Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 161002
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
602 AM EDT Sat Mar 16 2024

.KEY MESSAGES...

- Warmer today; low to mid 60s for high temperatures

- Breezy today through early next week

- Hard freeze likely Sunday and Monday nights

&&

.SHORT TERM (Today and tonight)...
Issued at 209 AM EDT Sat Mar 16 2024

Vorticity maxima seen in water vapor early this morning over
North Dakota will reach the Great Lakes region later today,
forcing a cold front southward through central Indiana during the
evening. Preceding this will be tightening MSLP gradient at the
periphery of central Ontario low supporting breezy conditions.
Mixing and transfer of stronger momentum aloft could result in
gusts to around 35 mph during the afternoon. 75th percentile
blended guidance was used for temperatures given the warm
advection and deep mixing patterns often over-achieving with
temperatures in March.

Moisture is meager, but forcing along flanking midlevel vorticity
ribbon could be enough for at least a band of virga or sprinkles,
and perhaps a brief shower during the evening. Probabilities of
measurable amounts will be <10 percent for most areas.

As mixing subsides this evening and overnight, winds will
decrease somewhat, though MSLP gradient will be tight enough for
10-15 mph winds through the night. The initial wave of cold
advection will be modest and most locations will not fall to
freezing tonight. Minimums should be in the mid-upper 30s.

&&

.LONG TERM (Sunday through Friday)...
Issued at 209 AM EDT Sat Mar 16 2024

Blocking synoptic-scale flow pattern in the west will influence
sharpening/deepening troughing over our region. Southward movement
of modified polar air mass arriving Sunday will restrain us to about
5-7 degrees below normal for temperatures Sunday, and 10-15 degrees
below normal Monday. Early onset to greenup will likely be impacted
by sub-freezing temperatures and probable hard freeze Sunday
night/Monday morning and again Monday night/Tuesday morning.
Widespread mid-upper 20s are expected for minimums across central
Indiana both nights. Forecast confidence is high since model
agreement at this range is good and MSLP pattern should preclude a
more significant radiative component, thus model guidance is fairly
tightly clustered.

As western high-latitude ridging and blocking pattern break down mid-
week, a quasi-zonal split flow regime will develop. The most
uncertain part of the forecast in the long term period is onset of
warming, which in some ensemble clusters is more rapid than others
(i.e., non-EPS weighted clusters). Regardless of specific
temperatures in the Tuesday-Wednesday time period, a warming trend
will be ongoing by then.

These split flow patterns are notorious for confining the deepest
moisture to low latitudes and it appears only modest moisture will
return with warm advection late week. Ensemble clusters are split
into the EPS-weighted drier pattern with dominate southern stream
wave, and GEFS-weighted wetter more amplified northern stream wave.
Thus, mid-range/chance probabilities are assigned for late Thursday
into Friday. Regardless, this will be a light precipitation event
per even the wettest outlier ensemble members.

Day 8-14: Clusters are still out of phase, but this appears to
primarily be a symptom of multiple timing representations among the
ensemble suite due to a progressive amplified pattern. This means
periodic precipitation and varying temperatures and no strong signal
of deviations from average.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 602 AM EDT Sat Mar 16 2024

Impacts:

- Wind gusts up to 30 knots Saturday

Discussion:

Strengthening surface pressure gradient and deepening mixing during
the day today will lead to increased southwesterly winds and gusts
as high as 30 knots. Otherwise, weather impacts to aviation are
expected to be minimal and brief ceilings this evening will remain
well within VFR category. Wind speeds will decrease during the
evening. Forecast confidence is high.

&&

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

$$

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


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