Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 302324
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
624 PM EST Mon Jan 30 2023

...Updated Aviation Discussion...

.Short Term (This evening through Tuesday)...
Issued at 330 PM EST Mon Jan 30 2023

...Wintry Mix Overnight, Impacts to Morning Commute Expected...

Key Messages...

* Wintry Mix expected to begin moving in tonight after 8 PM EST,
  continuing into Tuesday morning

* Sleet/Snow/Freezing Rain accumulations in the overnight hours will
  lead to travel impacts during the Tuesday morning commute

* Highest ice accumulations of 0.1-0.2 inches are expected along and
  south of the WK/BG Parkways, highest snow/sleet accumulations of
  up to one inch are expected along and north of the Parkways

Discussion...

Complex forecast for the short-term period as our next wave of
wintry precip moves through the area tonight into Tuesday morning.
In the mid and upper levels, WSW flow will remain in place across
the region with subtle mid-level energy rippling through during the
overnight period. At the surface, Arctic front will be to our
southeast extending from the Mid-Atlantic down into the Deep South,
with steady northerly flow at the surface causing our temperatures
to steadily decline into Tuesday. By Tuesday morning, expect temps
to range from the lower 20s across southern IN to the lower 30s
across southern KY.

Isentropic lift will increase after 31/00Z tonight with precip
overspreading the area from west to east, although initially expect
the main area of precip to remain across southern IN and north-
central KY. While all precip types will be possible, expect the
predominant p-type to walk a fine line between snow and sleet along
and north of the WK/BG Parkways. Model soundings indicate a subtle
warm nose will be possible between 850-700 mb as surface temps will
be in the 27-32 degree range. Snow and sleet accumulations of up to
one inch will be possible along and north of the WK/BG Parkways
although the presence and strength of the warm nose across the
northern half of the CWA will have a large impact on accums. If the
subtle warm nose pans out, would expect lower snow amounts with
higher sleet accounts but if the mid-levels end up being a degree or
two cooler, higher snow amounts (and less sleet) would be possible.
Also worth noting that some of the hi-res guidance is indicating the
possibility of some banded snow along the I-64 corridor with locally
higher accumulations of 1-2+ inches not out of the realm of
possibilities.

As we move towards the 31/03-06Z time frame, precip will then begin
to intensify across central and south-central KY. Model soundings
indicate the 850mb warm nose will be more pronounced across central
and south-central KY, leading to increased potential for freezing
rain and ice accumulations. P-type will likely start as a cold rain
across southeastern portions of KY as surface temperatures are
expected to be in the mid 30s initially (roughly Scottsville, KY to
Richmond, KY), whereas points northward will be mainly a freezing
rain/rain/sleet mix. As temperatures continue to fall near or below
freezing overnight though, expect the rest of central and south-
central KY (save for the Lake Cumberland region) to transition as
well to the wintry mix of freezing rain, rain, and sleet. Overall,
ice accumulations of 0.1-0.2 inches will be possible along and south
of the WK/BG Parkways, although with surface temperatures hovering
right at/below freezing, slightly warmer surface temps would result
in decreased ice accums with longer periods of plain cold rain.

Main precip shield will then gradually exit from NW to SE between
31/09-15Z as drier air works its way into the mid-levels. The lower-
levels will remain saturated and as we lose saturation into the DGZ
(and therefore ice nucleation in the clouds), drizzle and freezing
drizzle will be possible across the area and could cause additional
very minor ice accums into the afternoon.

.Long Term (Tuesday night through Monday)...
Issued at 250 PM EST Mon Jan 30 2023

==========================================
Synoptic Overview
==========================================

Pattern aloft over the CONUS will remain progressive and wavy with
several perturbations moving through.  Split flow pattern out west
will be noted with a fast northern stream pushing through the
northern US.  In the southern stream, a baroclinic zone will set up
from TX northeastward to the Mid-Atlantic.  This zone will feature
above normal precipitation through the end of the week before the
northern stream pushes south and suppresses the southeast ridge.  For
the Ohio Valley, a few disturbances will affect the region in the
early-mid week time frame followed by drier pattern for the end of
the week and into the weekend.  The few disturbances that move
through our part of the world will feature added complexity due to
low-level thermal profiles which could promote more mixed wintry
precipitation.

