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Area forecast discussion
National Weather Service Shreveport la
352 PM CDT Sat Oct 19 2019

Short term.../tonight through Sunday night/

A weak frontal boundary is continuing to try to make a push into
NE Texas but is running out of gas so to speak. Narrow ribbon of low
level moisture with weak warm air advection has expanded north and
east ahead of this boundary across all but our eastern third this
afternoon but look for this moisture to continue to scatter out as
the afternoon and evening continues. Low level moisture will
continue to advect northward overnight, encompassing much of our
eastern most zones and latest hrrr and 12z NAM output suggests we
could see some weak isentropic lift induced showers late this
evening across the lower Toledo Bend and Sam Rayburn country of
deep East Texas into west central Louisiana and farther east
encompassing more of north central Louisiana and south central
Arkansas after midnight.

On Sunday, what's left of the current boundary should wash out
and/or return back to the north as a warm front with the return of
a moister and more unstable airmass. A tightening pressure
gradient will help to bring this low level moisture northward on
Sunday and with afternoon breaks in the low level overcast, look
for temperatures to soar on Sunday with highs ranging through the
80s. By Sunday morning, our much advertised upper level trough
will be moving out of the intermountain west and into the central
and Southern Plains. Look for upward forcing to really begin
ramping up across the middle Red River valley of NE TX, southeast OK and
SW Arkansas near or shortly after midnight Sunday night/Monday morning.
Storm Prediction Center currently has much of this region in a day 2 slight risk of
severe weather and this is warranted given the strong deep layer
bulk shear in place, increasing sfc based instability and descent
mid level lapse rates. If any discrete supercell thunderstorms can
develop ahead of what will become a broken line of strong to
severe thunderstorms along a cold front, they could pose a tornado
risk given the strong 0-3km srh values some of the latest high res
models are spitting out. While timing for this sort of scenario to
transpire will be short in duration, what is much more likely will
be strong to severe thunderstorms developing along a strong cold
front that should be near or just southeast of the I-30 corridor
by 12z Mon. It must be noted that the 12z NAM output is the
outlier given its frontal timing with this solution keeping the
frontal boundary still northwest of the I-30 corridor by 12z Mon.
A slower frontal movement would suggest that more of our southeast
half would be in play for a severe weather risk during the day
Monday, thus the reasoning in spc's day 3 risk across our
southeast half on Monday. Regardless, damaging wind gusts appear
to be the primary threat, followed by large hail and an isolated
tornado threat as well, especially seeing that this could become a
favorable pattern for qlcs oriented tornadoes or isolated
tornadoes embedded along the leading edge of an intense line of
thunderstorms late Sunday night through the day Monday.

While there will be a heavy rainfall threat as well, mainly along
and northwest of the I-30 corridor late Sunday night through early
Monday, quantitative precipitation forecast amounts do not appear significant enough to warrant a
Flash Flood Watch attm.


Long term.../Monday through Saturday/

A line of strong to severe convection will be ongoing at the start
of the long-term period Monday morning as a cold front continues to
quickly advance southeast across the region. Modest instability with MUCAPE
values in the 1500-2500 j/kg range along and ahead of the front will
contribute to stronger updrafts within some storms along the leading
edge of the line where deep layer shear will also be quite robust.
For this reason, a slight risk of severe weather is highlighted over
roughly the southeast half of the region from around sunrise Monday morning
through the early afternoon. Damaging winds will be the main threat,
but large hail and perhaps an isolated tornado or two will also be
possible given the increased shear component in play. Convection
will gradually clear the region by late afternoon through the early
evening hours as a more stable air mass infiltrates from the northwest in
wake of the cold front. Temperatures behind the front will only be
marginally cooler with readings near/just below seasonal averages
through mid week with highs in the 70s and lows in the 40s/50s.

Our next chance of rain will come on Thursday just ahead of the next
cold front due to arrive Thursday night through early Friday. There
are some discrepancies on the strength and evolution of this system
so the potential of another round of severe weather is still a bit
in question at the moment with another inch or so of rainfall quite
possible. In addition , it does appear a cooler air mass will follow
with this front compared to the early week system. Look for highs in
60s and lows in the 40s on Friday through Saturday with rain chances
diminishing into the weekend behind the front.



Previous discussion... /issued 1215 PM CDT Sat Oct 19 2019/


Dealing with a few remaining MVFR ceilings across our NE Texas
terminals but they should continue lifting and/or scattering out
as we transition into the afternoon hours. Meanwhile, a weak cold
front currently west of our western most airspace will make slow
but steady progress eastward into NE Texas/southeast OK and SW Arkansas but should
stall and eventually become washed out during the day Sunday. Have
included some patchy fog and MVFR/IFR ceilings developing late
tonight ahead of the remnant boundary for late tonight through the
tail end of the taf period on Sunday but did not add any precip
mention as some of the higher res progs are indicating the
possibility of isolated convection developing late tonight across
portions of north la.



Preliminary point temps/pops...
shv 61 86 70 77 / 10 20 60 80
mlu 60 86 71 80 / 20 20 30 80
deq 53 81 62 73 / 10 10 90 30
txk 58 82 63 73 / 20 10 90 50
eld 56 83 68 75 / 20 20 60 80
tyr 59 86 64 73 / 10 10 90 50
ggg 59 86 65 74 / 10 10 80 60
lfk 62 87 71 78 / 20 20 40 80


Shv watches/warnings/advisories...

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