044
FXUS63 KPAH 161118
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
618 AM CDT Thu May 16 2024

.KEY MESSAGES...

- Shower and thunderstorm chances will increase this afternoon
  into tonight. A few strong to severe thunderstorms are
  possible, with large hail and damaging winds being the primary
  threats.

- Widespread showers and isolated thunderstorms are forecast
  Friday into Saturday. While a strong to severe storm cannot be
  ruled out, locally heavy rain and flash flooding will be the
  primary threats.

- Dry and very warm conditions will return Sunday and Monday.
  The next chance of widespread thunderstorms is forecast
  Tuesday into Wednesday.

&&

.UPDATE...
Issued at 617 AM CDT Thu May 16 2024

Updated Aviation discussion for the 12z TAF issuance.

&&

.DISCUSSION...
Issued at 300 AM CDT Thu May 16 2024

Early this morning...Patchy fog has developed across parts of
the area, with visibility values of generally 1 to 6 SM being
observed. With mid and high cloud cover increasing from the
west, the risk of widespread dense fog looks rather low at this
time. However, locally dense fog could develop near daybreak,
and if this occurs, a Special Weather Statement or even a Dense
Fog Advisory may be needed.

Today through Saturday...A diffuse warm frontal boundary will
lift northward through the region this morning in association
with surface low pressure organizing across the southern Great
Plains. This will allow high temperatures to warm into the upper
70 to lower 80s over much of the area. As an H5 trough
approaches from the west this afternoon, scattered convection
will develop over southern and central MO and move eastward into
the area. The 16/00z HREF mean develops about 500-1000 J/kg of
SBCAPE over the area, along with 30-40 kts of 0-6 km shear.
These parameters will be marginally supportive of strong to
severe convection, and SPC has maintained a marginal risk with
their newest Day 1 Outlook across nearly the entire forecast
area. Hodographs look to be fairly straight, so isolated large
hail and perhaps a few damaging wind gusts will be the main
severe hazards. The convection will decrease in intensity
tonight as H5 flow weakens quickly.

On Friday, the surface low over the southern Plains will move
over the region. This will initiate widespread showers and
thunderstorms, with the potential for several rounds of moderate
to heavy rain for some areas and associated flash flood
potential. See the Hydrology section below for details. SPC has
introduced a Day 2 marginal risk for the areas near the AR/TN
border, but confidence in any severe potential looks is low due
to uncertainty regarding surface-based instability developing.
High temperatures Friday will be confined to the lower to middle
70s due to the the clouds and precipitation.

By Saturday, the surface low will begin to exit to the east,
allowing for a drying trend from west to east during the morning
hours. There will be some clearing of skies in the afternoon,
allow temperatures to warm into the upper 70s to lower 80s.

Sunday through Wednesday...Strong H5 ridging and surface high
pressure centered over the Mid and Deep South will allow for
high temperatures to climb into the middle to upper 80s
beginning Sunday into the first half of next week. A few
locations may even climb into the lower 90s. Dew point
temperatures will still be fairly tolerable in the lower to
middle 60s, but it will certainly be feeling like summertime as
we approach the end of May.

Precipitation chances look to ramp up Tuesday into to
Wednesday, and model guidance has come into better agreement
about another fairly deep neutral to negatively-tilted H5 trough
ejecting into the central Plains. As it stands, surface low
pressure is progged to develop over the southern Plains and move
into the Great Lakes, with convection firing ahead and near the
associated surface cold front. Given the positioning and
antecedent airmass, there could be a severe thunderstorm
potential with this system, but given the nearly one week range,
confidence in this solution is pretty low...but merits
watching.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 617 AM CDT Thu May 16 2024

Scattered low stratus and fog restrictions will quickly mix out
and dissipate by 13-14z. Afterwards, high clouds will thicken
and lower throughout the day, with some FEW-SCT CU decks
developing as well. Numerous to widespread showers and
thunderstorms will move into the region late tonight, mainly
in the 03-09z window, with periods of MVFR vsby restrictions
expected in addition to lighting activity at CGI, PAH, and MVN.

&&

.HYDROLOGY...
Issued at 300 AM CDT Thu May 16 2024

Recent rounds of heavy rain over the last seven days have
resulted in much of the region receiving 100-200% of normal
rainfall for this period, with isolated areas seeing up to 300%
of normal rainfall. With a prolonged period of dryness
stretching back to February, the top 100 cm of soil remains in
the 20th to 50th percentile. Nevertheless, streamflows have
recovered to near average values (between the 25th and 75th
percentile).

The incoming system tonight through Saturday morning could
bring multiple rounds of locally heavy rain, and potentially
some flash flooding. The first round would be from any
thunderstorms that develop tonight, followed by widespread
showers and pockets of heavy rain associated with the surface
low moving through the region Friday into Saturday.

Six hour flash flood guidance is about 2.5-3.5 inches over the
area. The latest WPC QPF has a broad brush of 1-2 inches for the
area, but as we get closer, several CAMs have shown corridors
of 2-4+" of QPF, particularly over southeast MO into western
KY.

The corridor of higher rainfall appears to be in response to a
cold-pool boundary developing over the region from the
convection forecast for today and tonight. If this feature does
materialize, it would act as a focus for training convection
with higher rainfall amounts. PWAT values are forecast to be in
the 75-90th percentile, so efficient warm rain processes are
possible as well.

Since we are still 24-36 hours away from the start of the
heaviest rain, confidence was still too low for a Flood Watch,
but one may be needed with later forecast packages.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.

&&

$$

UPDATE...DWS
DISCUSSION...DWS
AVIATION...DWS
HYDROLOGY...DWS