Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
FXUS64 KLIX 280054
Area Forecast Discussion
National Weather Service New Orleans LA
754 PM CDT TUE SEP 27 2016
The atmospheric moisture content remains above normal with a
precipitable water value measured at 1.95 inches this evening.
There may be a hint of the nocturnal inversion developing with a
surface inversion up to about 200 feet. Otherwise, the boundary
layer was well-mixed today. Some drier air was noted around 15000
feet and no significant dry air was observed until passing 38000
feet. Winds in the low levels were from the north or north-
northwest and from the west or northwest in the middle and upper
levels. A peak wind speed of 70 knots was at 37600 feet.
00z balloon info: A routine flight ascending for 106 minutes to a
height of 20.6 miles above the ground bursting over Lake Borgne 22
miles downrange from the office.
.PREV DISCUSSION... /issued 356 PM CDT TUE SEP 27 2016/
A stalled frontal boundary continues to linger over the forecast
area this afternoon. This front should continue to linger along
the Louisiana coast during the overnight hours, and keep slight
chance POP of around 20 percent in place through the evening
hours. By tomorrow morning, the front should be just offshore over
the coastal waters, and keep a POP of 20 to 30 percent over the
coastal waters and extreme lower Plaquemines Parish into the
morning hours. Given the position of the front along the Louisiana
coast tonight, there will be a gradient of both dewpoints and
temperatures across the region. For areas farther inland, a rather
cool and pleasant night is expected with dewpoints falling into
the upper 50s and lows dipping into the lower to middle 60s.
However, farther south along the coast, rather humid conditions
will persist for one more night with lows only cooling into the
lower to middle 70s.
By tomorrow afternoon and night, an upper level trough axis will
rotate around the base of a parent upper level low over the Great
Lakes States and pass through the Lower Mississippi Valley. This
upper level trough will provide enough forcing to drive the drier
and cooler airmass parked across North Louisiana and Mississippi
southward into the forecast area. As this airmass moves in, a
noticeable drop in humidity and cooler temperatures can be
expected for tomorrow night. Lows should dip into the upper 50s
and lower 60s north of I-10 and the middle to upper 60s farther
south. These cooler and drier conditions will persist through
Friday with overnight lows running around 10 degrees below normal
in the 50s and lower 60s, and daytime highs only climbing into the
lower to middle 80s.
Deep layer northerly flow and strong ridging throughout the
atmospheric column will persist into early next week. This pattern
will keep mostly clear skies and lower humidity in place across
the region. Temperatures will slowly modify, but readings will
remain cooler than average through the period. Overnight lows will
cool into the 50s and lower 60s through Sunday night with some
modification into the lower to middle 60s by Monday night. Highs
will also gradually warm from the lower 80s into the middle to
upper 80s by early next week. Overall, a very benign weather
regime is expected throughout the entire forecast period.
Lingering isolated convection along and near the coast will
dissipate by sunset while continuing to move southeast at around 5-
10 knots. Perhaps KGPT and KHUM may have VCSH briefly through 2130Z,
but this is even limited. otherwise, VFR conditions expected all
terminals through 29/00Z. 24/RR
Leading edge of shallow frontal zone continues to push off
the coast this afternoon with limited cool air advection initially.
Better advection takes place Wed night with offshore winds likely to
respond to boundary layer instability mixing in the overnight hours
Thursday night and possibly again Friday night. Northeasterly winds
should then prevail over the coastal water for the duration of this
forecast package except for some variation in wind direction on
tidal lakes with lake breeze processes during the mid-afternoon
hours during the weekend. 24/RR
DSS code: Green.
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 62 87 59 81 / 10 0 0 0
BTR 64 87 62 83 / 10 0 0 0
ASD 68 87 62 85 / 20 0 0 0
MSY 72 87 69 84 / 20 0 0 0
GPT 69 88 64 86 / 20 0 0 0
PQL 69 88 62 85 / 20 0 0 0