Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 181018
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
418 AM CST Mon Feb 18 2019

.DISCUSSION...

Short Term...Today...

This morning`s surface analysis shows high pressure building in
behind the cold front that moved through the region during the day
yesterday. This area of high pressure will result in dry
conditions today. Northeast winds will result in cold air
advection across the entire region throughout the day. However,
breaks in the cloud cover should allow for temperatures to climb
to near 60 during the day today.

Long Term...Tonight through Sunday...

A wet weather pattern is forecast through much of the upcoming
week with a trough axis centered over the southwest CONUS and a
ridge centered over the Bahamas. The height pattern will be very
amplified with magnitude of the standardized anomalies of the 500
hPa heights of both these features exceeding 2 sigma. This will
result in an atmospheric river developing over the Lower
Mississippi River Valley which will transport tropical moisture
from the eastern Pacific and Caribbean over the region during the
upcoming week. Due to this prolonged moisture transport, PWAT
values are forecast to be near record values for the month of
February (per the SPC sounding climatology) during much of the
long term period.

While the long wave trough will be centered over the SW CONUS
during this time frame, two main shortwaves are forecast to rotate
around the base of the trough bringing the highest and most
widespread rainfall chances. The first shortwave will eject from
the base of the trough and lift northeastward during the day on
Tuesday. This will support the deepening of a surface low over the
W Gulf of Mexico which will lift northeastward tonight into
Wednesday. This will result in showers and thunderstorms
overspreading the region beginning late tonight and continuing
through Wednesday.The best synoptic setup for heavy rainfall
during this time is expected to be north of the region near the
Tennessee Valley. However, given the abundant deep layer moisture
and a favorable environment for ascent, WPC still has the CWA
highlighted with a 5%-10% chance of flash flooding occurring from
Tuesday into Wednesday.

In addition to increasing deep layer moisture, the return flow is
expected to contribute to at least some weak destabilization
across the CWA on Tuesday. 0-6 km shear in excess of 50 knots will
support the potential for organized to convection to develop
embedded with in the showers and possibly form a squall line.
Therefore, SPC is forecasting a Marginal Risk of severe weather
across much of the region from Tuesday into Wednesday. The main
hazard will be a few damaging wind gusts.

The atmospheric river will continue to produce showers across the
region until the second main shortwave trough is expected to
eject across the central Plains on Saturday. This will support lee
cyclogenesis and a stronger surface low on Saturday. The surface
cold front associated with this low is forecast to move through
the region late Saturday into Sunday morning. Once this front
clears the area, the upper level height pattern is expected to
become more zonal and should result in dry conditions for the
early part of next week.

&&

.MARINE...

A tight pressure gradient will result in strong winds over the
coastal waters today into Tuesday. A Small Craft Advisory remains
in effect for the entire coastal waters through 6 AM Tuesday and
may need to be extended through Tuesday afternoon.

Showers and thunderstorms will begin to develop over the coastal
waters later this evening as an area of low pressure develops over
the western Gulf. This will result in NE winds becoming easterly
and eventually southerly by late Tuesday. Chances for showers and
thunderstorms will linger through Saturday as a surface front
meanders across the coastal waters. By Saturday, another area of
low pressure will push through the coastal waters and possibly
resulting in another period of Small Craft Exercise Caution or
Advisory conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  57  44  60  52 /   0  70  80  80
LCH  59  50  69  60 /   0  60  70  70
LFT  60  51  71  65 /   0  50  50  70
BPT  60  50  67  55 /   0  70  80  60

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Advisory until 6 AM CST Tuesday for GMZ430-432-435-
     450-452-455-470-472-475.

&&

$$

PUBLIC...26



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