gradually tapering snowfall
rates for the Saturday afternoon time, impacts should ease and
possibly quickly, but difficult to say. Only change to Winter
Weather Advisory was to back up start time for parts of the
central and south metro to 8 p.m.
The latest hand surface analysis places a broad surface low across
the southern forecast area and into central Illinois, meandering
its way slowly north-northeast. This will soon take better shape
over northwest Indiana and into north central Indiana this
evening as an upper jet maximum rounds the pesky closed upper low
over southern Illinois. With light winds into early evening and
low temperature-dew point spreads north of the warm front,
visibility in fog will be around a quarter mile in places
along/north of I-80. An uptick in rain showers should continue
across northwest Indiana into northeast Illinois through late
afternoon and that should abate any persistent sub quarter mile
visibility, but at least occasionally being down to that level is
expected into the commute. The Dense Fog Advisory was
expanded/extended northeast across the metro for the commute.
GOES-16 water vapor imagery has a magnificent presentation of the
closed upper low as well as the jet streak rounding its eastern
side over the Ohio River Valley. This jet maximum will continue
to blossom precipitation from northern Indiana into northeast and
far northern Illinois into early this evening. This precipitation
will be fed by a moist conveyor belt, also clearly evident on
satellite imagery into far northern Illinois, as well as a
developing trough of warm air aloft (TROWAL) and associated steep
lapse rates aloft. With the juxtapose of upper level forcing and a
convergent focus in the lower-mid levels across the northern CWA,
precipitation should increase in rate fairly quickly. As such,
dynamic cooling will support probable changeover to snow not that
long after onset. The challenge is precisely where this developing
deformation sets up residence. Have felt that the low-level and
even mid-level trends being a tad further west than earlier
indications point toward the western/central portions of the
Advisory area early this evening seeing that rapid onset. The RAP
and HRRR have been consistent with this today. For the Chicago
area there likely will be some rain/snow mix even shortly after
sundown, but low-level wet bulb profiles and being southeast of
the deeper convergence point toward less potential of going fully
snow early this evening, and thus less evening impacts.
While guidance varies on nitty gritty details such as placement,
the snow area`s morphology through tonight and even into Saturday
morning is pretty well agreed upon. Not surprisingly given the
placement with respect to the upper low, it is expected to pivot
over part of the area...most likely north central Illinois...and
then expand and creep southeastward. This makes conceptual sense
in the deformation and also with column winds turning
northwesterly. Within this snowfall area, 7.5+ C/km lapse rates
above 650 mb and a deeper dendritic growth zone support more
efficiency in rates to overcome the marginal surface wet bulb
values and shortly thereafter accumulate quicker. Because of the
slow movement of the upper low, this zone of snow should continue
over part if not a good portion of the CWA into at least early
Saturday morning. Coming out of the nighttime period, snow should
be able to continue accumulating on most surfaces even in the
southern and eastern CWA, so impacts during that time due to rate
and total accumulation should match that of the worst conditions
of overnight. The overall persistent depth of the system and
broad nature of the TROWAL look like they would support snow into
the rest of the day Saturday, but it should become more streaky,
and possibly more snow showers as a mode, as the system occludes
and drier air pivots in.
The big impacting factors with this will be the duration and
rates, especially where this pivots, again most likely over a good
portion of the Advisory area from the western Chicago suburbs on
westward. Totals of 4+ inches in that area that we have forecast
are supported by much of the guidance, just different placement
and orientation. Isolated amounts over six inches given the
attributes are certainly possible, even with the broadly lower
snow ratios (8:1-10:1). On the eastern edge of that over the
Chicago metro, there could easily be a very sharp cutoff in
amounts, depending on the behavior of the snow area. Also to note,
that Saturday morning, especially early morning, should be having
notable impacts continuing during that time even possibly beyond
the Advisory area. With marginal temperatures and the snow area
becoming more limited in coverage, that should support more
marginal impacts during the P.M. hours. It seems like the Advisory
could be able to be peeled away in parts earlier than its end
time, but no changes made at present.
MTF/KMD
&&
.LONG TERM...
315 PM CST
Saturday night through Thursday...
At the start of the period Saturday evening, our slow moving upper
level low is expected to be centered somewhere over lower
Michigan, before it shifts eastward over New England during the
day Sunday. Because of its slow movement, some lingering light
snow will be possible over the area Saturday evening. We will also
have to keep an eye on the potently for any light drizzle or
freezing drizzle Saturday night as drier air moves over the area
aloft. I certainly do not have a degree of confidence that there
will be much in the way of freezing drizzle Saturday night,
especially since surface temperatures are likely to continue to
hover right around 32. For this reason, I have kept the mention
out of the forecast.
