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Office: JAN

FXUS64 KJAN 171141
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
541 AM CST Mon Dec 17 2018

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
Mostly IFR/LIFR conditions prevail at TAF sites this morning and
this will continue until 15-16Z. The fog/stratus should begin to
burn off after this time with VFR conditions prevailing through
the day into tonight. A dense fog advisory is in effect for the
entire area until 10AM. Patchy areas of fog are likely once again
tonight which will bring another round of MVFR/IFR/LIFR conditions
after 08-09Z on Wednesday. /15/

&&

.DISCUSSION...

Today and tonight:

Areas of dense fog this morning will give way to partly cloudy
skies later in the morning. A dense fog advisory is in effect
until 10AM. High pressure ridging at the surface and aloft will
prevail today, with high temperatures in the low/mid 60s across
most of the area. Strong surface ridging will continue to prevail
across the area tonight. As the temperatures cool tonight and the
winds de-couple, areas of at least patchy fog is likely once again
early Tuesday morning. Low temperatures will range from the mid
30s in the northeast to the low 40s in the west. /15/

Tuesday through Sunday:

The upper level pattern will remain progressive but amplified as
we go through mid/late week and into the weekend with most
attention being paid to the strong shortwave trough expected to
cross the ArkLaMiss later this week. For now, dry conditions will
continue through Tuesday night as the current shortwave ridge
pushes east of the forecast area, but a southern stream shortwave
trough will begin to approach Wednesday morning with the
southward displacement of the height falls easily transporting
Gulf of Mexico moisture northward for fairly widespread shower
development by afternoon.

The situation becomes a bit more complex as we go through
Wednesday night into Thursday. A very intense Pacific Jet stream
(160+ kts) will drive into the western Conus before digging
southward through the Plains and into the base of the southern
stream trough. Global models are in good agreement that the
trough will begin amplifying just far enough east so that we
should avoid significant return flow and severe weather concerns,
and this fits local empirical studies on the relationship between
extreme Pacific jet positioning and potential severe weather
outbreaks in the southeast CONUS.

Nonetheless, the weather will be quite unsettled with higher end
chances for convective rainfall continuing through Thursday night
and perhaps into early Friday. Given steep low level lapse rates,
a deepening low pressure system, and tightening pressure
gradient, expect that surface winds will become impactful from
Thursday into Friday, and this will be something to monitor as we
get closer. Moreover, temperatures will be rather chilly, and
combined with the wind and perhaps considerable cloud cover,
Friday looks like it will be a very uncomfortable day.

Going into Saturday, shortwave ridging will take place with
surface high pressure bringing a return to dry weather with
seasonable temperatures. There are some indications that a weak
cold front could bring small increase in rain chances by Sunday,
but this would be a light rainfall event if it occurs. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       66  40  62  42 /   0   3   0   3
Meridian      65  38  62  40 /   0   3   0   3
Vicksburg     64  42  63  44 /   0   2   0   6
Hattiesburg   68  41  63  43 /   0   1   0   3
Natchez       66  41  64  45 /   0   2   0  12
Greenville    60  40  59  43 /   0   4   0   3
Greenwood     61  40  60  42 /   0   4   0   3

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Dense Fog Advisory until 10 AM CST this morning for MSZ018-019-
     025>066-072>074.

LA...Dense Fog Advisory until 10 AM CST this morning for LAZ007>009-
     015-016-023>026.

AR...Dense Fog Advisory until 10 AM CST this morning for ARZ074-075.


&&


$$

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