LIX issues Area Forecast Discussion (AFD) at Dec 30, 4:42 AM CST ...New UPDATE, AVIATION...734
FXUS64 KLIX 301042
AFDLIX
Area Forecast Discussion
National Weather Service New Orleans LA
442 AM CST Mon Dec 30 2024
...New UPDATE, AVIATION...
.UPDATE...
Issued at 434 AM CST Mon Dec 30 2024
Traffic cameras and surface observations indicate enough fog
development south of Interstate 10 to justify expanding Dense Fog
Advisory across entire land area, as well as tidal lakes and
sounds. That being said, some areas may not see fog develop, but
with rapidly changing visibilities over short distances, travelers
need to be prepared for the changing conditions. Products have
already been issued.
&&
.SHORT TERM...
(Today through Tuesday)
Issued at 301 AM CST Mon Dec 30 2024
Strong upper trough that brought Saturday's severe weather
extended from the eastern Great Lakes to the Carolinas early this
morning. A weaker shortwave was moving out of the Rockies this
morning, with another shortwave behind that one near Vancouver. At
the surface, weak high pressure was centered off the Louisiana
coast. Developing low pressure was noted over eastern Colorado
with a frontal boundary moving into west Texas. Skies were mostly
clear across the local area early this morning with mainly calm
winds. Areas of dense fog had developed, primarily north of
Interstate 10. Early morning temperatures ranged from the mid 40s
to mid 50s across the area.
The main forecast issue over the next 36 hours will be late night
and early morning fog, primarily across the northern half of the
area. Fog should burn off by mid-morning across the area this
morning as we get surface heating and winds become southerly. High
temperatures today should be at least as warm as what occurred
Sunday afternoon. Any adjustments to the current Dense Fog
Advisory are likely to be made right at forecast issuance time,
but would only be additions, if necessary, not cancellations.
The fog situation overnight tonight isn't quite as straight-
forward as this morning. The low pressure developing over Colorado
this morning will deepen and be centered over Missouri this
evening and over Ohio by Tuesday afternoon. Moisture will be
returning to the area as soon as this afternoon, and with the
moisture gradient tightening a bit, we won't be in a radiation fog
scenario, but more likely an advective one. Additionally, it
currently appears that the frontal boundary will arrive prior to
sunrise. Bottom line is that there will be at least a brief window
for fog development overnight, but the threat may end prior to the
morning rush Tuesday morning.
Frontal boundary is unlikely to be accompanied by precipitation,
as there just isn't enough time for moisture recovery.
Precipitable water values struggle to get past 0.70 inches this
afternoon and overnight. What will be noticeable will be a drop in
humidity. Dew points that will be in the mid 50s this evening will
be closer to 40 by sunset Tuesday. Cold advection won't really
plug in until late in the day on Tuesday, so high temperatures are
likely to still reach the lower or middle 70s across much of the
area on Tuesday. It may turn out that the Mississippi coast will
be the warm spot on Tuesday, as is occasionally the case with
northerly winds behind a frontal passage.
&&
.LONG TERM...
(Tuesday night through Sunday)
Issued at 301 AM CST Mon Dec 30 2024
Wednesday and Thursday will be noticeably cooler/colder than the
last several days, as high pressure to the north passes east of
the area. Beyond that point, medium range models begin to depart
from previous solutions, although there's actually a decent amount
of agreement between the 00z GFS and ECMWF operational solutions.
The axis of the surface high will be east of the area by late
Friday with winds turning onshore and moisture beginning to
return. However, it is likely to take until Saturday afternoon for
moisture levels to even reach climatologic norms around 0.75 inch.
A strong shortwave will move out of the Rockies Sunday, into the
Ohio River Valley by next Monday. Strong low pressure is again
expected to develop with this system, but is likely to track a
couple hundred miles further north than the most recent system.
This would bring a frontal passage across the area next Sunday
night, accompanied by rain and thunderstorms. That's one period
beyond the end of this package.
The NBM deterministic PoPs look like they will need to play "catch
up" as we get into next weekend, as the operational medium range
PoPs would indicate a need for a rain mention as early as Saturday
afternoon, while the current NBM deterministic would hold things
off until Sunday. For now, will hold with the neighbors using the
NBM deterministic PoPs.
Similarly, the NBM deterministic temperatures for next weekend
look like they will need to play "catch up" for Friday through
Sunday, as they are a category or two cooler than the medium range
deterministic numbers. Bottom line is that adjustments to the
weekend forecast are possible, if not likely, in later packages.
Would also note that just beyond the end of this forecast package,
the GFS is a day or so slower with a plunge of cold air into the
area. The current ECMWF deterministic would have temperatures
struggling to warm above 50 next Monday, while the GFS holds that
off until Tuesday of next week.
&&
.AVIATION...
(12Z TAFS)
Issued at 434 AM CST Mon Dec 30 2024
Most or all forecast terminals will be carrying conditions at or
below field minima at forecast issuance. Improvement will likely
occur around 15-16z to VFR as radiation fog burns off. Those
conditions will probably continue through about 06z Tuesday,
before a short period of IFR or lower conditions (roughly about 6
hours) onsets ahead of a frontal passage that will occur near or
shortly after sunrise Tuesday. All terminals likely to return to
VFR conditions prior to 18z Tuesday.
&&
.MARINE...
Issued at 301 AM CST Mon Dec 30 2024
A quieter day today over the coastal waters as high pressure
transits the waters. May need some Small Craft Exercise Caution
headlines over the outer waters overnight into Tuesday morning as
the pressure gradient tightens ahead of the next frontal passage.
Will definitely need headlines Tuesday night into Wednesday night
as cold advection moves across the waters behind the cold front.
Additional headlines look necessary as we get into next weekend.
That's not really a surprise, as conditions generally don't stay
quiet for long over the waters during the winter season.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 72 52 67 37 / 0 0 0 0
BTR 77 56 72 41 / 0 0 0 0
ASD 74 55 74 40 / 0 0 0 0
MSY 75 58 73 45 / 0 0 0 0
GPT 68 55 72 40 / 0 0 0 0
PQL 74 55 77 38 / 0 0 0 0
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Dense Fog Advisory until 9 AM CST this morning for LAZ034>037-
039-046>048-056>060-064>071-076>090.
GM...Dense Fog Advisory until 9 AM CST this morning for GMZ530-532-
534-536-538.
MS...Dense Fog Advisory until 9 AM CST this morning for MSZ068>071-
077-083>088.
GM...Dense Fog Advisory until 9 AM CST this morning for GMZ532-534-
536-538.
&&
$$
SHORT TERM...RW
LONG TERM....RW
AVIATION...RW
MARINE...RW
Source:
LIX issues Area Forecast Discussion (AFD) at Dec 30, 4:42 AM CST ...New UPDATE, AVIATION...---------------
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