Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/26/23
Area Forecast Discussion
National Weather Service Indianapolis IN
940 PM EDT Wed Oct 25 2023
.Forecast Update...
Issued at 940 PM EDT Wed Oct 25 2023
- Added small shower chances to NW sections through Midnight
305 Hi-Res Isentropic data suggests the atmospheric column may
saturate far enough down to squeeze out a few showers over
northwestern sections the remainder of the evening. Radar was
showing weak echoes moving across this area which also features some
weak low level convergence per SPS Mesoanalysis data. Otherwise, IND
ACARs and BUFKIT soundings were showing the atmosphere too dry below
700 millibars for anything other than perhaps a sprinkle or two over
areas near and south of I-70. Warm advection along with mid and high
clouds should keep temperatures mild overnight with lows around 60.
&&
.Short Term...(This evening through Thursday)
Issued at 300 PM EDT Wed Oct 25 2023
* Continued warmth tonight into tomorrow with gusty winds
A warm, cloudy, and breezy weather pattern continues tonight and
tomorrow for the state of Indiana as a strong baroclinic zone
remains parked over the region. Current satellite imagery clearly
depicts a ridge of high pressure over the Southeast CONUS with
tropical moisture streaming northward on its western periphery. At
the surface, high pressure is centered over North Carolina with an
elongated area of low pressure/frontal boundary from Central Texas
to Iowa to Ontario. As mentioned above, deep tropical moisture is
brought northward along that boundary into the US and Canada. Over
the next few days, mid and upper level waves will ride along the
boundary periodically bringing increased clouds and showers to the
region. See the Long Term Forecast for details on when the heaviest
rain is expected for Central Indiana. For the rest of today and
tomorrow, the best forcing for ascent and moisture advection will be
located just north and west of the region, keeping the best threat
for rain towards the main surface boundary and waves of low
pressure. Broad isentropic lift over the region within a moist,
southerly flow regime will however keep clouds and warmer air around
through most of the period.
.This evening and tonight...
Latest IND ACARS sounding shows fairly dry air in the surface to 5km
layer with a saturated layer above that. Mid and upper levels have
seen a drying trend today as the region is in between upper level
waves. Drier air aloft has allowed for scattered breaks in the
clouds, mainly along and south of the I-70 corridor resulting in
temperatures rising into the low to mid 70s for those areas. Thicker
clouds persist north of I-70, closer to the main surface boundary,
with temperatures a few degrees cooler in the upper 60s with
isolated showers. Short term guidance indicates shower activity
within the baroclinic zone pushing northward this evening and
tomorrow as the ridge nudges north and the area is in between waves.
For this reason, expect diminishing showers for northwest and north
central Indiana this evening and overnight. Persistent southerly
flow and warm air advection will keep lows near what daytime highs
normally are for this time of year in the 50s to low 60s!
.Thursday...
Warm, cloudy, and breezy day expected on Thursday as the same
weather pattern persists. The pressure gradient increases slightly
tomorrow resulting in southwest winds around 10-15mph with gusts of
20-25 mph. Higher gusts possible during the afternoon hours in areas
where boundary layer mixing increases due to greater breaks in the
cloud cover. Highs won`t be reaching record levels tomorrow, but
will still be well above average for this time of year with low to
mid 70s in North Central Indiana and the potential for a few
locations to reach the 80 degree mark in far Southwest and Southern
Indiana. Best forcing for ascent and moisture advection is northwest
of the region so most areas should remain dry. Best chance for a
stray shower is in the northern and western portions of the forecast
area later in the afternoon and evening. Better chances for rain
arrive later tomorrow night, with more information for that in the
Long Term Discussion below.
&&
.Long Term...(Thursday night through Wednesday)
Issued at 308 PM EDT Wed Oct 25 2023
* Main transition of the fall season to occur within long term
* Potential for heavy rainfall this weekend
* Much colder mid-next week...widespread hard freeze likely
Thursday Night and Friday...
Central Indiana`s proximity within the warm sector of open wave
surface low pressure crossing the Great Lakes into southeastern
Canada will be enhanced by robust south-southwesterly breezes to at
least 15-25 mph...focused around the periphery of seasonably strong
surface high pressure over the carolinas. Southwesterly flow
continuing through the mid levels will boost precipitable water to
over 1.25 inches by late Friday...although lack of organized forcing
should only produce thickening clouds and a few mainly light
showers.
The passing low`s trailing cold front...elongated Friday evening
from eastern Ontario to the southern Plains...will approach and
possibly enter at least the northwestern corner of the region...
before slowing its advance through the weekend. Unseasonably high
temperatures will range from lows in the low to mid-60s to highs in
the mid- to upper 70s. Corresponding 153-year record highs for the
Indianapolis area are 62F (currently in jeopardy) and 83F.
Saturday through Tuesday...
The majority of the long term will then turn to a pattern regime
change to unseasonably chilly conditions as a highly amplified ridge
along the Pacific coast through Alaska allows the polar low to shift
to near Hudson Bay...with a corresponding conveyor of Canadian high
pressure plunging southward through North America. The transition
for the Midwest will, however, be gradual this weekend...with the
surface high advancing quickly from Montana to the southern High
Plains...while the downstream frontal boundary and corresponding
gradient slows, if not stalls somewhere between the CWA and Ohio
Valley. This set-up will present at least 2-3 periods with the
potential for periods of .much-needed. rain within the Saturday-
early Monday timeframe, with the potential for event totals
exceeding 1.00 inch along/south of I-70. Rainfall could be further
enhanced by the entrainment of any remnant tropical moisture from
Mexico...with this potential refined in future updates.
The very broad Canadian high should then advance eastward across the
Mississippi Valley...finally pushing the once-slowed frontal
boundary and surrounding unsettled weather east of the region around
the Monday timeframe. The long term`s final period should find the
large dome over the central Plains...with corresponding local
minimums in both 1000-500 thickness (530 dm) and H850 temperatures
(negative 8 Celsius) along the region`s northern tier around the
Tuesday timeframe. Dry and mainly clear conditions amid lighter
northwesterly breezes should oversee several mornings with low
temperatures in the mid to upper 20s. The normal max/min at
Indianapolis through the long term is 60/41.
&&
.Aviation...(00Z TAF Issuance)
Issued at 734 PM EDT Wed Oct 25 2023
Impacts:
- Southerly wind gusts over 20 knots after 15z Thursday
- A few sprinkles possible this evening and chances of
showers after 00z Friday
Discussion:
Gusty southerly winds Thursday afternoon will be the main hindrance
to aviation as the terminals reside in between high pressure, over
the southeastern states, and quasi-stationary fronts, over the
northern Great Lakes and Missouri Valley. This has resulted in a
fairly tight low pressure gradient. Moisture advecting northward in
this regime as been mostly at the mid and higher levels, per ACARs
and BUFKIT soundings with only a few intermittent sprinkles occurring
over the Wabash Valley.
Flying conditions will be predominately VFR with some in MVFR
possible in showers, mainly at KLAF and KHUF, Thursday night.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...MK
Short Term...CM
Long Term...AGM
Aviation...MK