Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
442 am CST Thursday Jan 29 2015
Short term...today through Saturday night.
A clipper type system will track quickly eastward across the Ohio
Valley region today and drag a cold front into central Alabama
tonight. There will not be sufficient time for Gulf moisture to
advance northward ahead of the front...and shower activity will be
limited. The models do show a slight increase in showers this
evening as the front moves through central Alabama...mainly east
of I-65. Clearing and colder on Friday with highs slightly below
average. A cut-off upper low over the southwest states will shift
into northern Mexico on Saturday and pull moisture northward into
Texas. A drier air mass over the southeast states will hold in
place a little longer and delay the onset of rain across central
Alabama until Sunday.
Long term...Sunday through Wednesday.
A fast moving northern stream short wave trough will pick up the
moisture over Texas and quickly expand it eastward into Alabama on
Sunday. An inverted surface trough will form near the Mississippi
River on Sunday with a closed surface low forming over the
Carolinas Sunday night. The better maritime air will likely stay
near the coast as a southerly flow never has a chance to get
established...and any thunderstorm activity will likely stay
south of central Alabama. The heavier showers should be exiting
east Alabama by midnight Sunday night as the surface cold front
shifts east of I-65. The deepening surface low will help pull cold
air rapidly southward into north Alabama late Sunday night. There
will likely be a transition to a mixture of light rain/snow across
the northwest counties starting shortly after midnight. The
transition zone will shift to near the I-59 corridor by sunrise
Monday. After sunrise...there could be a few hours during the
morning with some flurries across the northern counties.
Surface temperatures will stay just above 32 degrees during this
time..so no impacts expected. Clearing and cooler Monday night
with lows in the 20s.
The model solutions diverge on what to do with the remnants of the
Mexico cut-off low. The European model (ecmwf) model shows better phasing which
allows the deeper moisture to expand farther northward into the
central Gulf states. The GFS model shows a stronger Gulf system
and keeps the rain confined to South Alabama. Model blends bring
the rain farther north and will show a chance of rain for all of
central Alabama on Wednesday with rain the pulling out of the area
06z taf discussion.
VFR conditions currently in place with high clouds moving across
the terminals. A cold front will approach the area late in the taf
cycle with winds switching around to the northwest. MVFR ceilings
are expected with the frontal passage. Models indicate light
precipitation after the frontal passage but confidence is not high
enough to include in the tafs at this time.
Preliminary point temps/pops...
Gadsden 60 35 48 27 52 / 10 30 0 0 0
Anniston 60 37 50 29 53 / 10 30 0 0 0
Birmingham 63 37 50 30 53 / 10 20 0 0 0
Tuscaloosa 67 39 53 31 55 / 10 20 0 0 0
Calera 64 39 52 32 54 / 10 30 0 0 0
Auburn 60 40 53 32 55 / 0 30 0 0 0
Montgomery 66 42 56 32 58 / 0 20 0 0 0
Troy 64 42 56 32 57 / 0 20 0 0 0