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FXUS64 KBMX 142100

Area Forecast Discussion
National Weather Service Birmingham AL
400 PM CDT Mon Oct 14 2019

/Updated at 0326 PM CDT Mon Oct 14 2019/

Quasi-zonal but also broadly anti-cyclonic upper-level flow 
remains in place over the area, downstream of a southern trough 
over the southwest CONUS. Meanwhile in the northern stream the 
upper low associated with an occluded remnant mid-latitude cyclone
remains near James Bay while a shortwave is digging into the 
Northern Plains. Water vapor indicates a moisture plume and 
embedded waves emanating from a former eastern Pacific tropical 
disturbance over northwest Mexico. At the surface a quasi- 
stationary front remains over the Florida Panhandle, serving as a 
focus for showers there. Earlier showers over Pike and Barbour 
Counties have dissipated but an isolated shower cannot be ruled 
out over the southeast counties late this afternoon. Regional 
radar mosaics indicate some light reflectivity aloft associated 
with a 500mb vort max, but an area of dry air at 700mb is 
preventing this from reaching the ground, for areas from Jackson 
MS northeastward. 

A surface low associated with the northern Plains shortwave will
move from the Northern Plains to the Midwest on Tuesday. Southerly
low-level flow ahead of this will cause the quasi-stationary front
to attempt to lift back north as a warm front. Combined with 
continued waves in the southern stream mid/upper-level flow and 
increased moisture, the result will be strong moist isentropic 
lift and some frontogenesis developing late tonight and tomorrow, 
resulting in widespread precipitation developing. There's some 
spread regarding how quickly the column saturates, but chose to 
lean towards the faster guidance given past experience, with PoPs 
quickly increasing after midnight. Many areas may see their lows 
around/shortly after midnight before temperatures become steady or
rise slightly given increasing cloudcover. Did lower lows a bit 
in the far northeast counties where clouds will be late to arrive,
allow for favorable radiational cooling conditions, and they may 
need to be lowered further.

The widespread isentropic lift precipitation north of the surface warm
front should inhibit its northward progression on Tuesday, causing
it to become hung up along our southern border. Latest model
guidance and HREF members have continued to trend a bit further to
the north with the warm front's progression, however. This could
result in weak surface-based instability developing in our far
southern counties, mainly in Pike and Barbour Counties. If this
were to occur, 0-6km bulk shear values around 45kts would support
a marginal risk of severe storms. Lapse rates are expected to
weak, with hail not expected. Saturated profiles would limit
damaging wind potential, though with enhanced 0-3 km shear there
could be some wind potential with bowing segments, though shear
vector orientation supports more cellular rather than linear
structures. There will be an enhanced area of low-level shear/SRH
right along the warm front, with a possible weak wave of low
pressure riding along the warm front. While this could support a
non-zero threat of a brief tornado mainly for Pike and Barbour
Counties, this threat is too conditional and limited in space to
mention in the HWO at this time. The 12Z guidance was the first to
show this, and would prefer to wait for the 00Z guidance to see if
this is a sustained trend. Warm fronts do have a tendency to not
lift as far north as expected with widespread rainfall to the
north of them. But will continue to closely monitor trends. Forecast
rainfall amounts are in the 1-3" range. Given the high FFG from 
antecedent conditions, flash flood potential is too low to mention
in the HWO at this time.


/Updated at 0418 AM CDT Mon Oct 14 2019/


Cooler, drier air is expected to advect into the region by 
Wednesday morning, signaling the end of rain chances as subsidence
and upper- level confluent flow overspreads the Southeast ahead 
of a potent shortwave ejecting across the Ohio Valley. Lingering 
areas of rainfall are expected to remain south of I-20, with best 
chances south of I-85, before exiting the area Wed evening. 
Thereafter, dewpoints drop into the 30s near the Tennessee Valley,
with 40s as far south as the I-10 corridor. Clearing skies and 
light northerly winds support widespread lows in the 40s Wed night
and into Thursday morning.

Thursday through Sunday.

A period of dry, stable weather is expected for the rest of the week 
after a wet Tue/Wed. High pressure will build across much of the 
eastern CONUS with northerly winds likely through Thursday evening. 
As the surface anticyclone moves toward the East Coast by Friday, 
winds should become more easterly. As a result, warmer afternoon 
temperatures will develop that afternoon with mid to upper 70s 
expected, and a run for the 80s possible during the weekend. 
Meanwhile, an active jet stream pattern seems to be underway as 
guidance is suggesting a rather dynamic and amplifying trough to 
develop across the Intermountain West by Sunday. This will bring 
another chance of widespread rainfall as a broad area of warm, moist 
low-level advection overspreads the Gulf Coast Region with more 
focused thunderstorm activity possible along a warm front. 
Nonetheless, have truncated PoPs until higher confidence & 
predictability can be achieved in future updates.



18Z TAF Discussion.

Cloudy conditions will continue today, but VFR conditions are 
expected for the remainder of this afternoon. A stalled boundary 
along southern Alabama will begin to lift northward shortly after 
sunset. Showers are expected to begin developing across the south
and west initially by 06Z. Rain coverage and intensity is 
expected to increase across all sites after sunrise. Drops in 
visibility and ceilings are likely at all terminals as a result of
widespread rainfall. Ceilings at MGM and TOI may fall into IFR 
criteria by 12Z where the axis of heaviest rainfall is expected to




A disturbance to our west will foster more widespread and 
potentially heavy rain beginning tonight from the southwest. This
will continue eastward through Tuesday evening. Rainfall amounts 
of 1-3" are expected, with locally higher amounts in heavier 
embedded thunderstorm activity. Rainfall amounts generally taper 
off in areas farther north. Thereafter, a cooler, drier airmass 
moves in Wednesday night with rain-free conditions expected for 
the rest of the week.

The Alabama Forestry Commission continues to have a fire alert in
effect that includes all of Central Alabama. For more information
about restrictions, visit their web site at


Gadsden     54  67  59  69  42 /  30  90  60  10   0 
Anniston    60  68  60  71  44 /  40 100  70  20   0 
Birmingham  61  68  62  70  45 /  50 100  70  10   0 
Tuscaloosa  63  69  62  71  45 /  80 100  70  10   0 
Calera      61  68  62  71  45 /  60 100  70  20   0 
Auburn      62  68  64  75  46 /  80 100  90  30   0 
Montgomery  66  73  66  76  48 /  90 100  90  30   0 
Troy        66  77  66  77  47 /  70  90  90  40   0 



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