IND issues Area Forecast Discussion (AFD) at Mar 21, 9:27 AM EDT588
FXUS63 KIND 211327
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
927 AM EDT Fri Mar 21 2025
.KEY MESSAGES...
- Southwest winds gusting at 30 to 35 mph this afternoon and
evening, possibly as high as 40 mph in the northern Wabash
Valley
- Small threat of showers over the northern half of the area tonight
- More widespread rain for Sunday and Sunday night
- Temperatures hovering around normal for much of the upcoming week
&&
.FORECAST UPDATE...
Issued at 927 AM EDT Fri Mar 21 2025
Forecast is on track this morning. High clouds will be on the
increase today, and as the pressure gradient tightens, winds will
increase. Mixing will bring down some gusts over 30 mph, especially
northwest.
The southwest winds will bring in warmer air with highs in the 50s
expected for most areas.
&&
.SHORT TERM (Today and tonight)...
Issued at 310 AM EDT Fri Mar 21 2025
Clear and cold first night of spring with a high pressure ridge over
the region. Winds had lightened considerably and were near calm in
some locations. 06Z temperatures had dropped colder than previously
thought into the upper 20s and lower 30s due to the ideal
radiational cooling conditions currently.
As has been the case in recent days and weeks...the primary focus
for today into this evening will be the wind with a gusty afternoon
developing again as the pressure gradient tightens up with a cold
front moving into the upper Midwest and eventually into the region
by tonight with a few showers.
The surface ridge axis is directly overhead and as that moves east
in the predawn hours...should see a subtle gradient develop with
light southwest flow. This may lead to temps rising back up a couple
degrees prior to daybreak from current readings. Winds will pick up
quickly by late morning in response to the tightening pressure
gradient and increase this afternoon as the boundary layer becomes
well mixed in the dry airmass. The strongest gusts will be focused
over the northwest half of the forecast area in closest proximity to
the low level jet positioned over the mid Mississippi Valley. Gusts
may peak briefly late day as the boundary layer flow strengthens and
the mixing layer rises into the 750-700mb. The potential exists for
a few gusts to approach 40mph over the northern Wabash Valley.
Elsewhere expect peak gusts in the 30-35mph range during the mid and
late afternoon.
Despite the development of the nocturnal inversion in the near
surface layer this evening...sounding profiles maintain dry adiabatic
flow above the inversion through 750-700mb which will aid momentum
transfer to the surface and keep gusts healthy all evening as the
low level jet pivots into the region from the west. Mid and high
level clouds will be on the increase by late day and continue
tonight as the front approaches. A few showers will move across the
northern half of the forecast area late evening into the predawn
hours Saturday aided primarily by subtle isentropic lift immediately
ahead of the front. Most of the forcing aloft will remain well to
the north as low pressure tracks into western Quebec. Moisture also
remains paltry and at least initially confined primarily to the mid
levels which will limit shower coverage to widely scattered at best.
It should be noted based on the model soundings that the showers may
be able to pull slightly stronger winds to the surface for a brief
period as they pass late this evening with an abundance of dry air
present below 700mb prior to gradual moistening of the column. Any
showers will move east of the forecast area prior to daybreak
Saturday with clouds diminishing as well from the west.
Temps...the onset of warm advection and a gusty southwest wind will
enable a nice recovery in temperatures from Thursday, Low level
thermals support mid to upper 50s across central Indiana.
Temperatures should remain in the 40s over the region for much of
the night but will slip back into the mid and upper 30s north of I-
70 once the front passes in the predawn hours.
&&
.LONG TERM (Saturday through Thursday)...
Issued at 310 AM EDT Fri Mar 21 2025
Near normal conditions for mid to late March expected over the next
week with periodic chances for rain.
This weekend...
The period begins with mainly dry weather Saturday with high
pressure overhead and near normal highs in the low to mid 50s. Focus
this weekend will be on Sunday as an area of low pressure and
associated frontal boundary bring widespread rain to the region. An
occluded front extends southeastward from a moving through the
Northern Plains on Sunday. Latest guidance triple point and warm
front setting up right over Central Indiana with a 40-50 kt
southwesterly low level jet pumping moisture northward into the
region. Expect rain to develop from the west/southwest and move into
Central Indiana during the early morning hours Sunday. Forecast
soundings suggest the possibility of a a brief mix of rain and snow
on the leading edge due to wet bulb cooling and such dry antecedent
conditions. P-type will quickly transition to plain rain, so do not
expect any issues from snow mixing in. Models are showing enough
elevated instability to produce some isolated thunder; however will
keep this out of the forecast for now until this system can be
better viewed by hi-res CAMs. There also looks to be some decent
shear and tight gradient that will produce breezy conditions, but
all other severe parameters are expected to remain minuscule for
central Indiana with the severe threat further south of the state
for Sunday.
Next Week...
A general northwest flow pattern sets up for the Great Lakes region
Monday through Thursday, keeping near normal temperatures around and
periodic chances for light precipitation due to weak passing systems.
While Monday looks mainly dry and breezy, the next chance for rain
arrives Tuesday as a weak upper level disturbance drops
southeastward from Canada. Overall light rain expected are possible
from this system. Since this is a few days out, timing and track of
the subtle feature could easily change, so keeping PoPs only at
chance wording for now. Will increase PoPs accordingly once track
and timing of this system are more solidified.
A slow warm up takes place the middle and latter half of next week
as the pattern begins to shift toward a set up more favorable for
much warmer, above average conditions. The northwest flow pattern
transitions into ridging with the main storm track pushing further
north as well. Do have low PoPs late week as guidance is showing a
system and front likely moving through; however confidence is higher
that Indiana will be on the warmer side of things by then.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 525 AM EDT Fri Mar 21 2025
Impacts:
- Peak wind gusts up to 25 to 30kts from the southwest this
afternoon and evening, then veering to westerly late tonight
- Low level wind shear possible for a few hours late evening into
the early overnight
- Widely scattered showers overnight
- MVFR ceilings possible at KLAF predawn hours Saturday
Discussion:
A high pressure ridge is shifting east of the region early this
morning. The movement of low pressure into the upper Midwest will
tighten the surface pressure gradient over the region by midday and
combined with modest mixing through the boundary layer...will
promote wind gusts up to 25 to 30 kts through the afternoon and
evening. Skies will begin mostly clear through the first half of the
day with a gradual expansion of mid and high clouds later this
afternoon into the evening as a weak front approaches from the west.
A few showers are possible overnight as the front passes through but
anticipated coverage only warrants a prob30 for 3-4 hours at this
time. MVFR stratus may impact KLAF early Saturday morning. The
expansion of a strong low level jet into the Ohio Valley this
evening will promote low level wind shear at all terminals for a few
hours late this evening before diminishing overnight. Surface winds
will veer to a westerly direction behind the front.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...50
SHORT TERM...Ryan
LONG TERM...CM
AVIATION...Ryan
Source:
IND issues Area Forecast Discussion (AFD) at Mar 21, 9:27 AM EDT---------------
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