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Area forecast discussion 
National Weather Service Birmingham Alabama
538 am CST Friday Dec 26 2014

Update...
for 12z aviation.

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Discussion...

Surface high pressure is centered over the western Carolinas this
morning...with calm to light easterly winds across central
Alabama. Patchy fog has developed where some low level moisture
remains from rainfall a few days ago. At middle and upper levels...a
trough has amplified over the western Continental U.S. As ridging builds
northeastward across Florida and into the southeast. With
southwesterly flow aloft...an extensive cirrus deck streams
across the area...the first indication that moisture is returning
to the area. Today will remain dry with temperatures several
degrees warmer than yesterday...highs in the middle 50s to lower 60s.

Cloud cover will continue to increase tonight...as the airmass
moistens. Added clouds will keep temperatures in the middle 30s
northeast to middle 40s southwest tonight. As the longwave trough
shifts eastward across The Rockies and plains...impulses rotating
through the trough will increase rain chances for central Alabama.
The first of these will approach the area Friday night and
Saturday. With dry lower levels...expect rainfall to hold off
until after sunrise tomorrow for most of the area. Will keep a
slight chance of rain in the far west prior to sunrise. With
continued moist southwesterly flow and the added lift associated
with the impulses...the weekend continues to look wet with one to
two inches rainfall accumulation possible Saturday through Sunday
night. Highest rainfall totals will be over the west and north
where convergence will be best near a surface front. Because
rainfall is falling over a couple days...flooding is not expected
to be a problem. Will continue to mention isolated thunder but
severe threat looks low at this time.

The front will slowly push through the area...clearing central
Alabama on Monday as one shortwave pulls to the east and another
drops southward from the Pacific northwest region to re- enforce
the longwave trough. Behind the exiting cold front...a piece of
Arctic high pressure will slide southward down the plains. A
secondary push of cold air on Wednesday will bring temperatures
down to just below normal for late December. Depending on how much
the colder airmass moderates...could see temperatures for
Wednesday and Thursday needing to be lowered...closer to raw model
numbers.

The longwave trough closes off an upper low over Southern
California Wednesday...which slowly tracks eastward and opens over
the Southern Plains late in the week. This will incite generation
of a northeastward tracking surface low over the western
Gulf...and widespread rain returns to central Alabama late
Thursday afternoon/Thursday night. Although a cold rain is
expected before warmer air spreads northward ahead of the
surface low...the airmass will be too warm for any frozen
precipitation. At least part of next weekend looks wet as well.

14



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Aviation...
12z taf discussion.

Surface high pressure will keep terminal forecast VFR through the
period. Saturated ground conditions will allow some patchy fog
development around central Alabama...most prevalent near water
bodies and short lived. With light winds...do not expect the fog
to move or advect and cover any significant area. Did not mention at
any terminals a this time. The high pressure gradually slides
eastward overnight as a front approaches from the west. Very dry
atmosphere overhead today will give way to increasing moisture
after 00z. Ceilings drop to around 100 around 00z and between
040-060 by 12z. Surface winds will remain light and east to
southeast through the period.

75

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Preliminary point temps/pops...
Gadsden 57 35 57 49 62 / 0 10 60 90 80
Anniston 59 35 59 52 65 / 0 10 60 90 80
Birmingham 58 41 59 54 63 / 0 10 70 90 80
Tuscaloosa 59 45 60 53 63 / 0 10 90 90 80
Calera 59 40 60 53 65 / 0 10 80 90 80
Auburn 58 40 59 54 68 / 0 10 70 80 60
Montgomery 60 41 63 57 73 / 0 10 90 80 60
Troy 60 40 63 56 72 / 0 10 90 60 50

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Bmx watches/warnings/advisories...
none.

&&

$$

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