Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 212359
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
659 PM CDT Sat Oct 21 2017

.UPDATE...
Aviation Discussion.

&&

.SHORT TERM...
This afternoon through Tonight.

The low levels of the atmosphere continue to moisten up with
surface dewpoints in the upper 50s to lower 60s. The total column
of the atmosphere is still very dry with precipitable water
values below 1 inch. Cloud cover overnight will mostly be high
clouds with a few cumulus. No rain expected overnight due to dry
air mass in place, but moisture will increase rapidly after
sunrise Sunday as strong upper trof approaches the Mississippi
River. Temperatures overnight will be rather mild overnight due to
warm air advection, with lows in the upper 50s to lower 60s.

58/rose


.LONG TERM...
Sunday through Friday.

Our dry weather will come to an end on Sunday afternoon into the
evening as a potent upper-level trough approaches from the
Southern Plains. A mass of rain and embedded thunderstorms or
perhaps a QLCS will arrive from Mississippi in the late afternoon.
Aside from a few stray showers, areas east of I-65 should stay
mostly dry through sunset, but West AL should see increasing rain
chances after 3 PM. An area of meager instability will become
pinched off near the MS/AL due to drier southeasterly low-level
flow over Alabama. Therefore, severe weather is not expected as
the area of moderate to heavy rain with embedded thunder moves
eastward into the nighttime ours. This forecast heavily leans
toward the open wave or more progressive scenario shown by the
ECMWF. The GFS appears to be be way too amplified and closed off
with the 500mb trough. I have sped up the departure of high rain
chances through the day on Monday into Monday night, and a further
increase in forward speed is possible. In fact, Monday afternoon
could end up dry for most of the forecast area.

A very strong upstream shortwave will reinforce the cold advection
regime on Tuesday into Wednesday with afternoon temperatures
barely reaching 60F in the North on Wednesday. A transition to
warmer conditions is expected on Thursday and Friday as southerly
flow develops in response to a developing large trough in the
western CONUS.

87/Grantham

&&

.AVIATION...
00Z TAF Discussion.

Winds remain at 4-7kts from the southeast to east overnight. Low
level moisture slowly increases ahead of an approaching storm
system. Coupled with isentropic lift, sct to bkn MVFR cigs will
spread from south to north early Sunday morning. Cig heights improve
through the morning with winds increasing from the southeast, at 10-
10kts with gusts to 18kts.

A line of rain and embedded thunder will approach the area late in
this taf period. Have added RA VCTS at TCL at 22/20Z and at BHM and
EET at 22/22Z. This timing will likely need adjusting with future
forecasts.

14

&&

.FIRE WEATHER...

Mild and dry weather will continue through Saturday and early
Sunday. Widespread soaking rainfall is expected Sunday night into
Monday. Relative humidity values should remain above critical
thresholds. There are no fire weather concerns.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     57  79  66  72  52 /   0  10  90 100  30
Anniston    59  80  67  72  53 /   0  10  90 100  30
Birmingham  63  81  68  72  54 /   0  30  90  80  20
Tuscaloosa  64  82  68  74  54 /   0  70 100  60  20
Calera      63  80  67  72  54 /   0  40  90  80  20
Auburn      62  78  69  73  55 /   0  20  80 100  30
Montgomery  64  84  70  75  56 /   0  30 100  80  20
Troy        63  83  70  75  56 /   0  30 100  90  20

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
None.

&&

$$


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