Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
549 am CST Sat Dec 20 2014
An upper level shortwave trough is moving east across lower
Mississippi and Tennessee Valley region this morning. At the surface
the rain is quickly shifting east in Georgia with drier air aloft
moving in from the west. There is also a weak surface low in the
central Gulf just off the la coast. The best chance of rain this
morning will be south of I-85 with rain coming to an this
Another upper shortwave will cross the plains on Sunday and allow
the current surface low in the Gulf to eject northeastward along the
Atlantic coast. This will bring another chance of rain to central
Alabama...primarily in the east...Sunday and Sunday night. Showers
could linger into Monday with southeasterly flow and continued low level
moisture thanks to a wedge in place along the Atlantic Seaboard down
into eastern Alabama.
The system of interest will impact the forecast area on Tuesday into
Wednesday as a trough deepens across the plains states. Models still
show a surface low developing across eastern Texas late Monday but the
track of this low has shifted more to the north vs east as the
system occludes. With the surface low passing just to our north and west
this would generally put central Alabama in a favorable spot for
severe weather potential. Although there is sufficient shear and low
60 dew points are prognosticated to surge northward into southern portions
of the County Warning Area...there are some potential limiting factors. Current
model guidance indicates ongoing shower activity and overcast skies
across the forecast area Tuesday morning...and there is also
indications of a large cluster of rain/storms that develops in the
northern Gulf. Taking this in consideration it's uncertain has to
how much instability will be realized across our area. Due to low
confidence have decided to leave out any mention of severe in the
severe weather potential statement at this time. However will continue to monitor trends closely.
The surface cold front will shift east of Alabama Wednesday morning but
isolated/scattered showers will remain possible in the North/East Wednesday
morning due to some wrap around moisture. It will be a bit windy on
Wednesday with westerly winds of 15 miles per hour and gusts up to 25 miles per hour.
Temperatures cool down briefly in the wake of the front but quickly
rebound by the end of the work week as surface southerly flow returns
ahead of the next system.
06z taf discussion.
While there is a certainty that rain will continue for several
more hours across central Alabama taf locations...there is still a
great bit of uncertainty regarding visibility and ceilings
associated with the rain. Mgm and toi are the most likely
locations to see conditions get down to at least MVFR...
potentially lower. The rest...especially bhm and anb...will be on
the northern edge of the lower clouds. Expect frequent updates due
to the variable cloud conditions.
Things don't get much easier...even after the rain pulls out later
this morning. Computer model moisture profiles...and other
available guidance...suggest the lower clouds may stick around
longer in the south than previously though.
Preliminary point temps/pops...
Gadsden 51 36 53 44 55 / 20 10 10 40 30
Anniston 52 39 55 47 56 / 20 10 10 50 30
Birmingham 53 40 57 47 60 / 20 10 10 40 30
Tuscaloosa 55 39 57 47 60 / 10 10 10 30 30
Calera 53 41 56 47 59 / 20 10 10 40 30
Auburn 54 46 55 48 59 / 50 10 30 60 40
Montgomery 56 45 58 49 63 / 40 10 20 50 30
Troy 56 46 57 50 65 / 60 20 40 50 30