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000
FXUS63 KIND 250655
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
255 AM EDT Thu Apr 25 2024

.KEY MESSAGES...

- Some frost possible across North Central Indiana this morning

- Active pattern returns Friday into next week with above normal
  temperatures and frequent storm chances

&&

.SHORT TERM (Today and tonight)...
Issued at 255 AM EDT Thu Apr 25 2024

Latest satellite imagery shows an area of stratus clouds extending
from near Kokomo eastward into Pennsylvania. Leftover moisture from
recent rains remains trapped within the boundary layer under a
strong subsidence inversion from high pressure building in to the
north. This area of stratus is slowly pushing southward, however
this thickest cloud cover remains over areas that received higher
rainfall amounts on Tuesday. The cloud shield seems to dissipate
some on its southward side as it approaches the I-70 corridor, where
boundary layer RH is a little drier. While confidence is lower on
the southward progression of this stratus deck, trends in satellite
imagery do show the stratus deck shrinking some. Expect this trend
to continue into the morning hours, with the clouds expected to
dissipate even faster after sunrise and daytime mixing increases.
These clouds do lower confidence in frost potential for a good
portion of North Central and Eastern Indiana where temperatures have
remained elevated in the 40s with dew points holding steady in the
33-35 degree range. Best chance for frost through the morning hours
remains west of the cloud deck, mainly along and west of the I-65
corridor and north of I-70, including Crawfordsville, and Lafayette.
Will keep the headlines out for now, even for areas under the cloud
deck, as temperatures will likely plummet into the mid 30s for areas
where the stratus does dissipate before sunrise.

For the rest of the day, surface high pressure continues to slide
eastward through the Northeast while upper level ridge axis pushes
closer to the region from the west. Cross sectional views on the
atmosphere in BUFKIT do show some upper level moisture/high clouds
rounding the top of the ridge and making it into Indiana during the
day. But overall, expect mainly clear skies once the low stratus in
NE Indiana dissipates. Low level temperatures still remain below
average for this time of year and easterly flow at the surface isn`t
necessarily going to advect warmer air in. With a low level
subsidence inversion still present, this may limit mixing heights
this afternoon, keeping highs on the cool side once again with highs
in the upper 50s across the north and low to mid 60s further south.

&&

.LONG TERM (Friday through Wednesday)...
Issued at 255 AM EDT Thu Apr 25 2024

Friday, a quick atmospheric transition will be underway across
Indiana. Upstream trough will already be responsible for high level
clouds, but a dry lower troposphere will remain until leading edge
of anomalous moisture plume arrives. Warm frontal circulation at the
leading edge should produce a band of rain moving northeastward
across central Indiana. The greater ascent should be on the dry side
of the front, and the core of the IVT signal will be just northwest
of our area. Thus, rainfall amounts may be limited with this first
round (generally under one quarter inch). Timing appears to be
midday through mid-afternoon with greater amounts and higher
probabilities northwest, tapering with southeastward extent.
Duration should be roughly 2-3 hours. Temperature forecast Friday
has error potential depending on rain timing and associated diabatic
cooling effects.

Saturday, residual midlevel front and core of the warm conveyor belt
moisture stream may be enough for some rain and perhaps isolated
deeper convection. As weakening shortwave trough continues to pull
northeast, midlevel height rises and limited mechanism for ascent
should limit rain coverage later in the day Saturday, despite
building instability. Position and magnitude of ridge should favor
strong enough warm advection for temperatures most areas around 80
degrees, as long as morning clouds and precip aren`t delayed in
departing or diminishing.

Mostly dry and warm conditions are expected to continue Sunday.
Another upstream shortwave trough will take a similar track as the
first one, but not weaken as much per model depictions. Its trailing
vorticity ribbon and cold front should result in convection to our
west during the diurnal maxima, which would move into Indiana Sunday
night. How this impacts Monday`s diurnal convective cycle is unclear
at this point. Scenario #1 is lingering weaker convection and clouds
will be ongoing but gradually diminishing will simultaneously
limiting diurnal destabilization, and Scenario #2 is it weakens
sufficiently for diurnal destabilization to yield a new round of
convection Monday afternoon. Deep saturation within warm conveyor
belt at at least modest instability with a band of ~40-50-knots of
midlevel flow could be enough for some convective organization and
severe potential, in a reasonable worst case scenario.

Track of the mid-latitude system is not favorable for meaningful
cold advection, and so temperatures should only be a few degrees
colder Tuesday. Post-frontal continental air will be less moist, and
so less humid conditions are expected. Toward mid-week, moisture
gradually returns but midlevel heights rise and become anomalous
with building ridging. A warmer pattern emerges with above normal
temperatures. Mechanism for precipitation would be minor
perturbations on the periphery of building ridge, which at this time
looks insufficient for organized/substantial precipitation.

Day 8-14: Multi-model ensemble mean continues to show strong signal
for above normal temperatures. No large-scale systems appear present
to produce widespread/significant precipitation, so smaller scale
features interacting with instability look to be the primary impetus
for convection. So, near or below normal precipitation is expected
during this period.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 154 AM EDT Thu Apr 25 2024

Impacts:

- Light winds veering from northerly to easterly overnight

Discussion:

While high pressure building into the region will promote mainly VFR
conditions through the period, latest satellite imagery does show an
area of MVFR stratus across North Central and Eastern Indiana. This
area of stratus is slowly shrinking and should dissipate into the
morning hours. KLAF and KIND are are the far southern and western
fringes of this cloud deck. Mainly VFR conditions expected at those
TAF sites, but it is not out of the questions ceilings briefly go
BKN025 during the overnight hours. Confidence is not high enough to
put that in the TAF, so for now keeping SCT025 in the TAF through
the morning hours.

Other than that, expect mainly VFR conditions at Central Indiana TAF
sites through the day on Thursday as dry air and subsidence under
the high will result in mainly clear, tranquil conditions. Winds
will shift from the NE to the E today and remain at or below 10 kts.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM EDT this morning for INZ021-028>031-
035>043-049.

&&

$$

SHORT TERM...CM
LONG TERM...BRB
AVIATION...CM