Area Forecast Discussion
Issued by NWS Birmingham, AL

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS64 KBMX 230503

Area Forecast Discussion
National Weather Service Birmingham AL
1103 PM CST Fri Feb 22 2019

Evening Update and 06Z Aviation.



Battle of the airmasses continues over Central Alabama late this
evening. The warm front was still located just north of the US 80
corridor. South of the boundary, unseasonably moist airmass in
place. Surface dew points in the 60s and temperatures rose into
the 80s earlier this afternoon. North of the front, east southeast
flow was hanging on with temperatures in the 50s. This northern
airmass was undergoing modification as dew points continue slowly
climbing. Southerly isentropic lift and larger scale ascent will
keep showers in the forecast area wide overnight. The low level
jet ramps up west of the area and the heaviest rainfall will be
just to our north. Many locations remain totally saturated, so any
rainfall may have detrimental affects.

The latest HI-RES/CAMS have the warm front shifting northward on
Saturday afternoon. The airmass has near record precipitable
water, dew points, and warmth associated with it. Something more
like we experience in Spring. There are challenges as to where the
best forcing develops and where the instability forms. But all
indications are that severe thunderstorm development looks better
for tomorrow. More discussion on this in a few hours.


Previous short-term discussion:Through Tonight.

The surface warm front gradually lifted northward today and was
currently located near a Demopolis to Jemison to Wedowee line.
The warm front has not moved much the past few hours, and forecast
boundary layer winds do not show much northward push until later
tonight. Temperatures south of the warm front have risen into the
lower and middle 80s, with 50s north of the front. Most of the
shower activity has lifted north of Central Alabama, but some
showers have developed just south of the warm front. Do not expect
much shower activity this evening, but increasing isentropic lift
after midnight will likely produce more shower activity, especially
north of I-20. Temperatures trends will be difficult overnight as
clouds decrease north, then increase later tonight. Lows north of
the cool front will stay steady this evening, then rise after
midnight as low level winds veer. Temperatures in the warm sector
will fall with the usual diurnal trend, but may bottom out by
midnight. Fog may become an issue overnight, especially if clouds
clear near or just north of warm front.


Saturday afternoon and Saturday night.

An upgrade to the severe weather risk appears warranted across our
far northwestern counties for Saturday night. Some important changes
have occurred in the latest model runs, including the appearance of
a more prominent elevated mixed layer and steeper mid-level lapse
rates. Dewpoints are also trending higher as models catch on to the
highly anomalous airmass lurking across the Gulf of Mexico. Several
days of moisture advection has resulted in 72-73F dewpoints in the
northern Gulf, and widespread 67-70F dewpoints should move inland
across Mississippi and West Alabama on Saturday afternoon. 2-3
decameter 500 mb height falls are indicated by the ECMWF from Noon
to 6 PM across our northwestern counties as a sharpening surface
trough approaches from the west. This feature is likely to result in
development of deep convection to our west in the presence of strong
low-level and deep-layer shear. Shear vectors over the warm sector
are oriented at a approximately a 45 degree angle to the surface
trough, which will be favorable for a broken line of supercells or
perhaps discrete supercells through about 9 PM as storms enter our
northwestern counties. Thereafter, shear vectors become more
parallel to the convective band, and storms should become more
linear as they approach I-59. Height and pressure falls may extend
far enough south for our northwestern counties to be impacted by one
or two robust supercells with risk for strong tornadoes. Confidence
decreases with southward extent toward the I-59 corridor, but a
tornado and damaging winds cannot be ruled out if the surface
pressure trough ends up as strong as indicated by some model


Sunday through Thursday.

Improved weather & a much needed dry/drier period looks to move into
the region as a stable continental airmass & zonal split-flow aloft
encompasses much of the CONUS & the Southern Gulf Coast after Sunday
morning. Expect this to stick around through at least mid-week
before some rain showers possibly impact the area on Wednesday as a
shortwave trough moves along the Gulf Coast. Otherwise the overall
weather theme for next week should remain mostly tame with no
significant storm systems currently expected. Would hopefully start
to see some improvement with any lingering river flooding concerns
during this time.



06Z TAF Discussion.

A big mixed bag of flight categories...VFR to IFR. Expect these
varying conditions to continue a few more hours. Ceiling/vis
restrictions quickly materialize after 08z. Winds will start
increasing and veering around sunrise. This will also trigger the
ceiling/vis improvement with MVFR by 16z and VFR by 20z. A cold
front will move into western areas around the 00z time frame with
thunderstorms/ceiling restrictions developing again.

A warm front still located between BHM/MGM has the northern sites
in lower ceilings, while southern sites have some clearing. The
shower activity will generally be scattered at the terminal
locations and most likely will amend for specific timing of any
rain at any particular site, but overall chance look low.

Ahead of an approaching front on Saturday, winds will increase
into the 10-20kt range and possibly higher. These winds will
linger into the evening hours ahead of the front. This will occur
outside the rain areas.




A prolonged period of rainfall will continue through the end of the
week, with a strong storm system expected to move through Central
Alabama Saturday night. Very wet conditions are expected, especially
across the northern half of the area. Drier conditions return to the
area for at least a couple days to start next week. There are no
fire weather concerns at this time.


Gadsden     53  73  50  60  34 /  70  40  80   0   0
Anniston    56  75  53  63  36 /  60  30  80   0   0
Birmingham  54  77  52  62  37 /  50  40  80   0   0
Tuscaloosa  57  79  50  63  37 /  50  50  80   0   0
Calera      54  78  52  63  37 /  40  40  70   0   0
Auburn      61  78  57  66  39 /  20  20  70  10   0
Montgomery  66  82  58  68  40 /  30  20  70  10   0
Troy        65  83  59  68  41 /  20  20  60  10   0


Flood Watch through late Saturday night for the following
counties: Bibb...Blount...Calhoun...Cherokee...Clay...Cleburne...
Shelby...St. Clair...Talladega...Tuscaloosa...Walker...Winston.


$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.