593
FXUS63 KIND 130711
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
311 AM EDT Sat Jul 13 2024

.KEY MESSAGES...

- Patchy fog this morning, locally dense
- Periodic shower and thunderstorm chances through Wednesday, with
  lower confidence in strong/severe storm potential
- Hot and humid Sunday through Tuesday, possibly nearing Heat
  Advisory criteria

&&

.SHORT TERM (Today and tonight)...
Issued at 300 AM EDT Sat Jul 13 2024

Fog is beginning to develop across portions of the CWA as of 2am.
Currently, fog is not widespread but a few instances of dense fog
have already been reported. Expect continued fog development and
expansion through morning. Some locally dense fog can be expected as
well.

Fog will diminish quickly after sunrise as mixing begins in earnest.
Diurnal cumulus growth should occur quickly as well. A much drier
column along with weak lapse rates should limit convective potential
compared to the past few days. Nevertheless, enough instability
exists so that we cannot rule out a very isolated shower or storm.

Surface high pressure, currently overhead, is modeled to slide
eastward today. This in turn allows the MSLP gradient to tighten
enough for the development of a light southwesterly breeze. This
breeze should allow for weak warm air advection through the weekend.
As such, a gradual warming trend is anticipated going forward.

A weak system passing to our north looks to trigger convection over
Minnesota today. Some members of guidance show this organizing into
an MCS and propagating southeastward overnight tonight. It`s
possible that this activity begins to enter Indiana around the end
of the period or early in the long range period. Shear is quite weak
across Indiana, so any MCS propagating southward will likely be in a
weakening state.

&&

.LONG TERM (Sunday through Friday)...
Issued at 309 AM EDT Sat Jul 13 2024

Sunday through Tuesday...

The very broad subtropical ridge spanning the entire contiguous
United States will promote hot and humid conditions for next week`s
first three days.  Height maxima approaching 600 dm over the central
Rockies and the southwesterly return flow around a broad surface
ridge over the CONUS` southeastern third will combine to produce a
warm frontal type gradient from the Upper Mississippi Valley in a
southeastward direction into at least northwestern portions of the
Midwest.  Southwesterly surface winds sustained 10-15 mph and
gusting up to 20 mph will have no problem boosting dewpoints through
the low to mid-70s for nearly all of the region...while partly to
mostly sunny skies return temperatures 15-20 degrees into widespread
low 90s, and probably areas into the mid-90s, especially on Tuesday
when sunshine should be greatest.  Resultant heat indices are
expected to peak around 100F Sunday...and 100-105F for most areas
both Monday and Tuesday.

Diurnally driven instability that should reach high levels most
days, especially over northern counties where mid levels will be
cooler...will likely have drier mid-levels and less wind shear to
utilize for any organized or longer-living convective cells...
although latest data is trending shear up slightly. Perhaps the best
shot at strong to severe weather would be earlier on Sunday when a
possible MCS, after forming closer to Chicago, potentially enters
the CWA`s far-northern zones while dissipating.  So far lower
confidence in this conditional threat that will be updated through
the next day.  Expect rain chances to increase for all counties into
the mid-week as a cold front approaches and then crosses Indiana
from northwest to southeast.  Any stronger storms also appear
conditional with this boundary as better shear should be delayed
until have theta-E values drop significantly.

Wednesday through Friday...

Guidance is continuing to indicate the Tuesday night-Wednesday
timeframe as a rather sharp transition to milder and noticeably less-
humid conditions as a broad upper ridge over much of western North
America...allows a staunch area of Canadian high pressure, more
indicative of late summer, to plunge into the northern Plains before
its center slowly drifts into the southern Great Lakes by the end of
the workweek.  Rain-free conditions should be the rule after the
frontal zone departs southward, with precipitable water values
falling below 0.80 inches for all of the region through Thursday and
Friday.

We will see how far below normal (now at the year`s peak) readings
will fall, but with latest model data now bringing H850 temperatures
under 10 degrees Celsius for most locations throughout a 40-hour
period amid consistent light northerly breezes...two or three
mornings falling into the mid- to upper 50s... and two or three
afternoons failing to surpass 80F may well be in play.  The normal
max/min at Indianapolis will maintain its peak tandem of 85/67
through July 22.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 134 AM EDT Sat Jul 13 2024

Impacts:

- MVFR/areas of IFR conditions redeveloping overnight tonight into
  daybreak Saturday.

Discussion:

Surface high pressure will allow for mainly clear skies and light
winds through morning. With high moisture levels, we`re expecting
fog to develop by morning with MVFR/IFR conditions possible.

Fog should mix out within a few hours after sunrise. Diurnal cumulus
growth will be quick, with periods of SCT or perhaps BKN possible.

Winds gain a southwesterly component during the day, becoming more
southerly Saturday night.

&&

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

$$

SHORT TERM...Eckhoff
LONG TERM...AGM
AVIATION...Eckhoff