JKL issues Area Forecast Discussion (AFD) at Aug 18, 3:20 PM EDT060
FXUS63 KJKL 181920
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
320 PM EDT Sun Aug 18 2024
.KEY MESSAGES...
- Below normal temperatures are expected today through Wednesday
behind a cold front passage today.
- Showers and thunderstorms will remain possible today and
Monday, especially in the afternoon and early evening, with a
drying trend for Tuesday into Wednesday.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 320 PM EDT SUN AUG 18 2024
This afternoon the upper level low and surface low pressure
continues to push across the Great Lakes this afternoon. The upper
level and mid-level trough continues to swing across the Ohio
Valley. This coupled with west and northwest flow and weak but
sufficient low level lapse rates have lead to numerous showers and
isolated thunderstorms (coverage in the 60 percent range). Overall
no big changes made in the grids for the afternoon. The coverage
of showers and storms will decrease through the evening and
overnight. Given this opted to lean toward the short term blends
for tonight in terms of PoPs. There is decent agreement in the
HREF and other guidance on there being some stratus that develops
later tonight and therefore increase clouds toward dawn Monday.
Given the increasing clouds expect more uniform overnight lows in
the lower 60s tonight.
Monday, we will continue to see influence from the exiting mid-
level trough axis as it swings eastward. There is also good signal
for a lingering surface trough that seems to keep showers and
isolated storm activity mainly in the far eastern portions of
Kentucky mainly in the afternoon. There is also notably drier
airmass building southward under the increasing northerly flow.
This as afternoon highs climb into the upper 70s to around 80
degrees. Monday night, the ensemble and deterministic guidance is
in good agreement on an area of high pressure continuing to build
eastward toward the Ohio Valley mainly providing continued
northerly flow and drier air at the surface. However, this will
also lead to clearing skies through the evening and will set the
stage for patchy to areas of fog through the night especially in
the valleys. This northerly flow and high pressure will help to
drive overnight lows into the lowers 50s in most locations, with
HREF showing around a 60 to 90 percent chance of overnight lows
below 55 degrees.
.LONG TERM...(Monday night through Saturday)
Issued at 432 AM EDT SUN AUG 18 2024
This particular long term forecast package is defined by clearer
skies and cooler temperatures than what we have witnessed here in
Eastern Kentucky as of late. This drier and cooler air will advect
into the region via northwesterly/northerly flow throughout the
atmospheric column on the backside of the now-ejected upper level
low pressure system that caused this weekend's active weather. At
the surface, a high pressure system will drop into the Great Lakes
Region from Canada. Together, these features will work to instill
a modified continental polar airmass over the forecast area. This
notion is confirmed by modeled NOAA HYSPLIT back trajectories for
next week, which suggest that this airmass originated in
Northwestern Ontario/Saskatchewan. This particular piece of
forecast guidance also suggests that the air will be subsiding
(sinking) as it approaches the Ohio River Valley, which reaffirms
the notion that this airmass will be dry. As such, skies should be
mostly clear next week, although the potential for some Canadian
wildfire smoke to advect into the air aloft will need to be
monitored closely in the coming days.
In short, fall-like sensible weather should settle into Eastern
Kentucky on Monday night and stick around until Thursday, when the
surface high shifts east and southerly return flow begins to
slowly reintroduce warm, moist air into the column. Under clear
skies, expect well-defined ridge-valley temperature splits and
perhaps the formation of patchy valley fog on Monday, Tuesday, and
Wednesday evenings. In low-lying areas, overnight lows could drop
down into the upper 40s on Tuesday and Wednesday, whereas
ridgetops will see MinTs in the lower 50s. Afternoon highs will be
climatologically cooler than normal for this same time period,
with temperatures staying in the 70s across the entire area on
these dates. By Thursday, a warming trend will emerge, and
afternoon highs will incrementally increase into the 80s and then
perhaps the lower 90s in the Bluegrass by Saturday afternoon. Both
low temperatures and dewpoints will recover into the 60s in this
same time frame, and cloud coverage should subtly increase in
response to these warmer temperatures. Precipitation chances,
however, remain suppressed below 10 percent for the entirety of
this week's forecast. Thus, no hazardous weather is expected at
this point for the Monday night to Saturday timeframe.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 128 PM EDT SUN AUG 18 2024
We are seeing a mix of VFR to even IFR conditions this afternoon
and this wide range it because we are seeing numerous showers and
even some isolated thunderstorms develop this afternoon. Given
this did opt to put in a tempo group to cover the occasional
lowering CIGs and Vis due to this activity. These showers will
decrease in coverage this evening and into the night. We will be
left with a mix of clouds and clearing skies tonight. The HREF or
short term blend of models is showing the potential for lowering
CIGs tonight as we see stratus develop through the night into
Monday morning. There would also be some visibility issues as a
result of what looks to be more of a vertical visibility issue.
Given this went with lower CIGs at most sites later tonight into
Monday morning. These will mix out through the late morning and
VFR to MVFR cigs will be the story. The winds will be out of the
west and northwest generally below 5 knots for much of the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...DJ
LONG TERM...MARCUS
AVIATION...DJ
Source:
JKL issues Area Forecast Discussion (AFD) at Aug 18, 3:20 PM EDT---------------
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