Scientific Forecaster Discussion
fxus64 klch 200307
Area forecast discussion
National Weather Service Lake Charles la
907 PM CST Tue Nov 19 2019
Update...fog is developing across deep southeast Texas and far
southwest Louisiana this evening. An advisory has been hoisted
through mid morning tomorrow. Patchy fog is expected to expand
outward through the night and the advisory may need to be
broadened. The remainder of the forecast looks on track.
Previous discussion... /issued 523 PM CST Tue Nov 19 2019/
for the 20/00z taf issuance.
weak surface ridge is close enough to the terminals that light
winds are expected during the overnight. Meanwhile, still an
overall dry atmospheric profile across the area will provide
mainly clear skies. Thus, a potential for patchy fog to develop
again tonight. Expect prevailing MVFR conditions. However, IFR
type visibilities can not be ruled out at times, especially near
sunrise. Any fog should quickly dissipated by mid morning from
daytime heating, along with an increase in wind speed.
Previous discussion... /issued 341 PM CST Tue Nov 19 2019/
Short term [tonight through thursday]
The 1016 hpa surface high pressure currently centered over the
northwestern Gulf of Mexico is expected to lift northeastward
overnight tonight and through the day on Thursday. The increasing
pressure gradient will result in onshore flow which will advect
greater deep layer moisture from the Gulf of Mexico into the
region. The increasing low level moisture and mostly clear skies
tonight will produce conditions favorable for areas of fog to
develop. Similar to last night, some areas of fog could be dense
reducing visibilities to below 1/2 mile.
Temperatures are expected to remain above normal on Wednesday and
Thursday with highs in the upper 70s. A strengthening pressure
gradient will resulting in southerly winds increasing and
additional moisture transport into the area. Pwats are forecast to
increase to over 1.5" by Thursday (which is roughly the 90th
percentile of the November klch precipitable water climatology). Meanwhile,
upper level support will be increasing as an upper level trough
begins to dig into the Southern Plains. This will result in
at least slight chances for precipitation beginning Thursday
Long term [friday through monday]
Model guidance is continuing to trend towards a consensus on the
evolution of the upper level trough progressing across the eastern
two-thirds of the Continental U.S. During the long term period. The
associated surface cold front is expected to move through the
region on Friday. Rain is likely and most of the model guidance is
indicating enough instability to support the potential for
thunderstorms. Deep layer shear across the region on Friday is
forecast to range from 30 to 50 knots. However, there is still
uncertainty as to whether enough instability will be able to
develop in order to support a greater threat for severe weather.
Currently, the probability of severe weather on Friday appears to
be low, but could possibly change with future forecasts.
Regardless of the potential for thunderstorms, the above normal
deep layer moisture in place across the region will support a
heavy rain threat. Fortunately, long range model and ensemble
guidance for this system continues to trend to a more progressive
solution which would limit the potential for flooding.
The surface front is expected to exit the region Saturday morning
bringing an end to precipitation. High pressure will build in
behind the front, resulting in cooler temperatures and drier
conditions for the weekend into early next week.
A light onshore flow will develop late this evening and
gradually increase through Friday. This could result in periods
of winds of 15-20 knots over the outer coastal waters,
particularly during the overnight hours on Wednesday and
Thursday. A cold front is expected to move through the coastal
waters Friday afternoon into Saturday morning and will bring a
chance of showers and thunderstorms. Moderate to strong offshore
winds will develop behind the cold front and small craft exercise
caution or small craft advisories may be needed on Friday. Winds
and seas are expected to decrease on Sunday into Monday as high
pressure builds into the region.
Preliminary point temps/pops...
aex 45 75 53 76 / 0 0 0 10
lch 52 76 62 77 / 0 0 0 10
lft 49 75 58 77 / 0 0 0 0
bpt 56 76 64 76 / 0 10 10 20
la...dense fog advisory until 9 am CST Wednesday for laz041-042-073-
Texas...dense fog advisory until 9 am CST Wednesday for txz201-215-216-