Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 031601
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1201 PM EDT Mon Oct 3 2022

...Updated Aviation Discussion...

.Forecast Update...
Issued at 858 AM EDT Mon Oct 3 2022

A few 2m observations fell to between 37 and 34 in north-central
portions of the area. Several personal weather stations that may
not be sited as well fell into the mid 30s between Lafayette and
Kokomo, likely in low-lying areas and/or areas sheltered from
wind. Some patchy frost may have occurred in these areas. We`ll
look closely at the potential for greater coverage of frost
tonight for the forecast refresh this afternoon.

Mixing will increase over the next couple of hours and temperatures
will warm to near climo for early October, albeit slightly lower
than yesterday. MSLP gradient and momentum transfer will be less
significant than the last two days, so winds won`t be quite as
strong and gusty, but still in the ~10 mph range through the
afternoon.

Previous forecast looks great so far.

&&

.Short Term...(Today and tonight)
Issued at 253 AM EDT Mon Oct 3 2022

* Some patchy frost tonight north

Central Indiana remained on the edge of an upper ridge to the west
and under the influence of surface high pressure which was across
Michigan early this morning. The result was clear skies and
temperatures in the 40s to around 50.

The upper ridge and surface high will continue to provide quiet
weather to central Indiana throughout the short term period.
Soundings show a very dry atmosphere in place currently, and not
much change is expected as the surface high moves farther south
into the area.

Some models are showing more stratus developing early this morning
in Ohio and moving southwest into the area, similar to what happened
Sunday. However, nothing has developed so far, so it appears the
models are overdoing in in this drier airmass. Will continue to
monitor, but at the moment plan on keeping skies mostly clear.

Other than the low potential for stratus, skies will be clear to
mostly clear with the very dry atmosphere in place. Winds will be
lower than previous days as the surface high moves south.

Some weak cold advection will keep temperatures cooler than Sunday,
but highs will still be in the upper 60s to lower 70s. Tonight, as
the winds diminish, temperatures will dip into the middle 30s to
lower 40s.

Humidity levels will fall into the 30-40 percent range this
afternoon, and the ground remains dry. However, winds won`t be as
strong today, helping keep the fire threat lower.

The diminishing winds and lows in the mid 30s tonight will allow
some patchy frost to form north. Temps/winds do not look to get cold
enough for a period of widespread frost though.

&&

.Long Term...(Tuesday through Sunday)
Issued at 253 AM EDT Mon Oct 3 2022

* Possible frost in the northern counties Tuesday morning

* Much cooler air with widespread frost potential this weekend

After the passages of a weak backdoor cold front yesterday, cold air
advection has nudged 850mb temps down a bit from about 12C to 8C.
While not a significant drop, advancing surface high pressure will
allow for decent radiational cooling Tuesday morning. Lows should
dip down into the 30s across the northern half of the CWA. Mentions
of frost will be carried in these zones. Some isolated instances of
frost may occur further south as well, but slightly warmer
conditions should preclude this from being widespread. Additionally,
some fog is also possible Tuesday morning. Deep low-level moisture
is lacking, however, so any fog would be patchy in nature and
confined to areas prone to fog development (river valleys, basins,
farmland).

After Tuesday, slight air mass modification will keep temperatures
warm enough to prevent another frosty night. Ridging aloft will
maintain high temperatures in the mid 70s for another few days,
which is above normal for this time of the year. High clouds are
expected to invade the sky from the west on Wednesday, as an
advancing and deepening trough drops down from Canada. The thin
clouds will act to lessen the effect of nocturnal cooling, and lows
Thursday morning should only drop into the 50s. Thursday will be the
last day this week with highs in the 70s, as a cold front associated
with the trough will usher in much cooler temperatures by the end of
the week.

The front should arrive late in the day on Thursday, or even
Thursday night. A few rain showers may accompany the front, but
moisture is limited and there is no real subtropical connection to
provide any last minute moisture source. Guidance has been trending
drier in recent runs, but will maintain at least slight chance PoPs
across our northern counties for now. No mentioned of precipitation
will be carried on Thursday south of I-70. Winds in the immediate
post-front environment could be gusty at times, but if the timing of
fropa is more at night this could be limited. However, gusts to
20kts seem probable given the strong pressure gradient behind the
front.

By Friday, surface high pressure should drop down behind the front
as ridging aloft is replaced by broad troughing. Ensemble guidance
keep the post-frontal airmass rather cold, with 850mb temps ranging
from 0C to -4C. As the surface high pressure passes overhead,
radiational cooling potential will be maximized. Lows would be well
into the 30s, and even below freezing in some places. Frost and even
freeze potential exists this weekend. In fact, frost may be rather
widespread Saturday and Sunday. Peeking at next week, cool
conditions may linger but modifying air mass may lead to a gradual
warm up. Ensembles show the trough flattening a bit, but model
spread remains high.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1201 PM EDT Mon Oct 3 2022

Impacts:

* No noteworthy impacts.

Discussion:

Winds may vary around 20 degrees either side of the forecasted
direction, and wind speeds should be at a minimum in the early
morning hours (possibly briefly calm). VFR will prevail.

&&

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

$$

Update...BRB
Short Term...50
Long Term...Eckhoff
Aviation...BRB


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