IND issues Area Forecast Discussion (AFD) at Sep 9, 6:41 AM EDT107
FXUS63 KIND 091041
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
641 AM EDT Mon Sep 9 2024
.KEY MESSAGES...
- Noticeable moderation today nearing seasonably mild levels...under
upper-level smoke from upstream fires
- Moderation continues through mid-week...low humidity to bring
cool mornings, marginally hot afternoons
- Slightly elevated fire weather Tuesday-Wednesday
- Weak tropical system approaching Friday will return clouds,
moderate humidity...and rain chances, especially south of I-74
&&
.SHORT TERM (Today and tonight)...
Issued at 230 AM EDT Mon Sep 9 2024
The short term will find stacked, broad ridging across the central
CONUS...overseeing gradual moderation back towards seasonably mild
levels. Surface high pressure aligned from the Ozarks to the
Delmarva coast will guide an axis of anomalously low precipitable
water values from northeastern Texas to West Virginia which will
block the return of any Gulf of Mexico moisture from the Midwest.
Outside of a few afternoon gusts to 10-15 mph across central
Indiana's northern tier...mainly light westerly flow will continue
to promote dewpoints in the 40s...although proximity to the ridge's
dry axis should allow values dropping into the mid-30s south/west of
Columbus this afternoon. Resultant minimum relative humidity values
south of Interstate 70 near 20 percent will present a slightly
elevated fire weather threat...although high confidence that winds
generally 10 mph or lower will mitigate this risk.
Mostly sunny skies and H850 temperatures rebounding to at least 15
degrees Celsius will increase surface readings by about 35 degrees
Fahrenheit today...with afternoon highs nearing seasonable levels
for the first time since last Thursday's marginal heat. Mid-level
haze from upstream wildfires will be noteworthy today...as shown by
NOAA forecast vertically integrated smoke, where a narrow plume
streaming from western Ontario into the Midwest, is expected to
widen while tracking across much of Illinois/Indiana/Kentucky today.
Have therefore increased sky cover slightly from NBM guidance,
however left smoke out of grids with none expected below the LND.
Following another chilly morning starting with widespread low to mid-
40s...expect today's highs in the upper 70s/lower 80s...and
tonight's minimums around 50F, excepting mid-50s inside of
Interstate 465.
&&
.LONG TERM (Tuesday through Sunday)...
Issued at 230 AM EDT Mon Sep 9 2024
Tuesday through Thursday...
High and dry will be the rule through central Indiana's mid-week
under a very broad upper ridge that will span the entire CONUS at
the start of the long term...before building farther north into
south-central Canada courtesy of an upstream H500 trough plunging
across the Pacific northwest. The greatest transition amid this
overall moderation is expected Tuesday...when temperatures will
range from about 10 degrees below normal at dawn, to 5 degrees above
normal in the afternoon, with a 40-degree diurnal change possible
along the middle to lower Wabash Valley.
A thermal maximum nudging east from Iowa will bring H850
temperatures approaching 20 Celsius for Wednesday and Thursday.
Increasing confidence that, when coupled with light southeasterly
breezes, this will promote widespread afternoon maximums around 90F
both days. Autumnal humidity levels, with dewpoints mainly 45-55F,
will however mitigate heat risk concerns...with corresponding
maximum heat indices likely staying below 90F during all afternoons.
Instead, a greater concern of elevated fire weather will be present,
with daily minimum relative humidity values around 20-30 percent
each day...albeit coupled with generally lighter winds that would
not favor spreading fires.
Moderate Drought (D1) which returned to far southwestern central
Indiana on the 9/5/2024 weekly map will have the opportunity to
expand into more of the region with this Tuesday's update. By the
numbers this week will be the epitome of a dry September, with
diurnal ranges of 35 to 39 degrees expected over the majority of the
realm on 2 or 3 days.
Friday through Sunday...
The plunging western trough will provide modest southwesterly
steering over the southern High Plains...which should guide a weak
tropical wave/cyclone from the western Gulf...northward into the
Lower Mississippi Valley by the late workweek. While this will
likely back surface flow to easterly moderate breezes for at least a
couple periods, under an increase of at least mid cloud...less
certainty surrounds the northward expansion and amount of any
associated rain. A very wide distribution of rainfall potential
exists for the region's southern half, with low confidence in
appreciable precipitation for any one location given the amount of
moisture flux needed neutralize the antecedent very dry column.
The end of the long term should find the region between surface high
pressure aligned across the eastern Great Lakes with the remnant/
filling tropical feature stalling not too far to our southwest.
Expect considerable cloudiness mitigates both max and min
temperatures closer to normal...while the return of moderate
humidity promotes at least widely scattered showers with slight
diurnal enhancement. The normal max/min at Indianapolis decreases
through the forecast period from 81/60 to 79/58.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 640 AM EDT Mon Sep 9 2024
Impacts: None
Discussion:
VFR conditions will continue over central Indiana terminals through
Tuesday morning under a stacked ridge of high pressure. The surface
high center will drift from the Ohio Valley to the Appalachians
through the TAF period. Expect limited cirrus and mid/upper-level
smoke...with gradually increasing smoke likely peaking tonight.
Light winds this morning will reach 8-9 KT at KIND/KLAF through
much of this afternoon, with lighter flow expected at KHUF/KBMG,
all from 250-280 degrees. Winds will become light and variable
tonight.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
SHORT TERM...McGinnis
LONG TERM...McGinnis
AVIATION...McGinnis
Source:
IND issues Area Forecast Discussion (AFD) at Sep 9, 6:41 AM EDT---------------
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