IND issues Area Forecast Discussion (AFD) at Mar 5, 2:47 PM EST276
FXUS63 KIND 051947
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
247 PM EST Wed Mar 5 2025
.KEY MESSAGES...
- Wind Advisories in effect this evening with gusts up to 45 to 50
mph at times.
- Rain changes over to snow this evening with up to a half inch of
accumulation possible overnight
- Additional light precipitation likely Friday and Friday night
- Well above normal temperatures expected next week with breezy
conditions at times
&&
.SHORT TERM (This evening through Thursday)...
Issued at 245 PM EST Wed Mar 5 2025
Multiple items to focus on in the next 24 hours as the weather will
remain quite active across the region. Strong winds, rain changing
to snow, and crashing temperatures are all in the forecast for most
of Central Indiana the rest of this evening and into tomorrow.
Set up: A strong occluding 980mb low continues pushing northeast
through the Great Lakes region while cold air wraps around the
backside of the low into Indiana. Upper level trough axis is
currently over Illinois and will slowly push eastward this evening.
Cyclonic flow about the low and PVA ahead of the trough axis will
work to keep precipitation around through at least midnight tonight
with the best moisture for shower activity departing to the east
thereafter. The low level jet rounding the base of the low continues
to overspread the region and will be responsible for strong wind
gusts through tonight before diminishing tomorrow.
Wind threat: Two separate Wind Advisories are out for the region.
The first one is for SW portions of Central Indiana from Terre Haute
to Bloomington to Vincennes, in effect until 1 AM EST. Currently the
core of the cold air advection and strongest winds within the LLJ
stretches from Western Illinois southward into Southern Illinois
then east into SW Indiana. Steepening low level lapse rates have
allowed for stronger wind gusts upwards of 45+ mph to mix down to
the surface. Expect this activity to continue into the evening as a
50-60 mph wind max within the LLJ pivots into that region. Wind
gusts upwards of 50 mph will be possible early this evening before
diminishing into the 30-40 mph during the overnight hours.
The second Wind Advisory is for areas along and north of the I-70
corridor from 5pm to 5 am. While conditions have been windy
throughout the day, expect winds to slightly increase later this
evening and overnight as cold air advection steepens low level lapse
rates for more efficient momentum transfer from the LLJ to the
surface. With the low occluding, colder air will actually be pushing
in from the Southwest, which is why portions of SW Indiana may see
higher wind gusts and colder air first. The LLJ weakens somewhat
overnight; however still thinking gusts over 45 mph will be possible
at times for much of the area, diminishing to 25 to 35 mph toward
sunrise.
Temperatures and Precipitation Type: As mentioned above, strong cold
air advection is wrapping around the area of low pressure as it
departs to the northeast. Temperatures have already fallen from the
50s into the mid to upper 30s in some spots with all locations
expected to drop to or below the freezing mark tonight. Hi-res cross
sectional views of the atmospheric profile reveal enough moisture
present through the column and in the DGZ for rain to transition to
snow showers everywhere through the evening. Rain has already
changed to snow where stronger cold air advection is across SW
Indiana...so expect the rain to snow transition line to push further
north and east through the evening hours. Not expecting much in the
way of accumulation as the ground is largely above freezing
resulting in quick melting; however would not be surprised for some
spots to pick up around a half inch of snow overnight. Gusty winds
may lead to fracturing of dendrites and blowing snow, keeping SLRs
and accumulations on the lower end as well.The majority of the
precipitation should be pushing east of the region within the 1am to
3am timeframe. A few slick spots are possible for the morning
commute tomorrow as temperatures fall into the upper 20s to low 30s
for all of Central Indiana.
Tomorrow...
High pressure builds in south of the region tomorrow with a strong
drying trend expected during the morning hours. Forecast soundings
show enough dry air coming in with a well mixed boundary layer that
clouds quickly clearing from west to east during the mid to late
morning. Sunshine plus mixing and steep low level lapse rates should
yield highs in the low to mid 40s with such cold air aloft. Wind
gusts will be on a diminishing trend through the day with strongest
winds in the morning and gusts closer to 20 mph by the afternoon
hours. Wind chill in the morning will likely make it feel like the
teens outside with afternoon wind chills only in the 30s.