==========================================
Meteorological Discussion and
Sensible Weather Impacts
==========================================

Tuesday Night through Thursday Night...

Surface high pressure is forecast to be in the vicinity of Chicago
Tuesday evening but will drift southeast toward Richmond, IN by
Wednesday morning.  Low-level northeast flow will be present over
the region and temperatures should dip into the low-mid 20s over
southern IN and the northern half of KY.  Upper 20s will be found
primarily across southern KY.  A southern stream perturbation will
move northeastward and will push into the TN Plateau overnight.  As
mentioned previously, the trend in the last few days in the
modeling show this wave passing further south of the region than in
previous runs.  The Euro/Canadian are in pretty good agreement here,
though the GFS continues to show its bias of producing very light
QPF over a larger area.  Current thinking is that a wintry mix will
be possible over our southern two tiers of KY counties.  Soundings
suggest freezing rain and sleet here with generally light amounts.
If current trends continue, another Winter Weather Advisory will be
required for this area.  Further north, soundings suggest low-level
stratus and the potential for some light freezing drizzle.  This may
occur as far north as the WK/BG Parkways.  Overall, this threat is a
bit lower in the latest runs, compared to previous ones, but we`ll
continue to watch.

Wednesday should feature a generally cloudy day with temperatures
warming into the mid-upper 30s with a few 40s down near the KY/TN
border area.  Another weak disturbance may affect the region
Wednesday night and into Thursday.  The Euro and GEM are much further
south on today`s runs, while the GFS is a bit further north.  Given
the trends in the models of the northern stream starting to become
more dominant, not overly confident in the GFS solution here.  For
now, will trend PoPs downward slightly to indicate the drier trend
from the Euro/GEM.  Thermal profiles here pretty marginal here, but
temps could be close enough for yet another wintry mix, especially
on the northern edge of the precipitation shield.  Highs Thursday
are expected to top out in the lower 40s.  Lows Thursday night will
be in the low-mid 20s.

Friday through Monday...

By late week, current data trends continue to show drier and calmer
conditions for the area.  The northern stream looks to carve out a
broad trough over the eastern US with high pressure building into
the region from the northwest.  As the weekend wears on, the flow
will likely transition over to a more zonal flow pattern as we head
into early next week.  Highs on Friday in the mid-upper 30s with
lows in the upper teens to lower 20s.  Highs on Saturday will
moderate slightly with highs in the low-mid 40s over southern IN and
northern KY and upper 40s over southern KY.  Highs on Sunday look to
warm into the upper 40s to near 50 with similar readings expected on
Monday.

==========================================
Forecast Confidence
==========================================

Forecast confidence in the first part of the extended (Tuesday night
through Thursday night) remains generally low given the uncertainty
about the track of the system.  Forecast for the Friday-Monday
period is generally medium-high given the good model agreement.

&&

.Aviation (00Z TAF Issuance)
Issued at 620 PM EST Mon Jan 30 2023

A mix of wintry weather set to arrive later this evening will cause
impacts to flight categories through much of tomorrow. Already
seeing IFR/LIFR conditions at HNB/LEX/BWG, and we`ll see conditions
deteriorate at SDF in the next few hours. Ceilings will be on the
border between IFR and LIFR for much of the night, with different
precip types at each terminal. There has been little change from the
previous forecast, with SDF/HNB expected to see mostly snow or
snow/sleet mix. Guidance continues to suggest a brief period of
heavier snow bands possibly impacting SDF between the 03-07z time
frame tonight. BWG and LEX will get a full mix of precip types, but
BWG still appears have the best chances for freezing rain as the
dominant precip type tonight. Ceilings will remain in the IFR range
by tomorrow morning, though some scattering out of the cloud deck
may result in HNB returning to VFR by the afternoon hours.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Winter Weather Advisory until 1 PM EST /noon CST/ Tuesday for
     KYZ023>031-033>043-045>049-053>057-061>067-070>077.

IN...Winter Weather Advisory until 1 PM EST /noon CST/ Tuesday for
     INZ084-089>091.

&&

$$

Short Term...JML
Long Term...MJ
Aviation...CJP


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