Scientific Forecaster Discussion
fxus64 kbmx 061141
Area forecast discussion
National Weather Service Birmingham Alabama
541 am CST Tue Dec 6 2016
for 12z aviation.
Short term...today and tonight.
The stationary front remains in the Florida Panhandle early this
morning. It was unable to move northward due to widespread
convection, and possibly due to a weak meso-low that tracked along
the front coming onshore around Pensacola and moving northeast
towards Dothan, re-inforcing east-northeast winds and a cool stable
air mass in our southeast counties. A squall line is currently
moving quickly eastward across the Florida Panhandle, closing any
remaining window for any severe storms to move into our southeast
Widespread showers are currently moving over the forecast area due
to upper-level forcing associated with a compact shortwave trough
over Mississippi. A few lightning strikes have been noted over
northern Mississippi and northwest Alabama due to elevated
instability associated with cool air aloft. Rain chances will
quickly diminish from southwest to northeast later this morning as
the shortwave exits and mid and upper levels dry out. However, low
levels will remain moist and expect mostly cloudy skies to prevail
through the day and overnight as well. Cloud cover and weak cold
air advection will keep temperatures from moving much during the
day. Temperatures will cool off into the upper 30s to upper 40s
tonight due to cold air advection. There should be enough of a
pressure gradient for a few knots of wind which combined with the
clouds should prevent fog formation.
Long term...Wednesday through Monday.
Despite weak warm air advection on Wednesday, lingering cloud
cover will likely keep temperatures on the cool side with highs
ranging from the lower 50s northwest to lower 60s southeast. No
rain is expected due to relatively dry air above 850mb. A strong
cold front will approach northwest Alabama Wednesday night and
possibly bring some showers to areas north of I-59 before sunrise
Thursday. The better chances for rain will come Thursday morning
as the cold front passes through central Alabama. A broken line of
showers is expected along the front, with rainfall amounts
generally less than one-quarter of an inch.
The coldest air mass of the season will invade Alabama this week with
temperatures well below normal for early December. The coldest
daytime temperatures will be on Friday with forecast highs in the
upper 30s northwest to middle 40s southeast. The coldest morning
will likely be Saturday as the surface highs settles over the
area. Lows Saturday morning will be in the lower to middle 20s,
with some upper teens likely in the colder valleys. A gradual
warm-up on Saturday as the surface winds become southeast. A
northern stream short wave trof will push across the Great Lakes
region on Sunday and push a cold front into Alabama on Monday. The
GFS model shows a more progressive system with a deeper surface
low than the European model (ecmwf) model, but either way rain chances will be
increasing early next week.
12z taf discussion.
LIFR to IFR cigs continue at all sites except for anb/asn where
cigs are currently MVFR but that is expected to be temporary.
Low-level moisture remains abundant even as the upper-level system
moves away, so low cigs are expected to continue. Expect mainly
IFR cigs through the period. There is a chance cigs to lift to
MVFR for brief periods this afternoon, but this is expected to be
temporary for most sites with toi having the best chance of seeing
slightly higher cigs. Cigs will fall to or remain IFR overnight.
Thunderstorms have passed the taf sites, but showers will continue
to affect the northern taf sites through mid-morning.
Light to moderate rainfall will continue across the area through
this morning. Rain will exit to the east by early afternoon, with
drier conditions returning to the area tonight and Wednesday. Another
storm system will bring a chance of showers to the area on Thursday,
with conditions turning much colder Thursday night through Saturday.
Preliminary point temps/pops...
Gadsden 59 40 56 39 45 / 90 10 10 30 40
Anniston 60 42 59 41 48 / 90 10 10 20 40
Birmingham 59 41 57 41 47 / 70 10 10 30 40
Tuscaloosa 59 45 57 42 47 / 30 10 10 30 30
Calera 59 43 58 41 48 / 50 10 10 20 30
Auburn 61 46 60 44 51 / 70 10 0 10 30
Montgomery 63 47 62 45 53 / 30 10 0 10 30
Troy 65 49 62 43 55 / 30 10 0 10 30