Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/02/24
Area Forecast Discussion
National Weather Service Hastings NE
950 PM CST Mon Jan 1 2024
...Short Term and Key Messages Update...
.KEY MESSAGES...
- Although transient/brief/localized fog still cannot be ruled
out late tonight, any chances for more widespread and
potentially dense fog development appear to be dwindling, and
have removed from Hazardous Weather Outlook (HWOGID) as it
just can`t be justified based on latest model guidance.
- A winter storm system will move across the region Thursday
night into Friday, bringing a chance for snow, possibly mixing
with rain to portions of the area. Accumulations currently
appear overall-minor with this system.
- A second storm system is expected to move across the southern
portion of the nation toward the end of the forecast period,
bringing another chance for precipitation/snow to our region
around next Monday (this one COULD be more impactful, but a
lot of questions remain).
&&
.UPDATE...
Issued at 948 PM CST Mon Jan 1 2024
-- Regarding fog potential through the rest of tonight into Tues
AM:
- Although tonight never had the fog potential that last night
did, earlier-day runs of higher-res visibility progs (such as
HRRR) were hitting at least brief/transient fog (and possibly
dense fog) potential somewhat aggressively especially in our
east-northeast...largely tied to the back edge of the
vacating/retreating pesky low stratus deck that as of this
writing has all but vacated the far northeast fringes of our
coverage area (CWA).
- However, reality thus far has yielded essentially zero fog
development, and latest HRRR visibility run shows only the
possibility for very localized/transient fog potential tonight
at most within our CWA. Conceptually, this makes sense as our
predominantly westerly-to-northwesterly breezes (especially
post-midnight), albeit light, are typically quite unfavorable
for widespread fog development (due in part to subtle
downslope flow). In addition, at least minor batches of
passing, mid-high level clouds should work against widespread fog
development as well.
- Thus, while cannot totally rule out somewhat "random" patches
of fog late tonight-Tues AM as temperatures further cool over
shallow/lingering/patchy snow cover, have (at least for now)
not only removed a formal inclusion of fog from our Hazardous
Weather Outlook (HWOGID), but also from our forecast itself.
&&
.DISCUSSION...
Issued at 328 PM CST Mon Jan 1 2024
Although most of the state is sunny, stratus has persisted over our
CWA for much of the day. There is potential for redevelopment of
fog this evening across portions of the area, although confidence is
fairly low in exact locations. A weak shortwave trough will move
across the region this evening, with winds shifting from the south
to the northwest. This will help to clear out any fog that is able
to develop.
Heading into Tuesday, expect dry conditions and cool temperatures.
Highs will range from the mid-30s in the north to the mid-40s in
north central Kansas. Lows will be primarily in the teens.
A frontal passage on Wednesday will bring a shot of cooler air into
the region. Highs will range from the low 30s in the north to the
upper 30s to mid-40s in north central Kansas. Lows will once again
be in the teens.
Thursday-Friday, a storm system will cross the southern portion of
the nation, bringing a chance (20-40%) for precipitation across
south central Nebraska, and slightly higher chances in north central
Kansas. Models currently show the system lifting northeast into
Kansas and portions of south central Nebraska Thursday evening into
Friday. The CWA will be on the northern side of this system with
lows Thursday night in the 20s and highs on Friday in the 30s. Given
the current trajectory of the system, snow will be possible between
Thursday night and Friday. Snow, possibly mixing with rain, may be
possible along and south of the Kansas-Nebraska border, where
temperatures will be warmest. Precipitation chances diminish
heading into Friday night.
Expect a quiet, cold, and dry conditions on Saturday, with highs in
the 30s. Sunday, an upper trough slips southeast, into the Desert
Southwest. This system will move across the southern U.S. bringing
the potential for precipitation to areas toward the end of the
forecast period.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 622 PM CST Mon Jan 1 2024
- General overview for KGRI/KEAR (including winds):
This is a somewhat tricky period with regard to especially
ceiling and possibly visibility trends, especially right away
these first few hours this evening (ongoing IFR ceiling at KGRI
and possibly some brief fog at both sites), and then again late
in the period Tuesday afternoon (possible MVFR ceiling both
sites). Otherwise, the majority of the period (and particularly
the middle 12 hours 06-18Z) actually features fairly high
confidence in VFR. As for winds, they will not be much of an
issue speed- wise (sustained mainly only 6-10KT), but there will
be a direction shift from southerly right away this evening, to
westerly and eventually northwesterly overnight-Tues AM behind
a weak, passing front and then more northerly by Tuesday
afternoon.
