Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 231741
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
1241 PM CDT Tue May 23 2017

.UPDATE...
Stratus deck slowly scattering out early this aftn, though broken
to overcast mid to upper level cloud cover remains entrenched
across the region. Temps are warming a few degrees faster than
anticipated courtesy of low clouds scattering out, so elected to
increase the maxT grid to reflect this trend. Also tweakend the
dewpoint temps and relative humidity values to current obs.
Otherwise, the isolated showers nearing east Texas have been
struggling to maintain its intensity, however additional scattered
showers and thunderstorms continued to develop along and behind a
cold front which is close to knocking on our door across east TX
and southeast OK. Will elect to maintain likely POPs across the
the western zones as computer models continue to hint at
precipitation activity gradually expanding to across the
aforementioned areas later this aftn.

&&

.PREV DISCUSSION... /issued 1012 AM CDT Tue May 23 2017/

UPDATE...
Isolated showers and thunderstorms have developed ahead of front
across east Texas just west of the County Warning Area. The HRRR
solution seems to have a decent handle on the ongoing convection
and thus, this activity will gradually develop and expand to
across east Texas, southeast OK, southwest AR and northwest LA
through this afternoon, to the remainder of the area through this
evening due to increased upper level support. Computer models are
in good agreement with showing this activity slow to move across
central and northeastern LA this afternoon, so dropped POPs to
slight chance category there, with chance category elsewhere this
morning, and showing likely POPs across all but the central and
northeastern LA /chance POPs/ for this aftn. Otherwise, tweaked
the MaxT grid to show some locales warming a few degrees more than
initially thought, given a few breaks in the cloud cover.
Subsequently, tweaked the dewpoint temps and relative humidity
values.

PREV DISCUSSION... /issued 650 AM CDT Tue May 23 2017/

DISCUSSION...
MVFR/IFR conditions to continue through at least mid morning, with
some improvement expected by mid day at most sites. Shwrs/tstms
develop and spread from w to e today, as a cold front moves across
the terminals. Convection should move e of the area by 06Z, with
VFR conditions to prevail thereafter through the end of the 12Z
TAF pd. Otherwise, expect nwly winds 5-10 kts throughout the pd.
/12/

PREV DISCUSSION... /issued 306 AM CDT Tue May 23 2017/

DISCUSSION...
Deep longwave trough developing across the middle portion of the
country this morning associated with a well defined upper jet
structure along the east, south and western flanks of this
vigorous trough. The center of this closed low will slowly shift
southward today into the Central Plains and as it does, a spoke of
PVA will be exiting the OK/TX Pndl and into the Middle Red River
Valley of Northeast Texas, Southeast Oklahoma and Southwest
Arkansas. Splitting upper jet structure in association with this
wave in the trough will only serve to enhance upper level forcing
as a strong surface cold front accompanies the feature aloft. Some
drier mid level air has worked its way into our region from the
west in the wake of the disturbance which brought widespread
rainfall to our area Monday but the atmosphere should quickly
saturate this drier layer as the lift approaches from the west.
Went with likely pops today across our northwest zones this
morning and more areawide during the afternoon in association with
this feature. Increasing cold air advection aloft suggests that
we should see more in the way of lightning with this activity
compared to what we saw on Monday and some small hail cannot be
ruled out, specifically late this afternoon into the evening hours
before the activity quickly exits our region to the east after
midnight as we quickly become dry slotted aloft in the wake of the
surface cold front.

Upper low will continue to drop due southward overnight and should
be in the vicinity of the Mid Miss Valley on Wed. At the surface,
a tight pressure gradient should be in place at this time with
some areas likely approaching Lake Wind Advisory criteria during
the day with sufficient mixing. Strong cold air advection will be
felt across our region on Wed as well with an extensive cu field
likely developing during the day as wrap around moisture along the
southwest flank of the upper low itself will aid in keeping the
temperature down somewhat. Upper low finally takes a jog eastward
Wed Night and after sunset, the cu field should move eastward with
it. Surface pressure gradient relaxes as well as the sfc ridge
should be directly ovhd Wed Night/early Thu. This should result in
ample radiational cooling conditions and thus have undercut fcst
min temps Wed night a couple degrees. As a result, we may see
record low temperatures across a good portion of the area Wed
Night with lows in the 40s across our northern half and near 50 to
the middle 50s across our southern half. These temperatures are
some 15 to 20 degrees below normal for late May.

The unseasonably cool weather will not last long as the sfc ridge
will quickly shift eastward on Thu allowing for southerly winds to
return to our entire area with daytime highs on Thu in the 80s.
This warming trend will quickly be followed by low level moisture
return, especially as we get into Friday and the upcoming weekend.
Some disagreement with the medium range progs concerning our next
weather maker this weekend into next week. A flat ridge of high
pressure aloft will remain anchored across the Northern Gulf but a
disturbance to the north of this ridge will quickly shift
eastward across the Southern Plains during the day Sunday into
Monday of next week bringing a frontal boundary with it. Showers
and thunderstorms should increase along and ahead of this boundary
for Sunday and perhaps into early next week depending on if the
boundary stalls across our region or not.

Prelims to follow...13.

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  53  75  52  85 /  60  10   0   0
MLU  56  74  50  83 /  60  10   0   0
DEQ  47  72  43  84 /  30  10   0   0
TXK  52  72  49  84 /  40  10   0   0
ELD  53  72  46  82 /  60  10   0   0
TYR  52  76  54  87 /  30   0   0   0
GGG  54  76  52  87 /  40   0   0   0
LFK  57  80  54  90 /  60   0   0   0

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&

$$

29/12



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