Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
536 am CST Tuesday Feb 9 2016
for 12z aviation.
today and tonight.
Cold air advection continues to move into the area this morning as
the base of the main trough begins to move through central Alabama.
This trough will begin to lift to the northeast during the afternoon
while another lobe of vorticity rotates along the bottom side. This
energy will help generate more snow showers during the day mainly
across the northern half of the area. Of the 50 model solutions that
are available for this time...each one gives a different scenario
with very little consistency. This is causing the lack of confidence
to continue even with the event upon US. So while the environment is
primed for snow aloft...there is also the factor of a very dry
airmass at the surface that is also contributing to the drying up of
what flurries we are seeing...resulting in no accumulation other
than car tops and roof tops. Most areas are in the low 20s for
dew points and are forecast to fall into the upper teens this
afternoon. At the same time...ground temperatures are still in the
upper 30s to even low 40s this morning. As of 3 am...the only
location in central Alabama at or below 32 degrees at a recording
location was in the northwest at Haleyville at 32 degrees.
Right now we will be watching a band of snow moving across northern
Mississippi. As this band has been approaching the gwx radar the
returns are disappearing...thus confirming the dry airmass at the
surface. So what we have right now is mainly virga across the area.
So the big question for today will be what areas may see some
accumulation. At this time I would say the northeast has the best
chance...generally north of a Birmingham to Montana cheaha/Anniston line.
Again as mentioned before the activity will be in the form of
showers so it will really be determined as the afternoon and evening
approaches. Again not everyone will see accumulations even within a
County that has higher chances. We will continue to monitor the
trends through the morning...but there just is not enough confidence
this morning to issue an advisory. Snow chances been to decrease
from south to north this evening as the trough begins to lift out of
Wednesday through Monday.
A chilly day is anticipated for Wednesday as the ridge builds
further to the east but at least the skies are expected to clear
for the most part as only maybe a few scant clouds across the far
northeast may be left by Wednesday morning but should exit
quickly as the upper system continues to depart. Wednesday night
will continue to be cold but not as much as tonight as the
developing low to our west looks to churn up a little quicker and
thus weaken the ridge quicker. We could also get winds turned
around with a little southerly flow overnight.
Some cloudiness will move in on Thursday ahead of the next system
but overall moisture looks more shallow. Should see some
moderating conditions as low pressure continues to develop to the
west. Although this could still set up a weak stationary boundary
by early Friday...moisture continues to look limited and too low
for mentioned rain chances...but some clouds should be noted.
Another surface front is still expected to move southward into the
state late Friday...with a colder airmass scheduled to move back
into Alabama for the weekend along with rain free conditions once
again as a very strong ridge over the Dakotas (1046mb) late Friday
swings southeastward into the Ohio Valley by Saturday night and
then eastward toward the Middle Atlantic States by late Sunday.
Here's where the headache begins. Our models diverge greatly
Sunday night. The Euro breaks down the ridge much quicker than the
GFS with return flow and warmer temperatures ahead of the next
front along with rain moving into the area Sunday night and all
done by late Monday. The GFS since it is much slower breaking down
the ridge keeps things dry for the most part for Sunday night and
holds off the precipitation until Monday...with much colder
temperatures (10-15 degrees colder!!) model blends handle this
poorly and thus the headache. With a stronger ridge as this i'm
tending to lean toward the GFS in theory. However...confidence is
low this far out with zero agreement in models in timing...return
flow...etc. So have gone with only low probability of precipitation northwest and went a
little higher than sunrise-blend with temperatures to account for this
above mentioned model dilemma. So with that said in the north
during the late night and morning have a rain/snow mix...but again
we need to work out the timing kinks for confidence to increase.
12z taf discussion.
Steady winds from the west-northwest will continue this morning and then
increase after 15z. Ceilings will average around 5k to 8k through
the evening and then clearing late overnight. A few light bands
of snow may be possible over the next 18 hours but nothing
predominant at most locations. Did go ahead and go with -shsn at
anb and asn after 21z until 3z.
No fire weather concerns are expected at this time. A strong
upper level system will dominate the weather across the eastern
United States early this week and bring much colder temperatures
into central Alabama through Wednesday. Precipitation chances
remains in the forecast through tonight...with the system finally
exiting by Wednesday morning. Best precipitation chances will be
across the north. Any precipitation today will be in the form of
snow showers. Activity will be showers...and will not be continuous.
Light accumulations underneath a heavier shower is possible.
Northerly winds will be gusty through the afternoon.
Preliminary point temps/pops...
Gadsden 34 20 37 22 48 / 50 20 0 0 0
Anniston 35 22 38 23 50 / 50 20 0 0 0
Birmingham 36 21 40 25 53 / 30 20 0 0 0
Tuscaloosa 40 22 44 26 58 / 20 10 0 0 0
Calera 38 25 41 27 55 / 20 10 0 0 0
Auburn 39 24 42 26 55 / 20 10 0 0 0
Montgomery 43 26 47 27 62 / 10 10 0 0 0
Troy 45 24 46 26 61 / 10 0 0 0 0
Wind Advisory until 6 PM CST this evening for the following