Area Forecast Discussion
Issued by NWS Birmingham, AL

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438
FXUS64 KBMX 211727
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
1227 PM CDT Sat Oct 21 2017

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...
Today and Tonight.

High pressure centered over Virginia will remain the predominate
feature for the region once again today and tonight. Really the
only weather we will see will be an increase in clouds as
southerly flow begins to increase over the area, once the high
pressure system begins to push further east. Highs will be another
1 to 2 degrees warmer than Friday for highs with a much more mild
night across the entire area tonight and with mostly cloudy
skies.

16

.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...
18Z TAF Discussion.

The air mass will remain relatively dry thru 06z with only a few
cumulus and mostly cirrus. An approaching upper level trof has
increased the low level pressure gradient and southeast winds
7-10 knots will prevail thru 00z, then decrease to 4-7 knots. Low
level moisture will slowly increase overnight along with some
isentropic lift. Enough confidence for some lower cigs to develop
in the 12-15z time frame to include cigs arnd 4k feet. Sct shwrs
possible late in the period near KTCL, but probability not high
enough to include in forecast.

58/rose

&&

.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  30 100  80  20
Tuscaloosa  64  82  68  74  54 /   0  70 100  60  20
Calera      63  80  67  72  54 /   0  40 100  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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