Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 281739
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
139 PM EDT Thu Aug 28 2014
...Updated Aviation Discussion...
Issued at 941 AM EDT Thu Aug 28 2014
Have updated the forecast for this afternoon to include scattered
thunderstorm mention across the south and west and isolated across
the north and east. With plenty of moisture to work with today and
plentiful boundaries in and around the forecast area, shouldn`t take
much to fire up convection once again. Look for a similar situation
to yesterday afternoon/evening but with the focus across
south-central KY. Expect strong to possibly damaging winds and heavy
to torrential rain.
.SHORT TERM (Now through Friday)...
Issued at 245 AM EDT Thu Aug 28 2014
Typical summertime conditions are expected through the short term
period. Aloft the region will remain on the northwestern side of a
500 mb ridge through Friday. At the surface a weak front will
continue to slowly sink southward towards the KY/TN border this
morning and eventually stall out along or just south of this border.
This front will then begin to lift back northward as a warm front
late tonight through Friday.
We will start out with some patchy fog this morning, particularly in
normal fog prone locations and in areas that saw rain yesterday
afternoon and evening. This will dissipate shortly after sunrise.
With the moist and unstable airmass remaining in place isolated to
widely scattered storms are expected to develop once again this
afternoon. These storms look to fire near the front, so the best
chance will be across southern and western portions of the forecast
area. A few stronger storms could be possible with strong winds
being the main threat, similar to yesterday. Any storms will
dissipate near sunset. Friday will again see afternoon storm
development. However, the main area of concern for Friday will be
southern Indiana and north central KY along the warm front.
Temperatures will remain around or just above seasonal normals.
Highs will be in the upper 80s to lower 90s with lows mainly in the
upper 60s to lower 70s. The Bluegrass region may be just a bit
cooler tonight in the mid 60s as slightly lower dewpoint air filters
in behind the front.
.LONG TERM (Friday Night through Wednesday)...
Issued at 315 AM EDT Thu Aug 28 2014
High pressure along the U.S. east coast will combine with increasing
southwesterly winds aloft to bring us back to a period of above
normal rain chances, perhaps bringing us close to all-time record
total rainfall for the month of August at our climate sites. KBWG,
currently at fourth all-time August, needs another 1.24" to reach
that level, whereas KLEX, currently third, would need 1.98". KSDF is
farther back in the list, currently in 8th. A little less than an
inch will get them in the Top 5. A trough to our west will serve as
the focus for storms during the day Saturday. Will have a little
higher chances west of I-65.
Small scale disturbances moving through the southwest flow will
determine how widespread the coverage is beyond that period, from
Saturday night through Sunday night. Have gone into the likely range
based on precipitable water values and the likelihood of these
disturbances along the front. Temperatures should be well above
normal Saturday, with continued muggy conditions. Sunday looks to be
a little cooler with the better rain chances.
As we start the new work week, a more focused upper trough will move
in from the Central Plains. It may stay far enough away during the
day Monday to keep us more with scattered airmass thunderstorms that
day. By Tuesday the 12Z Euro had the front stalling east to west
across our region, which would mean trouble for possible flooding
concerns. The new Euro looks fairly similar. The new GFS stalled the
front just to our north for Tuesday, whereas the GEM pushes the
front to the south. Certainly something to watch given our
antecedent rainfalls for August.
For temperatures the rest of the period, will keep them above
normal, but trend back some for midweek, owing to the chance the
front could be stalled over the region keeping readings down.
.AVIATION (18Z TAF Update)...
Issued at 130 PM EDT Thu Aug 28 2014
Convection is already beginning to develop across portions of
southwestern KY and this activity is expected to increase in
coverage and intensity over the next few hours. Given the isolated
to scattered nature of the storms expected (much like yesterday),
have introduced VCTS into the BWG TAF through the remainder of the
afternoon and will update for approaching storms as necessary. This
convection is anticipated to stay south and west of the SDF and LEX
terminals, although not completely out of the question for some
vicinity activity to pop-up. However, chances in and around those
two terminals appear to be lower and confidence in direct impacts is
Winds are generally out of the NE this afternoon and are expected to
become variable and light or calm in the overnight period at all
three sites. Light fog could once again develop by the pre-dawn
hours across the region with BWG having the best chances if rain
falls in the area. For now, have gone with low-end MVFR and will
wait to see how close precip falls around the terminal. LEX should
also see MVFR, regardless if rain doesn`t fall in that area. SDF is
expected to either teeter MVFR/VFR or maintain VFR conditions unless
rain dictates otherwise.
For tomorrow, winds will become primarily southerly as warm, moist
air advects into the region in front of a large-scale system
approaching the Ohio Valley over the holiday weekend. Another
afternoon CU field is expected to develop by Friday afternoon.