FXUS64 KLIX 210056

Area Forecast Discussion
National Weather Service New Orleans LA
756 PM CDT Tue Mar 20 2018


A routine flight terminated about 5 miles south of Petit Bois
Island in the Gulf of Mexico, at a height of 100,500 feet or 19
miles above the surface.

The airmass is relatively dry with a precipitable water value of
0.40 inches. What little moisture there is, appears to be trapped
below an inversion based around 870 mb. Tonight's freezing level
is near 11,000 feet, and the -20C level is at 21,000 feet.

Northerly winds at the surface at launch quickly became
northwesterly in the first 2,000 feet and remained northwest to
west for the remainder of the flight. The max wind of 117 knots
was observed near 41,000 feet. 35


.PREV DISCUSSION... /issued 402 PM CDT Tue Mar 20 2018/


Cooler and drier air will continue to stream into the central Gulf
coast region through Wednesday as surface high pressure builds
from the plains into the Mississippi Valley and an upper level
trough slides east towards the eastern seaboard. Clear skies and
light to near calm winds in most areas tonight should allow the
low temperatures to drop into the low to mid 40s, except near 50
near the marine influenced areas of the south shorelines of the
tidal lakes and southeast Louisiana coast. The very dry airmass is
expected to result in very low humidity values down around 25
percent over most areas during peak heating on Wednesday and 25 to
30 percent on Thursday. Continued clear skies and light winds
Wednesday night should again allow the temperatures to drop to
values similar to tonight.

Northwest flow aloft and surface high pressure will keep the
forecast area dry on Thursday with moderating high temperatures
returning closer to the seasonal normals. Upper level troughs on
both the west and east coast regions will be gradually sliding
east which will allow the shortwave ridge to move over and east of
the forecast area over the weekend. Southerly surface winds and
rising heights aloft will allow the highs on Friday to warm 3 to 5
degrees higher than Thursday. Southwest flow will become more
active in the southern stream out of Mexico and Texas, so the next
initial weak shortwave trough may bring our next chance of
showers about Monday into Tuesday, but it appears it should be dry
and rather warm this weekend with highs reaching near 80 to the
lower 80s. 22/TD


Although VFR conditions are occurring at all of the terminals, a
bank of clouds ranging around 3500 feet will persist over KMCB for
the next several hours. Conditions should begin to improve after
00z at KMCB as the thermal trough driving the cloud development
shifts further to the northeast. Winds will also remain in
excess of 12 knots through the overnight hours at KNEW. 32


Gradually improving conditions are expected over the coastal waters
between now and tomorrow morning as a broad surface high pressure
system settles over the area. Continued strong offshore flow over
the sounds and open Gulf waters will persist tonight, and have
continued small craft advisories for these areas. However, the
tidal lakes should see winds decrease slightly to between 15 and 20
knots tonight. As the high becomes more firmly entrenched over the
area, gradient flow will continue to relax. Offshore flow should
drop into exercise caution range of 15 to 20 knots over the open
Gulf waters and sounds from tomorrow afternoon through Thursday. A
continued relaxing of the pressure gradient over the Gulf should
allow winds to drop to 15 knots or less on Friday. However, by the
weekend, the high will shift to the east and increased onshore flow
of 15 to 20 knots should take hold of the coastal waters. 32

DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Monitoring river flooding
Small Craft Advisory

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.


MCB 43 67 40 70 / 0 0 0 0
BTR 45 69 43 72 / 0 0 0 0
ASD 43 69 41 70 / 0 0 0 0
MSY 50 69 50 69 / 0 0 0 0
GPT 45 69 43 68 / 0 0 0 0
PQL 43 69 40 69 / 0 0 0 0


GM...Small Craft Advisory until 10 AM CDT Wednesday for GMZ536-538-

Small Craft Advisory until 10 PM CDT this evening for GMZ532.

GM...Small Craft Advisory until 10 AM CDT Wednesday for GMZ538-550-


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