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Area forecast discussion 
National Weather Service Birmingham Alabama
443 am CST Monday Mar 2 2015

Discussion...

Fog is being reported just about everywhere across central Alabama
early this morning...although there does not seem to be a
discernible pattern to the visibility values (which range from 1/4
to 5 miles). There's bound to be plenty of dense stuff out
there..and we've gone ahead and issued a dense fog advisory until
9 am this morning.

Surface analysis this morning showed a cold front draped across
the northwest corner of the state...dropping down into
southwestern MS. The front is forecast to get into the south half
of Alabama today...turn around (and not drown)...and push back
north as a warm front tonight and Tuesday. Low/middle level flow
(above the boundary layer) will be out of the southwest...tapping
Gulf moisture and overrunning the surface front. This will produce
plenty of clouds and areas of rain through the day today and into
tonight. The focus of the wet weather pushes north with the front
on Tuesday.

An elongated upper level trough will swing across the eastern half
of the country Wednesday and Wednesday night. Models continue to
depict another strong (arctic) surface cold front being forced
southward into our region by the upper trough. Condition ahead of
the front will actually become quite mild. But the front will
usher in another very cold air mass late Wednesday into Wednesday
night.

While the models agree on the general idea of a strong cold front
passage mid-week...there are still some differences on timing of
the front. 00z and 00z runs of the GFS will noticeable faster than
the 00z and 06z NAM and the 00z European model (ecmwf). The forecast was loosely
based on the slower models...delaying the arrival of the front
in our northwest counties until Wednesday afternoon (about 4-6
hours slower than the gfs).

The models do show plenty of moisture on the cold side of the
surface front. While very cold in comparison to the air mass ahead
of it...the inbound cold airmass looks to be quite shallow. Model
soundings continue to show the potential for wintry weather for
several hours after frontal passage. The strength of the warm nose
and the depth/magnitude of the low level cold layer suggest that
we would be dealing primarily with a freezing rain and sleet
situation. Any snow getting into our counties would be right as
the precipitation was ending...and limited to the northwestern
counties.

We are now within 2 1/2 days of the start of the potential wintry
weather. Confidence of getting something wintry continues to
creep up. Not sure if the amount of freezing rain or sleet
currently forecast would qualify for a Winter Storm Warning based
on criteria alone. But the fact that the event would be occurring
before and during what would be the morning rush hour...and
temperatures would be falling as the precipitation fell...may
eventually make US consider a watch/warning based on the
significant impacts associated with the time of day. Stay tuned.

/61/

&&

Aviation...
06z taf discussion.

We've seen some highly fluctuating ceilings the past few hours but IFR
ceilings are expected at all terminals within the hour. Conditions
will likely deteriorate to LIFR at most locations later tonight
thanks to continued isentropic lift and low level moisture. The
low ceilings will cause restrictions to visible as well. Still not seeing
anything that would suggest significant improvements on Monday so
will maintain IFR ceilings through the day for now. Winds will remain
light and variable through the period.

19



&&

Preliminary point temps/pops...
Gadsden 51 46 67 60 66 / 70 60 50 40 60
Anniston 54 50 69 61 67 / 60 60 40 30 60
Birmingham 53 50 72 62 66 / 70 60 40 30 60
Tuscaloosa 54 51 73 62 70 / 70 50 30 30 60
Calera 56 53 73 61 69 / 70 50 30 30 60
Auburn 63 56 73 61 71 / 40 40 20 10 40
Montgomery 65 57 76 61 74 / 40 40 20 10 40
Troy 68 58 76 61 74 / 40 30 20 10 40

&&

Bmx watches/warnings/advisories...
dense fog advisory until 9 am CST this morning for all of
central Alabama.

&&

$$

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