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Area forecast discussion
National Weather Service New Orleans la
742 am CST sun Feb 19 2017

..sounding discussion...
The profile is drier this morning with precipitable water at 0.6 inches. Radiation
fog this morning will quickly mix out under sunny skies. There is
a strong inversion through 925 mb and another elevated inversion
near 700 mb. Winds are southerly at low levels and become more
northwest by 800 mb through the rest of the sounding.



Previous discussion... /issued 410 am CST sun Feb 19 2017/

Short term...
another beautiful day is expected across the forecast. A dense
fog advisory remains in effect through mid morning. Some places
have lower visibility down to a quarter mile. We expect the fog
to mix out by 9 or 10 this morning. High pressure will continue to
move eastward. Temperatures rebound today up into the lower 80s
over a good portion of the area. The next shot of rain looks to
come in on late Monday night into Tuesday. A slow moving upper low
will become cut off from the main flow and move across the
Southern Plains and lower Mississippi Valley. Models continue to
struggle with consistency in timing and strength of the system.
Both the GFS and emcwf take the low south of the area and that
would suggest much lower chances of any severe storms. They also
have slowed the system a little bit and keeps most of the rain to
the west on Monday. Any rain that falls on Monday will be in the
far western portions of the forecast area. The greater chances of
rain for most of the area will be Tuesday morning. Have not made
major changes from previous forecast.

Long term...
the upper low over the central Gulf of Mexico Wednesday will move
toward the Florida Straits Thursday night. A northern stream
shortwave will push a cold front through the area on Friday.
Moisture will be rather sparse, so rain chances will be rather
low. Temperatures do not drop much with that front and temps will
remain above average through next weekend. The next big rain
chance looks to come into the area next early next week on Monday
or Tuesday.

vis will be the issue this morning for all sites. All terminals will
observe reduction in vis to some degree with most actually falling
to IFR through sunrise today. Fog could be an issue around midnight
tonight but a low level ceiling at around ovc015 should move in
after midnight causing sfc vis to improve if degraded. Ceilings are
expected to remain fairly stable at ovc015 after 12z Monday.

dense fog advisory will be cancelled for the remainder of this
morning. Dew pt temps are hovering in the low to mid 50s for most of
the area while the South Shore does have dew pt temps around 60.
Very little advective processes this morning will cause these
numbers to remain fairly stable. Water temps are running 63 to 66
degrees which is providing a small amount of heat to the adjacent
air which should keep fog from getting 1sm or less. Although the
Mississippi River water is still at a chilly 50 degrees so fog is
expected within the levee systems.

Tightening pressure gradient between high pressure to the east and
lowering pressure to the west will cause a gradual increase in winds
to 10-15kt today and 15-20kt over western/southern coastal waters

A cold front associated with an upper level storm system will get a
push from Texas into the northwest Gulf of Mexico Monday night into
Tuesday, however the northern portion of this boundary will not see
much airmass change over areas near the coast and inland. A broad,
slow moving inverted trough, with a possible embedded surface low,
is expected to meander southeast to the central Gulf Tuesday into
Wednesday, this will cause a shift in wind to a northerly direction
in western waters Tuesday night with a more easterly wind elsewhere.

A high pressure ridge is expected to rebuild along the central Gulf
Coast Thursday into Thursday night with a return of southeast winds
in 10-15kt range. Another cold front will move through the northern
Gulf Friday night.

Decision support...

Dss code: blue.
Deployed: none.
Activation: none.
Activities: dense fog advisory through mid morning.

Decision support services (dss) code legend
green = no weather impacts that require action.
Blue = long-fused watch, warning, or advisory in effect or
high visibility event.
Yellow = heightened impacts with short-fused watch, warning or
advisory issuances; radar support.
Orange = high impacts; slight to moderate risk severe; nearby tropical
events; hazmat or other large episodes.
Red = full engagement for moderate risk of severe and/or
direct tropical threats; events of National significance.


Preliminary point temps/pops...
mcb 82 56 80 60 / 0 0 10 70
btr 80 61 79 63 / 0 10 20 70
asd 79 58 78 61 / 0 0 10 70
msy 79 61 78 62 / 0 0 10 70
gpt 76 59 74 62 / 0 0 0 20
pql 77 54 76 59 / 0 0 0 20


Lix watches/warnings/advisories...
la...dense fog advisory until 9 am CST this morning for laz034>037-

MS...dense fog advisory until 9 am CST this morning for msz068>071-

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