Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/17/22
Area Forecast Discussion
National Weather Service Indianapolis IN
926 PM EST Fri Dec 16 2022
.Forecast Update...
Issued at 926 PM EST Fri Dec 16 2022
Enough justification per radar and ob trends to continue slight
chance of light snow showers over northern sections through the
early overnight as the upper low spins over northern Wisconsin. Any
sort of other support for snow showers was lacking and moisture was
rather shallow confined to 2-5K per BUFKIT and ACARS soundings.
Thus, not expecting any accumulation with mostly no more than
flurries. Cold advection will allow temperatures to bottom out in
the lower 20s despite the solid stratocu.
&&
.Short Term...(This evening through Saturday)
Issued at 245 PM EST Fri Dec 16 2022
- Cloudy and cold with Flurries or snow showers this evening and
Saturday Afternoon
Surface analysis early this afternoon shows deep low pressure in
place over MN/WI. This deep low was providing broad cyclonic flow
across the region, including Indiana, reaching as far south as the
Tennessee River Valley. GOES16 shows extensive cloud coverage across
Central Indiana. A weak upper wave was found over IL and was pushing
east into Indiana. Radar shows some light snow showers entering NW
Indiana associated with this wave. Temps were holding in the mid
30s. Aloft, large and broad cyclonic flow was in place, again
centered over WI/MN, impacting much of the midwest and plains.
Tonight...
Cloudy skies are expected to remain across Central Indiana tonight.
Models suggest the upper short wave will depart east early this
evening and effectively take the best forcing along with it.
Furthermore the loss of any minimal surface instability due to
heating also points to a diminishing trend. Forecast soundings show
a bit more dry air within the lower levels as the wave departs.
Still however soundings suggest a thin area of low level saturation
indicative of trapped cold air advection strato-cu beneath an
inversion aloft. HRRR also suggests some scattered flurry/snow
shower coverage tonight, but again they trend toward dry overnight.
Overall any accumulation will be minimal to a dusting. Thus will
include some early evening pops for some light snow showers as the
forcing departs but trend to just an isolated flurry overnight.
Expect cloudy skies given the cold air advection and continued
cyclonic flow, with lows in the lower 20s.
Saturday...
The broad and deep upper low over WI is expected to push across the
Great Lakes on Saturday. This will keep cyclonic upper flow in place
across Indiana and our region. While the models suggest dry mid
levels, a weak short wave within the flow once again is suggested to
push across Central Indiana during the afternoon. Once again
forecast soundings show steep lapse rates favorable for convective
snow shower development. Thus will continue with cloudy skies on
Saturday and focus on small pops for these minor snow showers or
flurries during the afternoon hours. Again, any accumulation will be
minimal to a dusting. Given ongoing cold air advection and expected
cloud cover will look for only a minimal rise in temps with highs in
the upper 20s to near 30.
&&
.Long Term...(Saturday night through Friday)
Issued at 245 PM EST Fri Dec 16 2022
* Continued cold with an Arctic blast arriving late in the period.
* Mostly dry late weekend through early next week.
* Potential for at least light snowfall mid to late week, possibly
impactful.
The weekend will come to an end with the large upper low that has
brought significant weather impacts to much of the central CONUS and
much cooler conditions to central Indiana centered over the eastern
Great Lakes and rapidly departing.
In its wake, modest ridging at the surface and aloft will bring
continued cool and dry weather to the area through the start of the
work week. A pair of upper level disturbances, one large upper low
well to our north and another weak wave near or just to our south,
will pass through the region late Monday into Tuesday. While a few
flurries cannot be ruled out with these disturbances, their forcing
look to be much too far away for measurable precipitation, and the
most likely scenario at this point is an increase in cloud cover as
the midlevels moisten up but the lower levels remain quite dry. Will
keep flurries out for now given the magnitude of the dry low level
air.
A strong Arctic high will be poised to push toward the region mid to
late week, whether it leads or trails the coming weather maker, with
high confidence that significantly below normal temperatures can be
expected, including highs in the teens or perhaps lower by week`s
end, and lows in the single digits and perhaps sub zero depending on
snowfall. Dangerous wind chills well below zero appear likely late
in the week as the holiday weekend approaches.
