Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
1200 am CST Monday Dec 22 2014
for 06z aviation.
Southwest flow aloft combined with a rather deep low level layer
of isentropic lift will keep skies cloudy until Christmas. This
isentropic lift was strong enough to produce some areas of drizzle
this evening. The precipitation was very light and not measuring...but
certainly helping thicken and lower the clouds. Actually decreased
measurable probability of precipitation overnight...slightly bumping it eastward. But did
expand the mention of drizzle to all places but far northwest.
Additionally...the low clouds and drizzle will combine to drop
visibilities in spots to 1 mile or less. Added this mention into
the severe weather potential statement and forecast overnight. Otherwise...with the cloud
cover...temperatures will not fall too much overnight and raised
lows a few degrees.
The latest model runs are still indicating a severe thunderstorm
threat Tuesday and Tuesday night. More on that in a few hours.
06z taf discussion.
Over the next 24 hours...we will be in the slightly odd situation
of having largely steady state conditions of IFR or LIFR. Computer
models continue to depict a saturated low level air mass...with
ceilings expected to remain within a couple/few hundred feet
either side of 1000 feet. There may be a general trend of lowering
in some areas in the first 12 hours tonight...followed by limited
improvement during the daylight hours. Trying to time those
excursions above or below 1000 feet is quite problematic however.