Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 122353 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
553 PM CST Tue Dec 12 2017

Updated for 00Z aviation discussion.



00Z TAF discussion:
VFR conditions will prevail through the period at all sites.
Light northwesterly winds will become light and variable to calm
by 06Z Wednesday. Then expect winds to become southerly with
speeds increasing to near 10 to 15 kts for the daytime hours on
Wednesday. Peak gusts of up to 20 to 25 kts are expected at all
sites except KHBG and KMEI, where winds will generally be less
gusty. /NF/



Through Wednesday afternoon:

Very dry air is continuing to filter down into the Arklamiss this
afternoon with weak to moderate cold air advection in the boundary
layer keeping highs generally from topping out above the upper
50s. These temperatures are perhaps just slightly below average
for the calendar date but the occasionally gusty winds may make
people reach for a jacket this afternoon.

Folks will definitely need a jacket this evening as winds die off
under clear skies and radiational cooling drops temperatures
quickly. Owing to the really good setup for radiational cooling
and drying atmosphere we opted to go on the chillier side of
blended guidance with widespread lows in the 20s anticipated.

Tomorrow will be a bit like yesterday in the fact that model
blends will likely not be warm enough on maximum temperatures
expectations. Like yesterday, lower tropospheric flow will be from
a largely westerly vector and the dry atmosphere in conjunction
with this wind regime will promote overachieving mixing. Went with
a range of mid 60s (west) to upper 50s (east) for highs, which is
pretty impressive given a start in the 20s in most areas. The
somewhat gusty winds that better mixing will promote and the low
afternoon RH will help boost wildfire potential, especially in the
Arklamiss Delta. See the dedicated "fire weather" section for
details. /BB/

Wednesday night through Monday:

A rather amplified, upper level ridge in the west and upper level
trough in the east pattern will continue over the CONUS until
late Friday. This will maintain northwest flow aloft across our
region and help keep a dry airmass in place. Wednesday night a
shortwave within the upper level trough will be tracking southeast
toward the Ohio valley. This shortwave will support a weak
surface low that will drop another dry cold front across our CWA
during the day Thursday. This cold front will drop through our CWA
a little faster than depicted yesterday resulting in cooler
afternoon highs Thursday. Friday morning temperatures will start
out below freezing north of Interstate 20 and in the low to mid
30s south. Another sharper northern stream shortwave will swing
farther south and across our CWA Friday. This will help reinforce
the cool dry airmass over our region and lead to colder than
normal temperatures through Saturday morning. In the wake of
Friday`s shortwave, our winds aloft will back to the southwest
while return flow strengthens over our region. PWATS will surge
back above one inch areawide along with surface dew points in the
50s by Sunday morning. There remain differences in the models with
the pattern for the weekend but the ECMWF and GFS suggest rain
could move back into our southwest most zones before Saturday
evening. Another shortwave, possibly closing off into a low will
move over the central CONUS and develop a surface low that will
move across our area and bring decent rain chances and amounts
Saturday night and Sunday. Have opted for a progressive open
trough versus a closed low and end the rain Monday as cooler and
drier air filters into the area. /22/



Afternoon RH values should range from 25 to 30 percent for most
areas along and northwest of the Natchez Trace corridor midday
through afternoon on Wednesday. Sustained 20 foot winds will range
from 10 to 15 mph with gusts up to 25 mph possible, mainly
northwest of this corridor (where significant rainfall occurred at
least 7 days ago). Just northwest of our region the very dry
conditions will approach red flag criteria tomorrow and this
general regime may bleed into my far northwest (and these latter
areas were included in an elevated fire risk for tomorrow).
Other locations northwest of the Natchez Trace were included in a
limited risk. It is not impossible red flag conditions could be
met in the "elevated" area tomorrow and the next few shifts will
be monitoring the situation closely. /BB/


Jackson       28  63  37  60 /   0   0   0   3
Meridian      27  58  35  59 /   0   0   0   3
Vicksburg     26  63  36  58 /   0   0   0   3
Hattiesburg   28  58  37  62 /   0   0   0   3
Natchez       26  62  38  60 /   0   0   0   3
Greenville    29  63  37  52 /   0   0   0   3
Greenwood     27  61  35  53 /   0   0   0   3





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