FXUS64 KSHV 202005

Area Forecast Discussion
National Weather Service Shreveport LA
205 PM CST Tue Nov 20 2018

.SHORT TERM.../Tonight through Wednesday night.
Cloud free skies expected through at least midday Wednesday
with sfc high pressure centered over Red River valley north of
dfw metro. Light norherly wind today will quickly diminish before
sunset with excellent radiation cooling overnight and lows in the
mid 30s north to around 40 south expected as curent dewpoint
fields ranging thru the 30s expected to change little, so keeping
these temps below model blend. A sunny start to Wednesday will
allow for at least a 20 degree diurnal swing. An upper lvl
disturbance movg out of southern Rockies will create isentropic
lift north of old frontal boundary which is well offshore. Thus,
most of this rain will occur south of cwa, although some lgt rain
may brush East TX lakes area by early eve and possibly eastward
into southern tier of LA parishes later Wed night. Overnight lows
Wed night similar to Tue night, but perhaps remaining in the 40s
south of I-20 with incrreased cloud cover./07/.

.LONG TERM.../Thursday through Tuesday night/

Thanksgiving day will be dry and mild with a mostly sunny sky due to
a large surface high pressure system covering most of the county
East of the Rockies and extending across the Four State Region.
Ridging aloft will also be shifting over the region while longwave
troughs of low pressure extend along the West and east Coasts. By
Thursday evening moisture aloft will be increasing as the upper
ridge axis shifts East of the area as a series of short wave trough
eject around the base of the Western trough returning Pacific
moisture followed by low level return moisture around the back side
of the surface high pressure system as it shifts along and off the
Atlantic Coast and front side of surface low pressure that will
shifting out of the Rockies into the Plains with and ahead of the
upper trough. The deepening supply along with the approach of the
upper trough and disturbances and a surface cold front will increase
showers and thunderstorms during the day Friday. Due to the rapid
movement of the upper trough and its passage convection will end
from West to East with most of the rainfall over by or near midnight
Friday Night and early Saturday morning.

A zonal flow aloft and dry air mass in place will contribute to
tranquil conditions Saturday and Saturday night. The next upper
trough of low pressure amplifies across the Rockies Saturday night
and the almost vertically stacked low to the surface shifts out into
the plains driving our next cold front into the forecast area Early
Sunday. Thanks to the zonal flow prior to the approach of the upper
system, the low to middle levels of the atmosphere will be dry except
for high level moisture off the Pacific. Low level moisture will
return for Southern sections of the forecast area briefly on Sunday
which will allow for small chances for showers through mid day.
Under the influence of high pressure on the surface and aloft for
the remainder of the long term no rainfall is expected. /06/


.PREV DISCUSSION... /issued 1124 AM CST Tue Nov 20 2018/

Vfr skc areawide thru the 21/18z fcst cycle. Light north winds
today bcmg near calm after 21/00z. Gradually falling dewpoints
should preclude fog development./07/.


SHV 40 59 38 60 / 0 0 10 0
MLU 38 58 38 61 / 0 0 10 0
DEQ 34 58 33 59 / 0 0 10 0
TXK 36 57 35 59 / 0 0 10 0
ELD 34 57 34 61 / 0 0 10 0
TYR 40 59 39 59 / 0 0 10 0
GGG 38 59 39 60 / 0 0 10 0
LFK 42 61 43 60 / 0 0 40 0



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