053 
FXUS64 KBMX 240014
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
714 PM CDT Fri Oct 23 2020

.UPDATE...
For 00Z Aviation.

&&

.SHORT TERM...
/Updated at 1151 AM CDT Fri Oct 23 2020/

The slow moving frontal boundary will finally get the push forward
through the overnight hours bringing likely rain chances to much 
of Central Alabama. However, the rain totals look meager at best 
with qpf values around a quarter-inch or so. Showers should 
linger through the day tomorrow, mainly east where they will be 
slow to exit into Georgia. 

17/KLAWS

.LONG TERM...
/Updated at 120 PM CDT Fri Oct 23 2020/ 
Saturday Night through Thursday.

Features.

In the long term forecast period, the upper level flow looks to 
be overall zonal with relatively low amplitude features 
progressing eastward with time. The Polar Jet will sink southward 
Sunday into Monday across the Intermountain West while the 
Subtropical Jet persists in a southwest to northeast orientation. 
Most global modeling depicts the jets trying to phase late Monday 
into Tuesday over the Four Corners States as the Polar Jet 
amplifies further to the south. A closed low looks to develop 
aloft and move into the Central Plains by Thursday before 
gradually opening up into a trough that moves over the Mid South 
toward the Ohio River Valley region on Thursday into Friday.

Zonal flow in the mid levels will persist from Sunday through Monday 
with a gradual transition to a more southwesterly flow over the 
area. Mid-level ridging is progged to amplify over the Florida 
Peninsula while a sharp positively-tilted longwave trough develops 
from the High Plains southwest into the Desert Southwest.

Increasing uncertainty in the ridge position, whether it be to our 
southeast or further east over the Southwest Atlantic Basin, will 
affect the amplitude of the closed low as it cuts off from the main 
flow and moves over Western Texas by Wednesday. Global modeling 
differences only increase with time regarding the position and phase 
of the closed low as it moves across the Mid South and into the 
Tennessee Valley region from the Friday through Saturday time frame.

Forecast.

The cold front that moves through much of the area Saturday will
be slow to push out of the area late Saturday night and into
Sunday and carried low-end PoPs across our east and southeast
counties for this time frame. Expect dry conditions to prevail 
late Sunday followed by more clouds with low-end PoPs north and 
northwest Monday with isolated PoPs all but east on Tuesday.

Expect a gradual increase in moisture in the low levels late 
Tuesday into Wednesday. Model families differ in moisture 
advection with some tapping tropical moisture in the Caribbean Sea
as a potential source. Differences in the moisture gradient from 
Wednesday into Thursday further reduce confidence in timing/extent
of shower and thunderstorm potential. Generally, period of 
greatest moisture availability over the area appears to be in the 
late Wednesday through Thursday time frame followed by drier air 
overspreading the area late Thursday into Friday.

Examining shear profiles in the lower levels, there is 
disagreement on timing, placement and intensity but overall, a 
Low-Level Jet is depicted in the late Wednesday into Thursday time
frame with much of the forecast area potentially experiencing 
this fast flow off the surface. The lower-level low track 
generally is depicted to be near or just north of the Interstate 
40 corridor. Looking at the layer column precipitable water, the 
highest values over our area just exceed 2 inches in the late 
Wednesday through late Thursday time frame. Forecast instability 
values increase during the day Wednesday generally across the 
southern half of the area, decreasing overnight and re-emerging 
across the southeastern and eastern counties during the day on 
Thursday, followed by decreasing values late Thursday into early 
on Friday.

Will cap PoPs below 50 percent from the Wednesday through Friday
time frame given the persistent uncertainties with timing and
position of features. An important question is the potential of
tropical moisture over the Western Caribbean Sea advecting north
and being absorbed into the approaching trough in the late week
time frame. The amount of moisture along with cloud and
precipitation patterns that result will affect instability
distribution and this will be crucial for assessing thunderstorm
potential. At this time with fairly marginal instability and
decent low-level shear a few stronger storms can not be ruled out
with this next storm system. The resolution of further details
will depend upon decreased spread and improved run-to-run
continuity on feature placement and depiction.

05

&&

.AVIATION...
00Z TAF Discussion.

We currently do not have any convection near any of the TAF sites
at this time. There is an area to the south of TOI drifting
northward. Will monitor to see if its progress warrants adding to
the TAF. Otherwise, activity will move into C AL overnight from
the northwest ahead of a front. MVFR cigs will initially move in
as convection increases in the wee hours before dawn. After
daybreak, some IFR will be in the mix as well. No strong winds are
expected overall with this front as it should weaken and stall
across S AL. However, some reduced vsbys are possible with the
showers. TS probability is not zero, but low and will not mention
in TAFs at this time. 

Note: Please disregard TAFs with the time stamp of 232322z. A
glitch occurred causing old TAFs to be transmitted. The correct
TAFs have a timestamp of 232349z after correct ones could be
transmitted. 

08

&&

.FIRE WEATHER...

Moisture continues to increase ahead of a cold front that will
advance eastward toward the area tonight and Saturday with 
scattered showers and a few thunderstorms. Dry weather returns
from northwest to southeast across the area from late Saturday
through Sunday with fairly dry conditions across much of the
forecast area through Tuesday.

05 

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     63  77  59  78  60 /  60  60  30  10   0 
Anniston    64  78  62  79  62 /  50  60  30  10   0 
Birmingham  65  77  60  79  62 /  60  40  20  10   0 
Tuscaloosa  65  77  60  80  62 /  70  40  10  10   0 
Calera      65  77  61  79  62 /  60  50  20  10   0 
Auburn      65  78  63  79  63 /  30  60  40  10   0 
Montgomery  67  82  64  83  64 /  50  60  30  10   0 
Troy        67  81  64  82  64 /  40  60  30  10   0 

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
None. 

&&

$$