Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 11/01/23
Area Forecast Discussion
National Weather Service Indianapolis IN
1020 PM EDT Tue Oct 31 2023
.Forecast Update...
Issued at 1020 PM EDT Tue Oct 31 2023
* Snow showers diminishing into the overnight hours
* Another anomalously cold day tomorrow
The forecast for this evening remains on track with isolated to
scattered snow showers pushing through Central Indiana. Current
satellite and radar imagery show a small area of low pressure near
the MI/IN border with snow showers and clouds rotating about it.
Nice set set up late this halloween night for early season snow
showers in Indiana with a trough axis and upper vort max pushing
through the region providing lift for these showers. While moisture
is limited, IND ACARS sounding shows a saturated layer just over 1
km thick within the DGZ. A quasi low level sting jet on the
southwest side of the aforementioned surface low has resulted in 0-
1km unidirectional shear of 27 kts and 0-3km shear of 31 kts
according to the latest 02z IND ACARS sounding. With steep low level
lapse rates, a saturated DGZ, sufficient wind shear, and very cold
air advecting in, a few convective snow showers have been able to
form across the Southern Great Lakes region. While little to no snow
accumulations are expected, the strongest showers have been able to
produce wind gusts to 30 mph and brief periods of low visibility. So
keep an eye out for them if out on the roads tonight. Expect snow
showers and flurries to diminish within the next few hours as much
colder and drier air filters in.
This anomalously cold pattern has also led to one of the top 3
coldest Halloweens on record for the region, with the low of 25 this
morning being the 2nd coldest low temperature on record for October
31st for Indianapolis. Lows tonight will plummet back into the 20s
across the entire region once again with clearing skies by morning.
Another cold day is expected Wednesday as well with highs remaining
in the lower to mid 40s. High pressure centered just south of the
region will result in west to northwest flow through Indiana keeping
the anomalously cold airmass in place for one more day before a
warming trend begins and persists through the weekend.
&&
.Short Term...(This evening through Wednesday)
Issued at 219 PM EDT Tue Oct 31 2023
* Gusty winds into the evening hours
* Scattered snow showers into early evening, mainly north
* Continued cold
Rest of This Afternoon into Early Evening...
A cold front will continue to march east across the area and will
bring clouds as well as low chances for some light rain/snow,
especially east.
Colder air aloft moving in behind the front will steepen lapse rates
and will create a favorable environment for some scattered snow
showers to develop. Forcing from an upper trough will aid in
snow shower creation. Will continue chance PoPs north and slight
chance to dry south.
Mixing plus a decent pressure gradient will keep blustery conditions
going, along with some gusts around 30 mph.
Mid Evening through Overnight...
Lapse rates will ease tonight, diminishing the snow shower threat.
Will gradually lower PoPs through midnight. A few lake effect snow
showers or flurries may impact far northern portions of the area, so
will keep a mention into the early overnight there.
Otherwise, some decrease in clouds will occur, especially west as
high pressure begins to work in overnight.
Temperatures will once again fall into the 20s for lows.
Wednesday...
High pressure will build in during the day. Flow from Lake Michigan
will be disrupted by the high, so clouds from the Lake will
dissipate during the day. By afternoon, most areas will be sunny to
mostly sunny.
Winds will be lower with the high moving in, but temperatures will
remain cold. Highs will only reach the lower to middle 40s.
&&
.Long Term...(Wednesday night through Tuesday)
Issued at 219 PM EDT Tue Oct 31 2023
Wednesday Night Through Friday.
Generally dry conditions expected through the first half of the long
term period with wet weather arriving late this weekend into early
next week. Flow will gradually become more zonal Wednesday night
into Thursday which will end the advection of moisture from Lake
Michigan and combined with the upper level forcing moving to the
east will allow for conditions to dry out. The only other bigger
weather impacts will be occasional wind gusts to 25 mph Thursday
with modest mixing up to around 900mb and relatively tight surface
pressure gradients. Wind gusts during the overnight hours should
taper down with a weak surface inversion but low level wind shear
will be a concern for aviation partners with the strong winds above
the inversion layer. Temperatures will then begin a warming trend
that is expected to continue into the early weekend.
Saturday Through Tuesday.
Dry conditions will continue into Friday with zonal flow aloft
gradually becoming more southwesterly ahead of a weak system that
will move through the Great Lakes Region during the early weekend.
As is typically this far out, both deterministic and ensemble model
solutions have a fairly wide spread on the timing of the system but
have good agreement in the impacts being primarily north of the
forecast area initially across the Great Lakes with with some light
rain along the front afterwards. A more robust upper level trough
and associated cold front then looks likely early next week with
highest confidence around the Tuesday timeframe with moderate to
locally heavy rain being the primary impact.
&&
.Aviation...(00Z TAF Issuance)
Issued at 729 PM EDT Tue Oct 31 2023
Impacts:
* Wind gusts up to around 25kt this evening diminishing overnight
* Scattered snow showers mainly along and north of I-70 this evening
* Some chance for MVFR ceilings overnight
Discussion:
A small yet potent area of low pressure associated with the upper
level trough axis swinging through is responsible for the breezy
conditions and snow showers this evening. Latest IND ACARS sounding
shows steep lapse rates in the lowest 3km resulting in stronger
winds within the low level jet to continue to mix down to the
surface. Gusts upwards of 25 kts will continue over the next few
hours as the low level jet remains over the region. Expect gusts to
begin to diminish after around 6z but winds may remain elevated at
or above 10 kts through the overnight hours.
Radar imagery continues to show scattered snow showers in the
region, mainly along and north of the I-70 corridor. Expect snow
showers to continue through the next 2-4 hours then begin to
diminish and push east around 06z. Brief periods of MVFR cigs and
vis possible at KLAF and potentially KIND in the strongest snow
showers.
Improving conditions and lighter winds expected Wednesday as high
pressure slides just south of the region. Clouds are forecast to
break up Wednesday morning with mainly clear conditions likely by
tomorrow evening. Winds will diminish and slowly veer back to the
WSW tomorrow afternoon and evening as well.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...CM
Short Term...50
Long Term...White
Aviation...CM