135
FXUS63 KDMX 071112
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
512 AM CST Thu Nov 7 2024

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- More fog this morning, though not as widespread as yesterday.

- Dry and quiet today and Friday, with high temperatures
  generally in the 50s.

- A period of showers will move through late Friday night and
  Saturday, followed by lingering light rain through Saturday
  night. The early part of next week is then dry before rain
  chances return around midweek.

&&

.UPDATE...
Issued at 512 AM CST Thu Nov 7 2024

Dense fog has expanded across about the southeastern third of
the forecast area early this morning, and have issued a Dense
Fog Advisory through 10 AM accordingly. Also introduced patchy
fog mention generally across southern Iowa late tonight into
Friday morning, due to persistence from the previous two nights
and the persisting influence of surface high pressure/calm
winds at that time.

&&

.DISCUSSION...
Issued at 200 AM CST Thu Nov 7 2024

A surface ridge remains draped across Iowa early this morning
and once again, fog and stratus have developed in the nearly
calm winds. However, as opposed to last night, there is more
widespread cirrus over our forecast area currently which is
limiting the areal coverage of dense fog, so far limited to only
a few sites. Will continue to monitor in case another advisory
is needed this morning, however, given satellite presentation of
upstream cloud cover the window of opportunity appears narrower
today.

The ridge will remain over Iowa through Friday, yielding a
couple of dry and quiet days, other than the fog this morning,
with highs both days generally in the 50s, near or just above
seasonal norms. By Friday evening, the next weather-maker will
be approaching our region in the form of a large cyclone
centered somewhere near the Texas panhandle at sunset Friday.
This gyre will steadily progress northeastward and slowly deepen
over the weekend, eventually moving along the Iowa/Minnesota
border Saturday night or Sunday morning before departing quickly
to the east. As this system approaches Iowa a swath of rain will
advance on its leading flank, traversing our area from southwest
to northeast between late Friday night and Saturday evening.
Broad lift and deep moisture within this swath will promote
several hours of soaking rain, but given the transient nature of
the band amounts will not be remarkable. Immediately behind this
leading surge of rain, a relative dry slot will rotate through
however forecast soundings indicate a shallow dry layer will
persist, and it is likely we will see a continuation of low
clouds and perhaps drizzle/light rain Saturday afternoon and
evening. More widespread light rain will then develop, mainly
across the northern half of Iowa, as the core of the low moves
through Saturday night into Sunday morning before departing.
Throughout the entire system instability does not support
mention of thunderstorms, and no hazardous weather is
anticipated, but it will certainly make for a wet and dreary day
on Saturday.

During the early part of next week, from Sunday into Tuesday,
the 500 mb flow overhead will become nearly zonal, making for a
period of quiet and uneventful weather. By Tuesday, however, a
deep longwave 500 mb trough will be moving eastward over the
U.S. Rockies, spreading southwesterly steering flow and
sharpening/deepening until it crosses Iowa around Wednesday.
Just ahead of this system, low-level flow will come around to
south southeast and increase over us on Tuesday, which should
allow for some degree of warming, then a band of showers and
possibly thunderstorms will wheel quickly through on the leading
flank of the trough, sometime Tuesday night or Wednesday. Little
can be discerned about the evolution of details related to this
scenario at such a long range, such as timing of rain, presence
of thunderstorms, and potentially robust synoptic winds, but it
will certainly be the most notable weather system of next week
and we will be monitoring it in the coming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 512 AM CST Thu Nov 7 2024

Fog has once again developed early this morning and will affect
all terminals to some extent in the next few hours, but
especially OTM where LIFR or lower conditions will prevail
through at least 14Z. The fog will once again clear off by late
morning after which VFR conditions will prevail across the area,
however fog/stratus may form again toward the end of the TAF
period, early Friday morning. That potential will be assessed
in future TAF issuances.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CST this morning for IAZ050-061-
062-073>075-082>086-092>097.

&&

$$

UPDATE...Lee
DISCUSSION...Lee
AVIATION...Lee