Area Forecast Discussion
Issued by NWS Birmingham, AL

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249
FXUS64 KBMX 231723
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
1223 PM CDT SAT JUL 23 2016

.SYNOPSIS...

An MCV was located across northern Mississippi this morning while
a few upper level disturbances were noted in water vapor imagery
across eastern Tennessee. Our area remains on the east side of a
sprawling deep ridge centered over the southern plains states.
Relatively weak north to northeast flow aloft is continuing to
allow upper level features to move south across the area and to
help encourage shower and thunderstorm development.

.DISCUSSION...

Thunderstorm complex over northern Mississippi starting to organize
by cold pool. As the updrafts growing in a weakly sheared
environment, the propagation is generally south southwest due to
weak winds in the lowest 20k ft and a northerly component aloft. But
this complex has also produced some outflow boundaries which are
headed eastward into far northwest central Alabama.

Additional isolated showers and a few storms have initiated in the
northeast due to reaching convective temperatures, orographic
enhancement and a weak vorticity axis approaching the area from the
north northeast. Expect additional development and coverage increase
into the afternoon hours northwest and northeast with variable
movement. Once established, expect this convection to move southwest
with the highest coverage along and north of I-20. Therefore, the
morning update has increased rain chances for these areas.

Cumulus filed developing rapidly as the convective temperature is
reached. Bulk shear values may be isolated around 20kts, MLCAPE
values into the 2500 range, Downdraft Cape increasing to over
1000 this afternoon, poor mid level lapse rates, and high
precipitable water north with a large decrease south. Wet
microburst indices appear in the moderate range this afternoon so
will not ramp up completely on the isolated severe wording. But
certainly, any storms that gain stout updrafts or cold pools will
have the capability of wind gusts 35 to 45 mph and frequent deadly
lightning. With precipitable water values 1.75 inches or higher
and relatively slow movement of storms, locally heavy downpours
are also possible.

A hot and humid airmass near the surface will continue to provide
ample low level instability for shower and thunderstorm development
while also creating heat indices in excess of 100 degrees through
much of the afternoon hours for locations that do not experience
convection. A heat advisory will remain in effect until 9 pm tonight
but should not be necessary tomorrow as the ridging weakens and
heights begin to fall across the area.

75/05

&&

.AVIATION...
18Z TAF Discussion.

Adjusted VCTS starting at 20Z at BHM/TCL/ANB/ASN/EET to account
for shower and thunderstorm activity expected to develop early
this afternoon. Added TEMPO for TSRA at ANB/ASN from 20-22Z with
most likely convective initiation NE then drifting SW with time.
Uncertainty will be with storm motion as outflow will easily
overcome light low level flow. Added 5SM/BR with low CIG`s at
MGM/TOI at 08Z tonight but this may be experienced further north
depending on how much rain falls across the area with today`s
convection.

05

&&

.FIRE WEATHER...

Scattered showers and thunderstorms are expected over the next
several days with highs in the 90s. Critical fire weather
thresholds are not expected to be met with no watches or warnings
expected.

&&

.PREV DISCUSSION...
/Issued 1158 AM CDT SAT JUL 23 2016/

Thunderstorm complex over northern Mississippi starting to organize
by cold pool. As the updrafts growing in a weakly sheared
environment, the propagation is generally south southwest due to
weak winds in the lowest 20k ft and a northerly component aloft. But
this complex has also produced some outflow boundaries which are
headed eastward into far northwest central Alabama.

Additional isolated showers and a few storms have initiated in the
northeast due to reaching convective temperatures, orographic
enhancement and a weak vorticity axis approaching the area from the
north northeast. Expect additional development and coverage increase
into the afternoon hours northwest and northeast with variable
movement. Once established, expect this convection to move southwest
with the highest coverage along and north of I-20. Therefore, the
morning update has increased rain chances for these areas.

Cumulus filed developing rapidly as the convective temperature is
reached. Bulk shear values may be isolated around 20kts, MLCAPE
values into the 2500 range, Downdraft Cape increasing to over
1000 this afternoon, poor mid level lapse rates, and high
precipitable water north with a large decrease south. Wet
microburst indices appear in the moderate range this afternoon so
will not ramp up completely on the isolated severe wording. But
certainly, any storms that gain stout updrafts or cold pools will
have the capability of wind gusts 35 to 45 mph and frequent deadly
lightning. With precipitable water values 1.75 inches or higher
and relatively slow movement of storms, locally heavy downpours
are also possible.

A hot and humid airmass near the surface will continue to provide
ample low level instability for shower and thunderstorm development
while also creating heat indices in excess of 100 degrees through
much of the afternoon hours for locations that do not experience
convection. A heat advisory will remain in effect until 9 pm tonight
but should not be necessary tomorrow as the ridging weakens and
heights begin to fall across the area.

75/05

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     73  94  73  93  73 /  40  30  20  40  30
Anniston    74  94  73  93  73 /  40  30  20  40  30
Birmingham  76  95  76  94  75 /  40  30  20  40  30
Tuscaloosa  74  95  75  94  74 /  40  30  20  40  30
Calera      74  94  74  93  74 /  30  30  20  40  30
Auburn      75  94  74  92  74 /  20  30  20  30  20
Montgomery  75  96  75  95  74 /  20  30  20  40  20
Troy        73  93  73  92  72 /  20  30  20  30  20

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM CDT this evening For all of Central
Alabama.

&&

$$



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