We could also see another light batch of light snow or flurries on
Sunday as a weak mid level disturbance tries to drop southward
over the area on the far western periphery of the upper low.
However, given some model disagreements on this feature, I have
opted to keep this small mention out of the forecast as well,
since it would likely not cause much of any impacts. Otherwise,
expect temperatures Sunday to remain in the low to mid 30s under
mainly cloudy skies.
A period of dry weather looks on tap early next week, but another
weak weather disturbance could produce another period of light
rain and snow over the area around midweek. But with no real good
push of colder air with these Pacific systems, expect
temperatures to remain on the warm side of average, with highs
mainly in the 30s.
Later in the week, there is the potential to have a bit more
active weather pattern across the region as additional
disturbances of Pacific origin take aim on the area. As a result,
more inclement weather, with some rain and snow chances will be
possible over the area at the end of the current forecast period.
KJB/Lenning
&&
.AVIATION...
For the 00Z TAFs...
Low ceilings/visibility and moderate to briefly heavy snow are all
concerns through the TAF period, especially over the next 12-18
hours.
Ceilings are lifting and visibility is increasing early this evening
as steady -RA has spread over northern IL. This precip will begin to
switch over to snow by mid-evening, with all sites at SN by 04-05Z.
Once the switch occurs at ORD/RFD/DPA, the SN will fall moderate to
briefly heavy for several hours. Precip trends at MDW and GYY are
less certain as the precip shield pivots over northeast IL under the
upper-level low. The southern edge of the shield will bisect the
Chicago metro, and may even stall between ORD/MDW. If this occurs,
precip rates at MDW will decrease and ceilings/vis may lower again
for a period. However, the precip shield should rotate back into MDW
with steady moderate SN overnight.
As the low begins to shift east late tonight, a deformation snow
band will likely extend northwest from the low across all of the
TAFs sites. Snowfall rates under this band could be moderate at
times through the morning hours before intensity diminishes through
the afternoon. Ceilings will only gradually increase through the day
Saturday, and will likely remain IFR.
Kluber
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
ILZ022 until midnight Sunday.
IN...None.
LM...None.
&&
$$
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...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 305 PM CST Fri Jan 24 2020
The main forecast concerns are cloud cover tonight into Saturday
and lows for tonight.
Closed mid level low that was over KS at this time yesterday was
over southern IL this afternoon. That feature is quite
interesting in satellite water vapor imagery, with two vorticity
maximums rotating around the main circulation. Looking farther
west, an elongated shortwave trough extended from southeast
British Columbia down to near the AZ/NV border. Surface analysis
this afternoon showed high pressure over the Dakotas extending
down into KS and OK.
The surface ridge axis will build over the area tonight, with
winds becoming light. Models all pretty much show moisture depth
decreasing with time, but vary on how fast they break up the low
clouds. The 12Z GFS seemed to be one of the more aggressive models
with decrease of the low clouds, and thus has the lowest values
for suggested lows. Meanwhile, recent versions of the RAP model
keep lows much warmer. We will go with lows in the teens for now
but will need to watch cloud trends.
Surface ridge axis will continue to build east of the area on
Saturday, allowing winds to become southwest and then south. Look
for highs mainly in the upper 20s to mid 30s. The elongated
shortwave trough to our west that was mentioned earlier will break
into two pieces. One weak system will affect parts of the Dakotas
and MN Saturday afternoon into Saturday night, but this is not
expected to affect our forecast area. The other will stay well to
the south toward the southern part of the Plains. We anticipate
that mainly dry weather should continue Sunday into Monday, with
high temperatures close to average.
Monday night into Tuesday night.
There continues to be a moderate spread in model guidance in
regards to the details of a system moving through the region in
this period. The 12Z GFS is fairly dry, while the 12Z ECMWF
suggests up to 0.10 QPF. We will keep a 20-30 percent chance of
light snow or a snow/rain mix for now.
Wednesday into Friday.
Again in this period there is some variance between the GFS and
ECMWF solutions. We will include some lows POPs for snow and rain
from Thursday night into Friday. For this period, the GFS is
wetter than the ECMWF. Look for highs to vary from the upper 20s
to the lower 40s from Wednesday into Friday across eastern NE and
southwest IA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 518 PM CST Fri Jan 24 2020
IFR and MVFR ceilings will likely linger through the majority of
the TAF period. Some patchy fog could develop early Saturday
morning, primarily at KOFK and KLNK, before dissipating by the
afternoon. Expect ceilings will finally scatter out by late
Saturday afternoon.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Miller
AVIATION...KG