- Ceiling/visibility trends and uncertainty:
- Ceiling:
Right out of the gate, a pesky deck of IFR/LIFR stratus has just
vacated KEAR, but will likely persist until 01-02Z at KGRI
before also vacating. Once this batch of low stratus departs,
confidence is fairly high in VFR (only limited mid-high level
clouds) until at least 18Z Tuesday. Beyond that though, some
models (not all) are suggestive of MVFR ceiling potential moving
down from the north for the final few hours of the period. Do
not have enough confidence to go prevailing MVFR given the mixed
signals, but have at least "hinted" at it with a "SCT015"
group.
- Visibility:
Given the prevailing southwesterly to westerly/northwesterly
wind component tonight (typically unfavorable for fog
development), odds favor prevailing VFR and TAFs reflect this.
That being said, could easily see at least brief/light fog
settling in along/near the edges of the vacating stratus deck
for a time during these first 6 hours or so, so have "hinted" at
this with a low-end VFR "6SM BR" group.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Pfannkuch
DISCUSSION...Wekesser
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Goodland KS
315 PM MST Mon Jan 1 2024
.SHORT TERM...(This evening through Wednesday Night)
Issued at 146 PM MST Mon Jan 1 2024
At the beginning of the short term period, the latest RAP analysis
shows the CWA underneath an upper air ridge with an embedded
shortwave disturbance passing over the CWA within the ridge and a
trailing upper air trough residing in the southwestern CONUS
during the afternoon of New Year`s Day. Current satellite imagery
and surface observations report dry conditions across the region
while a northwesterly to southeasterly oriented swath of high
clouds moves across the CWA from the southwest along due to the
upper air disturbance. Going through the rest of the first day of
the New Year, models depict the CWA having a westerly flow aloft
by the late evening after the upper air disturbance moves through
the ridge to the east. The trailing trough then progresses a bit
eastward over AZ by the overnight hours. At the surface, dry
conditions are expected for the CWA with a surface trough moving
through the region during the overnight hours. This will turn the
surface winds to a north-northwesterly direction as well as usher
in some cooler air behind a weak cold front feature. Overnight
lows for tonight expect to be in the lower to middle 20s.
On Tuesday, models project the axis of the upper air trough moving
over the CWA by the afternoon hours as a trailing ridge moves over
the western CONUS. A north-northeasterly flow is seen over the CWA
by the overnight hours as models forecast the CWA to be between the
approaching ridge to the west and the departing trough to the
southeast. At the surface, models have a surface high passing
through the northern portion of the CWA during the afternoon hours
allowing for the dry conditions to continue and the existing cloud
cover to depart out of the region to the south by the evening hours.
Daytime highs for Tuesday look to be in the lower to middle 40s
while overnight lows range between the upper teens and lower 20s.
For Wednesday, forecast guidance shows the aforementioned upper air
ridge moving over the CWA during the day as another trough trails it
in the western CONUS. Models also have another surface trough moving
through the CWA during the day changing the surface winds from
northwesterly in the morning to southeasterly by the overnight
hours. Precipitation chances are not seen for yet another day. The
latest WSSI for Wednesday does show the potential for moderate
impacts due to flash freeze for portions of the CWA though there
does not seem to be any apparent reason at this time for it. Will
continue to monitor this in case this analysis is picking up on
something not currently seen. Daytime highs for Wednesday are
forecast to be between the lower 40s and the lower 50s followed by
overnight lows in the upper teens to lower 20s range.
.LONG TERM...(Thursday through Monday)
Issued at 1251 PM MST Mon Jan 1 2024
From the latest GFS and ECMWF, there continues to be two main wx
systems of concern for the Tri State region. The first one impacts
the area late Thursday into Friday, while the second system becomes
impactful Sunday night through at least next Monday.
An amplified upper ridge over the central Plains will shift east of
the area going into Thursday, allowing for a closed upper low to
move out of the Desert SW and into the south/central Plains. A
surface low associated with the upper system tracks a bit further
south over the Oklahoma area as it swings through the Plains.
Winds ahead of the low complex will be southerly with a slow shift
to a northerly fetch due to slow movement of an inverted trough
through the area that extends from the low to the south.
