Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 251519

Area Forecast Discussion
National Weather Service Shreveport LA
Issued by National Weather Service Memphis TN
1019 AM CDT Tue Sep 25 2018


A quiet morning underway across the region. A mild and moist
airmass is in place with temps climbing into the lower 80s across
northern LA/east TX. Dewpoints range from 70 to 75F with light
south winds. A weak upper level disturbance over east Texas will
push across the forecast area today resulting in isolated to
scattered showers and thunderstorms by this afternoon. Latest hi-
res models point toward greater coverage over northern LA this
afternoon. Given the deep moisture in place a few storms may
produce locally heavy rainfall. Forecast is on track. Will update
to remove morning wording.



.PREV DISCUSSION... /issued 705 AM CDT Tue Sep 25 2018/

For the 25/12z TAFS...Mostly VFR conditions across the Taf sites
this morning, except at MLU, where low ceilings and vsby have
resulted in MVFR/IFR/LIFR conditions. Eventually, all the sites
will return to VFR conditions this morning. However, isolated to
scattered showers/t-storms will develop during the late morning
and early afternoon hours, which could bring a mix bag of flight
categories back to the Taf sites. Convection will diminish after
sunset, then possibly return to the northwestern half of the
region after 26/06z as a cold front approaches the region./20/

PREV DISCUSSION... /issued 446 AM CDT Tue Sep 25 2018/

SHORT TERM.../Today through Wednesday Night/

Southerly flow will continue to increase across the region today
behind a departing sfc low and warm front. At the same time, a
weak upper level disturbance will move to the northeast from SE
Texas across the region today,resulting in the development of
isolated to scattered showers along with a few thunderstorms.
Coverage should become more numerous during peak heating hours.
Also, precipitable water values today are forecast to be in the
1.7 to 1.8 range, which is in the 90th percentile for this time of
year according to SPC sounding climatology. Because of this,
wouldn`t be surprised if some convection produced brief,locally
heavy rainfall.

As the disturbance departs from the region this evening, a cold
front will approach the region from the northwest. Isolated
showers and thunderstorms are expected to develop ahead and along
the front, as it pushes through the region on Wednesday. There is
some model discrepancy on how far south the front makes it on
Wednesday as GFS pushes it completely through by noon, with the
rest of the models having the front become stationary across our
southern parishes/counties through early Thursday morning. Current
thinking is that GFS is the outlier, so going to go with the
other model consensus in this forecast package, which keeps the
best chances of rain across the southern half of the region
through late Wednesday night/early Thursday morning. Model guidance
suggests precipitable water values will approach two inches,
along and ahead of this front which should promote efficient
rainfall. As of now, widespread flooding is not anticipated, but
any training of storms could lead to locally heavy rainfall and
isolated flooding.

Southerly winds will persist today ahead of the front generally ranging
from 5 to 10 mph with high temperatures in the mid to upper 80s.
Behind the frontal boundary on Wednesday, northwest winds near 10
mph, with higher gusts, will bring in noticeably drier air and
cooler temperatures, as highs behind the front will be in the mid
to upper 70s with overnight lows temperatures in the low to mid
60s. /20/

LONG TERM.../Thursday through Monday Night/

Upper low over w central TX at the beginning of the extended pd will
set up weak swly flow aloft atop a cool, post-frontal airmass.
Increasing mid level moisture will overrun the cool airmass,
producing isentropic lift and potentially widespread rainfall
especially by Friday into the weekend. The front will slowly drift
move back nwd as a warm front during the weekend, so temperatures
will warm through that period and into early next work week.

Upper ridge over the sern CONUS to begin nosing back wwd during the
latter half of the weekend. GFS solution is more prominent with this
intrusion, and is thus drier during the extended. The Euro/Canadian
solutions indicate weaker ridging and are therefore wetter. Have
leaned more towards the Euro/Canadian solution as these exhibit more
consistency/continuity with the ongoing fcst. Will continue to
monitor model trends over the next few days, as this setup has the
potential to bring some locally heavy rainfall back to the region.


SHV  86  73  82  66 /  30  30  60  30
MLU  88  74  84  66 /  40  30  60  40
DEQ  85  67  76  61 /  20  30  30  20
TXK  85  71  77  62 /  20  30  40  30
ELD  86  72  79  62 /  30  30  50  30
TYR  87  72  80  65 /  20  20  50  30
GGG  87  73  82  65 /  20  30  60  30
LFK  88  75  86  68 /  30  30  70  50



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