Scientific Forecaster Discussion
fxus64 kshv 190505
Area forecast discussion
National Weather Service Shreveport la
1205 am CDT Thu Sep 19 2019
for the 19/06z tafs, convection associated with tropical
depression Imelda will move northward and become widespread across
much of East Texas and western Louisiana during this taf cycle.
Outer bands of showers and thunderstorms may affect
southwest/southern Arkansas and north central Louisiana as well.
These areas may see a brief break before rain resumes as the
center of Imelda moves farther north.
MVFR/IFR flight conditions are already ongoing across East Texas
south of Interstate 20 and extreme western Louisiana and no
improvement is expected. Brief windows of LIFR conditions cannot
be completely ruled out during the periods of heaviest rain. VFR
conditions persist farther to the north and east, but expect
ceilings and visibilities to deteriorate as the convection
becomes more widespread.
The impacts of the convection will likely extend beyond the end of
this taf cycle.
Previous discussion... /issued 1023 PM CDT Wed Sep 18 2019/
the center of tropical depression Imelda continues to slowly move
northward through southeast Texas and towards our forecast area.
Convection has has become much more confined to near imelda's
center, which is typically observed at night. Much of this will
continue to impact our deep East Texas counties through the
remainder of the night. Based on the Lufkin ASOS, rainfall rates
have generally been less than one inch an hour. While the constant
rainfall has led to some minor flooding in the more low-lying and
flood-prone areas, significant flooding has yet to be reported.
Latest radar loops and infrared satellite images show the
strongest showers and thunderstorms and rainfall rates remain just
south of our area, generally between Jasper and Port Arthur. As
the center of Imelda moves north, the more robust convection will
move into deep East Texas during the early morning hours of
Thursday and will continue to spread north during the day, which
will also lead to an increase in the threat for heavy rainfall and
No changes were made to the Flash Flood Watch. Pops were trimmed
back slightly through 12z Thursday morning, especially across the
northeast half of the area, based on latest radar trends.
Updated text products have been sent.
Previous discussion... /issued 415 PM CDT Wed Sep 18 2019/
Short term.../tonight through Thursday night/
The remnants of tropical depression Imelda continue to lift north
into East Texas this afternoon with bands of showers and embedded
thunderstorms spreading across much of the region. This has been
enhanced by daytime heating, especially across the northern and
eastern sections of the area where temperatures climbed into the
lower to mid 90s this afternoon. Farther south and west near the
center of circulation around the remnants of Imelda, temperatures
have been held mainly in the lower 80s across deep East Texas with
mid and upper 80s farther north along the I-20 corridor eastward
into northwest Louisiana.
Decent coverage of convection is expected to continue through the
remainder of the afternoon with activity generally coalescing
closer to the center of circulation through this evening and
overnight over much of East Texas and western Louisiana. Overall,
rainfall rates have been very manageable thus far but that is
expected to become more problematic over the next 24-36 hours as
heavier bands of rainfall set up and train across parts of the
region. As a result, have expanded the Flash Flood Watch in time
and coverage, taking in more of East Texas and northwest Louisiana
generally along and south of the I-20 corridor. On average,
rainfall amounts should range from around 3-7 inches in the watch
area with isolated higher amounts of 8-10+ inches possible through
Friday morning, primarily across deep East Texas into Toledo Bend
Long term.../Friday through Wednesday/
The remnants of Imelda should be falling apart quickly through the
course of Friday as moisture begins to pull north toward a frontal
zone dropping into the Central Plains and Midwest. That said, there
could still be some pockets of heavy rain around the northern half
of the arklatex through the morning hours, but by afternoon the
precipitation activity should be scattered in nature. Temperatures
should be held down below 90 degrees due to lingering clouds and
showers, but expect plenty of moisture around to bolster heat
index values well above the actual temperature.
The forecast has not changed a great deal regarding expectations for
this weekend and through the early portion of next week. In short,
the front alluded to above should run out of the steam on its
southward journey by the time it approaches the northern portions of
the four state region. This boundary could be a trigger for at least
isolated showers and storms well north of I-20 Sunday night through
Tuesday and temperatures in the northern quarter of the region could
be knocked down a bit if the front makes slightly more progress than
expected. Otherwise, anticipate temperatures warming back to above
normal levels through the weekend and remaining in that neighborhood
through early next week. Away from the potentially-stalled boundary
in the north, expect only very isolated and diurnally-driven showers
and storms, at best.
Preliminary point temps/pops...
shv 73 83 71 83 / 50 80 90 60
mlu 72 89 71 88 / 10 40 60 40
deq 71 89 70 81 / 10 40 60 80
txk 72 85 70 79 / 10 50 80 70
eld 71 88 70 82 / 10 40 80 50
tyr 72 81 71 85 / 60 70 60 70
ggg 72 81 71 83 / 60 80 90 70
lfk 73 81 73 85 / 90 90 70 50
La...Flash Flood Watch through Friday morning for laz001-002-010-011-
Texas...Flash Flood Watch through Friday morning for txz126-136>138-