IND issues Area Forecast Discussion (AFD) at Dec 1, 5:59 PM EST649
FXUS63 KIND 012259
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
559 PM EST Sun Dec 1 2024
.KEY MESSAGES...
- Unseasonably cold conditions continue into Tuesday...with
overnight lows in teens and nighttime wind chills 5-15 degrees
- More flurries/snow showers possible...both southwest Monday midday-
early evening...and north of Indianapolis late Monday night
- Temperatures moderate above freezing midweek before another cool
down for next weekend
- Patchy drizzle and freezing drizzle possible on
Wednesday/Wednesday night. Confidence in occurrence is
currently low
&&
.SHORT TERM (This evening through Monday)...
Issued at 243 PM EST Sun Dec 1 2024
Upcoming areas of flurries and a few snow showers aside (see section
below), the synoptic pattern's broad, cold H500 trough will begin to
slide eastward through the short term...as the next broad mass of
arctic air approaches from the central Plains to the Mississippi
Valley. This track will maintain west-northwesterly winds that
should gust up to 10-15 mph during afternoons. Mostly clear skies
through most of tonight will yield to thickening clouds Monday under
an approaching mini-wave...with solid clearing through early evening
hours Monday as it departs to our southeast.
Temperatures will be regulated by light breezes and clouds to
diurnal spreads of 15 degrees or less...with overnights dropping
into the teens framing highs in generally the upper 20s Monday.
Overnight minimum wind chills will continue in the 5 to 15 degree
range...and only rebound to 15 to 25 degrees during the day Monday.
Monday and Monday night...
Two sub-regional light snow potentials exist for the second half of
the short term. Another quick shot at flurries/few snow showers will
cross southwest of the Indianapolis Metro within the Monday midday
to early evening timeframe. Expectations so far are for a repeat of
the recent overnight snow...with perhaps only 10 percent of the
liquid equivalent and snowfall. At least moderate confidence with
location again being focused over the CWA's far southwestern zones
per broad upstream ridge advancing eastward across British Columbia
which will serve a slight plunging trend to the supporting vort max
as it streams southeastward from the Twin Cities into northern
Kentucky. Forecast soundings over Knox County depict a perhaps 6
hour window where virga from saturation of the DGZ around the 850-
750 mb layer should make it to the surface as flurries and a few
snow showers in another WNW-to-ESE trend. Any minor impacts would
be from isolated very light coatings south of a Sullivan to Bedford
line...but with continual sub-freezing temperatures expected,
untreated surfaces could potentially turn slick in patches under the
few steadier snow showers.
Less confidence...in what should start as a more locally potent lake-
effect snow shower episode in Michigan...reaching our northern
counties late Monday night. A surface trough spinning southward
through the Great Lakes should induce convective, southward-
advancing snow...from S/S+ over northern/central Lake Michigan
Monday afternoon...to remnant S- around the Kokomo area going into
pre-dawn hours Tuesday. Uncertainty here is in how quickly the snow
showers diminish when approaching our region and entering better
ridging. Certainly cannot rule out flurries, and a lone snow shower
or two that could drop a thin coating just before the morning rush,
yet this potential is conditional.
&&
.LONG TERM (Monday night through Sunday)...
Issued at 243 PM EST Sun Dec 1 2024
The beginning of the long term is expected to remain well below
normal as central Indiana will remain in northwest flow aloft. Given
the amplified pattern, super-geostrophic flow over the northern
Rockies will induce weak upper level waves within the NW flow.
None of these waves will be within strong baroclinicity and are
expected remain weak as they reach central Indiana, however given
the abnormally cold air mass, only weak lift will be needed in any
saturated layer to produce scattered flurries. These flurries
will be more likely on Monday/Monday Night (See Short Term), as
low level pressure increases will push into Indiana from the west
beneath CAA. Due to low confidence in location/timing on Tuesday,
these have not been included in the forecast, but it's something
to monitor nonetheless.
Outside of low chances for scattered flurries, the main point of
emphasis on Tuesday will be the abnormally cold weather. Given the
departure from early December climatology, model guidance is
expected to be a touch too warm, especially within more conducive
radiational cooling environments. For this reason, temperature
forecasts have been lowered into the 25-50th percentile ranges with
lows in the teens to low 20s Tuesday night.
Wednesday and Thursday...
The pattern begins to shift slightly over the middle of next week as
one of the waves induced by supergeostrophic flow interacts with
stronger baroclinicity over the Northern Plains and moves north of
Indiana. With the center of the low moving well north of central
Indiana, winds will shift towards southerly pushing our temperatures
back towards seasonal. There will be a moderate amount of lift out
ahead of this low, but moisture convergence will likely be confined
to near the low center keeping the relatively dry air over central
Indiana. Still, pockets of precipitation will be possible Wednesday
into Thursday.
The main concern with Wednesday's precip will be a very dry surface
layer, along with some signals for saturation around 500-1500m above
the surface. If this saturated layer comes to fruition, it would be
too warm for ice crystal growth leading to potential for patchy
drizzle. Models are widely spread on temperatures Wednesday and
Wednesday night, but with dew point recovery being weak, there is a
low chance for this drizzle to become freezing drizzle.
A return to much colder air is in store as high pressure builds in
from Canada again. Lows in the teens to around 20 and highs around
30 can be expected. Cold advection may be able to squeeze out a
few snow showers/flurries.
A few ensemble members have a slightly stronger low passage late
Friday through Saturday, of which could lead to low QPF rain or
even wet snow. Low PoPs have been included but confidence is very
low at this point.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 559 PM EST Sun Dec 1 2024
Impacts:
- Some potential for MVFR ceilings Monday afternoon at KHUF/KBMG
Discussion:
Mid clouds will exit early in the period, but an increase in mid
cloud will occur again later tonight into Monday morning. Lower
clouds will then increase into afternoon with a system passing to
the southwest. Some MVFR ceilings may develop at KHUF/KBMG, but
confidence in those is medium at best.
In addition, a few flurries and snow showers may reach KHUF/KBMG in
the afternoon, but odds of impacts are low at the moment.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...AGM
LONG TERM...Updike
AVIATION...50
Source:
IND issues Area Forecast Discussion (AFD) at Dec 1, 5:59 PM EST---------------
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