Various models are struggling mightily to converge on a coherent
solution to the mid to late week pattern. In broader strokes, a
significant upper level system looks to drop into the central or
eastern CONUS mid to late week and induce strong cyclogenesis
somewhere in the eastern half of the country. This will have the
potential to produce a snowstorm, perhaps significant, for some part
of the country that may include central Indiana - this certainly
bears close monitoring given the busy pre-holiday travel timeframe.
Blend probabilistic guidance shows a high likelihood of at least
minor accumulating snowfalls in the Wednesday to Friday timeframe,
with low but still significant probabilities of impactful snow
accumulations. This will obviously depend upon which of the numerous
and varied model scenarios ends up verifying, but again, this will
bear close monitoring and scrutiny over the next several days.
Anyone with holiday travel plans should keep a close eye on the
forecast in the coming days.
&&
.Aviation...(00Z TAF Issuance)
Issued at 613 PM EST Fri Dec 16 2022
Impacts:
- Borderline VFR and MVFR ceilings through the TAF period
- Flurries or light snow showers mainly before 11z and after 18z
- Winds 230-250 degrees with gusts to near 25 knots, especially
after 18z Saturday.
Discussion:
Cyclonic flow with embedded impulses moving around the base of the
Great Lakes upper low will bring VFR and MVFR flying conditions
with flurries or light snow showers possible tonight and Saturday
afternoon. It will also be gusty with southwest winds gusting to
near 25 knots.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...MK
Short Term...Puma
Long Term...Nield
Aviation...MK
Area Forecast Discussion
National Weather Service Louisville KY
820 PM EST Fri Dec 16 2022
...Forecast Update...
.Forecast Update...
Issued at 819 PM EST Fri Dec 16 2022
Main forecast update was to remove snow/rain shower wording and
throw in small flurry chances for the next several hours. Regional
radars show very light echos but surface obs under those echoes
remain dry. AMDAR and model soundings reveal steep lower level lapse
rates but dry air near the surface and only very shallow moisture
near the top of the boundary layer. In this type of environment,
think it will be hard to squeeze out anything more than a few
sprinkles or festive flurries as the light precipitation
evaporates/sublimates before reaching the ground. Rest of forecast
remains on track.
&&
.Short Term...(This evening through Saturday)
Issued at 315 PM EST Fri Dec 16 2022
=======================================
Near Term Now through 800 PM EST
Impacts: Gusty winds and snow showers
Confidence: Medium-High
=======================================
Cyclonic flow continues across the Ohio Valley this afternoon.
Moisture has been a bit more limited than forecast and skies have
remained mostly sunny across much of Kentucky. Clouds, thus far,
have been limited to southern Indiana. Temperatures were generally
in the lower 40s across southern Indiana and northern Kentucky.
South of the BG/WK Parkways, temperatures were in the mid 40s. Given
the good mixing, gusty winds have been the main sensible weather
impact this afternoon. Sustained winds of 15-20 mph with occasional
gusts of 30-35 mph have been reported.
For the remainder of the afternoon and into the evening hours, cloud
cover will attempt to develop a bit more south with time. Some
scattered snow flurries will be possible under the clouds in
southern Indiana. The best chances of snow flurries look to be
confined to areas north of the Ohio River and I-64. After sunset,
look for temperatures to fall into the mid 30s.
=======================================
Tonight 800 PM to 800 AM EST
Impacts: Snow showers/flurries north
Confidence: Medium-High
=======================================
As we move into the evening hours, model progs show a bit more
moisture streaming into the region from the west/northwest. Current
thinking is that much of the cloud cover will remain north of the
line from Hartford to Richmond, KY. Subtle forcing due to a
passing perturbation may result in some snow showers/flurries.
Moisture isn`t all that great and deep into the DGZ. Highest risk
of snow showers/flurries would be mainly along and north of I-64,
but some scattered flurries may develop as far south as the BG/WK
Parkway corridor. Again, moisture does not reach that far into the
DGZ, so snow shower/flurry intensity doesn`t look to be all that
great. However, can`t rule out a few places getting a roof/deck
duster. Upper level perturbation will move east of the region after
midnight, and the snow flurry activity should diminish in the wee
hours. Lows overnight will be cold with low-mid 20s in most
locations.
