IND issues Area Forecast Discussion (AFD) at Apr 7, 1:19 AM EDT891
FXUS63 KIND 070519
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
119 AM EDT Mon Apr 7 2025
.KEY MESSAGES...
- Rivers have already reached or are expected to reach moderate to
major flood stage in Central and South Central Indiana
- Widespread, significant river flooding continuing through next
few weeks
- Frost and freeze conditions likely Monday night and Tuesday night.
Freeze Watch in effect Monday Night.
&&
.FORECAST UPDATE...
Issued at 740 PM EDT Sun Apr 6 2025
Light rain continues to pass through central Indiana as a string of
upper-level vorticity swings by. This is actually what remains of
the deep trough that has brought all the rain over the past few
days. On its way out, it may bring another 0.10" to as much as 0.25"
of rain across the region. Some snow or ice pellets have mixed in at
times and that will continue until precip ends. We've upped PoPs in
the near term based on radar trends and observations.
Precip ends tonight and skies should clear up from west to east.
Winds at the surface die down and with so much boundary layer
moisture it is not unreasonable to think that patchy fog may occur
before sunrise. Some higher-resolution models are hinting at it, but
the signal is mixed as others do not. Still, our conceptual model on
radiative fog formation pushes us in that direction. Clearing skies
and subsidence after abundant rainfall, high boundary layer
moisture, light winds, and no air mass change all adds weight to
that argument. We've added patchy fog to locations southwest of
Indianapolis. This may be expanded or trimmed overnight, depending
on how everything unfolds. Some of the more aggressive models, like
the HRRR, even show patchy dense fog.
Aside from the above, the rest of the forecast hasn't changed much.
We continue to expect a cold front arriving tomorrow afternoon with
a sharp temperature drop, gusty winds, and potentially rain/snow
showers.
&&
.SHORT TERM (This evening through Monday)...
Issued at 300 PM EDT Sun Apr 6 2025
After a week of widespread flooding and severe weather, Central
Indiana finally gets a break as a cooler and relatively drier
weather pattern sets up over the next week. Despite drier weather,
flooding will still be a concern throughout Central and South
Central Indiana as water levels slowly recede; therefore Flood
Warnings continue today for a majority of the region. Some rivers
may remain above flood stage for at least the next week.
.This evening and tonight...
Satellite and radar imagery continue to show clouds and showers
moving NE into the state ahead of a mid and upper level trough axis
just to the west. The surface boundary is well to the south
resulting in northerly winds and cold air advection keeping
temperatures only in the 40s today. ACARs soundings do show enough
saturation in the 0C to -5C layer for a few ice pellets to form with
a profile conducive for them to make it to the ground due to wet
bulb cooling in a dry 800-900mb layer. Added slight chance of sleet
mixing in along and north of I-70 through the rest of the evening.
For tonight, the drying trend continues as moisture advection
through the column pushes east of the state, resulting in thinning
clouds from NW to SE. Winds may briefly go calm overnight as a thin
area of high pressure moves in overhead ahead of an approaching
frontal boundary across the Great Lakes. Light winds and clearing
skies for the latter half of the overnight hours may result in
radiational cooling and temperatures dropping into the low 30s
across the entire region. Coldest spots will likely be low lying
wind sheltered locations that could briefly reach 30 degrees by
sunrise. Such saturated grounds may limit the overall frost threat.
.Monday...
A brief warm up expected tomorrow ahead of a very strong cold front
dropping south through the state. Winds briefly become SW tomorrow
morning and increase to 10-15 mph as low level mixing ramps up.
Steep low level lapse rates and deeper mixing will allow for higher
gusts of 20-25 mph to mix down to the surface much of the day.
Highs will likely not follow the typically diurnal pattern as the
front quickly pushes through from the north late morning through mid
afternoon. Temperatures may only have a few hours of daytime heating
to rise before crashing behind the front; therefore expect a sharp
north to south temperature gradient across the state with morning
highs in the upper 40s across the north and near 60 in Southern
Indiana. Temperatures may drop as much as 10-20 degrees tomorrow
afternoon behind the front with strong northerly winds creating wind
chills only in the 20s by the evening. Forecast soundings show the
potential for enough low level saturation along the front for very
isolated showers; however confidence in this is fairly low. Added
sprinkles and flurries along and north of I-70 late morning into the
afternoon to account for this.
