508
FXUS63 KIND 291101
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
601 AM EST Mon Dec 29 2025

.KEY MESSAGES...

- Peak wind gusts at 45 to 50 mph across the northern half of
  central Indiana at times through the first half of today

- Wind chill values near zero early this morning and again tonight
  and early Tuesday

- Return to seasonable winter temperatures the rest of the week with
  chances for flurries and light snow Tuesday and Wednesday evenings

&&

.SHORT TERM (Today and Tonight)...
Issued at 310 AM EST Mon Dec 29 2025

After record warmth on Sunday and a line of convection that produced
wind damage across parts of the region...winter has returned with a
vengeance early this morning. Westerly winds have been consistently
gusting at 45 to 50mph over much of the forecast area since last
evening. Temperatures which just a scant 6-8 hours ago were in the
mid and upper 60s now range from the mid 20s to lower 30s at 07Z.

Low pressure is in the process of reaching its peak intensity near
980mb over Lake Huron early this morning. The Ohio Valley is now
firmly in the backwash of the intense low but a surface trough
extending west from the low is set to pivot across the region later
this morning into the afternoon before high pressure finally begins
to exert its influence tonight.

The strong cold advection in the postfrontal environment was aiding
in flurries and narrow bands of light snow showers over central
Illinois in the vicinity of the elongated wave aloft to the
southwest of the upper low. The ongoing flurries and light snow
showers to the west will shift across the northeast half of the
forecast area over the next several hours then continue through the
morning as the upper wave swings through in tandem with the surface
trough. Steepening lapse rates within the boundary layer will aid in
coverage as well with snowflakes persisting into the early afternoon
before diminishing from the southwest as drier air aloft advects
into the region. Expecting little if any impact from the snow with
no accumulation as snow remains light and winds continue to
efficiently blow flakes around. Flurries may linger over northeast
counties until near sunset with dry conditions going forward into
tonight.

Sustained winds currently are at 20-30mph across the northern half
of the forecast area with gusts routinely hitting 50mph. Further
south...gusts have generally been no higher than 40mph. Plan to
continue the Wind Advisory over the entire forecast area but may be
able to remove southern counties by midday should gusts remain at
current levels. As the surface low pulls away to the northeast this
afternoon...gusts will begin to decrease with the pressure gradient
relaxing.

Finally...have kept cloud coverage high through tonight as model
soundings show moisture remaining trapped beneath an inversion.
Drier air aloft will work down into the boundary layer by tonight
but it may be the predawn hours Tuesday before lower stratus
significantly diminishes from the west.

Temps...should fall into the teens and lower 20s after daybreak
before subtle recovery occurs later today. Low level thermals
support highs largely in the mid 20s. Lows tonight will be in the
teens.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 310 AM EST Mon Dec 29 2025

A colder weather, more seasonable winter pattern sets up for next
week across the Great Lakes and Ohio Valley. A few weak clipper
systems bring light snow chances midweek, but overall no major
weather systems of concern in the long term other than minor systems
passing through.

Over the next week, the Eastern CONUS will feel the effects of a
negative NAO as blocking increases over Canada and the North
Atlantic. As a result, deep troughing remains in place over Southern
Canada with a strong northwest flow pattern setting up from
northwestern Canada down into the Ohio Valley. The upper jet remains
strong through the period in response to a sharp low level thermal
gradient across the CONUS, with Indiana located within the colder
arctic airmass at the surface. The main focus in the long term will
be on a few weak clippers traversing southeast within the upper flow
into the Great Lakes. Uncertainty increases by next weekend and into
the following week as long range guidance/ensembles hint at a more
progressive and relatively milder pattern setting up with more
influence from the southern branch of the upper jet.

Tuesday through Thursday...

