989 
FXUS63 KIND 091313
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
913 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

&&

.FORECAST UPDATE...
Issued at 912 AM EDT Mon Sep 9 2024

- Another super weather day

Surface analysis this morning shows strong high pressure was 
centered over the Ohio Valley. A surface ridge axis extended north 
from this high across western IL into the upper Mississippi Valley. 
Winds across our area were light to calm. GOES16 showed clear skies 
across the forecast area. Aloft, the upper pattern showed strong 
ridging found over the plains, while an upper low was over eastern 
Quebec. A trough associated with the low was found along the 
Appalachians. This continued to result in lee side subsidence and NW 
flow across Indiana. Some ridge riding Pacific moisture, high cirrus 
or smoke, was found over the upper Midwest, and this may drift 
across Central Indiana this afternoon.

Overall, little change is expected today. The surface high over the 
Ohio valley is expected to remain in control and remain anchored 
across the Ohio Valley this afternoon. Forecast soundings and time 
heights show a dry column with subsidence and unreachable convective 
temps. Some of the high CI or smoke should arrive this afternoon, 
resulting in a thin veil of high clouds. All of this should amount 
to Mostly Sunny skies. Given the slightly warmer air mass across 
Central Indiana, highs should be slightly warmer today, reaching the 
mid to upper 70s, with low humidity.

&&

.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.
&&

$$

UPDATE...Puma
SHORT TERM...McGinnis
LONG TERM...McGinnis
AVIATION...McGinnis