Area Forecast Discussion
Issued by NWS Birmingham, AL

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787
FXUS64 KBMX 160539
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
1139 PM CST Fri Feb 15 2019

.UPDATE...
For 06Z Aviation.

&&

.SHORT TERM...
Through Tonight.

With westerly, zonal flow aloft, a cold front has only inched
southward today into extreme northwest Central Alabama. South of
the front, low level winds have become more southerly this
afternoon. With this continued increase in moisture and isentropic
lift, will continue to see scattered light rain showers increase
this afternoon and evening.

Tonight, in response to a weak upper level wave moving across the
Tennessee Valley, a surface low will move along the nearly stalled
front, spreading rainfall that has been kept to our north
southward into Central Alabama. Best rain chances overnight will
be north of I-20, with only isolated coverage through sunrise
across the far southeast. Cold air will advect into the area
behind the front, with temperatures falling into the 40s across
the northwest. From I-59 corridor to the east, temperatures will
range from near 50 degrees to around 60 degrees.

14

.LONG TERM...
Saturday through Thursday.

The cold front is still sliding southward through Central AL early
on Saturday. Some of the higher resolution guidance is pretty quick
with the frontal passage and has it mostly out of our area by
Saturday morning. However, I`ll keep at least some lower chance for
rain mentioned in the forecast through noon. Any lingering precip
should clear out by the afternoon. Later Saturday evening and into
the overnight hours, the frontal boundary gets lifted back northward
as an effective warm front. As this happens, expect an increase in
rain chances north of the I-85 corridor.

The front becomes stationary for most of the upcoming week leading
to continued rain chances every day. There is a slight southward
movement of the boundary Sunday night into Monday, and we could see
a break in the rain for some locations by Monday afternoon before
another shortwave impulse slides along the boundary and lifts it
northward again. For now, I`ve kept roughly 40% chance of rain for
Monday because there`s a chance the front doesn`t dip that far south
to rule out at least scattered showers for the area.

The warm front is lifted northward again beginning on Tuesday,
leading to widespread rain once again. During the afternoon on
Tuesday, guidance suggests the low level jet could intensify, which
would lead to increased rainfall rates across the northern half of
the area. Instability will build in with the stronger warm air
advection by Tuesday evening and into the overnight hours. Another
shortwave slides through Wednesday and increases the lift along the
still generally stationary boundary. The moist air in the warm
sector continues to destabilize during the day on Wednesday. It`s at
this point that the forecast becomes a little more difficult. The
unstable air mass is across portions of Central AL with a frontal
boundary stretching through as well. Environmental shear is fairly
high, and lapse rates are sufficient to promote stronger updrafts.
However, the dynamic support for severe weather is well to the
north, and the frontal boundary that we`d normally focus on as a
trigger for convection doesn`t really move much at all for 18-24
hours. It`s possible that some strong to severe storms develop in
the warm sector Wednesday or Thursday, but without upper level
support, I`m not sure how deep the convection would be. For now,
I`ll hold off adding any mention of severe weather in the HWO. We`ll
see how guidance trends with the destabilization of the warm sector
and any convective initiation potential in coming days.

What`s more certain for the upcoming week is the prolonged rainfall
we`re likely to see. Due to the stationary nature of the frontal
boundary, it will likely be the end of next week before we see a
substantial break in the rain. The increased rainfall rates along
the boundary Tuesday evening, Wednesday, and Thursday could pose a
threat for flash flooding considering the already saturated soils by
that point. Current forecast rain totals from Sunday afternoon
through Thursday have 4-7+ inches for much of North-Central AL.

25/Owen


&&

.AVIATION...
06Z TAF Discussion.

A cold front will push southeast thru central Alabama and be
located near a TCl-BHM line by 11z and stall out or weaken by 18z
near TOI. Mainly light rain will continue south of the frontal
boundary with vsbys above 5 miles, but heavier showers along the
front itself will produce vsbys near 3 miles. The showers should
end within one hour of fropa. Cigs have already fallen blo 1000
feet agl across north Alabama, and will likely become IFR at MGM
and TOI between 08z and 11z. Cigs will remain IFR thru 15z, but
should see a rise above IFR conds between 15z and 18z. Models
indicate cigs improving considerably in the afternoon, but weakening
advection behind front may result in lingering MVFR cigs thru the
end of the period.

58/rose


&&

.FIRE WEATHER...

Moisture and rain chances will continue to increase tonight,
particularly across our northern areas. A cold front will slide
southward into the area tonight, stalling across the area
tomorrow. A break in rain chances is expected tomorrow, before a
prolonged period of rainfall from Sunday through Thursday begins,
with very wet conditions expected, especially across the northern
half. There are no fire weather concerns at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     48  59  46  65  45 /  90  20  50  70  60
Anniston    52  62  49  68  49 /  80  30  50  70  70
Birmingham  48  61  50  68  48 /  80  20  50  70  60
Tuscaloosa  49  62  52  69  48 /  70  10  40  70  60
Calera      51  62  51  69  50 /  70  20  40  70  70
Auburn      57  68  55  70  54 /  50  30  20  50  70
Montgomery  59  70  57  75  56 /  40  30  20  50  70
Troy        60  72  58  75  58 /  40  30  20  40  60

&&

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

&&

$$



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