IND issues Area Forecast Discussion (AFD) at Feb 9, 9:16 AM EST279
FXUS63 KIND 091416
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
916 AM EST Sun Feb 9 2025
.KEY MESSAGES...
- Active weather pattern with chances for wintry precipitation:
Tuesday, Wednesday night into Thursday, and next weekend.
- Cool and cloudy today with highs in the mid to upper 30s.
Clearing skies tonight, with lows in the low 20s to upper
teens.
&&
.FORECAST UPDATE...
Issued at 916 AM EST Sun Feb 9 2025
The clearing in the stratus deck during the predawn hours is in the
process of slowly filling back in with the addition of mid level
clouds moving over the region as well. 14Z temperatures were in the
upper 20s and lower 30s.
The cloud cover remains the primary focus for the rest of the day as
moisture remains trapped beneath a shallow inversion as high
pressure expands in. There remains pockets of clearing across
northern counties and the far southern forecast area. A predominant
northwest flow through the boundary layer combined with low level
heating will allow for the stratus to fill back in over much of the
region by midday and persist into the afternoon as the inversion
lingers. Stratus coverage will diminish slowly late day into the
evening as the center of the high approaches along with deeper
subsidence which should aid in mixing out the inversion.
Highs this afternoon will warm into the 30s with coolest
temperatures across northern portions of the forecast area. Zone and
grid updates out.
&&
.SHORT TERM (Today and tonight)...
Issued at 218 AM EST Sun Feb 9 2025
Cold air advection on the backside of the departing low will help
create a broad area of high pressure over central Indiana tonight
through tomorrow. Subsidence within the region of high pressure is
expected to trap some low level moisture, leading to a lingering
layer of lower stratus, of which will likely be stubborn in mixing
out, even throughout today. Ceilings currently are only 1000-2000ft
off the ground, but these should lift during the daytime as latent
heat fluxes, despite the consistent cloud layer, will warm the near
surface and PBL by a few degrees.
Diurnal temperature swings will be subdued in the presences of the
stratus layer with morning lows likely remaining near freezing, and
afternoon highs only a few degrees warming in the mid to upper 30s.
By tonight, a strengthening LLJ will likely lead to the stratus
layer pushing eastward and clearing skies for central Indiana.
Expect a cold night on Sunday night with continued subsidence, and
near surface drying leading to lows in the upper teens in some
areas.
&&
.LONG TERM (Monday through Saturday)...
Issued at 218 AM EST Sun Feb 9 2025
A transition to a more active pattern is expected next week. On the
global scale, guidance is in good agreement showing the Arctic
Oscillation (AO) turning negative, and the North Atlantic
Oscillation also turning slightly negative. The combination of these
two global drivers turning negative typically leads to a consistent
meridional jet stream pattern, with its location dictated by
synoptic scale pressure. In this instance, the subtropical high
looks to maintain strength over the north/east Caribbean, leading to
a SW to NE oriented jet stream. Long story short, we'll likely see a
trend towards a more progressive and active pattern; That is, more
storm systems moving quickly eastward within a wavy jet stream.
Initially, this will come with a quickly passing wave late Monday
through Tuesday, with a low developing over the Tennessee Valley.
Ensemble trends are becoming more precise, on a track that would
push greatest snowfall impacts south of central Indiana, mostly due
to the persistence of a strong surface high over the eastern Great
Lakes. However, modest easterlies on the north side of the jet may
induce weak lift at times on Tuesday, and with enough moisture could
lead to light snowfall over southern central Indiana. Snow totals
are expected to be less than 3" for this first wave, with most areas
that get snow seeing an inch or less.
As the next system arrives, weaker high pressure over the Great
Lakes will lead to greater influence of the subtropical jet will
likely create a greater northward moisture surge, and a more N/NE
track of the developing low. The greater warm air and moisture will
also likely lead to diabatic induced surface pressure depletion as
is progresses into the Ohio Valley/Great Lakes late Wednesday
through Thursday. Ensemble trends are still fairly spread on low
track at this point, and with central Indiana in the cross hairs for
the low centroid, a wide spread in outcomes, including snow totals
and precipitation types, are still present. Using ensemble
probabilistic tools, the greatest threat for 3+ inches of snow
within central Indiana currently resides N/W of Indianapolis. This
includes locations like Lafayette, Crawfordsville and Kokomo. With a
modest warm nose expected ahead of the surface low, ice accumulations
will also be possible. At this time, ice has been left out of the
forecast due to very high uncertainty on totals/location, but this
will likely be added as details become clearer in the coming days.
This pattern does not stop after Thursday, with another two part
system looking to arrive late week, through next weekend. Its
eventual evolution will likely 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.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 615 AM EST Sun Feb 9 2025
Impacts:
- Widespread MVFR ceilings should improve to VFR after 19z-23z
Sunday although there may be brief VFR conditions as early
as this morning
Discussion:
A sharp inversion will keep the MVFR ceilings mostly trapped until
this afternoon per Hi-Res soundings but then dry advection, in the
boundary layer, will lead to VFR flying conditions by this
afternoon. GOES-16 Night Fog product was showing a few breaks in the
overcast which will translate to some periods of VFR as early as
this morning.
Winds will be from the northwest less than 10 knots today as surface
high pressure builds in from the Plains.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
UPDATE...Ryan
SHORT TERM...Updike
LONG TERM...Updike
AVIATION...MK
Source:
IND issues Area Forecast Discussion (AFD) at Feb 9, 9:16 AM EST---------------
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