IND issues Area Forecast Discussion (AFD) at Feb 8, 6:14 PM EST
443
FXUS63 KIND 082314
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
614 PM EST Sat Feb 8 2025
.KEY MESSAGES...
- Rain and drizzle ending by early this evening, freezing rain or
drizzle may briefly mix in across far northern sections of central
Indiana
- Active weather pattern with additional chances for wintry
precipitation next week
&&
.SHORT TERM (This evening through Sunday)...
Issued at 257 PM EST Sat Feb 8 2025
Low pressure located over far SW Indiana at 19Z with a narrow band
of showers already moving quickly across eastern portions of the
forecast area with drizzle behind that. Still likely seeing patchy
freezing rain or drizzle mix in over the extreme northern portion of
the forecast area impacting particularly Carroll and Howard
Counties. Temps ranged from near freezing in those areas into the
40s across southern counties.
Been an interesting afternoon so far that saw convection produce pea
size hail...thunder and patchy freezing rain in a swath from Warren
County E/NE across the Lafayette and Kokomo areas. What is left now
is a narrow low topped band of showers as mentioned above rapidly
pushing across eastern counties. There remains a low threat for a
few rumbles of thunder within this line over the next hour or so.
Once this shifts east into Ohio...it will remain gray...damp and
dreary as moisture is trapped beneath a shallow but sharp inversion.
This will maintain areas of drizzle and where temperatures hover
near or just below freezing in north central Indiana...freezing
drizzle likely lasting into the early evening before diminishing.
Cannot rule out localized light icing over north central Indiana on
elevated surfaces but no impacts are anticipated. Winds will become
briefly gusty as they shift to northwest this evening on the back
side of the departing low pressure.
A broad area of high pressure over the northern Plains will expand
south and east into the region late tonight and Sunday with dry and
cool weather expected. Lower stratus will likely be stubborn in
mixing out as moisture remains trapped beneath a low level inversion
for most of the day Sunday. Will see ceilings lift on Sunday and
will be increasing breaks in the deck as the day progresses but the
overall state of the sky will be mostly cloudy all day.
Temps...gradually colder air will filter into the forecast area
tonight as cold advection develops but the low cloud deck and winds
will keep temperatures from bottoming out. Expect lows ranging from
the mid 20s north to near 30 south. Low level thermals support highs
predominantly in the 30s Sunday.
&&
.LONG TERM (Sunday night through Saturday)...
Issued at 257 PM EST Sat Feb 8 2025
A transition to a colder and more active pattern is expected this
weekend and into next week. On the global scale, guidance is in good
agreement showing the Arctic Oscillation (AO) turning negative.
During negative phase AO, the polar jet typically weakens and
becomes more amplified. Such jet configurations can lead to arctic
air moving more freely southward, as may be the case next week.
Another large-scale teleconnection, the North Atlantic Oscillation
(NAO), is shown by guidance to be generally neutral with perhaps a
slight trends towards negative. Negative NAO tends to bring about a
blocking pattern which can also lead to a more amplified jet pattern
and thus colder temperatures over the Midwest / Eastern US. However,
the AO turns sharply negative well before the NAO reaches neutral so
our long term weather should be more influenced by the AO. We'll
likely see the trend towards cooler temperatures but with a more
progressive and active pattern. That is, more storm systems moving
quickly eastward within a wavy jet stream.
The first substantial upper level system within the long term looks
to impact the Ohio Valley late Monday through Tuesday night with
models continuing to show agreement in the overall synoptic pattern.
Trends have pushed this system further south, leading to greatest
impacts with this system likely south of central Indiana. With that
said, there is still 96 hours until arrival and track changes are
still possible. This pattern consists of a relatively deep surface
low moving somewhere across the Tennessee Valley with central
Indiana remaining in the cold sector of the system, including modest
northeasterly surface flow. Although greatest FGEN and deformation
is likely to remain south of central Indiana. Moderate mid level
lift within the cold conveyor belt could lead to periods of snowfall
Tuesday if enough moisture is available. The greatest threat for 1
inch or more is along and south of a Bloomington to Columbus line.
Keep monitoring forecast updates in the coming days as details
become more apparent, and plan on the potential for Tuesday travel
hazards in the event snowfall comes to fruition.
Ensembles have come into better agreement regarding the second
system likely to impact Indiana next week around the Wed/Thur
timeframe. Both the ECMWF and GFS now more or less depict a
strengthening low pressure system lifting northeastward from Western
Kentucky into Ohio. Some notable trends in the past 24 hours are a
slightly northward low track and a stronger system overall. These
trends have been subtle so far, but enough that the likelihood of
mixed precipitation has increased. Who sees what and how much is
highly dependent on storm track and strength. Since nearly every
model depicts this system impacting Indiana, confidence is higher
than normal regarding precipitation chances this far out. However,
confidence is much lower regarding precipitation type and
amounts...as a variety of storm tracks and intensities are shown
within the ensembles each of which may lead to a different outcome.
A third system is suggested by guidance to arrive late in the period
over the weekend, and its eventual evolution may depend a bit on the
system that comes before it. As such, even greater model uncertainty
exists for the weekend system, but enough of a signal exists for
chance to likely PoPs. A storm track similar to the mid-week system
is possible, so all precipitation types are once again on the table.
Like before, confidence is low on any one particular outcome until a
clear consensus emerges regarding system strength and track.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 614 PM EST Sat Feb 8 2025
Impacts:
- Widespread IFR across most of the sites through this evening,
improving to MVFR late tonight into Sunday
- Brief period of gusty winds around 20KT from the NW early in the
period
Discussion:
As low pressure exits the region and high pressure begins to build
in this evening, moisture will remain trapped beneath a low level
inversion. This will continue to produce widespread IFR ceilings and
a few areas of visibility restriction as well through the evening
hours, before ceilings lift to MVFR late tonight and persist at MVFR
levels into Sunday afternoon. VFR should return to all sites in the
20-22Z time frame Sunday.
Winds will generally be between 290-350 through the period, more
toward the former earlier and the latter later. Sustained winds
around 8-12KT can be expected this evening, with steep low level
lapse rates below the inversion promoting a brief period of
gustiness to around 20KT early in the period before subsiding. Winds
will gradually weaken later tonight and during the day Sunday as the
pressure gradient relaxes.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
SHORT TERM...Ryan
LONG TERM...Updike/Eckhoff
AVIATION...Nield
Source: IND issues Area Forecast Discussion (AFD) at Feb 8, 6:14 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202502082314-KIND-FXUS63-AFDIND)
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