Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 312146
AFDLMK

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

...Updated Aviation Discussion...

.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 (21Z TAF Update)...
Updated at 546 PM EDT Fri Oct 31 2014

Breaks in the overcast and higher ceilings have developed over
southern Indiana and northern Kentucky recently as we sit between
clouds ejecting northeastward ahead of an upper level disturbance
over Indiana, and clouds streaming southward behind the
disturbance.  The prevailing low-end VFR conditions should last long
enough at SDF to go ahead and AMD the TAF for the next couple of
hours before MVFR cigs move back in.


Updated at 125 PM EDT Fri Oct 31 2014

Conditions beginning to worsen at the TAF sites as a second upper
level disturbance over northern Indiana is beginning to influence
our weather. This system is forcing a cold front across the region
at this time, with winds picking up at SDF and coming from the NW at
BWG. The best chance for precip will be at SDF/LEX, so have tempo
groups there for MVFR at those sites, and cannot rule out IFR
conditions either. Rain will switch over to snow at some point this
evening at both sites, and will have to watch for bands of moderate
snow to develop this evening. Winds should stay gusty from the
north/northwest through the night as a tight pressure gradient
remains across the region.

&&

.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.

&&

$$

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




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