Temp profiles are such the initial p-type will start as light rain,
but transition to all snow as through shifts east through the area,
allowing for more CAA into the cwa. With the highest QPF amounts
staying along/south of the Interstate, expecting highest potential
snow totals to occur there. With this being the latest guidance, the
next couple runs could show some shift in the system track and could
affect amounts due to a faster shift to northerly flow/CAA.
The entire CWA will be under northerly flow by the afternoon hrs
friday as the precip exits eastward. Right now, areas along/south of
the Interstate could see around 1-2" of a slushy mix. North of
there, an inch or less is currently expected. Daytime wind gusts
could approach the 20-30 mph mark before shifting lower going into
nightfall. There could be some areas that could see some blowing
snow where the transition occurs with the southerly moist air to the
CAA/northerly flow.
For Friday night on through the first half of the upcoming weekend,
an amplified upper ridge nosing east off the Rockies, combined with
a digging lee-side trough at the surface will provide dry conditions
area-wide ahead of the next system for the end of the forecast
period.
The second system from the latest runs of the GFS/ECMWF looks to be
a bit stronger and slower compared to the first event. There are
some decent differences to track/QPF, but overall looking like more
snow potential than the Thu-Fri system.
Looking aloft, a cutoff upper low will take an initial southerly
track like its surface counterpart, but continue easterly Monday
night onward through the event.
The surface low associated with this event sets up further south
into Texas with a strong inverted trough extending into the central
Plains. This trough does run into a strong ridge to the north. The
result will be a surface wind regime starting out as more easterly,
but transition to more north-northeasterly Mon-Mon night. Guidance
on winds could have gusts into the 30-40 mph range with some locally
higher numbers.
With the above mentioned, the wx focus will be on snow and blowing
snow potential impacting the area. Ample low level moisture does
feed into the area, with temps cold enough to have p-type
starting/continuing as snow going into late Sunday night/Monday
morning. Precip will overtake the CWA from west to east as the
system evolves. Some of the snow initially will result from the
easterly upslope component into the area with surface ridge north of
the CWA. The strength/speed of CAA into the area will determine snow
amount potential through the event. Currently looking at the latest
GFS temp/moisture advection behind the trough there is a enhanced
region along the western portion of the trough. From where this sets
up, points east and south of there should see the highest snowfall
totals. Looking for snow ratios to increase through the event from
the north, but best interaction between this and ample low level
moisture feed looks to occur east and south. Model snowfall spread
is wide but up to 4-8" is possible in the worse areas. Some areas
south of I-70 and east of Highway 27 could approach a foot of snow.
With the expected winds though the event, blowing snow/blizzard-like
conditions are possible. Of course any further shift south or north
of the system could drastically affect snow totals and thus impacts.
Stay tuned for further updates on this evolving system.
For temps, daytime highs from Thursday on into Sunday will range in
the 30s. As colder air wraps into the region next Monday, looking
for highs mainly mid and upper 20s for most locales. Some areas east
of Highway 83 could only drop to around 30F.
Overnight lows will start off in the upper teens to mid 20s Thursday
night, trending lower by Sunday night with lower to mid teens west
and upper teens to lower 20s east. Next monday night will be the
coldest with upper single numbers above zero west through the mid
teens east. Depending on snow pack/coverage from the expected
systems, the numbers at the end of the forecast could be even lower.
Wind chill readings for the overnight periods will range mainly in
the teens Thursday night, but by Sunday night into Monday morning,
mainly single numbers above zero for most areas. A few spots in
northeast Colorado could see single numbers below zero.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 302 PM MST Mon Jan 1 2024
KGLD...VFR conditions are expected throughout the 00Z TAF period
starting with south-southwesterly winds around 8 kts before
veering to westerly at 04Z. By 07Z, KGLD winds then shift to
north-northwesterly through the remainder of the TAF period.
KMCK...VFR conditions are also seen during the 00Z TAF period
beginning with southerly winds around 7 kts that veer to west-
southwesterly at 04Z. KMCK then expects its winds to become
northwesterly by 05Z before turning north-northwesterly at 17Z
through the rest of the TAF period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...076
LONG TERM...JN
AVIATION...076
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
929 PM CST Mon Jan 1 2024
.KEY MESSAGES...
* Fair weather and seasonable temperatures will be in place the
remainder of the week.
* There is a 20-50 percent chance (highest south of I-70) of rain
and snow Saturday. Any accumulations should be minor. There is
only a 10 to 25 percent chance of exceeding an inch of snow.
