IND issues Area Forecast Discussion (AFD) at Oct 31, 2:29 PM EDT189
FXUS63 KIND 311829
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
229 PM EDT Thu Oct 31 2024
.KEY MESSAGES...
- Showers with embedded thunderstorms this morning and early
afternoon.
- Gusty winds to 45 mph ahead of a frontal passage this morning
- Dry and breezy for trick-or-treating except for far southeastern
Indiana where light rain is likely.
- Cooler and dry early weekend and more rain chances and warmer late
weekend into next week.
&&
.SHORT TERM (This evening through Friday)...
Issued at 227 PM EDT Thu Oct 31 2024
Synopsis:
- Gusty winds to 40 mph ahead and after the frontal passage this
afternoon.
Surface analysis early this afternoon shows strong low pressure over
NW WI with an associated cold front extending south across Central
IL to SE MO and Arkansas. A moderate pressure gradient remained
across Central Indiana, with southerly flow ahead of the front.
Water vapor imagery, shows a plume of moisture streaming across
MO/IL toward Indiana, ahead of a negatively tilted upper trough over
WI/MN. Radar shows gaps developing in the rain shield that has been
arriving across Central Indiana through the day. Skies were cloudy
across Central Indiana and temperatures were falling in the 60s.
Halloween (Tonight) -
Beware! Models tonight reveal a chilling cold front sweeping across
Indiana in the witching hours from 5 PM to the end of trick or
treating. Forecast soundings show deep moisture lingering in the
shadows, rapidly drying out as eerie subsidence takes hold.
Aloft, an ominous upper trough is set to glide toward the eastern
Great Lakes, giving way to a nearly ghostly zonal flow by Friday.
The HRRR predicts that most of the spectral rainfall will creep to
SE Indiana between 8-10PM, fading into the night as it becomes
detached from the dynamic forces pulling away to the north. By 3 AM,
the pwats will drop below 0.35 inches, leaving behind a hauntingly
dry atmosphere.
A moderate pressure gradient will keep the winds howling this
evening, with gusts reaching 15-25 mph, creating an unsettling
chill. These winds will ease as high pressure rises from the plains
overnight. Prepare for strong cold air advection, with temperatures
at 850mb plummeting to a frigid 6C by dawn. Expect lows to dip into
the eerie lower 40s across much of Central Indiana. Stay cozy and
watch for ghosts and goblins in the night!
Friday -
The new month will arrive with sunny and cooler conditions. As
mentioned above, nearly zonal flow is expected aloft with little in
the way of forcing dynamics present. Meanwhile, strong high pressure
is expected to develop over the plains, strengthen and push toward
the Great Lakes. A strong mid level inversion and a very dry column
as seen on the forecast soundings will result in sunny skies with
light easterly winds. With cooler air in place, highs will only
reach the middle 50s to near 60s.
&&
.LONG TERM (Friday night through Thursday)...
Issued at 227 PM EDT Thu Oct 31 2024
The drier and cooler continental air mass will still be in place
Friday night but should begin to moderate Saturday as lower
tropospheric flow veers around to southeasterly. Temperatures should
be about five degrees above climatology. High-level Pacific moisture
and upstream cross-mountain flow should result in increasing cirrus
during the day, potentially becoming quite thick.
MSLP gradient will tighten between the eastward drifting high and
strengthening Plains cyclogenesis. This pattern will favor poleward
movement of deep subtropical moisture into Indiana Saturday night.
Warm/moist advection and weak broader isentropic ascent coupled with
a compact midlevel perturbation in southwesterly flow could result
in some precipitation Saturday night into Sunday. Multi-model
ensemble mean is sharper with the gradient on the eastern end of the
QPF maxima centered to our west, and generally has trended downward
for rainfall amounts in Indiana on Sunday. It appears the best
chance will be early in the day across the northwest half of our
forecast area, with minimal coverage the latter half of the day.
The entire synoptic trough/ridge pattern shifts slowly east Monday
placing the axis of QPF a little further east. A couple waves of
remnant convection will occur Sunday night and Monday, but timing
and amounts still need to be refined given the sensitivity of small
variations in modeling convectively-induced midlevel shortwave
perturbations and attendant precipitation footprint.
It appears the best chance of meaningful precipitation across
central Indiana will be Tuesday/Tuesday night as the Plains trough
and associated DCVA/forcing for ascent interact with the anomalous
moist plume resulting in a band of rain migrating through.
Convective intensity and potential for lightning will be limited by
the displacement of cooler midlevel temperatures closer to the
trough center to our north from the warm/moist lower troposphere
over us.
Post-frontal air mass Wednesday and Thursday will be similar to the
last couple of fronts. Drier, and near-climatology temperatures.
But, again, the southeast anomalous ridge holds and the departing
wave and associated cold continental air mass isn't very intrusive.
The Day 8-14 period has below normal predictability. At the start,
there is quite a dipole in handling of western trough. The
deterministic GFS and a handful of its ensembles are aggressive with
eastward movement and a potentially significant precipitation event
late next week into the weekend, while the EPS and several other
multi-model ensemble members are more dominate with the ridge and a
dry pattern. So, there's not much signal to determine if we'll be
above or below normal precipitation, but a reasonably clear signal
on a warmer than normal pattern.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 110 PM EDT Thu Oct 31 2024- Gusty winds to 40 mph ahead and after the frontal passage this
afternoon.
Impacts:
- Southerly wind gusts up to 35kts through 23Z.
- Winds becoming west.
- MVFR Conditions becoming VFR through the period.
- MVFR most likely from 18Z-22Z
Discussion:
Radar shows gaps within the precipitation shield across Central
Indiana as a cold front approaches Central Indiana. A strong
pressure gradient across Central indiana will persist through 06Z as
deep low pressure moves from western WI to northern MI. In the wake
of the front passing late this afternoon, forecast soundings show
the arrival of subsidence and drying. Thus have used a VCSH mention
through the afternoon hours prior to the frontal passage.
As surface high pressure begins to build across the area tonight, the
pressure gradient will relax and any cigs are expected to slowly
exit. This will lead to VFR conditions by late tonight which will
continue into Friday.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Voorhees
LONG TERM...Krueger
AVIATION...Myers
Source:
IND issues Area Forecast Discussion (AFD) at Oct 31, 2:29 PM EDT---------------
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