IND issues Area Forecast Discussion (AFD) at Dec 28, 9:58 AM EST
413
FXUS63 KIND 281458
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
958 AM EST Sat Dec 28 2024
.KEY MESSAGES...
- Cloudy and dry today with highs in the 50s
- Rain arrives tonight with periods of moderate rainfall through
Sunday, total rainfall up to 2 inches
- A mainly dry and progressively colder start to 2025, with wind
chills as low as 10 degrees Wednesday night and Thursday night
&&
.FORECAST UPDATE...
Issued at 957 AM EST Sat Dec 28 2024
Weak subsidence under broad surface high pressure has kept it dry this
morning and this should stay status quo today. Although, GOES-16
visible satellite was showing some breaks in the overcast, over the
upper Wabash Valley, Hi-Res soundings are showing a moist column from
around 1-5K feet, underneath an inversion. This should keep at least an
appreciable amount of stratocu around this afternoon.
Despite the cloud cover, southwest winds to near 10 mph, on the
backside of the high and temperatures already in the lower 50s supports
the potential for afternoon highs in the middle 50s north to lower 60s
south.
&&
.SHORT TERM (Today through Sunday)...
Issued at 957 AM EST Sat Dec 28 2024
Today.
Coverage of light rain is expected to continue to decrease through
the rest of the overnight hours as the low pressure system that
brought the rain yesterday continues to track northward into
Wisconsin and any remaining upper level forcing exits. Weak
subsidence above the cloud deck today will help to keep mostly
cloudy to cloudy skies in place through the day along with bringing
an end to any residual light rain/drizzle. This break in the
precipitation will be brief though as the next rain producing system
will be tracking northward through the day today and will bring a
return to widespread precipitation tonight. Temperatures today will
climb into the mid to upper 50s with some spots potentially as
high as 60 in the south.
Tonight into Sunday.
Confidence continues to increase in a moderate to briefly heavy rain
event late Saturday night into Sunday. A rapidly deepening surface
low is expected to track up the Mississippi River Valley into
Indiana tonight into Sunday with the center of the low directly
overhead central Indiana by Sunday afternoon. As the low matures, a
TROWAL is expected to form along the northwestern periphery of the
low which will bring enhanced precipitation with models showing a
narrow axis of very strong frontogenesis. Model soundings show a
saturated column with PWATs near climatological maximums for the day
which further highlights the potential for periods of moderate to
heavy rainfall. In addition to the rain, the tightening pressure
gradients associated with the deepening low will allow for
occasional wind gusts of 25-30 mph.
Total QPF with this system continues to trend higher with the
stronger expected cyclogenesis with the latest estimates around 1-2
inches tonight through Sunday. With this setup though, an axis of
locally higher precipitation is likely with another axis to the
southeast of the heavier rain likely to be underdone as a dry slot
develops during the daytime hours. With the moist adiabatic
temperature profile, instability will be near 0 so not expecting any
thunder. These 1-2 inches of rain will lead to rises along local
rivers/streams but any potential flooding looks to hold off until
later in the long term period and will be discussed below.
&&
.LONG TERM (Sunday Night through Friday)...
Issued at 259 AM EST Sat Dec 28 2024
Sunday Night through Tuesday...
An overall troughy...yet quasi-split and at times nearly zonal upper
pattern will prevail across the CONUS through the final four periods
of the calendar year. An ebb and flow mixture of disturbances and
fair weather will occur between the short term's more impressive
system's departure Sunday night...a 24-hour dry period centered
around Monday morning that should include partial clearing...and a
998mb Colorado Low that is expected to glide up the Ohio Valley
Monday night into early Tuesday.
Unseasonably mild conditions through the early week will be lead by
overnight low temperatures about 15 degrees above normal courtesy of
the Pacific maritime origin of the antecedent air mass, and then
light southerly surface flow around the Monday timeframe. The
system arriving from Colorado will be relatively small, yet locally
potent...with guidance continuing to suggest rain tracking west to
east across the region...dropping a rather quick, additional 0.50
inches or so of rainfall over the majority of the CWA. Latest
trends are favoring a precipitation maximum along and perhaps south
of the I-70 corridor, while greater rainfall across northern zones
would be optimal to quell long-standing Severe Drought conditions
from the Lafayette area to northern Madison County.
Forecast accumulated 3-day precipitation near/above 2.00 inches
through late Tuesday for central/southern counties will likely
promote marginal river flood concerns on the lower Wabash and lower
White Rivers. Action stage would be expected should this rainfall
potential be realized, with isolated Minor Flood possible following
any overperformance.
Tuesday Night through Friday...
New Year's Eve celebrations Tuesday night should mark the beginning
of a transition to a noticeably colder pattern that may well extend
weeks into January. Ensembles are continuing to suggest the
departing system will promote diminishing to isolated rain showers
around the Tuesday evening timeframe...with readings falling
to/below freezing by Wednesday morning for the first time in 9 days.
The remainder of the workweek should be overall dry and
progressively colder...as a building upper ridge over western North
America slowly directs a large mass of polar surface high pressure
in a southeastward direction into the central US. Seasonably cold
conditions on New Year's Day will continue to trend to below-normal
levels through the late week...led by afternoon highs that may
struggle to reach 30F for many locations by Friday. At times brisk
W to WNW flow will diminish through overnights...with resulting
overall wind chill values typically within the 10 to 25 degree
range. No organized precipitation is expected, although flakes and
a few flurries will be possible amid the upper cyclonic flow that
should be most prevalent on Friday.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 600 AM EST Sat Dec 28 2024
Impacts:
- Generally MVFR, occasional VFR cigs through 04Z
- IFR to LIFR cigs after 02Z as rain moves in
- MVFR to IFR vsbys afterwards with brief periods of moderate to
heavy rain
- Wind shift to the northeast after 02Z
Discussion:
Cigs will bounce between MVFR and VFR today before consistently
dropping to IFR to LIFR tonight as widespread rain impacts central
Indiana. Vsbys will generally remain MVFR through the rain but
periods of IFR are possible during the heaviest showers. Heaviest
rain looks to be from 08Z to 14Z with light to moderate showers
before and after. Southerly wind gusts will end at LAF shortly.
Winds will also shift to the northeast after onset of rainfall late
this evening.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...MK
SHORT TERM...White
LONG TERM...AGM
AVIATION...White
Source: IND issues Area Forecast Discussion (AFD) at Dec 28, 9:58 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412281458-KIND-FXUS63-AFDIND)
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