&&
.UPDATE...
Issued at 915 PM CST Mon Jan 1 2024
Updated forecast tonight to bring in some clearing further
eastward into heart of CWA near I-55 during overnight. Lows
mostly in the mid 20s over central IL with upper 20s in eastern IL
and near 30 along the Wabash river.
Latest Nighttime Microphysics (RGB) satellite loop shows clearing
line of MVFR clouds (bases 1-3k ft) was just west of a Moline to
Macomb to Pittsfield line and moving into far western Schuyler
county. Followed the RAP and HRRR low level RH fields overnight
into Tue morning which bring the clearing eastward toward I-55 by
dawn. 1030 mb high pressure over the AR/TN border and riding
northward into central/southern IL is giving a SW flow of 5-10 kts
over CWA with the lighter winds in southeast IL closer to high
pressure ridge. Think there is enough temp/td spread and wind to
limit fog formation in areas that do clear in western CWA as SW
winds pick up a bit later tonight over IL river valley as high
pressure shifts se and cold front moves se into central IA/WI by
Tue morning. Temps currently in the upper 20s north of I-72 and
mid 30s along highway 50 in southeast IL, should lower into the
mid 20s overnight over central IL, with upper 20s eastern IL and
near 30 along the Wabash river.
07
&&
.DISCUSSION...
Issued at 238 PM CST Mon Jan 1 2024
High pressure stretches from the southern Great Plains into the
Midwest this afternoon providing fair weather conditions, albeit
cloudy, across the region. Clearing across Iowa has accelerated
this afternoon, but will slow down again as we lose the sun this
evening, and much of the eastern half to two thirds may stay
overcast through the night. Southwest flow will set up behind the
ridge axis Tuesday and weak mid level warm air advection will
contribute to seasonably mild temperatures Tuesday afternoon with
highs around the 40 degree mark. This will also keep cloud cover
extensive again through the day Tuesday.
On Wednesday, an Alberta Clipper will dig across the Upper Midwest
and Great Lakes region. At the surface, a weak cold front will
push across central Illinois early Wednesday though midday.
Moisture may be lacking this far south during frontal passage
precluding any mentionable PoPs Wednesday. NAM, with its typically
low level moisture bias, does indicate some potential for drizzle
with the top of the moist layer not cold enough for ice nuclei.
Confidence in drizzle is low given mainly NAM based support but
bears watching as temps Wednesday morning will likely be below
freezing for most of central Illinois. High temps Wednesday will
only be in the mid 30s north of I-70, with seasonable temps
expected to continue the remainder of the week into the weekend.
This weekend, low pressure is set to lift from the Gulf Coast to
the mid Atlantic Coast with a broad precip shield extending
northwest to near the Ohio Valley. 01.12Z GFS keeps the forecast
area dry while the 01.12Z GEM and ECMWF continue to bring precip
into portions of central/southeast Illinois. Despite the southerly
track, temps appear marginal, especially in the boundary layer
which are forecast to be above freezing much of the day and could
result in rain or a rain/snow mix at times. NBM probs for
measurable snowfall are only about 20-40 percent Saturday and
Saturday night while the probability for 1 inch of snow is only 10
to 25 percent, highest southeast of the I-55 corridor. Meanwhile,
the ECMWF brings a second upper level disturbance Saturday night
into Sunday morning which could bring some more precip.
Through the first half of next week, models continue to advertise
a deep low lifting from the southern Great Plains across the
Upper Midwest or Ohio Valley. Uncertainty in the track continues
to lead to a large amount of uncertainty in details at the local
level, but regionally, anticipate a corridor of heavy snow north
of the low track with severe storms possible within the warm
sector. Most of this currently is beyond the current seven day
forecast period, but there has been some run-to-run consistency in
this high impact system next week so stay tuned for updates!
Deubelbeiss
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 514 PM CST Mon Jan 1 2024
MVFR conditions will prevail at all TAFs sites through most of the
next 24hrs. Satellite showing clearing line in IA & MO slowly
progressing toward IL. Not confident this will make it to any of
the TAF sites through morning and some HiRes models suggest more
low clouds will return tomorrow morning from the northwest. So,
going to be pessimistic through the period and TAF sites may see
improvement tomorrow afternoon. Winds will be westerly tonight and
then become southwesterly tomorrow. Speeds will be less than
10kts tonight but then increase tomorrow with gusts of 20-25kts
possible.
