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 181917

Area Forecast Discussion
National Weather Service Birmingham AL
217 PM CDT Thu Oct 18 2018

Through tonight.

Surface high pressure of 1036mb centered over Illinois and Indiana
continues to dominate the weather pattern over much of the
southeast. Very pleasant temperatures in the 70s with dry
dewpoints in the 40s and lower 50s are being observed at all
observation sites this afternoon. Only high cirrus clouds are
streaming in with the westerly flow aloft around the upper level
ridge centered over the Gulf Coast. Dry northerly to northeasterly
surface flow will continue into tonight where cool temperatures
ranging from the upper 40s in the far north to the upper 50s south
are expected. Enough easterly flow at the surface could bring
some cloud cover into our southeast counties overnight tonight
which would keep surface temperatures a little warmer for
locations at least along and south of the I-85 corridor. Rain
chances remain at zero through the short term period.


Friday through Thursday.

The ridging pattern begins to flatten across the Southeastern US as
a trough slides into the Northern Plain, pushing a cold front
through the Midwestern States. A pre-frontal shortwave develops
and moves across the Mid-MS Valley, spreading eastward through TN
and Northern AL late Friday night into Saturday morning. Lift
associated with the shortwave and the approaching cold front will
allow for rain development mainly after midnight north of I-59.
This will spread southward through the day on Saturday, reaching
the I-85 corridor during the early afternoon. Locations south of
I-85 could see a few rumbles of thunders with the rain as it
pushes through in the afternoon and some modest instability is
able to work its way in, but generally I don`t expect much
thunderstorm development with this system.

The cold front pushes south and east of Central AL by Saturday
night, so I`ve cleared out all mention of rain or thunderstorms
after midnight. A cooler and drier air mass gets advected into the
region with northerly flow persisting most of the day Sunday.
Therefore, high temps Sunday will generally be in the mid to upper
60s in the south with some locations in the northern counties
struggling to reach 60 degrees. The center of a surface high
pressure system slides through the Ohio River Valley Sunday evening
into Monday as ridging aloft builds in across the Southeastern US.
This will lead to synoptic scale subsidence, clearing skies
overnight Sunday into Monday, which will allow for effective
radiational cooling. This will setup for potentially our coolest
night of the season so far with Monday morning lows in the upper 30s
in the north to the low 40s for most of Central AL.

By Monday afternoon, the surface high pressure system has shifted
over the Outer Banks, veering our winds more southeasterly and
southerly. This will act to moderate temps across Central AL Monday
through Wednesday to seasonable diurnal ranges.

Wednesday into Thursday, another trough slides into the Central
Plains, developing our next system that will move in just beyond the
extended period. Details are uncertain as models have not shown run
to run consistency on the evolution or timing of the trough.
Therefore, I have introduced 30-40 PoPs area-wide Wednesday and
Thursday, but will need to adjust up or down depending on how models
trend over the next few days.



18Z TAF Discussion.

VFR conditions with low level winds from the northeast will
prevail for the rest of the afternoon and into the evening hours
as an expansive area of surface high pressure slides further east
across the Ohio River valley. Cool air advection along with
subsidence from aloft will maintain dry and stable conditions
through this cycle. Low-level winds will veer from the northeast
this evening to the east early Friday morning. Some increase in
mid and upper level cloud cover is forecast overnight and into
early Friday, especially south and east with the developing
easterly flow but cloud bases are expected to remain above
categorical thresholds.




High pressure builds in across the region. Cooler temperatures
overall with a rain break for late Wednesday into Thursday.
However, rain chances return again for late Friday into the
weekend as another frontal system moves into the area. No fire
weather concerns are expected.


Gadsden     50  74  59  66  42 /   0  10  50  60   0
Anniston    52  74  61  69  43 /   0  10  30  60   0
Birmingham  55  77  62  68  45 /   0  10  40  60   0
Tuscaloosa  55  80  62  69  45 /   0  10  40  60   0
Calera      55  77  62  69  44 /   0  10  30  60   0
Auburn      57  73  62  74  47 /   0  10  10  60  10
Montgomery  59  80  65  77  50 /   0   0  20  60  10
Troy        60  80  65  80  50 /   0   0  10  60  20




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