&&
.LONG TERM (Thursday night through Wednesday)...
Issued at 245 PM EST Wed Mar 5 2025
Thursday night through Friday night...
A weakening low pressure system and positively tilted trough will
move through the region early in the extended likely producing
precipitation across much of central Indiana. Despite upper level
ridging still in place at the start of the period, isentropic ascent
and warm air advection ahead of the approaching system may allow for
precipitation to begin around late Thursday night or early Friday
morning. The one caveat is that forecast soundings show considerable
subsidence-induced dry air which will delay top-down saturation
initially.
Increasing large scale ascent and overall forcing from the system
keeps precipitation chances elevated through early Friday night.
Thermal profiles suggest QPF should predominately remain liquid, but
there is some potential for snow to briefly mix in at times. The
best chance for snow to mix in would be around the onset of
precipitation before warm air advection warms temperatures or Friday
night when cooler air filters in on the backside of the system.
Impacts are unlikely due to marginal thermal profiles and ground
temperatures. However, minor snowfall accumulations on grassy or
elevated surfaces cannot be completely ruled out. Any lingering
precipitation is expected to taper off late Friday night as the
disturbance shifts east.
Saturday onward...
Look for mostly quiet weather conditions during the latter half of
the extended with gulf moisture remaining locked to the south.
Guidance shows an upper wave moving through over the weekend, but a
southern stream trough will substantially limit moisture return
keeping central Indiana dry. Upper ridging then builds in across the
central CONUS early next week allowing quiet weather to persist.
Precipitations chances return by the middle of next week as a strong
LLJ associated with a developing system helps transport gulf
moisture northward. Exact details on this system remain uncertain
due to diverging model solutions.
Breezy conditions are likely early to middle of next week with
almost all long range guidance showing a persistent tight pressure
gradient between surface high pressure across the Southeast and a
developing surface low across the Plains. Increasing southwesterly
flow will also help to quickly warm temperatures. Highs in the 40s
Saturday are expected to warm well into the 60s by early next week.
Some locations could even reach or exceed the 70F mark on Tuesday.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 1246 PM EST Wed Mar 5 2025
Impacts:
- SW winds becoming WNW with gusts of 35-40 kts into overnight hours
- MVFR cigs and vis becoming IFR this evening as rain
showers transitions to snow showers
- Improving cigs and vis after 04-06z
- Winds slowly diminishing tomorrow morning
Discussion:
A strong 980mb low continues to track northeast into the Great Lakes
while producing strong winds and MVFR cigs and vis across the state
of Indiana. A strong 35-45 kt low level jet rounds the base of the
low pressure system and will be overhead through the overnight
hours. Expect gusts to increase throughout the evening hours, first
at KHUF and KBMG with gusts 30-40 kts through 03-06z. Strongest
winds within the LLJ shift northward during the overnight hours
resulting in stronger wind gusts up to 35-40 kts at KIND and KLAF
22z-10z. Wind directions will slowly shift from 220-250 this
afternoon to 270-300 during the overnight hours.
Rain showers and MVFR cigs and vis will continue through the
afternoon hours before colder air transitions rain over to snow from
an unconventional direction from SW to NE. Expect rain to transition
to snow first at KHUF and KBMG later this evening then at KIND then
KLAF tonight. Periods of IFR cigs and vis likely, especially under
heavier snow showers. Conditions should improve back to MVFR after
around 04z then to VFR around or just after sunrise tomorrow.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 5 AM EST Thursday for INZ021-028>031-035>049-
054>057.
Wind Advisory until 1 AM EST Thursday for INZ051>053-060>062-
067>070.
&&
$$
SHORT TERM...CM
LONG TERM...Melo
AVIATION...CM
Source:
IND issues Area Forecast Discussion (AFD) at Mar 5, 2:47 PM EST---------------
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