IND issues Area Forecast Discussion (AFD) at Dec 13, 11:24 AM EST811
FXUS63 KIND 131624
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1124 AM EST Fri Dec 13 2024
.KEY MESSAGES...
- Warming trend starts today
- Rain is expected at times late Saturday through Sunday morning,
and again on Monday. Thunder is possible with Monday's rainfall
&&
.FORECAST UPDATE...
Issued at 913 AM EST Fri Dec 13 2024
First GOES-16 visible satellite pictures of the day were indicating
the snow field was extending from around northern Vermillion county
to around Noblesville and Lynn and north. The snow pack should keep
temperatures down there a bit, otherwise, east winds around a Great
Lakes high combined with some breaks in the mainly high clouds, per
ob and Hi-Res sounding trends, should allow temperatures to bounce
back to the mid 30s to around 40 degrees this afternoon. This is
still 5+ degrees below normal.
&&
.SHORT TERM (Today and tonight)...
Issued at 233 AM EST Fri Dec 13 2024
Snow has exited central Indiana early this morning. Lower clouds
linger across mainly the northern half of central Indiana, with high
clouds increasing across the south.
Quiet weather will continue across central Indiana through the short
term. Aloft, upper ridging will move into the area. At the surface,
high pressure will still be in control. This will keep the area dry.
Surface flow will continue from the east. Meanwhile, warm advection
will begin aloft today and continue tonight. This will result in
partly to mostly cloudy skies for much of the time, with mainly mid
and high clouds around.
Looking at temperatures, snow cover across the northern third or so
of the area will limit recovery today and keep highs in the upper
20s to around 30. Elsewhere, readings will peak in the 30s to around
40. Did trim back the model blend a bit even where no snow cover
exists, given expected sky cover and surface flow remaining easterly.
Tonight, with expected cloud cover and winds becoming southeasterly,
lows will be mainly in the 20s.
&&
.LONG TERM (Saturday through Thursday)...
Issued at 233 AM EST Fri Dec 13 2024
Central Indiana's weather will be rather active over the next
week as the 300mb pattern becomes increasingly meridional, including
the passage of 2-3 substantial waves.
The first wave to impact central Indiana currently sits over the
West Coast, and has a highly diffluent upper level flow pattern.
This will help further develop the trough as it progresses eastward,
but a deep high pressure system over the EC will keep this trough
negatively tilted. Due to the position of the high/low a strong
southerly LLJ will form out ahead, pushing temperatures and moisture
well above climatological normals for mid December.
The majority of the forcing with this initial wave will be within
strong isentropic ascent within the 800-600mb layer. This should
induce a broad stratus layer with widespread rain by late Saturday
through Saturday night. Ensembles remain generally clustered around
0.5" of QPF. Even with the general consensus on amounts, there are
some competing factors that could lead to slight trends in the
coming days. First is the depth of saturation which is currently
modeled to be nearly tropospheric. This would tend to lead to
greater rainfall efficiency, however mid level stability will work
to inhibit this some.
The second wave will shortly follow the first, arriving late Sunday
through Monday. This second wave shares similar characteristics
vertically, but with greater surface cyclogenesis expected over the
Northern Plains. Because of the first wave passage, antecedent low
level conditions will be much warmer/wetter in front of this wave.
This could allow for modest instability to develop, especially
between 800-500mb. Its too far out to pinpoint on depth of
convection/location of LFC at this point, but generally speaking
lightning creation is expected within rainfall on Monday. Convective
development co-located with deep saturation to the tropopause on
Monday will likely lead to higher rainfall totals with the second
wave. Ensemble members are still fairly spread on the greatest
precip axis, but narrow 24hr totals greater than 2 inches are not
out of the question.
The progressive meridional pattern will continue into the mid to
later portions of next week. There are some hints and greater
baroclinicity reaching the Ohio Valley by mid week as deeper
longwave troughing enters the central CONUS. This would allow for
greater cold conveyor belts within the midweek system, creating
chances for frozen P-types. This is conditional on the trough's
characteristics and track, as are precipitation amounts. There is
quite a spread with regards to amplitude and how much phasing occurs
with this system, so confidence on timing, precipitation amounts,
and precipitation type is low at this time.
Day 8-14: Medium-range ensemble data shows initial troughing and
colder than normal temperatures, moderating toward the end of the
period, along with near or below normal precipitation.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 1124 AM EST Fri Dec 13 2024
Impacts:
- None
Discussion:
High confidence in VFR flying conditions through 21z Saturday with
just mid and high clouds and winds 080-110 less than 10 knots. Then,
rain and MVFR flying conditions are increasingly possible after 21z.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...MK
SHORT TERM...50
LONG TERM...Updike
AVIATION...MK
Source:
IND issues Area Forecast Discussion (AFD) at Dec 13, 11:24 AM EST---------------
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