IND issues Area Forecast Discussion (AFD) at Jan 27, 5:58 AM EST715
FXUS63 KIND 271058
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
558 AM EST Mon Jan 27 2025
.KEY MESSAGES...
- Wind gusts to 40 mph this afternoon and evening
- Overall breezy and mild through the week, 50s likely by Thu
- Next chance for precipitation Friday into Saturday
&&
.SHORT TERM (Today and tonight)...
Issued at 312 AM EST Mon Jan 27 2025
Today.
High pressure will continue to gradually break down across the
Central United States as a strong low pressure system moves
southeastward across Canada. This low pressure system will gradually
tighten pressure gradients across the Great Lakes region with 850mb
wind speeds in excess of 40-50mph across north central Indiana. The
biggest forecast challenge will be determining the depth of the
boundary layer this afternoon with a wide spread on forecast
temperatures this afternoon among the models. With the clearing
yesterday, temperatures overachieved by 3-5 degrees compared to
model guidance which also looks to be running cool for today with
the expected sun and southwesterly surface flow. With the age of the
residual snowpack across the area, there won't be as much of a
negative impact to rising temperatures which further gives higher
confidence that temperatures may end up in the 90th-95th percentile
of model guidance.
If the higher end temperatures verify, the boundary layer may deepen
to around 3-4kft vs the 2-3kft models currently are forecasting.
This deeper mixing will tap into the core of the LLJ with wind in
excess of 50 mph aloft and would lead to higher end wind gusts as
high as 40 mph across central Indiana. Strongest winds are expected
across the northern portion of the forecast area where the LLJ winds
are maximized. Localized areas may see gusts of 45-50 mph, but
coverage should be low enough not to warrant a Wind Advisory,
especially considering those stronger winds are in a closer to the
reasonable worst case scenario. Model wind gusts look much lower,
but that is due to the underforecasted temperatures leading to a
shallower mixing layer.
Minimum RH values are expected to drop to around 30-35 percent this
afternoon which could cause a concern for fires with the strong
winds but with the wet ground and active snowpack, the threat will
be limited.
Tonight.
Surface gusts will gradually taper down after sunset as the boundary
layer begins to decouple, but with the very shallow LLJ, occasional
gusts of 20-25 mph may persist through the early overnight. Another
surge of upper level moisture will move in late this evening bringing
a return to mostly cloudy skies through the early overnight, but
expect that skies will then clear towards daybreak allowing for
temperatures to drop back into the mid to upper 20s. There is a low
but non-zero threat for a few light snow showers/flurries towards
Kokomo late this evening, but confidence is too low for a mention in
the forecast with the expected dry air near the surface and cloud
deck closer to 6-8kft.
&&
.LONG TERM (Tuesday through Sunday)...
Issued at 312 AM EST Mon Jan 27 2025
A relatively quiet and significantly milder stretch of weather is
on track for the coming week.
A more progressive weather pattern sets up for much of the country
as the polar jet retreats to the north, keeping the bulk of the
arctic air in Canada. An subtropical jet remains strong, yet quasi-
zonal and should stay south of the Ohio Valley, leaving much of the
region in an area of upper level convergence and sinking air. Broad
surface high pressure will generally be in control across the
southeastern and central CONUS, while multiple systems traverse
through the Great Lakes and Upper Midwest. This will allow for
mostly dry conditions over the weekend into mid week next week, and
for temperatures to moderate significantly, with highs and lows much
closer to seasonal normals.
At the surface, high pressure becomes centered over the Gulf states
for the first half of the new week with warm air advection kicking
out the colder airmass in place allowing for moderating
temperatures. Indiana will be sandwiched in the middle of high
pressure to the south and numerous low pressure systems moving
across the northern CONUS, resulting in strong westerly flow as the
low level pressure gradient tightens and a LLJ moves in overhead.
Most of the energy and moisture with the northern stream systems
will remain north of the region with high pressure keeping a much
drier airmass in place. The main impacts from these passing lows to
the north will be a reinforcing shot of cooler air in the Great
Lakes creating a sharper SW-NE temperature gradient across the state
and gusty winds Tuesday - Thursday.
Low level mixing mixing and steeper lapse rates Tuesday will result
in southwest winds 10-15 mph and gusts 20-25 mph, especially later
in the day Tuesday as the LLJ strengthens. The low level airmass
warms a bit more than the past few days with highs well into the 40s
across Central Indiana. In fact, a few spots may reach 50 degrees in
South Central Indiana with ample sunshine and good low level mixing.
A similar pattern remains in place midweek as weak, moisture starved
fronts pass by through the Great Lakes. Wednesday may be a few
degrees cooler than Tuesday as brief cold air advection moves in
behind a weak cold front and wind shift to the northwest. Still
expecting highs in the 40s for most locations as deeper mixing
occurs in the low levels. Once again, winds will be quite gusty
upwards of 30 mph making for wind chills in the 30s all day. A
significant warm up occurs Thursday as ridging builds with strong
warm air advection. Expect widespread highs approaching the 50
degree mark. From Mon-Thu, bumped lows and highs toward the NBM75-
90th percentiles to account for guidance underdoing the warm air
advection as the country comes out of the arctic weather pattern.
The next opportunity for precipitation will come toward the end of
the forecast period towards Friday Saturday, as a closed low, which
will slowly drift through California and the Desert Southwest next
week, begins to pull northeast toward the Great Lakes and be
reabsorbed into a larger longwave trough shifting eastward into the
central US. Guidance has sped up the arrival of the system, bringing
rain into Indiana much of the day Friday, so have trended the
forecast in that direction. Confidence is increasing that Indiana
will be on the warmer side of this system with the majority of the
precipitation falling as rain and highs potentially reaching the 50
degree mark again Friday and potentially again on Sunday as
southerly winds return.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 557 AM EST Mon Jan 27 2025
Impacts:
-Southwesterly wind gusts to 30kts this afternoon
Discussion:
VFR conditions expected through the TAF period with mostly clear
skies through 00Z. High clouds at around 10kft will then move
through central Indiana before exiting closer to 12Z tomorrow
morning. A few flurries are possible, but unlikely at LAF this
evening. Southwesterly winds will increase through the morning with
gusts to 25-30kts by the afternoon as surface pressure gradient
tightens. Strongest winds will be at LAF. Surface gusts will then
drop to around 20kts through the overnight hours going into
early Tuesday.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...White
LONG TERM...CM
AVIATION...White
Source:
IND issues Area Forecast Discussion (AFD) at Jan 27, 5:58 AM EST---------------
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