Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 241604

Area Forecast Discussion
National Weather Service Shreveport LA
1104 AM CDT Sat Mar 24 2018

Minor change to the current forecast to raise the daytime highs
about a degree for the region. Otherwise no other significant changes
needed. /06/


.PREV DISCUSSION... /issued 707 AM CDT Sat Mar 24 2018/

For the ArkLaTex, Several decks MVFR/VFR with MVFR likely for 3-4
hrs and could lift to VFR, but guidance is bent on keeping MVFR
until 21Z. SW sfc winds have been persistent with some gusts to
20KT but overall slacking with time. Climb is brisk SW 20-55KT
slacking a bit after 5kft. W/NW flow aloft 30-60KT. A weak cold
front is edging our way and could touch off a few showers.
Otherwise, only KTXK/KELD expecting a shift to E/NE overnight.
Boundary near I-20, but will lift N into work week, big ra coming.

PREV DISCUSSION... /issued 245 AM CDT Sat Mar 24 2018/

Pressure gradient remains very tight across the Southern
Plains/Lower Miss Valley but winds are trying their best to
decouple and this trend will continue as we head towards sunrise.
Will therefore allow the Lake Wind Advisory to expire at 7am.

Cannot rule out widely scattered showers today across our northern
and northeastern zones along and ahead of a frontal boundary which
currently resides across N OK into SE KS. This boundary will be
nearing the Ouachitas of SE OK and SW AR by this afternoon and
should backdoor into the Middle Red River Valley of N TX into S AR
overnight. Kept the mention of slight chance pops as far south as
the I-20 Corridor of NE TX into N LA to account for this boundary
as it could continue backdooring itself into NE LA during the day
Sunday before it begins to return back to the north Sun Night. A
weak disturbance aloft could result in more in the way of
scattered post frontal showers and thunderstorms Sunday into
Sunday Night across the Middle Red River Valley of NE TX/SE OK
into SW AR as well but all eyes will be on the developing trough
across the western CONUS that will be our big weather maker
through much of next week.

This trough is currently digging its way into the Pacific
Northwest while upper level ridging continues building across the
Southern Plains. Our ridge will begin to flatten late Sunday into
Monday as the longwave trough moves into the Inter Mountain West.
The trough will split off from the westerlies during the day
Tuesday, cutting itself off across the the Desert Southwest before
slowly ejecting eastward into the Four Corners area of the
country by early Wednesday. The latest runs of the GFS and ECMWF
have trended a little slower getting the excessive heavy rainfall
into our northwest zones with timing looking more and more likely
early Tuesday along and to the northwest of the I-30 Corridor of
NE TX/SE OK and SW AR so have made this adjustment to the grids.
The ECMWF remains a little slower with the ejection of this trough
into the Southern Plains Wed into early Thu than the more
progressive GFS so tried to blend the two with a little more
weight paid to the slower ECMWF solution.

Having said this, it still appears that much of our area will see
a prolonged heavy rain event beginning across our NW zones on
Tuesday with a gradual south and east progression of excessive
heavy rainfall Wed/Wed Night before upper forcing shifts east of
our region during the day Thursday. Over the last several days,
there had been concern for the heaviest rainfall axis to take
shape across the Middle Red River Valley of SE OK/SW AR and NE TX
but we are becoming more concerned now that there may be another
area of excessive heavy rainall extending from the southern half
of NE TX into N LA and SC AR in association with this slow moving
upper trough. Needless to say, Flash Flood Watches will likely
become necessary across portions of our region as early as Monday
Night but especially Tuesday through at least Wed Night of next
week until we can get this trough through our region late next
week. We cannot rule out the possibility of strong to severe
thunderstorms as well, especially Tuesday into Tuesday Night as
this appears when we will become the most unstable just about the
time upper level forcing becomes maximized across our region. /13/


SHV  79  63  77  63 /  10  20  20  20
MLU  78  62  75  61 /  10  20  20  20
DEQ  78  53  68  58 /  20  10  40  40
TXK  78  56  70  60 /  20  20  30  30
ELD  76  56  70  58 /  20  20  20  30
TYR  81  64  78  64 /  10  20  20  30
GGG  79  64  78  63 /  10  20  20  20
LFK  82  64  82  64 /  10  10  10  20




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