IND issues Area Forecast Discussion (AFD) at Feb 16, 11:44 PM EST025
FXUS63 KIND 170444
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1144 PM EST Sun Feb 16 2025
.KEY MESSAGES...
- Wind chills falling to near zero to below zero tonight
- Another round of accumulating snow expected Tuesday into Wednesday
with the greatest impacts along and south of I-70
- Temperatures remain well below normal through the week with
multiple mornings of sub-zero wind chills
&&
.FORECAST UPDATE...
Issued at 957 PM EST Sun Feb 16 2025
Scattered flurries continue across much of central Indiana at this
hour, but the clearing line of has made quicker eastward progression
than originally expected. Will maintain flurries where cloud cover
remains, clearing the mention as sky cover drops below about 70
percent or so overnight.
Given the quicker than anticipated clearing, have made downward
adjustments to low temperatures across portions of the region,
leaning toward low end of the guidance envelope overnight. These
adjustments are only a couple/few degrees at most in most spots, but
do bring wind chills down a bit as well.
That said, these adjustments are all relatively minor and do not
seriously alter the message of the forecast - bitterly cold,
scattered flurries, and breezy conditions contributing to near to
subzero wind chills overnight.
&&
.SHORT TERM (This evening through Monday)...
Issued at 245 PM EST Sun Feb 16 2025
Rest of This Afternoon into Early Evening...
Flurries and scattered snow showers continued across central Indiana
early this afternoon, with forcing continuing from an upper level
trough moving through. Little accumulation was occurring from these
though. Better lake enhanced snow showers were remaining north of
the forecast area.
Similar conditions will persist through the afternoon, although the
focus for snow showers should shift east with time as the upper
trough moves to the east. Will keep chance PoPs going with scattered
wording, with the higher PoPs gradually shifting east.
A tight pressure gradient and some steeper lapse rates will keep
winds gusty, and these could blow around any fresh snow that falls.
Given this and the lingering travel impacts, will keep the Winter
Weather Advisory in place through 700 PM.
Mid-evening through the Night...
Some flurries may linger tonight with the lower clouds, but there
are some indications that clouds may break some late tonight in
parts of the area. Satellite imagery this afternoon does show a more
cellular look to the western edge of the cloud deck in western
Illinois. However, as usual, confidence isn't great that clearing
will actually make it to central Indiana.
Also, some mid and high clouds will be on the increase later tonight
from lift well west of central Indiana.
Will go more pessimistic than guidance suggests, but will still
allow for some breaks in the clouds, especially west late tonight.
Cold advection will bring in below normal temperatures tonight, but
how cold it will get will depend on how much clearing actually
occurs. Even if winds stay up, clearing over the fresh snow would
allow readings to cool quickly.
Will trend toward guidance (even though it was too optimistic on
clearing) because even if it clears for a bit, readings could
quickly fall to those cold numbers.
Monday...
Clouds will thicken once again across the area on Monday as lift
strengthens upstream. With the lift staying west of the area though,
not expecting any precipitation during the day on Monday.
The cold airmass in place plus the thickening cloud cover will keep
temperatures cold. Highs will only be in the mid teens north to
lower 20s south.
&&
.LONG TERM (Monday night through Sunday)...
Issued at 245 PM EST Sun Feb 16 2025
An anomalously cold week is in store for Central Indiana as highs
struggle to get out of the teens and daily wind chill values fall
below zero. Additional light snow accumulations are expected
midweek, helping to keep a snowpack on the ground through at least
the weekend.
Two hazards to focus on Tuesday through Thursday...exceptionally
cold temperatures and the threat for more accumulating snow.
Cold Temperatures: A strong 1050mb Canadian high pressure system
centered over Saskatchewan slowly shifts southward into the Upper
Plains through the week keeping northerly flow and the arctic
airmass over the northern half of the CONUS. Ensemble guidance is in
great agreement with the strength of this arctic airmass with low
level temperatures 2 to 3 standard deviations below normal for this
time of year. Consistently cloudy skies, cold air advection, and a
subsidence inversion aloft will all work to inhibit surface heating,
keeping highs in the mid teens to low 20s all week. While conditions
are not the best for radiational cooling, a fresh snowpack on the
ground and a very cold airmass will still support overnight lows
falling into the single digits to near zero, with the coldest nights
likely being Wednesday night through Friday night. Expect nightly
wind chills to fall into the zero to -10 degree range as winds
remain slightly elevated through the overnight hours. Will highlight
this threat with a Special Weather Statement; however Cold Weather
headlines may be needed for portions of the region over the next
couple days.
Accumulating snow potential: Central Indiana will be under a sharp
baroclinic zone aloft with a strong south to north temperature
gradient across the Ohio Valley. Aloft, the region will be in the
right entrance region of a 140 kt westerly jet streak Monday evening
through Wednesday. At the same time, deeper troughing over New
Mexico and the Texas Panhandle will lead to surface cyclogenesis
across South Texas with moisture streaming northward out ahead of
it. A boundary sets up from Texas to the Ohio Valley to the Mid
Atlantic states where the weak mid level low will track Tuesday
through Wednesday while the surface low looks to remain weak and
stay along the Gulf Coast. BUFKIT cross sectional profiles do show
enough moisture flowing northward from the Gulf Monday evening
through Wednesday with enough lift aloft to support continued flurry
and light snow activity in the vicinity and north of this
aforementioned boundary setting up. Increased PoPs during this time
frame to reflect this.
The heaviest snowfall will likely occur Tuesday night through
Wednesday as the system passes by just to the south and the upper
trough axis passes through the region. While the best forcing for
ascent and moisture advection will likely remain further south
across the Gulf States and Tennessee Valley, it will not take much
moisture in this pattern to squeeze out accumulating snowfall,
especially with very high snow to liquid ratios. Would not be
surprised to see a couple inches of light, fluffy snow for much of
Central and South Central Indiana by Wednesday, with the highest
totals across Southern Indiana where deeper moisture will be
present. While this is a few days away and some of the finer details
may change, confidence is increasing in flurries and light snow for
much of midweek with snowfall accumulations for portions of the
area.
End of the week into next weekend...
The arctic air persists into the end of the week; however a slight
moderating may be on the horizon. Longer range guidance is in
agreement with the core of the arctic airmass pushing northeast as
ridging builds in by Sunday and low level flow becomes southerly.
Confidence is low on exact details; but typically guidance tries to
kick out deep arctic airmasses too quickly in the long range. Higher
confidence exists in a slow moderating trend with highs still in the
20s to maybe low 30s for the weekend.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 1144 PM EST Sun Feb 16 2025
Impacts:
- MVFR ceilings dissipating overnight but could potentially return
by midday Monday
- Northwest winds gusting to around 20-25kts for a few more hours
overnight. Additional gusts to around 20kts possible at KLAF MOnday
afternoon
Discussion:
The last of the flurries and light snow showers have moved east of
the terminals late this evening with the lower stratus clearing out
as well. Skies should remain generally clear for the next several
hours as the thicker stratus shield departs to the east. Northwest
wind gusts have been gradually weakening but will be a few more
hours before completely diminishing.
Mid and high level clouds will expand back across central Indiana
Monday morning with at least some potential for MVFR level stratus
to return at times during the afternoon. Westerly winds of 10-15kts
are expected Monday with some higher gusts possible at KLAF as well.
Ceilings will settle at around 5kft by late Monday with the
potential for flurries to return during the evening.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Nield
SHORT TERM...50
LONG TERM...CM
AVIATION...Ryan
Source:
IND issues Area Forecast Discussion (AFD) at Feb 16, 11:44 PM EST---------------
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