308
FXUS63 KIND 081902
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
302 PM EDT Sun Sep 8 2024

.KEY MESSAGES...

- Partly Cloudy Skies tonight and Monday due to high cloud/smoke.

- Slightly warmer temperatures.

- Dry air will oversee a trend to very warm/marginally hot
conditions by Wednesday-Thursday...with slightly elevated fire
weather this week, especially on Tuesday-Wednesday

- A developing tropical cyclone approaching from the western Gulf
will bring rainfall chances Friday-Saturday, especially towards the
Ohio Valley

&&

.SHORT TERM (This evening through Monday)...
Issued at 302 PM EDT Sun Sep 8 2024

Synopsis:

Surface analysis this afternoon shows strong high pressure was
centered over IL/MO/IN. A surface ridge axis extended east from this
high across Central Indiana. Winds across our area were light to
calm. GOES16 showed think high CI or smoke across Central Indiana
and point northwest due to the NW flow aloft. Aloft, the upper
pattern remained relatively unchanged as strong ridging was found
over the Rockies, while an upper low was centered over SW Quebec.
This continued to result in lee side subsidence and NW flow across
Indiana.

Tonight and Monday -

Slow progression of the overall pattern will result in dry and
slowly progressing warmer weather tonight and Monday.

The upper ridge axis over the Rockies is expected to push to the
Central Plains tonight and to the Mississippi Valley on Monday. This
will result in continued subsidence across Central Indiana amid NW
flow aloft. At the surface a slow progression of the surface high is
also expected, with eventual arrival over southern Indiana and the
Ohio Valley on Monday. Forecast soundings and time heights through
tonight and Monday continue to suggest a dry column with subsidence.
Thus the only cloud cover expected tonight and Monday may be due to
the thin smoke/CI streaming into our area from the NW. Thus we will
aim for partly cloudy skies tonight and again on Monday.

Lower level flow is suggested to become southwesterly tonight and
Monday. This will bring the start of warm air advection, as 850mb
temps rise to 12C by Monday morning and 14C by late afternoon
Monday. This along with the smoke aloft should inhibit max
radiational cooling. Lows tonight should reach the middle and upper
40s while highs reach the upper 70s to around 80.

&&

.LONG TERM (Monday night through Sunday)...
Issued at 302 PM EDT Sun Sep 8 2024

Tuesday - Thursday...

Much warmer temperatures are on the way early to mid week as high
pressure and ridging aloft dominate the weather across much of the
CONUS. With dry antecedent conditions and low humidity, expect
large diurnal temperature ranges Tuesday through Thursday. High
temperatures will be progressively warmer each day with max
temperatures potentially reaching or exceeding 90 Wednesday and
Thursday. Optimal conditions for radiational cooling and longer
nights will allow for much needed relief as lows fall into the upper
50s to low 60s. While skies will be mainly sunny through the week,
high level smoke may be advecting in from Canadian wildfires making
conditions hazy at times. Any smoke is expected to remain in the
upper levels and not affect conditions at the surface.

Lowered dew points each afternoon to the NBM10th percentile to
account for afternoon mixing and falling soil moisture. Rapid onset
drought conditions are expected to persist into this week; however
with light winds, the fire weather risk should be somewhat mitigated
despite RH values dropping into the 20s or lower each afternoon.


Friday and into Next Weekend...

All eyes turn to what is currently developing in the Gulf of Mexico
as guidance continues to indicate the potential for tropical
moisture to make its way northward into the Ohio Valley. Many
uncertainties still remain as the system is still very disorganized,
but with increasing run to run consistency, confidence is rising
that some of that tropical moisture could bring some rainfall to the
area Friday into the weekend. There are variable solutions on the
northward extent of moisture return, but if the ridge breaks down
enough in the presence of CVA and moisture advection, widespread
rainfall will be possible. Latest LREF probabilities of Central
Indiana seeing at least a tenth of an inch of rain this weekend has
increased to 30-40 percent. The dry environment in place this week
will likely make it difficult for more appreciable rainfall this
weekend; however if the developing system in the Gulf develops into
something stronger than what guidance currently depicts, then it is
possible tropical moisture will overcome the extremely dry air in
place. This is something we will be watching closely this week.

Even if moisture struggles to make it into the area, increased mid
and high clouds will likely keep temperatures a few degrees cooler
than earlier in the week. For now, keeping highs in the low 80s
Friday through the weekend, but those numbers could easily change
depending on how much moisture and rainfall make it this far north.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1144 AM EDT Sun Sep 8 2024

Impacts:

- VFR conditions this TAF period.
- SCT high cloud expected due to smoke.

Discussion:

VFR conditions expected through the TAF period as strong surface
high pressure settles over Indiana and the Ohio valley through
Monday night and beyond. Time heights suggest a dry column through
the period with subsidence.

The NW flow aloft is allowing for some high smoke and moisture to
stream across the TAF sites. This will result in some high, thin
smoke or thin cloud well aloft.


&&

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

$$

SHORT TERM...Puma
LONG TERM...CM
AVIATION...Puma