Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 041048
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
548 AM EST Tue Mar 4 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Wednesday)...
Issued at 235 AM EST Tue Mar 4 2014
The synoptic pattern this morning features broad WNW upper-level
flow across the Ohio Valley. This flow will slowly transition to a
more zonal pattern by Wednesday, allowing for a slow warming trend
through the short term period.
This forecast will mainly be a temperature forecast, as a strong
ridge of high pressure will keep us precipitation free through the
short term period. The temperature forecast is a bit difficult,
however, given the recent snowpack. Given the snow on the ground
and limited turbulent mixing due to very light surface winds, think
temperatures today will struggle a bit despite the expected
sunshine. Therefore, have gone below most guidance for highs today,
putting them in the low to mid 30s.
Tonight will be another cold night. It appears as they`ll be less
in the way of mid and upper level cloudiness, in addition to light
winds. Therefore, will once again go below guidance for lows, which
puts readings in the teens, perhaps the lower 20s near the TN border.
A slightly warmer airmass will attempt to work in on Wednesday.
Additionally, the surface pressure gradient will be tightening a
bit, helping increase mixing depths a bit when compared to today.
Therefore, think temperatures will be a bit warmer than today`s
expected values, which puts highs in the upper 30s and 40s.
.LONG TERM (Wednesday Night through Monday)...
Issued at 305 AM EST Tue Mar 4 2014
Split flow aloft will dominate much of the period, with the Ohio
Valley remaining largely high and dry between the two storm tracks.
Southern stream system will organize over the Deep South by
Thursday, but precip associated with that storm will remain to our
south and east. A northern stream impulse working its way into the
Great Lakes on Saturday will push a cold front into the Ohio Valley,
and that will be our one legitimate shot at precip. However, there
is still some model disagreement on how much moisture this system
will have to work with. GFS tries to phase the northern and southern
streams, which brings in enough moisture to spit out what is still
modest QPF, while the ECMWF is more moisture-starved. Either way,
the southern stream system hangs back over the TX Panhandle and
eventually closes off, so will favor low chance POPs at this time.
Southern stream closed low will start to lift out of Texas next
Monday, but sensible weather impacts will be delayed beyond the
scope of this forecast.
Temps will remain quite chilly for early March through Thursday
night. Should see a recovery to near climo Friday through Monday,
with Saturday sticking out as the warmest day in spite of the precip
.AVIATION (12Z TAF Update)...
Updated at 548 AM EST Tue Mar 4 2014
VFR conditions will prevail through the valid TAF period. Winds
will remain rather light and variable over the next 24-36 hours as
high pressure remains fixed over the Ohio Valley. The only clouds
to contend with will be some passing high-level cirrus streaming by