Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 261439
AFDJKL

Area Forecast Discussion
National Weather Service Jackson KY
1039 AM EDT TUE JUL 26 2016

.UPDATE...
Issued at 1039 AM EDT TUE JUL 26 2016

Fog and stratus are slow to clear in areas that saw heavy
rainfall yesterday, but this is now beginning to erode. Pushed an
update along that tweaked near term temps, dewpoints and sky cover
based on latest observations but made no other changes at this
point.

Current thoughts are that convection will develop and propagate
in a similar pattern today as it did yesterday with scattered
storms firing first up north near the stationary frontal boundary
and along our higher terrain. By late afternoon, outflows will
drive scattered convection just about anywhere. It is interesting
to note the lack of convection in the hi res models today across
our area and that does lower confidence some. A few spots such as
Carr Creek Lake and Somerset Airport received nearly 2 inches of
rainfall in yesterday`s storms and locally heavy rainfall will
again be a threat with any storms that develop today as PWATS are
analyzed to be around 2 inches. Gusty outflow winds will also be
a hazard. All of these threats are handled well in the HWO and web
products.

UPDATE Issued at 648 AM EDT TUE JUL 26 2016

High clouds have slowly diminished across a good portion of the
CWA overnight, with llvl moisture leading to decent fog coverage
across much of the area. We have seen visibilities as low as 1/4
mile or less in some of the deeper valleys for the last few
hours. As such, went ahead and sent out a SPS to cover the
potential for patchy dense fog through the morning commute. As
sun continues to rise this morning, expect fog to slowly lift and
dissipate...though this could take a bit longer in the deeper
valleys in the far southeast.

Did a refresh of the near term forecast for temps, dew points,
and winds, making sure they lined up with current observations.
All changes have been published and sent to NDFD/web. No updates
to the forecast package are needed at this time.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 403 AM EDT TUE JUL 26 2016

Abundant moisture with a general subsidence in the low levels and
light winds, have come together to create decent fog development
across much of eastern Ky early this morning. Fog should slowly lift
through about 12z, as daytime heating ensues. A stationary boundary
elongated from east to west across much of the state will remain in
place through the period. This will continue to be the epicenter for
convective development, especially during peak heating in the
afternoon/early evening. Since the boundary will remain across the
northern portions of our CWA, expect best coverage of storms to be
located in this area, especially at initiation. Much like yesterday,
storms will then propagate southward, with outflow boundaries
helping to initiate convection further downstream across the CWA.
That being said, the warm, moist, and unstable atmosphere will
create an environment in which initiation of convection may occur
anywhere, and possibly not even within the confines of afternoon
peak heating. Hence, went ahead and kept scattered pops in across
the CWA through the short term period, tapering to isolated in many
locations during the overnight hours tonight.

Winds in the mid and upper levels today will be similar to
yesterday, if not just slightly higher in magnitude. This will
continue to promote generally slow moving storms, though any
development along outflow boundaries may speed up storm motion. The
main concern with any of these storms will be gusty winds, in
addition to torrential rainfall and some isolated instances of flash
flooding. Flash flooding or urban flooding will especially be of
concern for any locations that see training storms, or received
heavy rains yesterday as well.

Temperatures will continue to be warm despite ongoing cloud cover,
with abundant moisture lending itself to high humidity values as
well. While highs will be in the upper 80s both today and
tomorrow, heat index values will feel closer to the mid and upper
90s, nearing 100 degrees in a few locations.

.LONG TERM...(Wednesday night through Monday)
Issued at 400 AM EDT TUE JUL 26 2016

Cyclonic flow will remain in place through the end of the week and
potentially into the first half of the weekend, as troughing from
the northern Plains into the Appalachians resides in between the
Bermuda high and Great Basin to Four Corners ridging centered west
of the Continental Divide. The subsequent lack of any substantial
meridional component to the upper flow will thus keep a frontal
boundary anchored near the Ohio Valley, keeping eastern Kentucky
firmly in the warm sector.

Phasing of a northward propagating Mississippi Valley wave with
approaching energy out of the upper Midwest and Great Lakes will
take place early Thursday. This will back the upper flow pattern
southwesterly and bring an even greater surge of moisture
northeastward toward the region. Precipitable water values will
approach 2.25 inches or greater as warm cloud processes ensue,
making for very efficient rain producing showers and
thunderstorms conducive of generating significant rainfall
amounts. Omega profiles suggest robust deep layer lift, further
aided by the development of a surface low/wave. Uncertainty at
this time is mainly confined to the exact timing and placement of
the aforementioned features. Overall consensus at this juncture
would be for heavier rainfall to begin Thursday morning and last
into mid-late afternoon, with the most favored locations locally
being along and north of the Hal Rogers Parkway. Will likely need
to hoist a flash flood watch at some point once timing and
placement become better defined. Storm motions look reasonable
ahead of the approaching synoptic features, but training could
certainly be an issue further exacerbating flooding concerns as
storm motions parallel the surface and upper waves.

Scattered storms continue to look like a good bet for the end of the
week into early this weekend as renewed troughing develops in the
wake of Thursday`s system complete with the presence of a continued
warm and moist airmass. Southwestern U.S. ridging looks to then
start building northeast into the Great Plains Sunday into next
week, perhaps bringing a spell of drier weather to eastern Kentucky.
Will keep isolated storm chances in the forecast through early next
week at this time given uncertainty in eastward expansion of deep
layer subsidence. Following seasonable high temperatures generally
in the mid 80s (although lower 80s may be more realistic Thursday pending
timing/location of the heavier rainfall) with lows in the upper
60s through much of the week, this may spell a possible return to
above average temperatures headed into the start of August.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 655 AM EDT TUE JUL 26 2016

Heavy rains yesterday led to abundant low level moisture and fog
development overnight. Several TAF sites are continuing to report
1/4 mile of vis or less, with all sites currently at airport mins
due to either low cigs or vis. Fog will slowly lift and dissipate
through 15Z this morning. A frontal boundary will stall out along
the northern half of the state through the TAF period, leading to
scattered convection today, mainly this afternoon and evening.
Kept with mention of VCTS at all sites during this time, since
confidence is still low on the exact timing and placement of any
of developing storms. Winds should remain generally light and
variable at all sites during the TAF period, but those sites that
happen to see a storm today could experience some brief gusty
winds. With llvl moisture expected to remain in place, fog will
likely develop once again tonight. However, to what extent is
still somewhat undetermined. Forecasted higher than model guidance
mainly because of uncertainties in exact impacts this far out.
Obviously any site that receives rain (especially heavy rain)
today will be at a higher risk for seeing dense fog tonight.

&&

.JKL Watches/Warnings/Advisories...
None.
&&

$$

UPDATE...JWM/ABE
SHORT TERM...JMW
LONG TERM...GUSEMAN
AVIATION...JMW



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