Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 010136
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
936 PM EDT Fri Oct 31 2014

...Forecast Update...
Issued at 936 PM EDT Fri Oct 31 2014

The forecast is overall in pretty good shape.  High-res models have
backed off a bit on post-midnight snow intensity in the Blue Grass,
but not enough to make substantial changes to the forecast.  We
lowered snowfall accums by a tenth or two.  Also, dropped min temps
a degree.  Tweaked PoPs a bit in accordance with current radar
trends.

Getting lots of great pictures in tweets of this evening`s light
snow on decks, garbage cans, etc., and at local high school football
games.  Fortunately the snow is light enough and the ground warm
enough to prevent problems.  Having said that, though, some slick
spots aren`t out of the question when temps bottom out around dawn,
especially on rural, elevated, lightly traveled surfaces.

.SHORT TERM (Now through Saturday Night)...
Issued at 250 PM EDT Fri Oct 31 2014

...Windy Conditions and Falling Temperatures Expected This Afternoon
and Evening...
...Wintry Mix Likely This Evening Changing to Snow with Minor
Accumulations Possible East of I-65...

Potent upper low, over northern Indiana this hour, will continue
diving southward this afternoon. It will get to central Kentucky
late this evening. As it does so, we should see continue
precipitation chances the next at least 12 hours. Colder air
continues to filter into the region behind now gusty northwest
winds. That should mean our first snowflakes of the season by this
evening for a lot of the region, though our western third of our
forecast area may dry out before that happens.

The main question here is how fast the snow will fall how long it
stays on the ground to account for accumulations. Soil temperatures
continue to be too warm to support light to even moderate snow rates
accumulating. Heavier bands may be able to dump half inch to an inch
over narrow swaths. Still think the main concern would be
visibilities within the heavier snow bands, but fortunately expect
the worst of the conditions to occur during non-rush hour travel
times. Will continue to handle with special weather statements for
now.

As for the cold, the freeze warning for Saturday morning will stay
up for now. Have a little less confidence in freeze conditions
occurring over south Kentucky, but again will maintain the product
for consistency sake with OHX. Temperatures will not warm much
Saturday under skies that should be clearing from west to east
through the day. Have max readings going up to around 40 over the
Bluegrass and the mid to upper 40s in the west. High pressure moving
in from the west late will mean lows Sunday morning in the 20s
areawide. Issued an earlier upgrade to a freeze warning for this
period, and this freeze should end the growing season and
consequently the need for further freeze/frost products.

.LONG TERM (Sunday through Friday)...
Issued at 244 PM EDT Fri Oct 31 2014

After a bitter cold start to Sunday, the long term forecast story
will feature slowly moderating temperatures with the next chance of
rain coming mid-week associated with another frontal passage.

Upper level ridging will move east over the Ohio River valley Sunday
as the anomalous upper trough begins to exit off the east coast. At
the surface, cool Canadian high pressure is expected to be directly
overhead, providing light winds and full sunshine. Despite this, the
unseasonably cold air mass will persist, keeping high temperatures
only in the lower to middle 40s across the east, around 50 degrees
along the I-65 corridor, and lower 50s in the west.

As a new upper level shortwave trough digs across the southwest US,
broad southwesterly flow will develop downstream across the central
Plains and into the Ohio River valley. 850 mb temperatures rise from
+2C on 18z Sunday to +11C on 18z Monday, so highs Monday should top
out in the upper 50s to lower 60s.

31.12z model guidance continues to show a low pressure system
developing across the northern Plains early next week and then
lifting into southern Canada. This looks to drive a cold front
across the area beginning on Tuesday afternoon. Moisture return from
the Gulf will aid in shower development as the front crosses Tuesday
night. Still some timing differences between various deterministic
models but a model consensus of 40-60 percent chances look good for
Tuesday night and Wednesday, dropping to 20-30 percent as the front
pushes out of the area. In the wake of this system, another shot of
cooler air drops south, though at this time doesn`t look to be too
unseasonably cold. Highs in the middle 50s to lower 60s and
overnight temperatures in the 30s.

&&

.AVIATION (00Z TAF Update)...
Updated at 732 PM EDT Fri Oct 31 2014

A band of snow, sleet, and rain will move through SDF before the
beginning of this TAF period, between 2330Z and 00Z. This band of
precipitation will likely take visibilities MVFR (maybe IFR for a
few minutes) and may also take ceilings briefly below 2000 feet.

Otherwise...an upper low will drift southward across central
Kentucky this evening, bringing low clouds and a variety of
precipitation along with it.  At SDF the most likely time for the
most wintry precip and most reduced cigs/vsbys appears to be before
midnight as a north-south oriented band moves southward out of
central Indiana.  At LEX, the most likely time for the most negative
impact appears to be between midnight and dawn as another slug of
moisture comes in from eastern Indiana and western Ohio.  BWG will
be on the westernmost edge of this area of inclement weather and
should only see some MVFR ceilings and passing showers.

Winds will continue to be gusty out of the northwest tonight, and
NNW on Saturday.

High pressure entering from the west and the departure of the upper
low will lead to gradually improving conditions tomorrow.  While a
few lingering patches of light snow will be possible at LEX early in
the morning, overall it should be a dry day with low ceilings slowly
lifting to VFR by afternoon.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...FREEZE WARNING from 5 AM EDT /4 AM CDT/ to 10 AM EDT /9 AM CDT/
     Saturday FOR KYZ023>028-053-061>064-070>076-081.

     FREEZE WARNING from 11 PM EDT /10 PM CDT/ Saturday to 9 AM EST
     /8 AM CST/ Sunday FOR KYZ023>043-045>049-053>057-061>067-
     070>078-081-082.

IN...FREEZE WARNING from 5 AM EDT /4 AM CDT/ to 10 AM EDT /9 AM CDT/
     Saturday FOR INZ076>079-083-084-089>092.

     FREEZE WARNING from 11 PM EDT /10 PM CDT/ Saturday to 9 AM EST
     /8 AM CST/ Sunday FOR INZ076>079-083-084-089>092.

&&

$$

Update.........13
Short Term.....RJS
Long Term......ZBT
Aviation.......13





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