Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
537 PM CST Monday Nov 30 2015
for 00z aviation.
Short term...tonight and tomorrow.
The persistent pattern we have been in for several days is finally
about to shift as a large trough over the plains begins to move
eastward. In response to this approaching trough...low pressure has
developed to the north of the front that was moving into northwest
Alabama this morning. This resulted in frontolysis...allowing warm
southerly flow to surge northward this afternoon. The remnant focus
for shower activity should remain across the extreme northwest part
of the County Warning Area...but most of the rain is now occurring well to our
north. A lingering thermal gradient to our northwest will be the
focus for a new front that will develop overnight and move into the
County Warning Area to near the I-59 corridor around midday tomorrow. Widespread
showers are expected near and behind the front. Afternoon
temperatures in the middle to upper 70s are expected once again on
Tuesday ahead of the front. Cold advection along with clouds and
rain will lead to 50s and 60s for highs across the northwest.
Long term...Tuesday night through Sunday.
As the cold front slowly crosses the area...the main rain axis
will shift southeastward Tuesday night and Wednesday. Rainfall
should be light to moderate. Given the recent dry period...flooding
is not expected. Rainfall amounts...in addition to what has fallen
across northwest central Alabama in the last couple days...could
total between 1-1.5 inches along and north of I-20 with lesser
amounts across the south. Despite being warm and moist outside for
November...instability remains very weak with this system and will
not carry thunder in the forecast.
A drier airmass will begin to spread into the area Wednesday night
as high pressure builds across the Tennessee and Ohio River
valleys. The upper level trough becomes sheared as the parent
closed low moves across New England with a trough axis extending
southwestward across Texas. Guidance continues to show moisture
pushing eastward away from the area and dry conditions prevailing
as the trough axis comes across the area late in the week.
Next system begins to take shape to our west over the weekend...with
rain back into central Alabama late Sunday or Monday.
00z taf discussion.
Shower activity should continue to avoid the taf sites through the
evening hours. Some redevelopment of MVFR ceilings is possible
overnight mainly across the north and west as southerly flow
strengthens. This is also where worsening conditions are expected
near the end of the taf period as ceilings drop with the arrival of
the front and rain.
A slow moving cold front will bring widespread rain to north
central Alabama tonight and tomorrow...with coverage shifting
southeastward Tuesday night and Wednesday. Drier and slightly
cooler conditions will spread into the area by early Thursday.
No fire weather concerns at this time through the week.