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fxus64 kshv 240027 

Area forecast discussion
National Weather Service Shreveport la
727 PM CDT Fri Jun 23 2017

for the arklatex, VFR for now, but a convective complex is looming
to our north from near kdeq to kllq in Arkansas. This feature will have
life potentially all night as a cold front is draping in as well.
This ts activity will likely be affecting Arkansas sites and perhaps la
tafs as well during the late evening and early morning. The cold
front will filter north/NE low level winds just as the morning stratus
is lifting after daybreak and may crop up some early convection.
Improvements back to VFR may take time in the afternoon on Sat. /24/


Previous discussion... /issued 338 PM CDT Fri Jun 23 2017/

the remnants of Tropical Depression Cindy may have shifted well
north and east of the four-state region today, but in its wake, a
rather moist atmosphere ensued. In fact, shv 12z sounding showed a
precipitable water of 2.28 inches which is quite impressive. This tropical-like
environment coupled with a mid-level shear axis and a 300-500
m2/s2 0-3 km srh axis resulted in lingering scattered showers
/moderate to heavy rainfall makers/ and a few thunderstorms across
portions of southwest Arkansas and north central la earlier this
morning. Some of the storms became strong to severe, with wind the
primary threat. The mid-level shear and srh axes have since waned
and thus so has the precipitation. Current radar analysis showed
the tail-end of a line of storms stretching from southern la to
across the Tennessee Valley that have brushed across our far
southeast zones late this aftn. Furthermore, an mesoscale convective system was
propagating southwest across southern MO to across northern Arkansas
late this aftn along a southeastward moving cold front. Isolated
showers and thunderstorms have struggled to develop across
southwest Arkansas given the airmass is likely worked over from the
earlier convection. However cloud cover has thinned across
portions of east TX, deep East Texas and southeast OK, which
therefore allowed for temps to warm into the lower 90s which could
Garner isolated showers/thunderstorms. In addition, with
dewpoints in the lower to middle 70s, there are concerns for heat
index values increasing to between 100-105 for some locales across
East Texas this aftn, which is one-half of our heat advisory
criteria. The second-half of our heat advisory criteria is that
these warm and rather moist conditions combine for heat index of
105 or greater are expected for consecutive days which is not the
case, but more on that in a bit. Temps remained in the 80s
elsewhere given the extensive mid-upper level cloud cover within a
tropical-like environment.

Attention will turn to a broad upper air trough that has extended from
southern Canada southwest to across the northern plains and to
near the Central Plains late this aftn. A 1020 mb sfc ridge across
the southern rockies was pushing a cold front southeast across
the panhandles and Southern Plains with it encountering the
Ouachita Mountains hence right on our doorstep. It is this same
front that has generated the mesoscale convective system to our north. Sfc winds have
veered to the northwest across Pittsburg County in southeast OK,
likely a pre-frontal feature, whilst Choctaw County in far
southeast OK has a calm wind, which at times occurs before a wind
shift. The timing for the impingement of the front is still of
much debate between the quicker NAM and the slower GFS. This time
of year, it is usually hard-pressed to get a cold front let alone
having a quick propagation as suggested by the NAM solution (the
NAM pushes the front through the entire County Warning Area by mid-morning
Saturday versus just south of the I-20 corridor per the GFS/. Will
elect to lean towards the GFS depiction of the front and as such,
the mesoscale convective system will continue to move southeast likely not affecting the
region, but additional storm development along the front will
affect the area. The precip will impact the far northern zones
between 24/00-03z, nearing the I-20 corridor between 24/09-12z and
spread to the remaining areas by mid to late morning. Per the
GFS, the front will clear the southern zones by late Saturday
aftn/early evening and will slowly see precip wane from north to
south as the fropa Ushers in a drier airmass. Model guidance hints
at 0-6 km bulk shear values of 30-50 kts across southeast OK and
portions of southwest Arkansas and extreme northeast Texas this evening,
suggesting that some storms could become organized and produce
gusty winds /primarily/ and intermittent large hail. The 0-1 km
helicity values are projected to be rather weak so attm, the
threat for tornadoes will be rather low. Nonetheless, the
existence of a frontal boundary still raises concern for the
plausibility of an isolated tornado given the right local
environmental circumstance, so can not discount it completely. The
cold front will also cause daytime temps to drop into the Lower-
Middle 80s tomorrow /some 8-10 degrees below norm/ which mitigates
the issuance for a heat advisory. Precip will linger across the
southern-half of the County Warning Area through Monday morning during which time
the front will be rather diffused and sfc ridging near the region
will maintain a drier airmass.

Thereafter a typical Summer-time pattern will take place with
diurnally driven sea-breeze convection nearing/moving across the
southern-half of the forecast area each aftn on Wednesday-Friday. Flow aloft
will back from the northwest to the southwest by the end of the
week, courtesy of a northeastward moving upper air low across the
northern plains. Its southern periphery could brush across our
northern zones late week/early weekend and perhaps generate
showers and thunderstorms.


Preliminary point temps/pops...
shv 74 82 69 85 / 60 70 30 30
mlu 74 82 69 85 / 60 70 20 20
deq 69 82 62 85 / 60 40 10 10
txk 71 80 65 84 / 60 60 20 10
eld 71 81 64 85 / 60 60 10 10
tyr 75 83 68 85 / 60 70 40 40
ggg 73 82 68 85 / 60 70 40 30
lfk 76 86 71 85 / 40 70 50 60


Shv watches/warnings/advisories...

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