&&
.LONG TERM (Monday night through Sunday)...
Issued at 300 PM EDT Sun Apr 6 2025
No significant changes within guidance regarding the overall pattern
through the long range. The exception is a trend towards a stronger
low developing on Wednesday-Thursday with increased precip amounts.
The overall forecast philosophy remains the same, and the previous
discussion will be retained. Added a Day 8-14 section towards the
bottom.
---------------Previous Discussion-----------------
A large-scale pattern change will occur in the long term as a quick
moving short wave will organized a push of much colder air into the
Ohio Valley late Monday. The slow-moving trough that has been
bringing us round after round of rainfall finally slides eastward
Sunday night. Still the mid level baroclinic zone and corresponding
jet streaks will aid in the creation of a modest shortwave.. High-
res models are showing temperatures dropping 20+ degrees Monday
evening, with further diurnal cooling Monday night pushing
temperatures likely below freezing. Due to the abnormal warmth and
moisture throughout late March and early April, growing seasons have
already begun. For that reason a Freeze Watch has been issued for
Monday night.
Surface high pressure quickly builds in Monday evening, with
diminishing winds and clearing skies. The center of the high doesn't
arrive until Tuesday, however, and there may be enough cyclonic flow
regionally to promote lingering stratocumulus through the night and
into Tuesday morning. Models tends to be a bit too optimistic with
stratocu in these scenarios by clearing things up too quickly. We
will retain some cloud cover in the forecast, especially northeast
of Indianapolis, for now. Questions regarding cloud cover translate
into questions regarding low temperatures, since lows will partly
depend on the radiative component in addition to the advective.
Should skies end up clearer, then we can expect values as low as the
low 20s. Conversely, cloud cover may keep lows closer to 30.
Regardless, sub-freezing temperatures are expected with widespread
frost and hard freeze conditions.
Sub-freezing lows are possible again Tuesday night, but by 00z that
evening the core of the upper trough will be exiting to the east.
Modest warm air advection begins and continues into the night as
winds turn westerly. Lows in the 20s are possible, especially east
of I-65. There remains some differences within guidance with how
fast the surface high departs. Slower departure favors colder temps
as ideal radiative cooling conditions linger into the night.
Our next chance of precipitation arrive on Wednesday evening or
early Thursday as a moisture-starved system zips by to our north.
Guidance shows some weak convective instability, which combined with
frontal forcing could lead to scattered showers and perhaps a
thunderstorm. Additionally, some breezy southwesterly winds are
possible immediately ahead of the system and its attendant cold
front Wednesday afternoon. Cold advection returns after Thursday as
northwesterly flow aloft and east coast troughing take hold.
Additional overnights with frost potential are possible towards the
end of the week and into next weekend.
Days 8 to 14: Ensemble guidance is showing a fairly amplified and
progressive jet pattern towards the middle to end of April. Such a
pattern could lead to renewed active weather. Temperatures likely
rebound and climb towards or even a little above average. Precip is
more uncertain, as an active pattern doesn't necessarily mean each
system impacts Indiana directly.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 118 AM EDT Mon Apr 7 2025
Impacts:
- Chance for patchy fog and IFR VSBY this morning at KHUF and KIND
- Winds will gust to near 30 knots from 290-320 degrees after 18z
Monday
Discussion:
Light to calm winds overnight along with already near saturated
surface levels should lead to patchy fog development at KIND and
KHUF. KBMG could also see fog, but confidence in occurance is lower
at this time. Any fog should quickly mix out after 13Z with strong
SW flow arriving. Continued cyclonic flow and lingering moisture
will result in some diurnal mostly VFR cu on Monday. Winds will
shift towards W and then NW throughout the day after a dry frontal
passage. Mixing will as result in gusty winds to near 30 knots.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Freeze Watch from late tonight through Tuesday morning for
INZ021-028>031-035>049-051>057-060>065-067>072.
Flash Flood Watch through Tuesday morning for INZ064.
&&
$$
UPDATE...Eckhoff
SHORT TERM...CM
LONG TERM...Eckhoff
AVIATION...Updike
Source:
IND issues Area Forecast Discussion (AFD) at Apr 7, 1:19 AM EDT---------------
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