Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/13/22
Area Forecast Discussion
National Weather Service Louisville KY
951 PM EST Mon Dec 12 2022
.Forecast Update...
Issued at 940 PM EST Mon Dec 12 2022
Current forecast is well on track as ridging at the sfc and aloft
will remain in control overnight. Went a little more optimistic on
the cloud forecast as the cirrus across our north remains scattered,
and the Gulf stratus coming up from western Tennessee should hold
off until closer to daybreak. Still expect a very gradual increase
in cloud cover east of I-65 on Tuesday. Changes to the forecast
aren`t impactful enough to update legacy products but did update hi-
res to reflect hourly trends.
&&
.Short Term...(This evening through Tuesday)
Issued at 300 PM EST Mon Dec 12 2022
Satellite imagery continues to show practically all of KY and
southern IN clear from clouds this afternoon. Overnight, we will
remain under the influence of strong sfc high pressure to our north.
AMDAR and model soundings this afternoon show a strong temperature
inversion at around 900mb while RH cross-section time heights show
plenty of low-level moisture remaining underneath. Visible satellite
imagery shows the remaining low stratus deck to our north and
northeast over northern IN and all of Ohio. Satellite loops shows
that this stratus layer is trying to move back west-southwest in the
anti-cyclonic flow aloft. Went with mostly clear to partly cloudy
skies overnight with lows dropping into the low 30s/upper 20s for
all of southern IN, and most of central KY with the exception of
counties to our west/southwest where clouds associated with the next
storm system will start to move in by early tomorrow morning.
Confidence is low on sky cover for tonight as models have struggled
with the clearing we saw today. If stratus does build back in
tonight, temperatures will be warmer than currently forecasted.
Deep upper-level low over the Intermountain West will continue to
work eastward tonight into tomorrow as upper level ridging builds in
response over the Ohio Valley tonight into tomorrow. This along with
the influence of the strong surface high remaining to our north
tomorrow we will stay dry. Sfc low will deepen and strengthen
tonight into tomorrow over CO/KS/NE. The system will mature and
become stacked with the upper low during the day tomorrow. This
system will draw moisture from the Gulf of Mexico northward and
spread increasing cloud cover over the area from the southwest to
northeast during the day. As the sfc low moves closer to the region,
pressure gradient will tighten increasing the southeasterly over
locations west and along the I-65 corridor during the afternoon with
gusts approaching 15-20 mph. Highs look to be a touch warmer than to
day warming into the mid/upper 50s across the southern half of
central KY with low 50s and a few upper 40s across southern IN,
north-central KY and and the Bluegrass.
.Long Term...(Tuesday night through Monday)
Issued at 320 PM EST Mon Dec 12 2022
...Widespread Showers on Wednesday with Possible Localized, Minor
Flooding in Southern Kentucky...
Synopsis...Amplified longwave trough and embedded upper low will be
moving from the Front Range to the Upper Mississippi Valley by
midweek imposing broad cyclonic circulation and negative height
anomalies over most of the Conterminous US. Then, a transient split
flow pattern will follow behind the slow upper low ejection through
the Northeast US. Although there is still model ambiguities with the
large-scale pattern heading into next week, most solutions depict a
southern-stream shortwave trough moving along the central US and
towards the lower Ohio Valley while an amplifying northern-stream
trough enters through the Pacific Northwest.
Model Evaluation/Confidence...Synoptic model consensus through
Friday has improved with the latest global deterministic runs. The
ECMWF and CMC models have trended towards the GFS in having
representing a slower and stronger upper low as this one translates
from the Upper Mississippi Valley to the Northeast. The lack of
confidence resides now on the amplitude and speed of shortwaves
embedded in the broader cyclonic circulation as the CMC and ECMWF
have a faster and less amplified solution than GFS. Ultimately, this
could impact the timing, intensity, and type of precipitation for
next week. As for the QPF amounts this coming event, there is fairly
low model spread as most runs have areawide precip. totals between 1-
2 inches with the highest totals still along southern Kentucky.
However, GFS has been very aggressive with storm total QPF between 2-
3 inches which at the moment is considered as outliers.
Wednesday - Wed Night...Previous reasoning has changed little with
just small adjustments made to the QPF totals. Heaviest
precipitation still expected in two different intervals as the
occluded surface low pressure system meanders over the north-central
US. First wave of heavy showers and isolated thunderstorms will
manifest approximately Wed/6-18Z in conjugation with lifting and
high moisture transport of the +50-kt LLJ. Convection should be
elevated given the stout low-level inversion which in combination
with low MUCAPE and poor mid-level lapse rates could be enough for
thunder mention but very conditional for any severe wind gust. The
CSU ML algorithm keeps advertising a very low threat of strong to
marginally severe wind gusts, but any wet downdraft would have to
overcome the DCIN related to the inversion. The second wave of heavy
showers is forecast to move around Thu/0-9Z ahead of the cold front.
It seems that the LLJ will be taking its time to depart through the
east, so will keep mentioning training convective elements and
continuous moisture transport that could maximize storm residence
time and rain rates over fixed locations. As a result, expect a risk
of localized, minor flooding along south-central Kentucky where WPC
has also highlighted a Slight risk of excessive rainfall. In
addition, the Lake Cumberland area will be the most sensible to any
flooding threat given the overlap of the highest QPF with the lowest
FFG.
Thursday...Breezy and cold conditions will settle in behind the
front. Even though a low chance of rain is probable for the
easternmost side of the forecast area, dry weather will be spreading
across central kentucky and southern Indiana throughout the day.
Friday - Saturday...Model ensemble from the GFS, ECMWF, and
especially CMC continue showing a mix of cold rain and wet snow
showers during this timeframe associated with cellular, low-topped
convection. There will also be some background synoptic lifting
provided by shortwave energy rotating around the departing upper low
in combination with near-surface destabilization as the 0-1 km lapse
rates steepen. QPF should be confined to less than a tenth of an
inch. Overall, low confidence on the timing and intensity of the
showers at the moment.
Sunday...Cold by the end of the weekend with breeze conditions but
otherwise dry conditions and some clearing in the afternoon.
Monday...The approaching southern-stream shortwave trough might
bring a cold front to the region with enhanced changes of a wintry
mix. As stated above, a lack of confidence inhibits timing and p-
type details for now.
&&
.Aviation...(00Z TAF Issuance)
Issued at 630 PM EST Mon Dec 12 2022
Light E-NE winds and sct cirrus expected overnight. Clouds thicken
on Tuesday as a warm advection regime gets established. Modest
isentropic lift in a layer of Gulf moisture will allow for stratus
ceilings to drop into MVFR for a few hrs in the morning. HNB will be
a close call from late morning onward but for now will keep it just
barely VFR. Quite a bit of dry air to overcome farther east, so the
lower cloud deck will be solidly VFR by the time it builds into SDF
and might not even make it to LEX. Winds will veer around to E-SE
in the afternoon, but only in BWG are we expecting any gusts, with a
modest 15 kt mentioned in the TAFs.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...RAS
Short Term...BTN
Long Term...ALL
Aviation...RAS