Auten
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Indianapolis IN
929 PM EST Mon Jan 1 2024
.Key Messages...
- Seasonable temperatures persist through the week
- Trends decreasing the threat for impactful weather this weekend
- Potential for a significant low pressure system and subsequent
cool down next week
&&
.Forecast Update...
Issued at 929 PM EST Mon Jan 1 2024
- Mostly Cloudy and cold
Surface analysis this evening shows a strong area of high pressure
in place over SE MO and NE Arkansas. A ridge axis extended north of
the surface high, across western IL and eastern IA. GOES16 shows
clouds east of this ridge axis, while clear skies were found west of
this axis. Light northwest winds were in place across Central
Indiana and temps were in the lower 30s.
Little change needed to the overall forecast. Satellite trends have
shown a very slow progression of the ridge axis moving eastward, and
the clearing line has made minimal movement over the past few hours.
HRRR shows 925mb RH fields failing to fall to less than 100 percent
overnight across Central Indiana. The clearing line is suggested to
only reach just west of the Wabash river by 12Z. Thus hope for
clearing overnight is fading fast. Will trend toward a cloudy sky
overnight. Given the expected clouds and dew points, will trend the
overnight lows to the upper 20s to near 30.
&&
.Short Term...(This evening through Tuesday)
Issued at 304 PM EST Mon Jan 1 2024
Mundane weather conditions are expected through the period with
upper ridging building in. Current satellite imagery shows extensive
cloud cover lingering across the region. Expect these clouds to
persist through most if not all of Tuesday, especially across the
southeast portions of central Indiana. Some forecast soundings show
gradual clearing may occur Tuesday afternoon with drier advecting
in, but not overly optimistic given the strong subsidence inversion
expected.
Limited diurnal cooling will only allow temperatures to
fall into the mid-upper 20s tonight. In addition, clouds will limit
diurnal heating on Tuesday. Highs were lowered from NBM guidance
with temperatures likely staying in the 30s. Moisture streaming in
aloft late in the day ahead of an approaching shortwave will lead to
increasing mid-high clouds.
&&
.Long Term...(Tuesday night through Monday)
Issued at 304 PM EST Mon Jan 1 2024
Tuesday Night through Thursday...
Initially the long term will remain influenced by a weak, meridional
upper level jet pattern, leading to minute surface pressure
depression Tuesday night into Wednesday. With very weak forcing
contained in the mid to upper levels, impactful conditions are not
expected. However, there will be some modest PBL moisture, with
pockets of near surface saturation and low cloud decks. With minimal
forcing and sprinkles or drizzle would be isolate, but I cannot rule
out a trace of precipitation, primarily over NW central Indiana. Any
precipitation that does fall should be liquid with the saturation
layer remaining well below the DGZ.
Ridging will begin to build in the presence of weak AVA starting
Wednesday night, clearing up skies and leading to seasonal, dry
conditions.
Friday through Sunday...
A deep trough will enter the Western CONUS later this weak, further
amplifying the upper level pattern, and connecting the subtropical
and polar jet streams. This will lead to a strong upstream jet
streak as early as Thursday, with cyclogenesis occurring over the
Gulf Thursday night into Friday. Initially, it looked like this Gulf
low would track northward along a developing East Coast ridge;
however, this ridge has weakened in latest ensemble means, leading
to a track more over the Appalachia region, and much more mundane
conditions over the Great Lakes and northern Ohio Valley.
There are still a few ensemble members keeping a more northern low
track, of which would lead to snow chances for the northern Ohio
Valley, including portions of central Indiana. For this reason, snow
cannot be ruled out this weekend, with current probabilistic
products placing chances of measurable snow fall in far southern
central Indiana around 10-20 percent.
With all that said, trends are pointing towards a seasonable, dry
weekend with highs in the upper 30s. Stay tuned for updates as
confidence in low track increase later this week.
.Beyond day 7...
Ensemble and long range guidance continues the trend towards a more
active and potentially colder pattern come mid January. There is a
possibility of a sudden stratospheric warming event in the arctic
displacing arctic air further southward over the next few weeks.
ECMWF and GFS ensembles support this, showing a big cool down
occurring towards Mid-January associated with this arctic air
displacement.
Confidence is rising that the January 9th-11th period will feature a
deep low pressure system pushing through the midwest region,
ushering in much colder air behind it. Will be watching the forecast
closely as this could lead to a period of more winter-like weather
and colder temperatures come mid January into February.
