Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lake Charles la
1257 PM CDT Monday may 25 2015
for the 18z taf package.
generally VFR across the area this afternoon with isolated showers
lifting north through the East Texas lakes and central Louisiana.
Southerly winds increasing/becoming gusty with diurnal mixing.
Prevailed VFR the rest of today with vcsh as the majority of
latest model guidance holds off significant convection until after
00z. Predominance of high resolution models depict a qlcs taking
shape across central/eastern Texas late this afternoon/early
evening...sweeping east/southeastward through the forecast area
generally in the 03z-12z time period. Given the relative
uncertainty in timing...carried probability groups at each site covering
the most likely 6 hour window of impact. Will monitor
radar/satellite trends and amend if needed...primarily if it appears
impacts will begin prior to the next scheduled 00z issuance.
Previous discussion... /issued 1049 am CDT Monday may 25 2015/
Discussion...local radar showing a lone shower over the lower
Atchafalaya and nothing more. Drier air aloft and higher
convective temperatures have squashed morning convection. Do expect
scattered showers and thunderstorms to develop this afternoon as
elevated moisture moisture returns ahead of active West Texas
shortwave trough. Models very divergent on probability of precipitation/quantitative precipitation forecast in the short-
term. With that said...not confident to bring any significant
changes to ongoing forecast and will leave as is. Have noted that
wpc has backed off on moderate outlook of flooding potential to
just interior southeast Texas. Previously the entire forecast area
was encompassed. Storm Prediction Center maintaining slight chance of severe for all
of the area with the exception of lower Acadiana.
Previous discussion... /issued 528 am CDT Monday may 25 2015/
12z taf issuance.
patchy fog possible this morning, leading to MVFR visibility through 13z.
Otherwise, vcsh later this morning, replaced with thunderstorms in the vicinity by the
afternoon as the next perturbation from the SW approaches the
region. The best chances of rain showers/thunderstorms and rain will likely be between
21-02z with the peak of afternoon heating and maximum uplift
Previous discussion... /issued 515 am CDT Monday may 25 2015/
the onslaught of deep moisture will continue through the coming
period as the area remains anchored between high pressure to our
east and low pressure centered over western Texas and the Southern Plains.
Meanwhile water vapor imagery shows a southwesterly flow aloft between
ridging along the southern Atlantic coast and a low moving out of The
Rockies keeping up a steady delivery of Pacific moisture in the
middle/upper levels. Regional 00z soundings showed precipitable water values well
above 100 percent of normal and forecast soundings indicate that
these conditions look likely to remain. In addition water vapor
showed yet another significant shortwave embedded in the flow
aloft currently moving out of the desert SW and into far western Texas.
Close to home 88ds show little in the way of shower activity
ongoing at this time...satellite imagery and surface observation just indicate mostly
cloudy skies with sporadic light fog.
Given all that heavy rain threat continues during the early part
of the forecast period...but not without questions on timing. The
western Texas shortwave will make steady progress eastward today...approaching
the Sabine valley by the afternoon. Combo of this feature with the
copious moisture and daytime heating/instability will lead to
another round of showers and storms developing over the forecast
area mainly this afternoon. Short-range models differ on location
of best quantitative precipitation forecast values but consensus is that best lift/moisture will
be found over the western portions of the forecast area...thus
afternoon probability of precipitation trend from good chance southeastern zones to high likely
over the northwestern areas. Also inserted isolated severe wording for the
western 1/2 of the area...in line with Storm Prediction Center day 1 outlook...given the
expectation of an increasing low-level jet and enhanced middle-level
winds already noted in regional 88d vwps. Forecast soundings also
shear decent shear so a tornado or two cannot be ruled out.
Most widespread high probability of precipitation are being carried tonight as the
shortwave passes the forecast area...with the threat of additional
heavy rains lasting into Tuesday morning. Toyed with the idea of
extending the Flash Flood Watch southeastward to include lower Acadiana
given the heavy rains which fell over the area on Sunday...but
with highest qpfs being carried elsewhere within the forecast area
elected to leave the watch as inherited.
Somewhat elevated afternoon probability of precipitation linger through much of the
remainder of the forecast period as the good moisture remains and
interacts with periodic disturbances aloft and daytime heating.
caution criteria winds remain in the forecast through tonight
thanks to a persistent tight gradient over the northwestern Gulf.
Preliminary point temps/pops...
aex 84 71 84 72 / 60 70 60 20
lch 85 73 86 74 / 60 70 50 20
lft 85 74 84 72 / 50 60 60 30
bpt 85 73 84 75 / 60 70 50 20
la...Flash Flood Watch through Tuesday morning for laz027>032-041-042-
Texas...Flash Flood Watch through Tuesday morning for txz180-201-215-216-
GM...small craft exercise caution through Tuesday morning for gmz450-