Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 202327

Area Forecast Discussion
National Weather Service Birmingham AL
527 PM CST Sat Jan 20 2018

For 00Z Aviation.


Rest of the Afternoon through Tonight.

Plentiful sunshine, a dry air mass, and developing moderate drought
conditions are allowing for a wide diurnal range in temperatures.
Last week`s Arctic air and snow is a distant memory with
temperatures in the 60s across the area. An upper low continues to
spin over southern Mississippi and eastern Louisiana. This upper
low is interacting with southerly return flow and warm air
advection to produce some light showers near the Mississippi
River. Models are in good agreement that these showers will dry up
as they move eastward across Mississippi into a drier air mass as
the upper low outruns the low-level moisture return. Can`t
entirely rule out a stray sprinkle or shower in the far northwest
counties late tonight or tomorrow morning, but chances appear less
than 10 percent. Do expect some more clouds to move into the
northwest tonight with another surge of 850mb moisture. Lows
tonight will once again have a west to east gradient, though less
so than this morning. Winds will go calm in the east closer to
high pressure, while some light winds will continue in the west
due to the gradient associated with developing low pressure over
the High Plains. Dew points in the 30s will keep lows in the east
from being as cool as last night, with upper 30s to low 40s
expected across the area, and mid 30s in the typically cooler
locations. With smaller dew point depressions tonight, could see
some patchy fog near bodies of water, but confidence is too low to
mention in the forecast at this time given the overall dry air

Shortwave ridging will be present aloft on Sunday ahead of the
next system. 1000-850 mb thicknesses continue to increase. Given
how temperatures have over-performed the past 2 days, went above
even the warmest guidance for highs with readings around 70 in
most areas.


Sunday through Saturday.

12Z model guidance indicated a small uptick in dew points and
instability for Monday. Will continue to monitor tonight`s runs to
see if this trend continues. Otherwise, the previous forecast
remains on track with only minor tweaks.


Previous long-term discussion:

A progressive pattern will take hold for the extended part of the
forecast. Height falls are expected on Monday as a strong Plains
trough moves eastward. Moisture return should be sufficient for
widespread showers and possibly a bit of thunderstorm activity
along a cold front. Instability appears rather limited due to
dewpoints only reaching the upper 50s to around 60F, but lapse
rates are not too shabby. We will monitor for any upward trends in
dewpoints, which could lead to a marginal or low-end threat for
severe storms. This system should move through rather quickly with
dry and relatively mild weather returning for Tuesday through
Thursday. The next chance of rain could come with another system
late Friday into Saturday.



00Z TAF Discussion.

--VFR conditions tonight through Sunday--

Tame weather is forecast through tonight, with a few clouds and
calm to light ~southerly breezes. For Sunday, fair weather
continues, with some low- and high-level clouds, and winds
increasing to between 5-10 knots, generally from the southeast.




RH values will slowly increase through the weekend with values
remaining above critical levels. Light southerly winds are
forecast through the short term period and critical fire weather
conditions are not expected. A cold front will bring widespread
rain chances on Monday.


Gadsden     35  67  44  63  36 /   0  10  10  80  40
Anniston    37  70  45  64  38 /   0   0  10  80  50
Birmingham  40  68  48  64  38 /   0  10  10  90  20
Tuscaloosa  40  70  50  65  37 /  10   0  10  80  10
Calera      39  69  49  64  38 /   0   0  10  80  20
Auburn      39  68  46  66  41 /   0   0  10  60  60
Montgomery  38  71  47  69  41 /   0   0  10  70  40
Troy        38  71  47  70  42 /   0   0  10  50  60




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