&&
.Aviation...(00Z TAF Issuance)
Issued at 540 PM EST Mon Jan 1 2024
Impacts:
- MVFR Cigs are expected for the first 6-10 hours of the TAF period.
- Improvement to VFR possible after 10Z
Discussion:
GOES16 continues to show extensive cloudiness across Indiana and
much of the region. Surface analysis shows high pressure in place
over the middle Mississippi Valley. The cloud shield showed a back
edge near the surface ridge of high pressure in eastern MO.
The cloud shield is expected to remain across the TAF sites this
evening. However overnight, the surface high is expected to
slowly nudge eastward leading to and eastward progression of the
clearing line late tonight. Confidence in this is medium, thus
have trended toward a return to VFR conditions at that time.
Forecast soundings show a drying out of the lower levels
overnight, suggestive of this clearing solution.
It is important to remember that winter stratocu often has
difficulty clearing out overnight, thus that is our caveat.
VFR Conditions are expected on Tuesday as a more zonal flow will be
in place ahead of an approaching surface trough.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...Puma
Short Term...Melo
Long Term...Updike
Aviation...Puma
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
853 PM CST Mon Jan 1 2024
.UPDATE...
Issued at 853 PM CST Mon Jan 1 2024
GOES-E nighttime microphysics RGB imagery shows back edge of the
stratus making steady eastward progress this evening. Often this
time of year, clearing will slow at night, but that hasn`t been
the case (yet) this evening. DVN VWP shows around 15kt of
westerly flow in the cloud bearing layer which has been pretty
effective so far in pushing clearing eastward. HRRR and RAP both
show clearing continuing east into and across much of our CWA
overnight into early Tue morning. Have updated sky grids to
introduce clearing from the west overnight, but trended slower
than guidance and extrapolation to give clearing some wiggle room
to slow down.
Warm air advection and a gentle 5-10 mph southwesterly wind will
hopefully be enough to keep temps for tanking too much when skies
clear. However, with the expected clearing, did lower forecast
lows some, mainly northwest half or so of the CWA. If winds ease
more, lows could get even colder tonight, like in more wind
sheltered valleys.
Sky cover forecast for tomorrow is low confidence. Some mid-level
cloudiness should advect into and across the CWA. In addition, we
will need to watch the stratus over the western Cornbelt, as
guidance suggests that will advect and expand into our area
tomorrow. Very plausible that we could get a few hours of at least
mixed sunshine tomorrow, but didn`t make any big changes to
tomorrow`s sky cover forecast this evening. The overnight shift
can reaccess that based on observational and model guidance trends
overnight.
Finally, still concerned that there could be a threat of some
freezing drizzle tomorrow evening. Overnight shift will take a
look at the 00z suite of guidance and may need to introduce that
into the forecast as well.
- Izzi
&&
.SHORT TERM...
Issued at 235 PM CST Mon Jan 1 2024
Through Tuesday night...
Key messages:
* Cloudy/mostly cloudy conditions now expected to persist through
the rest of the short term period
* Monitoring two low confidence potentials for freezing drizzle: one
tonight south of I-80 and another more concerning signal late
tomorrow afternoon and overnight
An expansive region of stratus blankets much of the region this
afternoon. Cloud bases have gradually been building down through the
morning, and anticipate that this will continue this evening.
Very light aircraft-effect snow showers (flurries) have been evident
off regional radars--a hallmark of cloud decks lacking condensation
nuclei. This lines up well with a smattering of moderate icing
PIREPs over the past few hours as well. No need for a flurry mention
in the grids as the stratus layer is otherwise too thin to naturally
support snow at this time.
While a defined back edge to the stratus is evident across central
Iowa and meandering eastward, modest low-level warm advection is
forecast to increase this evening which suggests we`ll eventually
see stratus backbuild and deepen. Have boosted cloud cover through
tonight with this in mind.
The RAP/HRRR--which have been handling stratus trends very well--
are squeezing out some extremely light precipitation tonight. Can`t
see any signs of an evident perturbation in water vapor loops but
925 mb warm advection is forecast to increase with time.
Cloud depths are right on the cusp of being deep enough to support
precipitation production (about 2000-2500 feet thick), so this casts
some doubt on how realistic this QPF output is. That said, can
already see a few light returns off the DVN radar (currently
reported as flurries). Did not add any mention of precip to the
grids tonight given how marginal the parameter space is at this
time. Should light precip materialize, we`d once again be right on
the cusp between flurries and freezing drizzle with cloud top
temperatures around -10 C.