The first in a series of clipper systems drops southeast into the
upper Great Lakes on Tuesday. The jet streak and associated surface
reflection track closer to the Canadian border, keeping the best
forcing for ascent and any precipitation north of Central Indiana.
Latest short term, higher-res guidance today have trended further
south with the overall system and swath of light snow. Have added
flurries to the forecast along and northeast of the I-74 corridor
Tuesday evening to account for this, but overall still expect any
impactful wintry weather to remain closer to the Great Lakes. The
main impacts from this system will be a surface wind shift to the
west-southwest and a brief temperature moderation as weak warm air
advection modifies the arctic airmass in place. West-southwest winds
Tuesday work to slowly erode the cold air at the surface; however
temperatures still struggle to get out of the upper 20s much of the
day. A non-diurnal temperature curve is expected Tuesday evening as
elevated winds and continued weak WAA ahead of the low level trough
keep temperatures steady in the upper 20s to low 30s through the
night. Deviated from guidance to add this non-diurnal temperature
curve late Tuesday night. A brief period of above freezing
temperatures is expected on Wednesday before Canadian high pressure
moving in from the northwest works to pull the arctic airmass back
south into Indiana.

The next wave within the upper jet dives southeast out of Canada
into the Ohio Valley Wednesday evening into Thursday morning. The
overall pattern remains relatively the same as the previous few days
with the parent upper low over all of SE Canada and Northeast CONUS
with small waves rounding the base of the trough. For Wednesday
evening, the main upper low is placed well to the northeast in SE
Ontario while the next surface reflection develops across Upstate
New York with a trailing arctic front west southwest into Indiana.
This is the one to watch for the possibility for more widespread
light snowfall across Central Indiana.  Trends today have
strengthened the incoming jet streak and nudged it a tad further
south, placing Indiana within a better region of upper level
divergence and enhanced lift. With origins out of the NW, there is
little to no moisture advection from the south, so any QPF will be
fairly light along the incoming frontal. Still the best forcing for
ascent and moisture return are located further northeast toward the
parent system, but guidance has been consistent showing enough
forcing and moisture for a period of light snow along and northeast
of the I-74 corridor wednesday evening into early Thursday morning.
Keeping PoPs at or below 50 percent 00z-12z Thursday for now to keep
snow shower wording in the forecast. With limited moisture, have any
mention of accumulations on the lighter side as anything that does
stick should be fairly minor. Will update the forecast accordingly
if confidence increases in the potential for accumulations.

.Next Weekend...

Going into the weekend, high pressure extending from NW Canada into
the Ohio Valley slowly shifts eastward; however low level
temperatures will be slow to respond as the colder, dense airmass at
the surface slowly retreats. Longer range guidance and ensembles
continue to show a system developing in the Plains then moving
across the Southern CONUS this weekend. Coming out of a blocking
northwest flow pattern, it is expected that guidance will not handle
this transition well, so low confidence remains in the forecast for
next weekend. Trends today have pushed any mention of precip further
south, so have trended drier with this weekend`s forecast. Keeping
the forecast on the drier side with temperatures moderating back
above freezing for the weekend.

Beyond next weekend, a progressive weather pattern looks to continue
to variable weather conditions and temperatures as each system
passes through.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 601 AM EST Mon Dec 29 2025

Impacts:

- Westerly wind gusts peaking at 35 to 40kts through midday then
  decreasing slowly into this evening

- Scattered flurries/light snow possible this morning, especially at
  KLAF

- MVFR ceilings lingering through tonight

Discussion:

MVFR ceilings will remain through much if not all of the forecast
period with winds continuing as the primary impact for aviators.
Westerly winds gusting at 35 to 40kts at times early this morning
will persist through midday along with scattered flurries or light
snow showers. Visibilities may briefly lower at times with snow
showers.

As the surface pressure gradient relaxes in the afternoon...wind
gusts will gradually decrease down to around 20kts by this evening
before completely diminishing late tonight. Moisture will remain
trapped beneath a boundary layer inversion with stratus likely to
linger into tonight.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 5 PM EST this afternoon for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

SHORT TERM...Ryan
LONG TERM...CM
AVIATION...Ryan