Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/06/24

Area Forecast Discussion

National Weather Service Louisville KY

 950 PM EST Mon Feb 5 2024

.KEY MESSAGES...

* Dry and above normal temperatures through Thursday

* Rain chances return Thursday Night through the weekend but there
  will be gaps in the precipitation

&&

.UPDATE...
Issued at 950 PM EST Mon Feb 5 2024

Stratus shield over Ohio and eastern Indiana is making substantially
better headway to the south and west since sunset. Will beef up the
cloud forecast a bit, bit impacts to the public side are minimal.
Also worth noting that the TAFs are being amended for earlier
arrival of clouds (now around 07Z), with a MVFR ceiling below
2000 feet.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 300 PM EST Mon Feb 5 2024

It is a beautiful day across the region with temperatures in the 50s
and 60s this afternoon under sunny skies. Latest sfc dewpoint obs
suggest ample dry air mixdown so far today, with readings in the
teens and 20s across the northern half of the CWA and readings in
the lower 30s across southern KY. Light-to-moderate NE winds have
continued throughout the day thanks to the low-level pressure
gradient oriented between high pressure over the north central
Plains and low pressure over south Florida.

Tonight, dry conditions will continue as the mid- and upper-level
ridge extending from the southern Plains northeastward into the
Great Lakes region creeps toward our region from the west. The
primary forecast challenge in the near-to-short term is determining
the fate of low-level moisture currently producing a stratus layer
over portions of eastern IN and northwest OH.

So far this afternoon, the clouds have remained northeast of a line
from Muncie, IN to Dayton, OH, likely scattering out thanks to
ongoing mixing of very dry air from above and below what is a very
thin layer of moisture. However, once we lose the sunshine this
evening, hi-res guidance tries to bring the clouds into much of the
CWA via low-level NE flow. There are some doubtful signs relating to
this solution. First, recent SDF ACARS soundings show considerably
drier air in the sfc-850 mb layer than indicated in HRRR/NAM
soundings. Second, there has been a trend all morning with hi-res
guidance trying to delay the time of arrival of clouds late tonight
and tomorrow morning, with global models continually showing little
to no cloud cover overnight. Taking these things into consideration,
will lean closer to the cloud-free solutions with this forecast,
while indicating the potential for stratus late tonight and tomorrow
morning, especially across southern IN.

Fewer clouds tonight would lead to colder low temperatures, although
a persistent light NE wind may keep temperatures from crashing
outside of sheltered valleys. The current forecast calls for lows
tonight in the upper 20s and lower 30s, though this would need to be
adjusted upward if there is more cloud cover.

For the day on Tuesday, ridging aloft and high pressure at the
surface will continue to move closer to the region as the low
pressure near Florida moves out into the North Atlantic.
Temperatures should be a few degrees cooler than today thanks to a
combination of upper clouds moving across the region as well as
advection of cooler low-level air from the NE tonight into tomorrow
morning. Just like with lows tonight, temperatures will be
controlled by the existence (or lack thereof) of any low stratus,
with cloudier hi-res solutions around 10 degrees colder than
"sunnier" global models. Will lean toward the globals, advertising
highs in the low-to-mid 50s, with warmest readings across south
central KY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 310 PM EST Mon Feb 5 2024

The axis of an amplified upper ridge over the eastern half of the
CONUS will be located over the Ohio Valley on Wednesday with a deep
broad trough over the western US. This will once again keep us dry
and unseasonably warm with temperatures warming into the mid/upper
50s and even near 60 across the KY/TN boarder.

The aforementioned western trough will begin to shift eastward late
Wednesday into Thursday as a closed upper low and associated sfc low
form over the Dakotas Wednesday night and move into the Upper
Midwest late Thursday into Friday. As this system takes shape,
pressure gradient over the Ohio Valley will tighten and increase
winds out of the south between 15-20 mph and gust of 25 to near 30
mph for Thursday afternoon. Warm moist air from the Gulf of Mexico
will advect northward into the Ohio Valley thanks to this strong
southerly flow. More clouds are expected on Thursday and rain
chances start to increase Thu night into early Fri morning as an
850mb LLJ works in over the area during this time frame. Late
Thursday night into Friday morning continues to be our best and
highest chance of rain showers across the Ohio Valley. While the
chance of a rumble of thunder is low, it is not zero. There could be
enough lift from the low-level jet but there is just not a lot of
instability in the model soundings. Highs Thu and Fri will be about
15-20 degrees above seasonal normals in the upper 50s to low 60s.

Rain showers look to diminish some Friday afternoon but could see
another round of showers/isolated thunder Friday night into Saturday
as the sfc cold front associated with the storm system coming out of
the northern Plains works across the Great Lakes. Sfc pressure
gradient will remain tight and gusty winds are still likely on
Friday. Wind gusts of 25-30 mph are still possible in the afternoon.

Models generally remain in good agreement, bringing a lull in
precipitation activity during the day on Saturday as a weak
shortwave ridging develops over the Ohio Valley. Expect the start of
the weekend to be mainly dry and still unseasonably warm with highs
near 60. For Sunday and beyond we`ve seen a swap in solutions from
the deterministic models. The 00z run of both the ECMWF and Canadian
had the next system suppressed mainly south while the same run of
the GFS was bring this system through the Ohio Valley with increased
rain chances. With the 12z package, the deterministic models show an
embedded shortwave trough work into the Ohio Valley Sunday into
Monday. The GFS is faster and drier while both the EURO/Canadian now
bring a deeper trough into the Mid Mississippi Valley and develops a
sfc low and works it across Indiana into Michigan. For now, will keep
PoPs from the NBM for Sunday into Monday as we wait for more
agreement for days 6 and 7 as we all know things will likely change
between now and then.

&&

.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 630 PM EST Mon Feb 5 2024

Main potential impact in this TAF set is whether or not the stratus
over NW Ohio makes its way this far south and west. Shallow layer of
moisture is slowly being advected in our direction, but the key word
here is slowly. Progs of 925mb condensation pressure deficit suggest
we could start to cloud up in LEX as early as 06-08Z, while tracking
the leading edge of the cloud shield on satellite wouldn`t get it
there until 14Z. Confidence is low given the significant discrepancy
in timing and extent of dry air to overcome, so will keep coverage
SCT and split the difference on timing, keeping some low cloud in
from just before daybreak until late morning. Best chance of a MVFR
ceiling would be in SDF or LEX. Even less confident in HNB and
didn`t mention it at all in BWG.

Otherwise expect VFR conditions with N-NE winds just below 10 kt
through the period.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

UPDATE...RAS
SHORT TERM...CSG
LONG TERM...BTN
AVIATION...RAS