IND issues Area Forecast Discussion (AFD) at Jan 16, 12:46 PM EST000
FXUS63 KIND 161746
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1246 PM EST Thu Jan 16 2025
.KEY MESSAGES...
- A few flurries or light snow showers north this morning. Little to
no impact expected. Winds will gust to 20-30 MPH at times today
- Warm up to end the work week, with rain likely Friday night and
early Saturday. Snow will mix in with the rain by Saturday morning
with a possibility for very light accumulations
- Bitterly cold air is expected Sunday through the middle of next
week with multiple nights of subzero lows likely. Single digit highs
expected in most areas Monday and Tuesday
&&
.FORECAST UPDATE...
Issued at 1006 AM EST Thu Jan 16 2025
No major changes made to the forecast with this morning's update.
Not as cold today across Central Indiana as temperatures finally
break the freezing mark later this afternoon... however windy
conditions will still make it feel like it's in the 20s. RAOB and
ACARs soundings show the shallow arctic airmass in place at the
surface slowly eroding away as a strong warm nose of +0-3C at 1 km
agl advects in aloft. Sunshine this morning will help "warm" the
boundary into the upper 20s to low 30s over the next couple hours
for the southern half of the state. Slightly colder air advection
pushes in aloft later this afternoon steepening low level lapse rates
and increasing low level mixing. This should result in winds within
the LLJ to mix to the surface with gusts upwards of 20-25 mph this
afternoon while helping to keep surface temperatures in the low to
mid 30s despite some increase in cloud cover. Satellite imagery
shows an area of lower stratus rounding the trough axis and moving
over Central and North Central Indiana through the rest of the
morning and early afternoon hours. Areas south of I-70 have the best
likelihood of remaining sunny with slightly more mild temperatures in
the mid and potentially upper 30s.
&&
.SHORT TERM (Today and tonight)...
Issued at 249 AM EST Thu Jan 16 2025
Expected moisture limitations along with a slight last-minute pivot
in the upper trough swinging through the area this morning have
largely led to scattered snow showers being limited to areas further
north than previously expected. Will carry low PoPs for light snow
showers or flurries across mainly the far north through just after
daybreak, with dry conditions expected thereafter, as profiles
rapidly dry from aloft. Accumulations beyond perhaps a dusting are
no longer expected, and even anything beyond a trace now seems
unlikely given the widespread 10-15 degree low level temp/dewpoint
spreads.
Once midlevel cloud clears the area, though some stratocu may
rebuild, plenty of breaks of sun should appear, particularly this
afternoon. This, along with modest warm advection early in the day
should help highs to reach the low to mid 30s across the area.
Modest boundary layer mixing will promote some gustiness to the
winds today, with occasional gusts of 20-30 MPH expected. This will
keep wind chill values in the mid teens to mid 20s today.
Quiet weather will continue into tonight, with partly cloudy skies
as mid and high cloud slowly ramp up ahead of the next frontal
system. An increase in low level warm advection will also keep low
temperatures nearer normal, in the low to mid 20s across the area.
&&
.LONG TERM (Friday through Wednesday)...
Issued at 249 AM EST Thu Jan 16 2025
Upper level ridging expanding into the eastern part of the country
on Friday will provide a brief thawing from the recent frigid
conditions experienced. A cold front will bring primarily rain to
the Ohio Valley Friday night and early Saturday before transitioning
back to light snow before ending as colder air spills back into the
region. The upper level pattern then reloads with an even deeper
meridional trough encompassing all but the far western part of the
country through the middle of next week with bitterly cold air and
multiple nights with subzero temperatures returning.
Friday through Saturday Night
Clouds will linger Thursday night but should be in the process of
clearing by Friday morning aided by the passage of a surface ridge
followed by strengthening southerly flow and the onset of warm
advection. Friday is easily set up to be the warmest day of the
extended period as highs range from the mid 30s north to lower 40s
south.
