Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 050806
Area Forecast Discussion
National Weather Service Louisville KY
306 AM EST Mon Dec 5 2016
.Short Term (Now through Tuesday)...
Issued at 245 AM EST Mon Dec 5 2016
...Widespread Rain Tonight and Tuesday...
An early morning analysis showed surface high pressure across the
mid-Mississippi River Valley while aloft, water vapor imagery and
500 mb heights continued to show an active southern stream with a
closed low over north central Mexico. Locally, an extensive stratus
deck encompasses the entire area with temperatures in the upper 30s
to middle 40s.
For today, expect a cloudy start with the low level moisture trapped
within an inversion between 800-900 mb. Mid-level drying will work
down on this layer and perhaps some peaks of sun will break out this
afternoon with the help of westerly winds bringing in slightly drier
air. Plan on highs right around normal for early December - mid 40s
to near 50.
The aforementioned closed low over Mexico will quickly lift toward
middle TN and northern AL late tonight and Tuesday while a surface
low tracks from the Gulf Coast toward eastern KY. Increasing deep
layer moisture and PWATs up to 1.25 inches combined with strong
forcing for ascent will break out rain across TN late this
afternoon, then spread north/northeast through the evening and
overnight hours across all of central Kentucky and southern Indiana.
An elevated thunderstorm remains possible across south-central
Kentucky. The highest chances for widespread steady rain will be
mainly after midnight through around noon Tuesday. Rainfall totals
during this period are expected to be between 3/4 and 1 inch.
Rain should end southwest to northeast Tuesday afternoon as the
shortwave tracks through the mid-Atlantic states.
.Long Term (Tuesday Night through Sunday)...
Issued at 245 PM EST Sun Dec 4 2016
The main weather highlight in the long term is the unseasonable cold
expected to arrive late in the work week.
The upper levels will feature generally zonal flow Tuesday night and
Wednesday and overall dry and near normal conditions are expected.
On Wednesday night, the large scale trough across the Upper Midwest
will work southeast toward the area. The 05.00z deterministic and
ensemble guidance came into much better agreement with the forecast
Wednesday night and Thursday with the strong cold front passage
coming through mainly dry. A few models still depict light QPF late
Wednesday night and/or Thursday morning which based on temperatures
would be light rain to snow showers or flurries. If light snow
showers were to develop, a minor dusting may be possible but overall
little impacts are expected. Given the trend toward a drier
forecast, lowered PoPs Wednesday night and Thursday morning to 20-30
percent. Plan on lows in the upper 20s to lower 30s.
Diurnal rise on Thursday will be minimal with strong cold air
advection throughout the day. It looks to be a blustery day with
temperatures holding in the low to mid 30s, or even falling some in
the afternoon across southern Indiana. Wind gusts 15 to 20 mph in
the afternoon will make it feel more like the teens to low 20s for
the afternoon and evening commute.
Strong cold Canadian high pressure will dominate the weather pattern
over the lower Ohio Valley Thursday night through Saturday. Expect
an unseasonable cold period. Highs Friday are forecast to be in the
upper 20s to lower 30s while Saturday will see some minor
improvement to the upper 30s/near 40. Morning lows each day will be
in the teens.
Late next weekend and early next week forecast guidance shows return
flow on the backside of the surface high interacting with an
approaching shortwave trough. This may bring precipitation back into
the area Sunday through Monday. For now, will side with a model
consensus of rain/snow mix based on temperatures.
.Aviation (06Z TAF Update)...
Issued at 1227 AM EST Mon Dec 5 2016
Low clouds blanket the Ohio Valley and will be slow to clear out as
surface high pressure moving in plus time of day keep mixing
minimal. Ceilings will likely hover around the one thousand foot
mark, varying back and forth between low end MVFR and high end IFR
through the morning hours.
The low clouds are expected to lift and break up by midday,
resulting in cirrus clouds and the TAF period`s best flying
conditions for the afternoon and early evening hours.
Low pressure lifting from Louisiana to Tennessee Monday evening will
bring low ceilings and rain back to central Kentucky.