Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 252003
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
303 PM EST Wed Feb 25 2015
.SHORT TERM (Now through Thursday Night)...
Issued at 250 PM EST Wed Feb 25 2015
...Light Accumulating Snow Likely for Portions of South Central KY
Winter storm system now organizing over the central Gulf coast, as a
potent shortwave moves along the Arklatex. 88D showing some returns
coming up into southern TN. Forecast models continue to show the
chance for snow as limited to south of the Bluegrass and Western KY
parkways for tonight. After running through forecast QPF and snow
ratios, am barely getting an inch of snow by daybreak Thursday for
our advisory area. As the values are close, will continue to hold
onto the advisory for now, to leave some room for error.
We should get a brief break from snow chances as that first system
departs and our next one comes in from the northwest. Forecast
soundings would call for more of a snow shower type setup, but
moisture is limited and it does not look as squally as a setup we
had a week or two ago with snow showers and stronger winds behind a
front. The best chance would be in the afternoon and continue into
the evening hours. Snows should be light enough for totals of just a
few tenths of an inch, so no need for an advisory at this time.
Temperatures tonight will fall into the low to mid 20s for most
locations, though upper teens are possible across the north.
Thursday highs should get back above freezing closer to the TN
border, whereas mid to upper 20s will rule southern IN and our
northern counties in KY. The warmer temperatures may make for a
brief mix of snow/rain showers down south during the day. Then
Thursday night we crash again as another cold high pressure builds
in from Canada. Lows should range from the single digits to the mid
teens, some 20 degrees below normal.
.LONG TERM (Friday through Wednesday)...
Issued at 300 PM EST Wed Feb 25 2015
Friday through Saturday...
Arctic high pressure will dominate as a 1040+ mb center moves east
from Iowa to Pennsylvania. The weather pattern will be quiet, but
still unseasonably cold. Highs on Friday will struggle to crack 20
along and north of I-64, with double-digit departures from normal
continuing on Saturday. Biggest question is just how well we radiate
on Friday night. GFS is quite bullish while the NAM is the mildest
as it keeps the high center to our north and west. Recent history
has not seen temps drop as dramatically as advertised by the models,
but the NAM seems to be an outlier solution. For now will split the
8-10 degree difference, which will still be enough for single digits
and wind chills just below zero in our north.
Saturday night through Wednesday...
Expect a progressive and active zonal pattern as a series of
disturbances will eject out of a southwestern CONUS trof. Best
chances for precip will be Sunday and Sunday night as one impulse
phases just enough with the northern stream to really tap the Gulf,
and then Tuesday and Tuesday night with another mid-level
disturbance running up and over the top of a flat Gulf of Mexico
ridge. The pattern will be milder, but still below normal as the
Sunday/Sunday night precip will be primarily cold rain, with snow
possibly mixing in, especially at night.
Precip type will again be in question at onset with the second
system early Tuesday. Model forecast soundings and our actual temp
forecast suggest that freezing rain is a possibility. However this
far ahead of time, will keep it rain/snow and make tweaks as needed
later. Temps do recover to near normal during the day on Tuesday,
and should remain warm enough that precip type is not an issue.
.AVIATION (18Z TAF Update)...
Issued at 1210 PM EST Wed Feb 25 2015
Mid and upper clouds will continue to increase through the day ahead
of a couple of weather systems. Winds are faily light at this time,
but will become more northeasterly late this afternoon and then
northerly overnight. The chance for light snow should be along and
south of a BWG/LEX line starting late in the evening. MVFR
conditions should be at each of the sites as the moisture increases,
but the BWG/LEX stand the best chance to get close to IFR, between
midnight and daybreak. Clouds should stick around behind the snow
chance, as low level moisture profiles stay saturated. Could even
have patches of light snow into Thursday, though accumulations, if
any, or would be light.
KY...WINTER WEATHER ADVISORY from 6 PM this evening to 6 AM CST
Thursday FOR KYZ073>078-081-082.