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FXUS64 KBMX 181145

Area Forecast Discussion
National Weather Service Birmingham AL
645 AM CDT Wed Sep 18 2019

For 12Z Aviation.


/Updated at 0348 AM CDT Wed Sep 18 2019/

Today and Tonight.

The large deep-layer ridge across the Eastern CONUS 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 AL/GA 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 RH values ~30% or less. 
Temperatures will drop into the upper 60s to lower 70s area-wide 
once again tonight.


/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.




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.


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 



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