National Weather Service Raw Text Product

400 
FXUS63 KIND 201118
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
618 AM EST Sun Feb 20 2022

...Updated Aviation Discussion...

.Short Term...(Today through Monday)
Issued at 300 AM EST Sun Feb 20 2022

Early this morning broad polar high pressure prevailed across most 
of the eastern two-thirds of the CONUS...supporting dry conditions 
over the Mid-West, albeit cold with temperatures across central 
Indiana ranging from the upper teens to lower 20s.  The center of 
the surface high will continue to drift from the Appalachians to off 
the Mid-Atlantic coast today, allowing the low-level gradient along 
the western side of the ridge to slide eastward and over the region. 
An H850 low-level jet of 70+ knots will simultaneously slide across 
the Great Lakes today, with the LLJ's still-potent tail of 40-55 kts 
crossing the CWA this afternoon.  Southerly winds at the surface 
will correspondingly increase to about 10G20 by 12z...and 15G28 by 
midday.  Highest winds, this afternoon, will be strongest across 
northern counties...peak gusts should be around 30-33 kts north of I-
70 and 25-30 kts south of I-70.  This strong WAA will combine with 
abundant sunshine to increase temperatures by about 35 degrees in 
just over 24 hours, with low to mid 50s common this afternoon. 
Moderate confidence in no need for Wind Advisory at this time, 
especially with most recent guidance backing off a bit with wind 
magnitudes slightly since yesterday's run.

Tonight, breezy return flow will continue, although the surface 
pressure gradient will slacken somewhat as the departing high 
pressure center exits further out to sea, and the LLJ diminishes 
significantly while sliding into the Ohio Valley.  However, the next 
arctic front, slowly plunging through the central Plains...while the 
eastward extent of this boundary stays nearly stationary across the 
northern Mid-West...should serve to re-tighten the gradient going 
into Monday.  Mostly clear skies and southerly wind gusts decreasing 
to under 15 knots for most locations by 9z, will allow temperatures 
to drop into the mid to upper 30s.

Monday therefore is expected to bring moderate to robust southerly 
breezes.  Similar flow aloft will continue to advect Gulf moisture 
within the column, leading to perhaps abruptly thickening clouds 
from south to north over the midday-afternoon hours.   The blend's 
max temperatures in the mid to upper 50s appeared reasonable with 
H850 temperatures of 6-8 Celsius reaching the area by the end of the 
period.  Although potential exists for an even warmer day should the 
recent dmodel/dt trend for slightly later arrival of H850 relative 
humidity >70-90 percent continue.  Kept slight chance POPs arriving 
in roughly the CWA's southwestern quarter during the afternoon, 
given the moistening column with any forcing occasional and weak. 
Precipitable water values will rise above 90% of seasonable normals 
by 00z Monday evening...with these 0.75+ inch values setting the 
stage for the next rain event.  The normal max/min at Indianapolis 
for the short term period is 43/26.

&&

.Long Term...(Monday night through Saturday)
Issued at 323 AM EST Sun Feb 20 2022

An active weather pattern will be in place this week across central 
Indiana, with multiple weather systems moving through and 
significant swings in temperatures.

Monday night through Tuesday night...

Strong warm advection on a 50 kt low level jet will quickly bring 
moisture northward from and open Gulf and into Indiana. Isentropic 
lift will provide the impetus for rain overspreading the area from 
the south Monday night, and with elevated instability making its way 
into the area during the night continued the inclusion of slight to 
chance thunder. With the warm front stalled across northern Indiana 
and a surface low moving along it through Illinois early Tuesday 
morning, forcing will remain across the area until the surface low 
pulls out to the northeast through the eastern Great Lakes and drags 
a cold front through central Indiana Tuesday evening/early Tuesday 
night. High pressure building in from the northwest behind the 
frontal passage advecting in cold and dry air should bring an end to 
the rain after the frontal passage, and temperatures plunge back 
into the 20s for lows. While the dynamics with this system are 
pretty strong, surface based instability appears to be lacking and 
this should preclude a severe threat. With the moisture, though, and 
prolonged forcing, heavy rainfall will be a threat, especially 
south. Probabilistic guidance indicates good potential for just over 
an inch across the southern counties with lesser amounts heading 
northward, but little potential for exceeding two inches. With 
saturated ground and elevated river levels, even an inch of rain 
could create some flooding issues, but staying below 2 inches should 
keep most of it at the minor/nuisance level.

Wednesday through Thursday night...

Cold air should remain in place through the day on Wednesday with 
the Canadian surface high sliding through the Dakotas and keeping 
northwesterly flow in place for the day. Wednesday night, though, a 
system could start to pull out of the Gulf to the northeast, pulled 
northeastward by a slowly progressing longwave trough over the four 
corners region. There is still quite a range of outcomes with this 
system in terms of the track of the low and how quickly it shifts 
off the east coast, and this may be partly due to differing 
solutions with the strength of the surface high to the north as well 
as the flattening of the upper ridge over the Caribbean. The result 
of all of this at this point looks like chances for snow or a wintry 
mix over the area, with perhaps rain in the southern counties for a 
few hours as this set of runs looks a little colder/further 
southeast with the low track, but again uncertainty is high. 
Probabilistic guidance shows a wide range from nothing to over 6 
inches for the northwestern counties which further illustrates the 
uncertainty and hence low confidence. This system will bear watching.

Friday on... 

Currently looks like cold air settles in as the system exits 
Thursday night, and below normal temperatures continue through 
Sunday with highs in the 30s and lows in the teens.

&&

.Aviation...(12Z TAF Issuance)
Issued at 617 AM EST Sun Feb 20 2022

IMPACTS:

-Afternoon south-southwesterly winds 13-17 kts, gusting to 26-30 kts
-LLWS conditions...today at KLAF...and at all sites 0z-9z tonight

DISCUSSION:

VFR and dry conditions will prevail over central Indiana through the 
TAF period courtesy of a broad, departing ridge of high pressure... 
while the tail of a potent low-level jet stream approaches, and then 
crosses the region.  The LLJ will create marginal LLWS conditions 
over KLAF with southwest winds at 2000FT through 9z tonight. 
Elsewhere marginal LLWS can be expected along Interstate 70 through 
16z this morning, but confidence too low to include in TAF...more 
widespread LLWS is expected overnight tonight, again with southwest 
winds at 2000FT.

Southerly winds will increase within the 10-15 knot range while 
veering slightly this morning.  South-southwesterly winds this 
afternoon of 13-17 kts will gust to 26-30 kts.  SSW flow will 
diminish slightly tonight to 7-12 kts as the LLJ weakens over the 
region, with gusts of 20 kts or less.  Monday morning at KIND, 
southerly winds will increase slightly to around 11 kts with gusts 
17 kts or less.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Short Term...McGinnis
Long Term...CP
Aviation...McGinnis