=======================================
Saturday 800 AM to 800 PM EST
Impacts: Scattered Flurries
Confidence: Medium-High
=======================================
Cyclonic flow is expected to continue across the region. Model
cross sections show a bit more low-level moisture trapped below an
increasing temperature inversion, so partly to mostly cloudy skies
are expected. Another weak perturbation looks to move through
during the day and may kick up a few snow flurries across the
region. Highs on the day will range from 35-40 degree.
.Long Term...(Saturday night through Friday)
Issued at 330 PM EST Fri Dec 16 2022
...BITTERLY COLD TEMPERATURES EXPECTED TO ARRIVE LATE NEXT WEEK...
...POTENTIAL FOR IMPACTFUL WINTRY WEATHER LATE NEXT WEEK
INCREASING...
Key Messages:
- Seasonably cold and mainly dry through Midweek
- Bitterly cold air expected to arrive around Thu (12/22)
- Increasing probability for impactful wintry weather as arctic air
arrives. Negatively impacting Holiday travel late week
- Bitter cold continues into the weekend into the Christmas Holiday
Discussion: Closed upper low that has been impacting the Upper
Midwest the past several days will accelerate eastward across the
Great Lakes and towards the Northeast US by Monday. Another vort
lobe embedded in the upper flow will push through central IN and the
Ohio Valley at the start of the period Saturday night. Model
soundings show a very shallow saturated layer around 800mb but
extending into the lower part of the DGZ. We will continue flurries
into the first part of Saturday night before clearing out as we go
into Sunday.
Upper level ridging along with sfc high pressure will build in over
the OH/TN Valleys for Sunday and Monday. This will provide us with
dry and quiet weather to to start the week. Temperatures will be
slightly below normal with lows near 20 both Sunday and Monday
morning and highs on Sunday in the mid 30s with upper 30s/low 40s on
Monday.
Split flow aloft Mon night into Tues will push a shortwave trough
across the Great Lakes in the northern stream. While in the
southern flow, a weak system moves along the Gulf Coast. Models
remain in disagreement with the Canadian/EURO still not phasing the
energy north to south keeping our area dry while the GFS has a
slight chance of precipitation, mainly over our southern counties
along the KY/TN border. Decided to go with clouds and a chance of
some light flurries but confidence is low and wouldn`t be surprised
if the trend in the GFS turns towards the Canadian/Euro
deterministic models.
We will remain dry for Wednesday as the upper flow becomes more
zonal and a strong Canadian high drops in over the Ohio Valley.
Colder air will advect in with highs Wednesday ranging from 40 along
and south of the Pkwys with mid/upper 30s to the north into southern
IN.
There continues to be high confidence and agreement in the
deterministic models of a deepening trough developing over the
eastern half of the US for the end of the week and into the holiday
weekend. This will allow arctic air to surge as far south as the
Gulf Coast and Florida with bitterly cold weather over the Ohio
Valley. While there is agreement on anomalously cold air arriving
there remains vast disagreement on timing of the cold and the
potential wintry weather impacts for Thursday into Friday.
Canadian/EURO ensembles continue to develop a sfc low over the Great
Lakes during the day Thursday which would put the Ohio Valley in a
warm sector to start before the temperatures plummet behind the cold
front. While the GFS is faster with the cold air arrival and
develops light wintry precipitation along the cold front. While
confidence remains low on the exact setup for the end of the week,
there is some growing confidence in the probability of minor impacts
for the end of the week. The latest probabilistic winter storm
severity index (PWSSI) continues to show a 20-30 percent probability
of minor impacts. There also remains an above normal chance at
seeing a White Christmas.
Winds will also be very gusty (20-25 mph) as this system moves
through and with temperatures falling into the single digits and
teens Thursday night into Friday, wind chills could be as cold as 10
to 15 below.
&&
.Aviation...(00Z TAF Issuance)
Issued at 603 PM EST Fri Dec 16 2022
VFR conditions expected through the forecast period. Recent AMDAR
and model sounding data suggest that snow shower chances have
decreased across the region. This is due to shallow moisture near
the top of the boundary layer and dry near-surface air. Think at
most there might be flurries, but they should not have an impact on
visibilities. Cigs will be around 5-6kft for most of the night, but
may scatter out toward dawn before returning by mid/late morning.
Winds will pick up once again tomorrow afternoon with gusts around
20kts.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...DM
Short Term...MJ
Long Term...BTN
Aviation...DM