Scientific Forecaster Discussion
fxus64 kbmx 231025
Area forecast discussion
National Weather Service Birmingham Alabama
525 am CDT Fri Mar 23 2018
for 12z aviation and morning update
today and tonight.
High pressure is centered over Alabama this morning and will remain
over the southeast through the afternoon. Aloft there is a
northwest flow and this is helping bring in some mid-level
moisture on the backside of the high. A few sprinkles may be
possible through this morning but accumulations are not expected.
The high pressure system will slide east of the area by Saturday
morning. This will allow the next storm system to push into the
plains and push/develop a warm front through the northern portions
of the area after midnight. Really the only effect it will have
will be a switch to a southerly flow and increased cloud cover.
Did add in a small chance at a shower in the far northeastern
areas as shortwave slides along the front overnight. Highs today
will be in the 60s/70s with lows in the 40s/50s.
Saturday through Friday.
A weak low pressure system moves southeastward through the upper
plains and into the Tennessee Valley Saturday into Sunday. This will
stretch a west to east oriented cold front through the Tennessee Valley by
Saturday evening. Expect rain chances to increase along the front in
the northern portions of central Alabama Saturday evening and into the
overnight hours through Sunday morning. The front begins to weaken
and stall across the area Sunday afternoon. Models show scattered
showers at best by this time, so i'm hesitant to go much above 40%
chance of rain for the region.
Cold air damming sets up in the Carolinas Sunday evening into Monday
morning, which results in a backdoor cold front moving east to west
across central Alabama. The global models develop a little more shower
coverage with this boundary than the NAM does, so will keep
chance pops in the forecast. The question for rain chances will be
just how far south the initial cold front pushes and whether any
moisture remains to fuel the showers as the backdoor cold front
moves in. The cold air damming pattern remains in place through
Tuesday, limiting any rain chances due to the drier easterly flow
in addition to the upper level ridging moving across the area.
Meanwhile, a deep trough moves through the western US and a surface
low moves quickly into the Great Lakes region, stretching another
cold front through the Ohio and MS river valleys. A high pressure
system remains in place over the Florida Peninsula Tuesday into
Wednesday, which stalls that front to our north and west. By
Wednesday evening/night, the deep trough shifts eastward through the
Great Plains and pushes the high pressure eastward. The GFS and
European model (ecmwf) are in decent agreement with the overall setup, hinting a
surface low developing and moving northeastward through the Tennessee
Valley. However, models are having a difficult time resolving the
low, which means they are keeping it weak at this time. For now,
will forecast for a positively-tilted trough and cold front to push
through the area Thursday into Friday, bringing increased rain and
thunderstorm chances. Modest instability and a good amount of shear
is in place, but the upper jet and low level jet aren't aligned in the current
model guidance. Confidence just isn't there with how the parameters
are lining up to mention any severe threat for Thursday/Friday right
12z taf discussion.
The terminals remain VFR through the period. Mid and upper level
clouds become ceilings over the area as surface winds start off
light and east to southeast. There could be a few sprinkles this
morning but terminals will remain dry. A front inches toward the
northern part of the state, but will stop short as another system
develops to our northwest. Surface winds will become southerly by
18-19z around 6kts. Ceilings should not dip below 070.
Relatively dry weather continues today with next chance of rain
coming over the weekend. A few sprinkles may be possible though
this morning. Rhs will be slightly higher today than the previous
afternoons. There are no fire weather concerns at this time.
Preliminary point temps/pops...
Gadsden 64 46 72 58 69 / 10 10 40 50 40
Anniston 64 46 73 58 70 / 10 10 30 50 40
Birmingham 67 51 75 60 72 / 10 10 30 50 40
Tuscaloosa 72 52 77 61 75 / 10 10 10 50 40
Calera 68 50 76 60 74 / 10 10 10 50 40
Auburn 66 47 75 60 71 / 0 10 10 40 40
Montgomery 72 47 80 61 78 / 0 10 10 30 40
Troy 71 48 78 62 78 / 0 10 10 30 30