A cold front will approach the region Friday night in advance of the
aforementioned deep meridional upper level trough poised to expand
across much of the country by the end of the late weekend through
the first half of next week. Model data continues to favor a
progressive moving frontal boundary that will impact the region late
Friday night and Saturday with an axis of deep isentropic lift set
to pivot across the Ohio Valley. Model soundings and low level
thermals support rain as the main precipitation type Friday night
although there is an exception over eastern counties where surface
temps may fall back close to freezing Friday evening prior to
precipitation onset overnight. This could enable snow to mix in
initially before the boundary layer warms enough to transition to
all rain. Another factor to consider is ground temps which are
likely to lag surface temp rises Friday night by a few degrees. With
the recent stretch of bitterly cold temperatures and the snowpack...
could see a scenario where light icing occurs in some areas for a
few hours Friday night even as temps rise into the mid 30s. Will
continue to provide additional detail as we get into range with the
short range guidance today into Friday.
While rain remains the main precipitation type as the deepest lift
and moisture passes Friday night...colder air will advect into the
region with snow mixing in as early as predawn Saturday over the
northern Wabash Valley. This will gradually expand southeast across
central Indiana through the day as low level thermals tumble.
Temperatures will drop all day Saturday into the mid and upper 20s
by the evening. While deeper moisture will already be moving away
from the region by Saturday morning...could see very light snow
accumulations of a few tenths of an inch before precipitation fully
ends Saturday evening.
Sunday through the Middle of Next Week
Yet another extended stretch of bitterly cold temperatures will
commence for late weekend and continue for much of next week as the
deep upper level trough settles over much of the country. An
exceptionally strong surface high potentially greater than 1050mb
will slide down the east side of the Rockies from western Canada and
across the eastern half of the country through the middle of next
week. Mid level heights will tumble in response with growing
confidence in the coldest weather yet for this winter by Monday and
Tuesday.
High temps will revert back to the teens by early next week... with
single digits likely Monday and Tuesday. The pattern supports
multiple subzero nights early next week as well...although what is
left of the snowpack after the rain Friday night and early Saturday
will be a factor in just how low those temperatures will be able to
go.
Frigid conditions will persist into the latter part of next week
until return flow develops and allows for moderation. Highs may
recover back to near freezing by late next week but there are hints
of the pattern recycling once again with another surge of arctic air
late January into early February.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 1246 PM EST Thu Jan 16 2025
Impacts:
- MVFR ceilings and wind gusts 18-24KT from 280 deg through this
evening
- Slight chance for fog tonight, with patchy dense fog possible.
Discussion:
Latest satellite imagery shows MVFR stratus pushing southeast
through Central Indiana associated with a weak mid level disturbance.
Latest IND ACARs sounding indicates a stronger low level inversion
that what hi-res guidance suggest for early this afternoon, so
expect lower MVFR stratus to persist under that inversion for at
least the next several hours, especially at KIND and KLAF. Despite
the inversion, gradient winds are strong enough to limit overall low
level wind shear. Still some slight shear to mention as surface
winds are from 260-280 gusting to 20-25 kts and LLJ winds around
2000 ft agl are from 280-300 around 30-35 kts. Not enough to mention
it in the TAF, but worth mentioning it here. Any threat for LLWS
should diminish after sunset this evening as the LLJ and surface
winds both weaken considerably.
Lower confidence in high fast MVFR cigs will lift or clear out
tonight as upstream satellite imagery and observations show a more
extensive area of MVFR stratus in Wisconsin and Iowa pushing
southeast towards Indiana. Guidance does show a rising trend in cigs
tonight, but confidence on that actually occurring for KLAF and KIND.
Tonight, as skies clear in the southern half of Indiana and winds
turn back to the south/southwest, some advection fog may be possible
over the remnant snowpack as warmer air continues to move into the
area. Guidance is struggling to handle this, but will include a
6SM/BR/BCFG mention for now as there may be some potential for at
least patchy dense fog as well.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CM
SHORT TERM...Nield
LONG TERM...Ryan
AVIATION...CM
Source:
IND issues Area Forecast Discussion (AFD) at Jan 16, 12:46 PM EST---------------
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