Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 180006

Area Forecast Discussion
National Weather Service Birmingham AL
706 PM CDT Sat Mar 17 2018

For 00Z Aviation.


Through Tonight.

Upper level shortwave is exiting southeast Central Alabama this
afternoon, and will see scattered showers and storms diminish over
the next couple hours. Will see a lull in rain activity tonight
for most of the area as we are in between upper level forcing
mechanisms. A weak surface boundary will sink southward tonight
and stall across the area. Expect low level moisture south of the
boundary to result in low clouds and fog. Currently, looks like
the boundary stalls just south of I-20. Lows will be in the 50s
and lower 60s.


Updated for the severe weather threat on Sunday and Monday.

No major changes to the previous long term forecast for the severe
weather potential on Sunday and Monday. The conditions on Sunday
still look marginal overall with the main threats being strong winds
and some small hail. Models continue to show a round of convection
associated with the warm front and upper level shortwave moving
through Central AL Sunday afternoon and night. Instability and low-
level shear is on the lower end during this timeframe, so will keep
the marginal threat mention in the HWO.

The biggest concern remains on Monday afternoon and evening with the
dryline boundary moving across the region. Latest model runs have
trimmed back on the mid-level lapse rates, which could limit the the
size of hail overall, but large hail is still possible. It`s worth
noting that the latest GFS and ECMWF develop some convection along
the Gulf Coast Monday morning that could disrupt the wind fields for
the afternoon, significantly limiting the severe threat. However,
the NAM has more scattered storms that move out earlier, allowing
more time for afternoon destabilization and backing of the winds
ahead of the dryline. The higher resolution models (3km NAM, ARW,
NMM, NSSL WRF) are starting to come in and seem to support the NAM
solution of clearing along the coastline and more backed surface
winds across Central AL, which would continue to promote the
enhanced risk area highlighted in the HWO.

So, for now will maintain the enhanced risk messaging for Monday
afternoon with large hail and damaging winds. The tornado threat is
still present as some of the higher resolution models are still
trying to keep the winds backed to 180-190 degrees (GFS surface
winds are veered, which would limit the tornado threat). Uncertainty
remains high due to the potential for coastal convection and the
lower trends in lapse rates.



00Z TAF Discussion.

Except for a thin line of TSRA skirting eastward near TOI a few
more minutes, TAFs are not expecting any rain until Sunday
afternoon. Mainly cirrus clouds are around right now on satellite
except far south Alabama. Some MVFR stratus will creep back
northward late tonight with moisture return affecting mainly
MGM/TOI till midday Sunday. Cigs should lift back to VFR during
the afternoon. Showers will spread across the area Sunday
afternoon with another wave of showers. MGM/TOI could see some TS
with the activity as well.




Several rounds of showers and thunderstorms are possible through
Tuesday. Rain chances will end quickly this afternoon across the
southeast, with a drier trend tonight. Better chance for
widespread rainfall and thunderstorms will be Sunday afternoon
and Monday. In addition, to this wet pattern, temperatures will be
warmer and RH values increased. Low clouds and patchy fog are
possible tonight and possibly again Sunday night. There are no
fire weather concerns.


Gadsden     52  72  56  75  51 /  10  30  80  70  80
Anniston    56  74  58  76  53 /  10  40  80  70  80
Birmingham  53  74  59  77  53 /  10  50  80  70  70
Tuscaloosa  57  73  61  80  52 /  10  70  70  50  40
Calera      57  74  61  78  53 /  10  60  80  60  70
Auburn      60  75  60  76  55 /  10  60  80  70  80
Montgomery  63  77  62  81  56 /  10  70  80  60  60
Troy        63  77  63  81  57 /  40  70  80  60  50




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