Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Jackson Kentucky
153 PM EDT Friday may 22 2015

issued at 630 am EDT Friday may 22 2015

Based on the latest observation and web camera images...have beefed up the
fog further in the grids adding dense to the valleys and some
ridges. As a result...also issued an Special Weather Statement for patchy dense fog that
now runs through 9:30 am. Sent out an updated set of zones with a
pre first period for the fog. Finally...for the grids...tweaked
the next several hours T/dew point grids per the latest observation and trends.
The grids have been sent to the ndfd and web servers.


Short term...(today through saturday)
issued at 350 am EDT Friday may 22 2015

07z surface analysis shows high pressure settling into the middle
Mississippi and Tennessee valleys with low pressure to the north
and southeast. This has helped to clear the skies through eastern
Kentucky as a narrow band of lower clouds is holding on near the
Virginia border. Patchy fog has developed in the valleys early
this morning in the wake of the clearing and left over ground
moisture. In addition...a few patches of dense fog are noted in
the Cumberland Valley and also on some of the ridges. Will monitor
this via the observation and web cams for a possible Special Weather Statement or npw this
morning. At a minimum...the patches of dense fog will be
highlighted in the morning portion of the forthcoming severe weather potential statement.
Readings are rather chilly this morning...mainly in the lower and
middle 40s while dewpoints are generally a degree or so lower than
dry bulb temperatures amid light northwest winds.

The models are in good agreement aloft with a departing trough to
the northeast early today followed by rising heights as a ridge
develops over the southeast part of the nation. A band of weak
middle level energy will lift through Kentucky and into the Ohio
Valley Friday night during this transition...before the ridge
sharpens over east Kentucky on Saturday. Given the model agreement
have favored the nam12 and hrrr for weather details due to their
higher resolution.

Sensible weather will feature a pleasant 48 hours and beyond...
once this morning/S valley fog...locally dense...breaks up by 10
am. Temperatures will be a bit warmer each day with a decent Ridge
Valley temperature split expected tonight...but milder for most
places than early this morning. High clouds will move in later
today and continue to build on Saturday as a mostly dry front
settles into the area. A stray shower cannot be ruled out tonight
to the northeast of the area as that front initially approaches
before the ridge aloft builds significantly over the County Warning Area by
Saturday morning.

Used the shortblend as a starting point for the T/dew point and wind
grids through today before following to the superblend. Did make
some moderate terrain based changes to the low temperatures
tonight. As for probability of precipitation...kept them minimal through the
line with MOS guidance.

Long term...(saturday night through thursday)
issued at 332 am EDT Friday may 22 2015

The models are in pretty good agreement to begin the extended
period...with a ridge of high pressure bringing warm and dry weather
to the area Saturday night through late in the day on Monday. It
looks as if the Ohio and Tennessee Valley regions will be firmly
entrenched in the warm sector of an approaching middle latitude
cyclone. The warm weather would be in response to persistent
southerly winds south of a strong northward moving warm front.
Should the models hold true...we would see the ridge begin to break
down Monday afternoon and a large storm system
approaches from the west. The first precipitation is forecast to
move into the area by early Monday morning as warm moist air off the
Gulf of Mexico begins to interact with what looks like a pre frontal
trough. The precipitation will gradually increase in coverage Monday
and Monday night as the front inches toward the area. The model data
suggests that there will be a good chance of rain from Monday night
through early Thursday the aforementioned cold front
moves slowly across the region...and perhaps even stalls out for a
time. The Memorial Day Holiday at this time looks like it will be
warm with only a small chance of rain across the area.

Temperatures during the extended will likely be well above normal
for the time of year...due to persistent southerly flow and
subsidence warming associated with the ridge of high pressure
mentioned earlier in this discussion. Highs are forecast to top out
in the lower 80s through middle week...with overnight lows in the


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 153 PM EDT Friday may 22 2015

A few diurnal clouds have popped up across the region...but should
pose little to no threat to taf sites. Otherwise...high pressure
ridging is in control with light and variable winds...and plenty
of sunshine. As we head into the night...lingering moisture could
lead to some patchy valley fog...especially in areas near bodies
of water. There is some uncertainty concerning if this fog will
make it into the taf sites...but confidence was not high enough to
remove from previous tafs...especially given the amount of fog
that occurred the night before. Expect a similar set up during
the day tomorrow to that of today...with light winds and the
possibility of a few diurnal middle level clouds. The only caveat
will be some high clouds moving into the region from the east as


Jkl watches/warnings/advisories...


short term...greif
long term...Arkansas

National Weather Service Glossary of Abbreviations