Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/16/24
Area Forecast Discussion
National Weather Service Indianapolis IN
929 PM EST Mon Jan 15 2024
.Key Messages...
- A Wind Chill Advisory in effect across areas near and north of I-70
from Midnight until Noon Tuesday.
- Light snow possible tonight. Total snow accumulations a half an
inch to an inch.
- Temperatures will remain bitterly cold through Wednesday
morning with sub-zero wind chills.
- Snow chances return Thursday into Friday. Bitter cold and
sub-zero wind chills return late week into the weekend.
&&
.Mesoscale Update...
Issued at 929 PM EST Mon Jan 15 2024
Radar imagery over the last two hours is showing the gradual
saturation of the low levels which lines up with the ACARs soundings
trend over Indianapolis with saturation now down to around 8000ft
with at least some snow making it to around 3000ft. At the rate of
this saturation, expect to start seeing some snow reach the ground
in the next 2 hours with snow rates picking up after midnight.
Forcing associated with the shortwave should peak around 06Z with
robust vorticity above the cloud layer. Moisture still looks meager
with PWATs well below 1/4 of an inch but with how dry the air is,
snow ratios will likely be near or even exceeding 20:1 which should
allow for some accumulations up to an inch. Another factor which
should help lead to higher accumulations will be the lack of
stronger winds which would break up the snowflakes as they fall from
a higher cloud deck than a more typical winter system.
&&
.Forecast Update...
Issued at 929 PM EST Mon Jan 15 2024
No major changes needed to the ongoing forecast but made a few minor
adjustments to hourly POPs to match current observational soundings
that will be discussed in the mesoscale portion above. Snow amounts
up to an inch still look reasonable in points north and west of
Indianapolis with subzero lows with wind chills around -20 to -15.
Areas further to the south will end up warmer in the low single
digits with wind chills closer to -10. With the more robust cloud
cover tonight and CAA being weaker, not expecting temperatures to
drop well below model guidance as has occurred the last two nights.
&&
.Short Term...(This evening through Tuesday)
Issued at 259 PM EST Mon Jan 15 2024
Tonight...
Wind chills have come up above advisory level this afternoon as
winds have dropped below 10 knots, and temperatures were now in the
single digits above zero to around 10 degrees.
Blocking pattern over Greenland has kept broad low pressure over
eastern Canada and Arctic high pressure from western Canada into the
southern Plains and Tennessee and Ohio Valleys. This will result in
more cold advection and bitterly cold weather into Tuesday. The
combination of overnight lows zero to slightly below and west winds
to 10 knots necessitates another Wind Chill Advisory, over areas
near and north of Interstate 70, from Midnight through Noon Tuesday
afternoon. Lowered temperatures a couple of degrees or so from the
blend based on trends with this Arctic air mass. Coordinated with
ILX, ILN, LOT and IWX.
Meanwhile, H20 vapor imagery was showing a broad trough from the
upper Midwest to Wyoming. This feature will pivot southeast across
the Great Lakes and Ohio Valley tonight. This feature will combine
with saturation, per Hi-Res BUFKIT soundings, and a 150+ knot polar
jet streak to bring a quick burst of an inch or less of snow this
evening and into the overnight and mainly over areas north of
Rockville and Noblesville, where PoPs, using a blend of Hi-Res
models and inter-office coordination, run 60% and greater from 04z-
10z. The jet streak will move into the Ohio Valley overnight and
provide broad divergence, potentially enhancing snowfall. In
addition, the Arctic airmass will support snow ratios 15:1-20:1.
Will continue the SPS to warn of the potential for slick roads
tonight.
Tuesday...
Tuesday will start off bitter cold once again, especially over
northern sections, where a Wind Chill Advisory will be in effect.
That said, part of the Arctic high will break off over the southern
Plains. This will allow the low level winds to shift to southwest,
which along with some sunshine in the wake of the trough, will
denote the start of moderating temperatures. Afternoon highs could
even reach the teens over southern sections.
&&
.Long Term...(Tuesday night through Monday)
Issued at 259 PM EST Mon Jan 15 2024
Tuesday night through Wednesday...
Surface high pressure will provide quiet weather conditions at the
beginning of the period. A quick warm up is expected midweek as the
surface highs moves east allowing and winds become southwesterly.
While temperatures will start to warm up Tuesday night, increasing
flow from a strengthening pressure gradient could support wind
chills as low as -15F. Expect highs to quickly warm into the 20s on
Wednesday, possibly even reaching 30F in a few spots across far
southwestern counties. However, wind gusts up to 35 mph during the
day will make it feel like temperatures are in the single digits
or teens.
Wednesday night through Friday...
Snow chances return for the latter half of the work week as multiple
upper level waves are expected to move through. The first upper
impulse should move through on Thursday. Modest moisture return
combined with increasing large scale ascent will likely support
light snow. A deeper trough will then quickly move in behind the
aforementioned system late Thursday night into Friday. This second
system will advect very cold air back into the region and support
additional chances for snow through early Friday. Some uncertainty
remains on how much moisture will remain across the area as the
deeper trough passes.
Accumulation is likely during this period, but disagreement between
models limits confidence in forecasting snowfall totals. Efficient
snow ratios are possible so it would not take much moisture to get a
quick 1-2 inches of snow. Especially with the deeper trough as very
cold temperatures return. Temperatures in the 20s on Thursday will
fall well into the teens by Friday
Friday night onward...
Strong surface high high pressure builds in over the weekend
supporting quiet weather conditions. Clouds and some flurries may
linger into Friday night depending on wind flow trajectories off of
Lake Michigan. A very cold airmass will settle into the region to
start the weekend. Look for widespread single digit lows both
Saturday and Sunday morning. Some locations could be near or
slightly below 0F. Dangerous wind chills will be a concern once
again, mainly Friday night into Saturday before winds begin to taper
off. Good news is that temperatures may finally get above freezing
early next week as southerly flow increases.
&&
.Aviation...(00Z TAF Issuance)
Issued at 606 PM EST Mon Jan 15 2024
Impacts:
- MVFR to brief IFR vsbys after 05Z.
- MVFR cigs 06Z to 11Z.
Discussion:
Snow is expected during the early overnight hours with greatest
impacts at LAF where IFR vsbys may be predominant. Mostly MVFR
vsbys expected at IND and HUF with little to no MVFR at BMG. Cigs
will also become MVFR later into the event with all snow ending by
11Z. Skies will then begin to gradually clear with VFR conditions
and westerly winds to 10kts through the rest of the TAF period.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until noon EST Tuesday for INZ021-028>031-
035>049-051-052.
&&
$$
Mesoscale...White
Update...White
Short Term...MK
Long Term...Melo
Aviation...White