Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/16/22
Area Forecast Discussion
National Weather Service Indianapolis IN
858 PM EST Thu Dec 15 2022
.Forecast Update...
Issued at 857 PM EST Thu Dec 15 2022
Radar trends suggest the light snow showers will be east of
Interstate 65 shortly after 9 pm and east of central Indiana after
10 pm as upper wave around the base of southern Minnesota low ejects
northeast across southern lower Michigan. Meanwhile, IR loop was
showing a few breaks in the stratus were moving into the lower
Wabash Valley, however stratus should mostly stay thick per upstream
IR and moisture trapped beneath a temperature inversion around 4K
feet per HRRR BUFKIT. This should keep temperatures from falling any
lower than the upper 20s overnight.
&&
.Short Term...(This evening through Friday)
Issued at 253 PM EST Thu Dec 15 2022
* Cooler temperatures
* Scattered snow showers and flurries today and tomorrow
* Breezy at times
Rest of Today
Clouds have thickened across the region today, and will likely stick
around through the short term thanks to the cool unstable air mass
overhead. Enough instability may be realized today to generate a few
snow showers or flurries. A vort max rotating around a big closed
low to our north will provide enhanced lift to further aid in precip
generation. Latest ACARS soundings out of IND show generally sub-
freezing temperature profile above 1500 ft. With a fairly dry
surface airmass in place, some of the precip may begin as a few rain
drops. However, temperatures should evaporationally cool to near
freezing which will change precip quickly to snow.
Tonight
Lingering snow showers or flurries will come to an end around
midnight as the vort max lifts northward and instability wanes.
Cloud cover should persist, but a few breaks could open up at times.
Breaks in cloud cover are not currently expected to affect low
temperatures all that much, as winds remain rather brisk during the
overnight around 5-10 kts. Lows in the upper 20s are still in the
forecast due to the robust CAA currently in place.
Friday
Tomorrow may end up being a carbon copy of today, weather-wise. Any
breaks in the stratus deck will quickly fill in, with more snow
showers possible during the late morning and afternoon hours. BUFKIT
soundings show a fairly deep well-mixed layer with some weak
instability. Of the Hi-res models, the HRRR is the most aggressive
regarding instability with 30-50 J/kg CAPE in the lowest 3km of the
atmosphere. While that`s not a lot in normal circumstances, in the
winter it`s something to keep an eye on. Consequently, the HRRR is a
bit more robust with snow shower development.
The deeper mixed layer and instability may be enough to encourage
momentum transfer to the surface after sunrise. Thankfully, the flow
at the top of the PBL isn`t substantial (only around 35 kts within
the 750-850mb layer). Accounting for some momentum loss as it mixes
downward, peak gusts around 25 kts are expected at times. Winds
should die down as the sun begins to set and the atmosphere
stabilizes. Cold temperatures will persist due to the continued CAA,
and highs should top out in the mid-30s.
&&
.Long Term...(Friday night through Thursday)
Issued at 253 PM EST Thu Dec 15 2022
Friday Night Through Saturday.
Occasional flurries and light snow showers will continue Friday
night into Saturday as the aforementioned strong upper level low
pressure system continues to occlude and move into the Great Lakes
region. This slow moving low pressure system will keep a fairly
persistent forecast in place through Saturday with surface flow
generally southwesterly while flow aloft is generally easterly to
somewhat northeasterly.
Areas of weak to moderate vorticity circling around the low will
combine very steep lapse rates near the surface will allow for a
return to flurries and light snow Saturday, especially during the
late morning and early afternoon hours. Flurries will be most
frequent across the northern counties where the upper level forcing
will be stronger.
Sunday Through Tuesday.
The low will finally push away Sunday with zonal to slightly
northwesterly flow aloft during the early work week. Temperatures
will remain near to below normal with the lingering cold air aloft
and lack of southerly surface flow. Another strong upper level
closed low will move through Southern Canada Monday into Tuesday
with the potential for light snow across the area late Tuesday into
Tuesday night. This all will be dependent on the strength of the
upper level low which remains quite uncertain at this time. A
stronger low would lead to stronger northwesterly flow which then
increases the lapse rates and allows for a quick burst of snow.
Wednesday and Thursday.
The pattern will begin to shift going into Wednesday as the next
major weather system approaches, but there remains a significant
amount of uncertainty as to how and when this system will impact the
area. Confidence is increasing that there will be accumulating snow
going into Christmas across portions of the Midwest, but locations,
timing, and amounts remain very uncertain.
There will be a potential for pockets of more significant snow
accumulations, but again it remains very uncertain as to where it
would occur. Models continue to struggle with the development of
this system as it dives into the area from the northwest and how the
late Tuesday system may impact moisture availability. Continue to
monitor the forecast this weekend into early next week as details
begin to become more clear.
&&
.Aviation...(00Z TAF Issuance)
Issued at 532 PM EST Thu Dec 15 2022
Impacts:
- Ceilings will teeter totter in between VFR and MVFR through
the TAF period.
- Scattered light snow showers or flurries possible tonight and
Friday afternoon
- Winds 210-240 degrees 9-13 knots with gusts to 20 plus knots
after 17z
Discussion:
Upper disturbance will lift northeast across the Great Lakes
tonight and more impulses will move northeast across northern
Indiana Saturday afternoon around the base of an upper Wisconsin
low. This will bring fringe VFR and MVFR flying conditions with
visibilities reduced at times in snow showers, mainly Friday
afternoon.
Winds will be southwest and gust to over 20 knots Friday afternoon.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...MK
Short Term...Eckhoff
Long Term...White
Aviation...MK