IND issues Area Forecast Discussion (AFD) at Jan 2, 3:29 AM EST809
FXUS63 KIND 020829
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
329 AM EST Thu Jan 2 2025
.KEY MESSAGES...
- Partly Sunny Today, still cool.
- Snow showers tonight, with accumulations.
- Cold Temperatures arrive for the foreseeable future tonight.
- A significant winter storm will likely effect the region Sunday-
Monday, low confidence on precipitation types and snowfall totals
&&
.SHORT TERM (Today and tonight)...
Issued at 329 AM EST Thu Jan 2 2025
Synopsis:
Surface analysis early this morning showed strong high pressure in
place over AR/W TN and NRN MS. Strong, large and broad low pressure
was found centered over Maine. These two systems were resulting in a
cold northwest flow across Central Indiana. Aloft, deep and broad
low pressure was found over northern Ontario. This low was allowing
a cold northwest flow in place across much of the United States.
GOES16 shows an area of stratocu exiting central Indiana to the east
resulting in mostly clear skies across the forecast area.
Temperatures were in the middle to upper 20s. High cloud was found
over the plains states, over NB, IA and the Dakotas within the
upstream flow aloft.
Today -
Quiet weather will be expected today with partial sunshine this
morning leading to increasing clouds this afternoon. This will
mainly be the result of the strong high pressure system to the south
pushing a surface ridge axis across Indiana through the day.
Forecast soundings and time heights show a dry column today, however
some upper level saturation is noted later in the day. This will be
due to the expected arrival of the mid and high clouds over the
Central and northern plains, within the upstream flow aloft. Thus an
increasing cloudiness type forecast is expected by this afternoon.
Minimal temperature advection is expected today. Thus the highs in
the upper 30s to around 40 will be expected.
Tonight -
Changeable weather is expected tonight. In the wake of the departing
high pressure system a quick moving clipper system is expected to
sweep across Indiana this evening and will exit overnight. Aloft,
this system does not appear to have much support as the models just
show a weak wave within the amplifying NW flow aloft. Within the
lower levels, a cool front boundary provides good lower level
convergence as the earlier high departs east. This frontal boundary,
as it passes, will be the triggering onset for the arrival of much
colder temperatures that will last for the foreseeable future.
Temperatures above freezing will not arrive for at least the next 7
days, likely more. But I digress, back to tonight's system. Forecast
soundings tonight show good saturation within the mid and lower
levels by 06Z at IND, including within the DGZ. Pwats for this
system do not appear too large, with values only near 0.3-0.4. HRRR
shows areas of snow showers pushing across Central Indiana between
03Z and 09Z, in conjunction with the frontal passage. Thus will
include best pops during this time. Best forcing and moisture
appears to be mainly north of I-70, thus highest pops and higher
amounts should be found at those locations. However it does appear
that most of the forecast area will be impacted. Snow falling late
overnight and during the early morning hours may result in a
slippery roads and surfaces if untreated during the Friday morning
commute. Snow amounts should be less around 2 inches across northern
parts of Central Indiana, including Kokomo, Anderson and Muncie. One
inch amounts will be more likely along the I-70 corridor with lesser
amounts south. As always with these systems, isolated higher amounts
cannot be ruled out. With the onset of strong cold air advection in
the wake of the front, expect lows in the lower 20s.
&&
.LONG TERM (Friday through Wednesday)...
Issued at 329 AM EST Thu Jan 2 2025
Friday through Saturday night...
Light snow should end just before dawn Friday with perhaps lingering
flurries over northeastern counties, yet minor impacts are possible
early Friday from slippery roads with readings slow to rebound
through the low 20s.
The remainder of the early-long term will feature dry and cold
conditions as polar/arctic high pressure steadily builds in from the
northwest. This will make for blustery conditions Friday with
sustained winds around 15 mph gusting to 20-25 mph through much of
the day...holding wind chills under 20 degrees for most areas. Under
at least partial clearing Friday afternoon, temperatures should
reach the mid-20s to low 30s.
The first half of the weekend will exhibit fair weather as
temperatures range from mainly the teens during overnights to 20s on
Saturday. Wind chills mainly under 10 degrees Friday night should
fall slightly below zero for several northern counties.
Sunday through Monday...
