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Area forecast discussion
National Weather Service New Orleans la
302 PM CST sun Dec 8 2019

Short term...
area is coming in transition from moderating high pressure influence
to onshore marine layer advection this evening. There has been a
convergence boundary off the coast of Jackson co, drifting westward.
Radar is indicating a few shallow showers associated with this
feature and should continue through sunset. This boundary passage
will be the onset of deeper maritime flow that should be more
conducive for sea fog formation in the coastal waters and near shore
areas tonight. Temperatures are expected to be warm tonight through
Tuesday morning despite extensive cloud cover. Deterministic model
guidance and MOS temps are cool, but nbm shows several degrees
warmer, which is more believable given recent cold biased model
trends. Leading edge of Arctic air mass moves shallowly into the
forecast area Tuesday with over=running rainfall to ensue and
continue into Wednesday. The models have come more in line with a
progressive open wave impulse moving through the southern branch
flow and have backed off the GFS notion of a negative tilt low
previously indicated.

Long term...
modifying Arctic air remains settled over the area Wednesday and
Thursday while a more vigorous upper level low develops in the
southern branch and amplifies troughing upon arrival into the
forecast area Friday. While the upper level pattern looks similar in
the European model (ecmwf) and GFS, the surface and low levels are dramatically
different. The European model (ecmwf) is considerably more south and slower in
indicating Gulf cyclogenesis Saturday morning. The GFS meanwhile,
shows stronger cold pooling in the Southern Plains that enhances
baroclinicity over the area for cyclogenesis in the north Gulf
Friday - about 18 hours sooner and well north. At this time, will be
blending solutions to show some pops for Friday, drier Saturday, in
deference to European model (ecmwf). Temperatures will remain cool during the period
but well above any critical values to consider winter precipitation,
generally lows in the 40s, highs in the lower 60s Friday and


there may be some sea fog considerations over the sounds and tidal
lakes as warm air advection brings dewpoints closer to water
temperatures tongight and again Monday night. Light to moderate
onshore flow through early Tuesday before wind shift with frontal
passage throughout the day Tuesday. Air mass is likely to be shallow
at first, with stronger cold air advection in lag but going in
earnest Tuesday night for Small Craft Advisory criteria winds and
seas, continuing through Wednesday. Gulf low pressure development
somewhere in the middle to upper Gulf later in the week to affect
winds, but does appear to maintain strong winds and rough seas
Friday into Saturday.


as winds continue to veer to onshore orientation, marine layer will
continue to spread inland, lowering and maintaining MVFR to IFR
ceilings. Sea fog advection into kgpt, kpql, kbix early this evening
and possibly lowering at knew, kmsy, kasd, khdc overnight into early
Monday morning. Some slow improvement to MVFR levels heading into
the afternoon.


Decision support...
dss code: blue.
Deployed: none.
Activation: none.
Activities: support to city of New Orleans.


Preliminary point temps/pops...
mcb 52 74 57 69 / 0 20 80 90
btr 54 77 59 69 / 10 20 70 90
asd 51 76 60 75 / 0 10 40 90
msy 56 76 64 76 / 10 10 30 80
gpt 53 71 61 72 / 0 10 20 80
pql 51 75 61 77 / 0 10 20 80


Lix watches/warnings/advisories...

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