Scientific Forecaster Discussion
fxus64 klch 171737
Area forecast discussion
National Weather Service Lake Charles la
1137 am CST Tue Jan 17 2017
for the 17/18z taf issuance.
a cold front has become quasi-stationary across northwest portions
of the forecast area at 17/17z from roughly a kaex-kdri-kbmt line.
Main shower activity will be behind the front therefore, expecting
just vcsh at terminals through the day. Ahead of the front...low
clouds running between IFR and MVFR ceilings will occur for the
remainder of the afternoon.
Frontal boundary is expected to remain nearly stationary through
the forecast period. Therefore, expecting another round of low
clouds and patchy fog tonight, with LIFR conditions. With lift
from upper level disturbances over-riding the front, looking for
the LIFR conditions from mainly very low ceilings than visibility
restriction from fog.
Previous discussion... /issued 945 am CST Tue Jan 17 2017/
the frontal boundary is located along a line extending roughly
from just southeast of Alexandria southwest through DeRidder and
back to near Liberty, Texas. Widespread showers continue to develop
near the boundary and move off to the north northeast. Raised pops
to 90% in the vicinity of the line through noon and up to 70% for
the afternoon hours. Also made significant changes to the hourly
temperatures and dewpoints for the remainder of the morning and
afternoon in the vicinity of the front as observations were
running over 10 degrees lower than forecast.
Wpc has Tyler, Hardin, Jasper and Newton counties hatched in a
marginal risk for excessive rainfall this morning. Storm totals
thus far have been unimpressive, but we will continue to monitor a
small flood threat through the day.
Closer to the coast, patchy dense fog continues to be observed
from Cameron east to Lafayette and down to Morgan City. Expect
this fog will slowly dissipate through the remainder of the
morning, but added mention to zones until noon.
Previous discussion... /issued 527 am CST Tue Jan 17 2017/
Aviation...showers, occasional thunderstorms, stratus, and thin
fog is occurring in the area this morning with LIFR to MVFR
conditions. Lower ceilings and vis will be possible through the
day as convection remains in place, although ceilings will
gradually lift this morning. Ceilings will fall again tonight.
Winds will south to southeast through the period.
Previous discussion... /issued 503 am CST Tue Jan 17 2017/
latest water vapor satellite imagery/upper air analysis showed an
upper low nearing the Great Lakes with a broad trof axis
stretching back to another upper low over the baja. Northwest Gulf Coast
region lies underneath an active southwesterly jet Lee of this
At the sfc, NE to SW oriented cold front is very near Jasper Texas early
this morning per surface obs and radar data, with the boundary
serving as a Focal Point for shower and thunderstorm development
amid broad synoptic lift.
Not too much overall change to the forecast this morning. The
boundary is progged to slowly sag further south with time, but
lift is forecast to wane as the lead upper low continues to pull
farther away. Late tonight, however, as the upstream baja upper
low begins to lift out across nm, the boundary is forecast to
retreat westward and sharpen while a weak frontal wave subsequently
develops over S Texas. As this feature tracks NE along the front,
numerous showers and thunderstorms are expected to develop and
spread across East Texas and into west central la from late tonight
into Wednesday. Coverage/intensity may decrease a bit Wed afternoon into
the evening, but activity is expected to increase and become more
widespread Wednesday night into Thursday as the upper low lifts out into the
plains with a neutral to negatively tilted trof axis pivoting
through the region, finally pushing the surface front on through.
Rainfall totals from today through Thursday are expected to
average 1 to 2 inches across most of the area, with a swath of 3
plus over interior East Texas. Amounts could be locally higher
pending the exact evolution and mesoscale details. There is also a
marginal risk of severe thunderstorms over the eastern third or
so of the area for Thursday.
Brief reprieve in rainfall expected in the wake of the front, but
it looks to be short lived with chances returning Friday night and
continuing into sun as another pair of upper trofs traverses the
region. The second of these appears quite robust and will finally
usher in more seasonal temperatures for US while posing a severe
weather risk for our neighbors farther east.
a light to modest onshore flow will persist through the period.
Isolated to scattered showers and thunderstorms are possible
today, mainly over the waters west of Cameron as a weak surface
front sags into the area. Showers and thunderstorms are expected
to become more numerous late tonight into Wednesday over the
waters west of Intracoastal City as a frontal wave develops along
the boundary and tracks off toward the northeast. Widespread
showers and thunderstorms are expected Wednesday night into
Thursday as an upper level trough of low pressure finally kicks
the surface front through the area, with rain chances diminishing
by Thursday night. A break is expected Friday, before showers and
thunderstorms return Friday night and Saturday as additional upper
level disturbances traverse the region. Warm and moist air riding
atop relatively cooler shelf waters will continue to yield patchy
sea fog over the coastal lakes and bays and nearshore Gulf waters
for the next couple of days.
Preliminary point temps/pops...
aex 70 61 71 64 / 70 30 60 90
lch 76 66 75 66 / 30 30 50 90
lft 78 67 78 68 / 20 10 30 80
bpt 77 66 76 64 / 40 50 70 90