Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Louisville Kentucky
107 PM EDT Sat Mar 28 2015
..updated aviation and forecast discussions...
issued at 1200 PM EDT Sat Mar 28 2015
Mostly clear skies and cold temperatures on tap for this afternoon.
Light north winds will tend to diminish towards evening as a high
pressure ridge approaches. Any scattered early afternoon flat fair
weather cumulus over the Bluegrass region will dissipate by mid to
late afternoon. Expect one more cold night before temperatures begin
to slowly moderate beginning Sunday.
Short term (now through sunday)...
issued at 300 am EDT Sat Mar 28 2015
The Ohio River valley will be positioned under amplified northwest flow
aloft today and most of tonight on the back side of a sharp trough.
Meanwhile, cold Canadian high pressure will settle over the area.
This will bring mostly sunny and dry conditions, although we will
have to endure high temperatures some 15 to 20 degrees below normal
today. This will leave the Mercury only topping out around 40 in the
NE and in the mid 40s SW.
Expect some upper clouds in our west today, however our east should
be clear and this will allow for dry air to mix down with dew points
possibly as low as 0-5 above in spots. The afternoon mix down may
allow for even colder temperatures by dawn on Sunday as the drier
low levels allow for faster cooling and lower temperature floor.
Also, the surface high settling over our east and good radiational
cooling conditions will exist. As a result, have lowered expected
min temps in the upper teens and low 20s east. Elsewhere, expect low
and mid 20s. Some upper clouds and a slight wind increase toward
dawn may keep temps from bottoming out everywhere. If everything
happens perfectly, record lows at fft (18, 1982) and Lex (17, 1964)
could come into jeopardy.
Progressive upper ridging dominates for the first half of Sunday,
meanwhile surface high pressure will be scooting off to the east.
The resultant pressure gradient will bring a steady southerly wind
back to the area with a few gusts up around 25 mph. We'll see
increasing clouds through the day, however good sunshine early and
the southerly flow will resultant in a nice warm up back toward (but
still short of) the normal mark. 1000-850 mb thickness increases
support a 12-15 degree warmup across the area which will support low
50s north and northeast, with temps around 60 in our far SW. Most
other spots should be in the mid and upper 50s. Will watch for
another dry air mix down in our southeastern County Warning Area on Sunday
afternoon, however cloud cover may play a role in limiting this
Did continue to mention the chance for some shower mainly north of
I-64 late Sunday afternoon ahead of the next system embedded in the
northwest flow aloft. The arrival should be late enough that early day
outdoor activities won't be affected.
Since hard freezes are occurring right now and again tonight, any
outdoor plants should be covered or protected.
Record cold maxes for saturday:
Mar. 28 forecast
sdf 41 (1916) 44
Lex 37 (1947) 40
bwg 39 (1899) 46
Long term (sunday night through friday)...
issued at 305 am EDT Sat Mar 28 2015
A weakening frontal boundary will move through the region Sunday
night, bringing a good chance for light rains that should end early
Monday morning. Sref guidance for amounts are around a tenth of an
inch or less, and this is in line with the consensus of the other
models. Another front moves through the region Tuesday, but it looks
to be moisture starved, so have no mentionable pops at this point.
Wednesday, the GFS brings a shortwave trough across the region with
enough moisture for some precip. However, the Euro has this feature
farther southwest and the Gem has the feature aloft but no precip.
Will carry a slight chance pop for now, with some chance for
thunder. The models come into better agreement on precip chances for
Wednesday night and Thursday, as additional disturbances cross the
region. The action is punctuated by a cold front crossing either
Thursday night or Friday.
Temperatures will start off near normal Monday, then go above
Tuesday through Thursday. Friday's highs will depend on the exact
timing of that cold frontal passage, so for now have leaned closer
Aviation (18z taf update)...
issued at 105 PM EDT Sat Mar 28 2015
Clear skies are expected through at least dawn Sunday. High clouds
will increase during the afternoon hours with VFR conditions
expected through the taf period.
At sdf mid-level clouds will thicken between 20z and 00z Monday,
with even a possibility of some sprinkles or light rain developing
by 00z, but ceilings will stay VFR.
Light north winds will become variable this evening and light
southerly by dawn. Winds will increase by late morning to south
southwesterly at around 10kt. Winds will farther increase by early
to mid afternoon Sunday to 12 to 15kt with some higher gusts as a