Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 221744 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1244 PM CDT Thu Oct 22 2020

Updated for 18Z aviation discussion


18Z TAF discussion:
The MVFR cigs over the se wl scatter in the next hour or two and
VFR conditions are expected to prevail areawide until 09Z. After
09Z IFR/LIFR cigs wl be psbl in the se again with VFR conditions
continuing to prevail elsewhere. The IFR/LIFR cigs in the se
should improve by 16Z with VFR conditions expected areawide
through 18Z. /22/


Stratus and patchy fog has developed over the southeast this
morning and looks to continue into the afternoon. Have updated
cloud cover to account for this trend. Afternoon highs may get
held a few degrees lower as well. Also, the increase in low level
moisture from the southeast is expected to fuel a few showers and
thunderstorms across the south later this afternoon. /22/

Prior discussion below:

Today and Tonight:  Ridging continues at the surface and aloft
this morning, but this will begin to break down today as a weak
shortwave moving through TX puts the area in a southwest flow/warm
advection regime this afternoon. Slight veering of the low level
winds, moreso from the south, will allow dewpoints to begin to
creep up. The slightly better moisture, increased ascent and
afternoon heating will allow for some isolated convection over the
south this afternoon. Maximums today will be similar to yesterday
with mostly mid 80s.

While patchy fog will once again be draped over southern portions
this morning, increased cloud cover tonight should hinder fog
production toward early Friday morning. /GG/

Friday through Wednesday: A more progressive weather pattern than
of late will bring a few weather systems across the CONUS through
the middle of next week. Longwave trough over the western and
central 2/3rds of the country will become more amplified as a
ridge over the eastern Pacific edges toward the West Coast. As a
series of shortwave troughs swing over the Northern Tier, a
frontal boundary will oscillate through our region. A southward
push of cooler air will reach our area with a cold front Friday
night into Saturday, with a chance for showers and thunderstorms
in the warm air ahead of the front on Friday. At this time, severe
weather is not expected.

The latest suite of model guidance have come into slightly better
agreement with a shortwave trough digging far south along the
West Coast over the weekend and closing off as a low pressure
system over the Four Corners region of the Desert Southwest. With
southwest flow aloft ahead of this amplifying system, and expected
cyclogenesis along the frontal boundary to its east, it is
looking more likely for the cold front reaching our area on
Monday/Monday night to stall out in the region. Coolest
temperatures and best rain chances look to stay north of the cold
front (and mostly northwest of our area) through Monday night.
Then depending on exactly how the trough to our west evolves, we
could set up for more intense thunderstorm and heavy rain
potential Tuesday and Wednesday.

Although guidance has been bouncing around, enough confidence in
the western trough closing off into a low pressure system over the
Southern Plains exists to edge temperatures warmer for Tuesday
and Wednesday ahead of the frontal boundary. And to increase POPs
closer to an ECMWF/GFS blend. Thunderstorms on Tuesday will be in
a drier environment and should be more isolated, but moisture will
really be increasing across the region as we head into Wednesday.
A fetch of mid- and upper-level moisture sets up from the Baja
Peninsula region off of Mexico, while a surge of very moist air
should be arriving from the western Gulf of Mexico. GFS showing
PWAT values of over 2.2 inches with this slug of moisture are
alarming, considering a dynamic low pressure system to the west
lifting this deep moisture over a warm frontal boundary. Longer
residence times for moisture wrapping back around into the low
could drive a flash flooding threat somewhere around the northern
and northwestern portions of Mississippi, Louisiana, and Arkansas
Wednesday into Wednesday night. These trends will be monitored
over the next several days. /NF/


Jackson       87  67  84  64 /  13   4  33  29
Meridian      86  65  84  65 /  12   4  40  29
Vicksburg     87  66  85  63 /  10   3  24  26
Hattiesburg   87  67  84  65 /  17   7  62  30
Natchez       87  67  84  64 /  21   4  36  18
Greenville    86  66  84  58 /   7   3  34  32
Greenwood     87  67  84  60 /   8   4  42  37





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