Confidence increasing in significant to potential major winter storm
impacting central Indiana within Sunday to Monday timeframe. Cold,
polar surface high pressure will be in place ahead of lee-side
surface cyclogenesis into Oklahoma early Sunday. System is expected
to then slowly track in an east-northeasterly direction, bringing
accumulating snow and/or ice across the Midwest and Ohio Valley.
Confidence in storm track and associated precipitation type
decreases through this 36-hr period...given location and timing of
potential development of additional surface low pressure to
south/east of original circulation. Lack such additional center of
circulation in/near Kentucky would encourage mixed/ice precipitation
further north into CWA...per original low curling in a more
northeasterly trajectory around predominant center of arctic high
pressure back over northern Plains. However the storm system's
overall detachment from the northern jet should favor at least a
secondary low that would serve to pull entire trough in a more
easterly direction...as favored slightly in latest set of ensembles.
Careful attention will be paid to any continuation of such trends in
upcoming updates.
Trends exhibited by latest data also include better agreement
between ensembles and operational solutions...albeit perhaps at the
expense of overall run to run consistency with a slight northern
trend in both the area of heavier precipitation and also potential
for mixed/icy precipitation types. Supporting wave and surface low
are also trending stronger in some guidance. If a broad and perhaps
double-barrel trough were to stretch west-to-east, likely somewhere
between the OH and TN Valleys...a very wide precipitation shield of
snow could extent from Virginia back to the central Plains around
the Sunday night timeframe. Locally, moderate to heavy
precipitation is possible around the Sunday and into Sunday night
timeframe along the warm frontal zone. Less certainty surrounds
probably less-intense, yet potentially steady precipitation into the
Monday timeframe...where any broad/multi-circulation surface trough
set-up would likely be slower to drag east, while also possibly
maintaining higher rates of accumulation.
Perhaps this system's greatest uncertainty still exists across our
CWA, yet confidence is increasing in both snow being the primary
precipitation type north of the I-70 corridor...and the potential
for heavy mixed precipitation is increasing for at least our far
southern zones and towards the Ohio Valley. Lower confidence in
precipitation type and amounts is found for the broad area in
between. However, the potential for heavy snow and/or mixed
precipitation is greater along/south of the I-70 corridor than
points north. And it is likely any part of central Indiana that
sees ample mixed precip likely receives at least light to moderate
accumulating snow before changeover. Also, forecast soundings
indicate that mainly sleet may prevail within any area of mixed
precipitation thanks to refreeze layer temperatures below -5 Celsius
near the surface...which would agree with the strength of the
antecedent cold air and ample diabatic cooling through the boundary
layer.
Expect precipitation to taper off as all snow by PM hours Monday
with low temperatures probably around 10F Monday night and wind
chill values around zero Monday night. We recommend partners and
public to stay tuned for further updates late this week and into the
weekend. Confidence in further details will increase as the
supporting upper wave enters the Pacific Northwest and can begin to
be resolved by upper air observations on Friday.
Tuesday and Wednesday...
Mainly dry yet very cold conditions should be the rule with
temperatures ranging from single digits to hopefully around 20F,
although highs in the teens may be a reality for anywhere with a
moderately deep snow pack. Flurries and a few snow showers will be
possible amid the overall cyclonic flow.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 1238 AM EST Thu Jan 2 2025
Impacts:
- VFR for much of the forecast period.
- MVFR returns after 030000Z Friday
Discussion:
High pressure over the southern plains will move east to the deep
south today. This feature will control Indiana/s weather, providing
mainly VFR conditions today. Early this morning, GOES16 shows some
VFR Cigs over Indiana, exiting toward the east quickly as the high
arrives in the region. High cloud within the flow aloft were found
over KS and western MO. These high clouds should pass across Indiana
through the course of the day, but will overall result in continued
VFR conditions.
A quick moving Alberta Clipper system will sweep across Indiana
tonight. Forecast soundings show deep saturation arriving with this
feature. Thus for now have included a period of snow after 030000Z
along with MVFR cigs and visibilities as these features pass.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
SHORT TERM...Puma
LONG TERM...AGM
AVIATION...Puma
Source:
IND issues Area Forecast Discussion (AFD) at Jan 2, 3:29 AM EST---------------
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