Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Jackson Kentucky
414 PM EDT Friday Oct 31 2014

Short term...(this evening through Saturday night)
issued at 413 PM EDT Friday Oct 31 2014

500mb low is currently making its way southward into the Ohio River
valley...with all models agreeing on it/S movement into central Kentucky
around 0z this evening...and exiting to the south of the region
between 6 and 12z. At the surface...a cold front has just swept east
of the state...pulling an area of prefrontal rain out of the County Warning Area
over the next few hours. There will be a Short Gap in the
precipitation...as is currently indicated by the radar...before the
deformation zone of the closed low brings yet another round of
showers to the region late this afternoon and evening. Temperatures
are still on track to drop around or just below freezing between 6
and 12z tonight. However...given the expected borderline freezing
temperatures...and the ongoing rain and snow potential...decided to go
ahead and cancel the freeze advisory. It will be highly unlikely
that we will see any frost form overnight with these conditions.

With temperatures dropping near or below freezing...still expecting rain to
switch to snow overnight...and then transitioning back to rain
during the daytime hours tomorrow. It is likely that the highest
elevations...and areas across the western County Warning Area will drop below
freezing first...so have snow developing in these locations as early
as 0z...with most of the region transitioning to all snow between 06
and 09z. Several things have changed from the previous forecast from
the midnight shift. New model runs brought in a stronger area of
Omega near 12z this morning...signifying the possibility for a
stronger band to move through the region around this time.
Also...the westward image seemed to be catching on to this trend...and
was placing more widespread one inch amounts across much of the
western portion of the County Warning Area...and into lmk and iln/S area. Ended up
increasing quantitative precipitation forecast slightly during the 06 to 12z time frame...and also
upped the snow totals slightly from a dusting to around 0.5 to 1.0
inch. Despite this...still expect what snow that does fall to most
likely melt fairly quickly...especially in the western portion of
the County Warning Area. Given the higher amounts...some of the higher terrain even
in central Kentucky /including here at kjkl/ could see snowfall amounts in
excess of 1 to 2 inches. Given that this is the first snowfall of
the year...and many of these ridges are populated...and that it is
the first of the month...decided to go ahead and add on to the
ongoing advisory...extending it as far west as jkl.

Snow will slowly transition back to rain through middle morning
tomorrow...before the entire system quickly exits to the southeast. Dry air
will slowly work in...with probability of precipitation expected to slowly taper off from
Saturday afternoon to Saturday night. Given such...a strong blast of
cold air is expected to interject into the region. Despite ongoing
cloud cover insulation...cold air advection will be strong enough to overcome...and
temperatures should drop well below freezing. What precipitation is lingering in
the eastern portion of the region will likely Switch Back to a
mixture of rain...freezing rain /which should have very little
impacts/...drizzle...freezing drizzle...and snow. Will keep the
freeze watch out for this time period...but impacts of the weather
should not require any further headlines.

Long term...(sunday through friday)
issued at 345 PM EDT Friday Oct 31 2014

As the dynamic ul system works its way up the Atlantic Seaboard
towards New England...an unseasonably cold air mass is left in its
wake. Sunday morning temperatures are expected to be the coldest of
the season with lows in the middle to upper 20s. Sub-freezing
temperatures are also expected Monday morning. However...as high
pressure builds into our region...temperatures will gradually warm
through mid-week. Southerly to southwesterly winds will help usher
in warmer and more humid air during this period with high
temperatures peaking in the low to middle 60s on Wednesday. A cold
front will push through eastern Kentucky Wednesday
afternoon/evening...but this is where there are discrepancies in the
models...mainly with the interactions between the northern and
southern stream energy. The 00z European model (ecmwf) shows the frontal precipitation
pushing through our County Warning Area between 12z Wednesday and 00z Thursday.
However...the 06z GFS is slower with the fronts mvmt...and shows
precipitation lingering from 18z Wednesday all the way through 00z Friday.
So until models come into better agreement with the frontal
system...decided to be fairly modest with the probability of precipitation and precipitation
amounts. Quiet weather will end the work week as a weak ridge of
high pressure builds over the region.

&&

Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 156 PM EDT Friday Oct 31 2014

Clouds have shown a lowering trend throughout the day today...now
hovering around the 500 to 700 feet IFR range. Given the latest
data...expect these IFR ceilings to stick around through much of the taf
period...perhaps fluctuating slightly up and slightly down into LIFR
throughout the night. The first band of pre-frontal rain is currently
moving eastward and exiting the County Warning Area. Ksjs and kjkl can expect to see
scattered showers for the next hour or so...before a brief break in the
precipitation occurs. This will be short-lived however...as the next batch of
precipitation is currently expanding across central Kentucky. This will be our
main weather system as we head into the night. Expect this rain to
continue to expand as it moves over eastern Kentucky. Then as temperatures drop
overnight...rain is expected to gradually change to snow through Sat
morning...before making the transition back to rain and coming to an
end after the taf period. Tried to best reflect the change- over
times from rain to snow in the tafs...though some slight adjustments
may need to be made as we see how the temperatures react as we head
into the overnight hours...especially for those taf sites that are at
the highest elevations. West-northwest winds should continue through the taf
period...increasing to 5 to 10 knots this evening and overnight.



&&

Jkl watches/warnings/advisories...
freeze watch from Saturday evening through Sunday morning for
kyz044-050>052-058>060-068-069-079-080-083>088-104-106>120.

Winter Weather Advisory from 8 PM this evening to 8 PM EDT
Saturday for kyz088-118.

Winter Weather Advisory from 8 PM this evening to 2 PM EDT
Saturday for kyz085>087-109-110-112-113-115>117-120.

&&

$$

Short term...jmw
long term...jvm
aviation...jmw

National Weather Service Glossary of Abbreviations