500
FXUS63 KIND 311348
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
948 AM EDT Fri May 31 2024

.KEY MESSAGES...

- Showers and a few storms expected much of the day Saturday

- Warming trend going into next week with periodic storm chances

- Long range 8-14 day outlook trending toward below normal
temperatures

&&

.FORECAST UPDATE...
Issued at 948 AM EDT Fri May 31 2024

GOES-16 visible satellite loop was showing patches of cirrus moving
across central Indiana. Otherwise, a sharp upper ridge extended from
Hudson Bay to the Ohio Valley, while a surface low was over Lake
Erie. Temperatures have climbed to the lower and middle 60s and
southeast winds and filtered sunshine will allow temperatures to top
out in the middle and upper 70s. The potential for deep mixing per
soundings will bring dry air down to the surface producing RH levels
as low as the upper 20s. Despite that, high 10 hour fuel moisture
and low 20 foot winds will eliminate fire danger.

&&

.SHORT TERM (Today and tonight)...
Issued at 302 AM EDT Fri May 31 2024

Conditions remain calm early this morning across Central Indiana as
high pressure is centered over Ohio. Latest satellite imagery shows
mainly clear skies over the region; however high clouds from an
approaching storm system in the plains are slowly creeping north and
east into Illinois.

Despite slowly increasing upper clouds today, conditions will remain
dry through late tonight. High pressure shifts eastward today, but
will still be the dominant weather influence despite the approaching
system. Winds shift southeasterly in the lower levels today leading
to weak warm air advection aloft. Strong solar heating of the
boundary layer is still expected despite high cirrus increasing with
highs reaching the mid to upper 70s. Latest IND ACARs soundings show
a very dry layer above ~1.5km agl. Short term models do suggest
mixing heights reaching into this dry layer later this afternoon
likely resulting in dew points falling to near 40 by mid afternoon.
Low RH values may dip into the 20-30% range as well during peak
heating of the day; however with very light winds through the column
and recent rainfall, fire weather concerns are very low.

Tonight, clouds continue to thicken and begin to lower as upper
level moisture increases ahead of an area of low pressure pushing NE
into N AR and S MO. Will have to watch how much the boundary layer
dries out today as this may slow the onset of precipitation in
Western and SW Indiana. Latest guidance has rain approaching the
IN/IL state line in the 06-09z timeframe; however if the low levels
are drier than what guidance suggests, rainfall may not reach the
ground until the 09z-12z. Confidence is higher in dry conditions
tonight for the eastern 2/3 of Central Indiana. Cloud cover will
also result in temperatures remaining slightly elevated overnight,
especially further west with lows ranging from the mid 50s to low
60s.

&&

.LONG TERM (Saturday through Thursday)...
Issued at 302 AM EDT Fri May 31 2024

Saturday and Sunday...

Wet weather moves in for the first half of the weekend as the
aforementioned low pressure system tracks northeast through Central
Indiana. Guidance continues to have a solid handle on both the
timing and strength of the low pressure system which allows for
higher than normal confidence on the forecast progression.
Isentropic lift and an increasing 30-40 kt low to mid level ahead of
the system pumping in ample moisture northward will result in
widespread rain across the state. Instability looks minimal for the
morning and early afternoon hours, so any thunder should be
isolated. The first wave of rain will likely be lighter with a few
pockets of moderate rain embedded in the rain shield. A weak dry
slot arrives by the afternoon, however the dry window may be short
as the cold front quickly pushes through behind the main round of
precipitation with additional showers and storms as early as mid
afternoon. If the dry break is long enough for surface temperatures
to increase ahead of the cold front, the atmosphere may become
unstable enough for thunderstorms during the afternoon and evening
hours. Severe weather threat is low as instability looks too weak to
support organized convection. The main threat Saturday is the
possibility of heavy rain and localized flooding with the timing of
the heaviest rain likely during the evening hours. Widespread
rainfall totals around a half inch to an inch are likely across
Central Indiana with totals as high as 1-1.5 inches in areas that
see repeated thunderstorm and heavy rain activity.

The area of low pressure slowly meanders into Ohio on Sunday;
however weak high pressure moving in with little forcing or dry air
may result in low stratus hanging around much of the day. Lowered
highs to the NBM25th percentile keeping temperatures in the 60s to
near 70 much of the day. Expect breaks in the clouds from west to
east during the mid to late afternoon hours.

Monday through Friday...

The chance for showers and storms sticks around for much of the
week, but confidence on timing and location of convection remains
low due to model inconsistencies. Flow aloft becomes much more
stagnant with the main jet energy near the Canadian border and the
pattern becomes more driven by mesoscale factors that are very
uncertain this far out. There does look to be at least occasional
showers and thunderstorms which will generally be diurnally driven
so will focus POPs highest in the 18Z to 00Z timeframe.  Surface
flow will generally remain southerly through the week which will
keep temperatures just above normal into the 80s with much higher
dewpoints of mid to upper 60s. More organized convection with higher
chances for rain exist Wednesday as a deeper trough digs into the
Great Lakes and a cold front moves through the region. While it is
too soon to talk about severe weather threats, with a warm and moist
atmosphere, a strong to severe storm cannot be ruled out. Will
continue to watch the Wednesday timeframe as this seems to be the
strongest storm system this week with highest chances for widespread
rainfall and storms.

Longer range guidance continues to indicate troughing setting up
over the region late week into the following weekend with below
normal temperatures expected.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 628 AM EDT Fri May 31 2024

Impacts:

- Rain and possibly MVFR cigs/vis arriving near the end of the TAF
period

Discussion:

VFR conditions will prevail through tonight.

Satellite imagery this morning shows VFR cigs across all of Central
Indiana with just high cirrus pushing in from the west. High
pressure becomes centered over the Mid Atlantic states by this
evening while an area of low pressure approaches from the southwest.
Expect winds out of the southeast (120-140 deg), but remaining under
10 kts despite afternoon mixing as winds through much of the column
are very weak. High clouds will increase during the afternoon and
evening hours today then thicken and lower late tonight. Sub-VFR
cigs/vis are not expected until the around the end or after this TAF
period around sunrise Saturday morning when widespread rain moves
in from the south and west.


&&

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

$$

UPDATE...MK
SHORT TERM...CM
LONG TERM...CM
AVIATION...CM