A somewhat more concerning FZDZ signal is now evident in guidance
for late Tuesday afternoon and night as the shortwave trough
currently arcing across Saskatchewan moves across the region.
Ascent profiles are more conducive for precip generation and
saturated depths are bit more significant compared to tonight
(assuming this stratus deck doesn`t budge). Initially, there might
be enough mid level cloud deck to inject ice crystals into the low
stratus deck via seeder-feeder, but it looks like we`ll lose this
mid deck rapidly during the evening. Cloud top temperatures warmer
than -9 C suggest that if precip manages to develop, it would
probably be drizzle. It`s hard enough forecasting FZDZ six hours out
(cloud top temps/inversion heights near -10 or -11 C could flip the
script entirely and just result in no-impact flurries), let alone
30+, so no mention in the grids at this time but something we`ll be
keeping a close eye on. Possible that dense stratus helps hold air
temperatures around 30-31 which would mitigate/blunt glazing impacts
as well.
Otherwise, looks like we`ll pick up some southwesterly breezes on
Tuesday with intermittent gusts to around 25 mph during the
afternoon. This certainly won`t feel great with air temperatures in
the low to mid 30s.
Carlaw
&&
.LONG TERM...
Issued at 235 PM CST Mon Jan 1 2024
Key messages:
* Lake effect snow (40-50%+ chances forecast) for primarily portions
of Lake and Porter IN Wednesday night-early Thursday
* Snow chances remain for Saturday, although a downward trend noted
A sharp shortwave trough will drop across the Upper Great Lakes on
Wednesday which will send a reinforcing cold front sweeping through
the region. Forecast soundings look a bit less supportive of
flurries during the day (less low-level saturation).
Eventually, colder air will spill south down the lake yielding a
period of lake effect precipitation, focusing primarily into Lake
and Porter counties in northwest Indiana. Guidance seems to be
trending towards a more marginal parameter space with inversion
heights solidly under 7 kft now. That said, due north winds will
yield a full fetch setup although widespread stratus may limit land
breeze assistance to lake convergence. Continue to boost PoPs above
NBM-delivered values into the high-end chance range given the setup.
The aforementioned cold front will deliver a briefly colder airmass
to the area, with lows Wednesday night slated to drop into the upper
teens and 20s. After another chilly night Thursday night,
southwesterly low-level flow returns as surface high pressure
departs to the east leading to a slight bump in high temperatures to
close out the week (mid and upper 30s).
In general, guidance seems to be largely trending southward with our
next disturbance on Saturday with a much deeper vort lobe scraping
the Gulf Coast and then riding northeastward into the Mid Atlantic.
A secondary shortwave/vort max is well-modeled farther north closer
to our region, but with a more limited supply of low-level moisture,
most precipitation of consequence may end up focusing south of the
CWA. Still plenty of time for additional northward wobbles here
though, so left the blended PoPs alone for now with broad-brushed
slight chances up to the state line and chance category PoPs south
of the Kankakee River.
Carlaw
&&
.AVIATION...
For the 00Z TAFs...
526 PM...Forecast concerns include...
Mvfr cigs through the period.
Gusty southwest winds Tuesday.
Possible freezing drizzle Tuesday evening.
Mvfr cigs remain locked in across much of the area this evening
and no improvement is expected until at least mid/late Tuesday
morning when some scattering is possible, but confidence is low.
Cigs may slowly lower into low mvfr or even ifr, though there
remains quite a bit of uncertainty if cigs will lower to ifr
overnight. If cigs were to scatter out Tuesday, additional mvfr
cigs are expected to spread back across the area Tuesday evening.
There is the potential for freezing drizzle mid/late Tuesday
evening across most of the area. While duration is a bit uncertain,
enough of a signal from guidance to include prob mention for the
30 hour ORD/MDW tafs. It appears that if freezing drizzle does
materialize, it would eventually transition to flurries early
Wednesday morning.
Westerly winds around 10kt will become southwest this evening and
speeds may increase into the 10-15kt range along with some higher
gusts possible. Gusts into the lower 20kt range are expected
Tuesday, which will diminish with sunset Tuesday evening. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL and IN nearshore waters...9 AM Tuesday
to 6 PM Tuesday.
&&
$$
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