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Area forecast discussion
National Weather Service Birmingham Alabama
645 am CDT Wed Sep 18 2019

for 12z aviation.


Short term...
/updated at 0348 am CDT Wed Sep 18 2019/

Today and tonight.

The large deep-layer ridge across the eastern Continental U.S. Has become
quite amplified now with an axis lingering just to our west
northward through the Great Lakes. With a trough to its immediate
east & Hurricane Humberto near Bermuda, northerly flow aloft
(850-300 mb) has overcome much of the deep south. A surface high
pressure system (centered near maine) extends down along the East
Coast with northeasterly surface winds east of the Appalachian
Mountains. This has been trending southwestward through the
Carolinas & should approach our eastern counties later this
afternoon in the form of a surface front. As such, a tightening
pressure gradient & increasing moisture content (pws 1.5-1.7") is
expected as we transition to increasing easterly flow, as well as
an isolated shower or thunderstorm. Pops have been adjusted to
~15-20% east of I-65 from 4- 9 PM, when the best available
moisture will coincide with a narrow axis of instability (~1,500
j/kg mlcape) near the boundary.

Otherwise, central Alabama is still amidst a relatively dry
airmass with more upper 90s to lower 100s for afternoon highs.
The highest temperatures should affect the same urban and/or
drought impacted areas as in previous days. The "cooler" weather
is mostly limited to the aforementioned areas across the east
(especially near the Alabama/Georgia border) where lower 90s have been
placed in anticipation of an increase in sky cover & isolated rain
chances. Elsewhere, particularly along the I-65 corridor & west,
dewpoints will likely mix down into the upper 50s/lower 60s once
again this afternoon resulting in relative humidity values ~30% or less.
Temperatures will drop into the upper 60s to lower 70s area-wide
once again tonight.


Long term...
/updated at 0348 am CDT Wed Sep 18 2019/

Thursday through Tuesday.

A cold front will continue to move westward on Thursday from West
Alabama into Mississippi. There may be enough moisture and lift
for isolated convection right along our western border. Otherwise
the main story will be the significant drop in temperatures behind
the front for Thursday through Saturday. Afternoon highs will
range from the mid and upper 80s in the east, to around 90 in the
west. Overnight lows will also trend downward into the lower to
mid 60s for most locations, but some upper 50s are possible in our
northeastern counties. As surface high pressure weakens on Sunday
and Monday, temperatures will head into an uptrend as easterly
flow transitions to southerly and southwesterly. A weakening front
may approach the region on Tuesday but is unlikely to lead to any



12z taf discussion.

VFR conditions will continue through much of the forecast period
across central Alabama. Winds will begin to transition out of the
east this afternoon as a surface front moves from east to west
across the state, but will remain light. The only forecast
uncertainty is with the chance of low stratus development across
eastern Alabama with easterly surface flow continuing. For now,
broken MVFR cigs have been added at anb and asn during the
overnight period tonight thru 12z Thursday morning. Trends will be
monitored to determine if low cigs will remain necessary on future
taf issuances.



Fire weather...

Aside from a slight chance of rain in the eastern fringe of the
state on Wednesday and in the west on Thursday, dry and hot
conditions will continue for the next several days. Afternoon
relative humidity values may locally drop below 30 percent late
this afternoon. Kbdi values will remain elevated as drought
conditions persist.


Preliminary point temps/pops...
Gadsden 95 67 86 61 85 / 10 10 0 0 0
Anniston 95 67 86 61 86 / 20 10 10 0 0
Birmingham 98 70 88 64 87 / 10 10 10 0 0
Tuscaloosa 100 73 90 67 89 / 0 10 10 0 0
Calera 100 69 88 64 87 / 0 10 10 0 0
Auburn 94 68 83 62 84 / 20 20 10 0 0
Montgomery 101 72 89 64 88 / 10 10 10 0 0
Troy 98 69 87 63 87 / 20 20 10 0 0


Bmx watches/warnings/advisories/...

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