IND issues Area Forecast Discussion (AFD) at Jan 30, 3:19 AM EST273
FXUS63 KIND 300819
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
319 AM EST Thu Jan 30 2025
.KEY MESSAGES...
- Above average highs mostly in the 40s and 50s into early next week
- Rain expected this afternoon into Friday, with rainfall amounts
from around a half inch to near an inch (highest south).
- Scattered thunderstorms possible Friday afternoon and evening
across South Central Indiana
- Warmer than normal conditions continue into the weekend with dry
weather afterwards until Wednesday
&&
.SHORT TERM (Today and Tomorrow)...
Issued at 318 AM EST Thu Jan 30 2025
Today...
The stretch of mild weather continues; however widespread
rainfall pushes into Central Indiana this afternoon into Friday. The
weather starts off quiet for the first half of the day today as an
elongated area of high pressure over the Eastern CONUS slowly slides
east. A closed upper level low ejecting east/northeastward out of
the Four Corners region pushes toward central Indiana through the
day today , with some weak isentropic lift pushing into the area by
midday. Dry antecedent conditions through the atmospheric profile,
as observed on local ACARs soundings, will likely take a while to
saturate today, working to delay the onset of rainfall reaching the
ground. IVT progs suggest the best moisture transport will be along
and south of the Ohio River for much of the day, further increasing
confidence that the first half of the day should remain dry with
areas in Southwest Indiana observing rainfall first as the system
moves in from that direction. Latest 00z ensemble probability
matched mean values suggest relatively light amounts for most of the
area within the 18-00z timeframe, with WPC amounts of up to a
quarter inch in the far south/southwest looking quite reasonable.
Fairly strong low level warm advection will push highs back into the
mid 40s to low 50s, though increasing cloud cover and evaporative
cooling as rain begins later in the day will limit this a bit. Kept
temperatures above guidance as strong warm air advection and low
level mixing should help temperatures quickly rise despite
increasing cloud cover.
Tonight...
Watching the evolution of the surface low tonight into Friday as it
pushes toward the Ohio Valley, as latest model trends suggest a new
low center forming along the triple point near the Ohio River with
the weakening parent low and associated energy moving toward the
Chicago area. This would essentially place Central Indiana right in
the middle with the best moisture advection and forcing for ascent
remaining in Southern Indiana along the new low. Better
frontogenetical forcing to the south and potential convection could
also inhibit some moisture advection northward into Indiana. Wrap
around moisture and heavier rain under the mid latitude low's TROWAL
would also remain to the north stretching across Northern Illinois
the IN/MI state line to Lake Erie. With the system potentially
splitting, Central Indiana could end up with lower rainfall amounts
compared to those areas north and south of the region..
Nonetheless, still expecting widespread light to moderate rain to
overspread Central Indiana from the southwest into tonight as a
strong southwesterly low level jet pumps moisture into the state.
Friday...
On Friday morning, the dry slot of the system works into the area,
decreasing rainfall coverage and intensity across the Southern 2/3
of the forecast area. Will have to watch where the northern extend
of the dry slot sets up as just north of that area is where another
axis of heavy rain will set up associated with the aforementioned
TROWAL. Keeping higher PoPs across far North Central Indiana through
the day Friday to account for this, while keeping only "Chance"
wording in the forecast for the rest of Central Indiana as as
southwesterly flow regime sets up south of the low. Steepening low
level lapse rates, a strong low level jet, and 0-3km CAPE values
potentially over 100 j/kg could result in scattered shallow
convection developing Friday afternoon and evening within the dry
slot. Added shower ans thunderstorm wording to the forecast for that
time period to account for this as short term model forecast
soundings do show a low level profile capable of producing isolated
convection and thunder. Low freezing levels may even result in a few
of the strongest cells to produce small hail.
Temperatures Friday will also be quite warm under the dry slot of the
low. Steepening low level lapse rates as cooler air advects in aloft
as well as a strong 40 kt LLJ just above the surface will lead to a
well mixed boundary layer. Low level temperature profiles support
temperatures in the mid to upper 50s for Central and South Central
Indiana while north Central Indiana remains cooler and less "mixed"
in the upper 40s to low 50s. Potential is there for winds to gust
over 30 mph through the morning and afternoon hours as well as winds
within the LLJ mix down to the surface. Any convection that does
develop within the dry slot could produce stronger gusts over 40-50
mph if these cells tap into that low level jet.
Total rainfall amounts now look to be around a half inch across the
northern half of central Indiana, with a tight gradient to around 1
inch in the far south.
&&
.LONG TERM (Saturday through Wednesday)...
Issued at 318 AM EST Thu Jan 30 2025
Friday Night Through Tuesday.
Precipitation will come to an end by Friday night as the upper level
flow becomes more zonal. Model soundings show some dry air will
gradually begin to filter in which should allow for at least some
clearing towards Saturday with cooler, but still above normal
temperatures for the day. An upper level system then looks to move
through the Northern Great Lakes region Saturday night into Sunday
which will bring a return to southerly flow for Sunday with a low
chance for a few light rain showers. This robust southerly flow will
bring dewpoints into the 40s with highs potentially as high as 60 in
spots.
With the frozen ground, the precipitation from Thursday into Friday
will lead to a higher ratio of runoff to infiltration which will
bring elevated river and stream levels trough the weekend into next
week. Action stage looks likely along the White River south of
Bloomington with a low threat for minor flooding.
A weak cold front associated with the exiting low pressure system to
the north will move through Monday night into early Tuesday with
little impacts other than the surface flow will become northerly
with slightly cooler temperatures as highs only climb to the mid 40s.
Wednesday and beyond.
Confidence in the forecast then quickly falls off Wednesday through
the remainder of the work-week as models have major differences on
the overall synoptic pattern with the GFS and its ensembles bringing
an intrusion of colder Canadian air with the potential for some snow
while the European and its ensembles showing broad ridging within
the subtropical jet with much warmer temperatures.
With those significant differences, blended model guidance is highly
variable with a 20-30 degree spread for the high temperature
Wednesday. The overall teleconnections pattern would favor the
European solution with little support for an intrusion of colder
air, so will try and trend the forecast to the warmer solution. The
pattern then favors wetter than normal conditions for the end of the
work-week into the weekend.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 1249 AM EST Thu Jan 30 2025
Impacts:
- Light and variable winds becoming southerly this morning
- Deteriorating conditions by mid to late afternoon Thursday as rain
overspreads the terminals
Discussion:
High pressure remains across the region this evening and will keep
skies mainly clear through daybreak. Light and variable winds
overnight will turn southerly by the morning and increase to around
10 kts. Potential is there for higher gusts or sustained winds 10-15
kts during the mid afternoon
Mid and high level clouds will encompass the terminals by midday as
progressively deeper moisture advects into the Ohio Valley. Low
pressure will track into Arkansas and Missouri by this evening with
a warm front extending east near the Ohio River. As moisture and
lift increase over the region...rain will become widespread over
central Indiana by late afternoon. Expect ceilings to drop rapidly
with the onset of rain with IFR conditions developing near the end
of the forecast period.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CM
LONG TERM...White
AVIATION...CM
Source:
IND issues Area Forecast Discussion (AFD) at Jan 30, 3:19 AM EST---------------
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