Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 271723
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
123 PM EDT Fri Mar 27 2015

...Forecast Update...
Issued at 115 PM EDT Fri Mar 27 2015

Updated the forecast as a decent area of snow showers/flurries has
developed over central Indiana and looks to move south into our
area.  The moisture will be moving into a warmer environment so
think that our area will mostly see a mix of very light rain
showers/snow showers vs mainly light snow showers/flurries that
exists to our north.  The mix may be experienced as far south as the
KY/TN border as afternoon soundings indicate moisture in the
dendritic growth zone allowing multiple ice crystals aloft, and some
of those crystals may survive to the sfc despite lower 40s sfc
temps. Some diurnal enhancement of low level clouds should increase
precip coverage so felt comfortable enough going with 20% chance of
precip area wide.  However, still think precip amounts will only be
a trace in many locations with the occasional 0.01 of inch possible.

We should be nearing our high temps soon in the low to mid 40s with
temps remaining steady or falling slightly for the rest of the
afternoon as clouds and CAA increase.

Issued at 940 AM EDT Fri Mar 27 2015

Overall the current forecast is in good shape.  Light precip chances
associated with a sharp upper trough passing through the region this
afternoon remain a challenge for today.  Light snow was occurring
over southern IL this morning due to forcing from the trough.
Models have not done a very good job picking up on this in QPF
fields.  Thus, relied on high-res model RH fields to come up with
the forecast for this afternoon.  Still think a 20% chance for very
light precip mainly in the form of rain will exist over central KY.
Areas along and north of the I-64 corridor may have temp profiles
cold enough for a few snowflakes or snow grains to mix in with the
rain this afternoon.  Precip amounts will generally be trace amounts
to 0.01 inch at best.   High temps still look to reach the low to
mid 40s this afternoon.

.SHORT TERM (Now through Saturday)...
Issued at 300 AM EDT Fri Mar 27 2015

A deep upper trough will cross the region today. Water vapor shows
this feature nicely. Forecast soundings still show some sharper
lapse rates as this feature crosses us, as well as a brief period of
ice crystal growth. Timing for this crossing looks to be during peak
heating, so the chance for snow mixing in with rain looks to be
limited. Precipitable water is pretty low with this system as well,
so the chance for measurable precipitation consequently is low.

As for temperatures today, we should see the 40s for most locations.
Skies should clear out quickly as the trough axis shifts to our
east. As northwest winds pour in colder air, most sites should see a
hard freeze by daybreak Saturday, with lows in the lower 20s.
Surface high pressure will become centered over the region by the
end of the day Saturday, but despite sunshine highs look to struggle
to reach 40 degrees, near record cold maxes for the day.

Record Cold Maxes for Next Couple of Days:
     Mar. 27   Forecast     Mar. 28   Forecast
     (year)                 (year)
SDF  32 (1947) 44           41 (1916) 42
LEX  29 (1947) 43           37 (1947) 39
BWG  33 (1947) 46           39 (1899) 44

.LONG TERM (Saturday Night through Thursday)...
Issued at 300 PM EDT Fri Mar 27 2015

The surface high pressure of Canadian origin responsible for
unseasonably cold temperatures Saturday will move east of the
Commonwealth by Sunday afternoon. This, and a vigorous low moving
north of Lake Superior late in the day, will bring a decent
southwesterly return flow Sunday afternoon, resulting in a distinct
warmup after a chilly morning. After lows in the mid 20s,
temperatures Sunday afternoon will rebound well into the 50s, albeit
with increasing afternoon cloudiness.

A cold front will move southeast of the Ohio River Sunday night with just
a chance of some light showers or sprinkles. This front is actually
of Pacific origin, meaning the air behind this boundary will almost
be warmer than the continental air ahead of it.

For the period Monday through Thursday, broad 500mb ridging and warm
temperatures centered over the northern Rockies will push east,
spreading much milder temperatures first towards the Mississippi
River, and then across the Lower Ohio Valley. Normal highs for the
first of April are in the lower to mid 60s. By Tuesday, we should
match or exceed these pretty easily, with highs rising from the
lower to mid 60s on Monday to the lower 70s from Tuesday onwards.
Any light precipitation will end Monday morning with clearing skies.

Expect mostly clear skies and dry weather Monday afternoon through
Wednesday morning. Modified Gulf moisture will begin to return
mid-week, but extended guidance is not in agreement when. Think the
GFS is way overdone in breaking out showers within a warm air
advection regime on Wednesday. Feel that the ECMWF and Canadian are
more on target in holding off a chance of showers until Wednesday
night or Thursday.

A cold frontal passage Thursday evening will bring a good chance of
showers and even some thunder. Distinctly cooler temperatures on tap
for Friday with highs in the 50s.

&&

.AVIATION (12Z TAF Update)...
Issued at 645 AM EDT Fri Mar 27 2015

Have some lower-end VFR vsby`s out there this hour, and may see a
couple hours below especially at BWG. Otherwise, an upper level
disturbance still looks to move into the region this afternoon,
bringing additional cumulus clouds as well as some isolated showers.
Think the best chance is down at KBWG, so have put vicinity wording
in for now this afternoon. Ceilings may briefly go into the MVFR
range as that moisture moves into the other sites as well. Expect
better conditions tonight.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Update.........AMS
Short Term.....RJS
Long Term......EER
Aviation.......RJS




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