Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 160624 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1224 AM CST Tue Jan 16 2018


Updated for 06Z aviation discussion


06Z TAF discussion:
Cold front has moved through the Delta and towards the I-20
corridor. Some lower ceilings are slowly moving in advance of this
front, with some MVFR ceilings moving into GLH. Expect lowering
ceilings & visibilities to slowly decrease down towards MVFR to
IFR as some light snow moves in overnight, mainly near GLH/GWO
before daybreak (09-12Z), GTR/HKS/JAN by just after daybreak to
mid-morning (13-16Z) and towards MEI/HKS by mid-day/early
afternoon (17-20Z). Expect lower ceilings &/or visibilities with
any areas of light snow. The front will continue south through the
area today, making it out of the area by mid-day, with some gusty
northerly winds around 25-30kts around GLH, while closer to
15-20kts+ further to the east & south. Expect light snow to
gradually taper off from northwest to southeast by mid-afternoon
after 16/18-20Z in the northwest Delta, while areas in the east
and south (MEI & HBG) will be just beginning to have light snow
moving in. These areas light snow & lower ceilings &/or
visibilities could linger into the early evening hours before
conditions improve. /DC/


As of 3z, a closed cold core upper-level low was centered over
southern Wisconsin with a positively tilted trough extending
through the Central Plains. A jet max entering the trough will
help it dig through the Southern Plains and through the ArkLaMiss.
At the surface, a strong arctic front was analyzed over far
southeast Arkansas with a cold arctic airmass spilling into the
Deep South in its wake. Latest regional radar mosaics show a
precipitation shield filling in from northeast Texas through
Arkansas and into western Tennessee. This precipitation is
associated with moist southwesterly flow characteristic of
0.5-0.75" PWATs and a 290-300K low level ThetaE ridge. Sufficient
forcing for ascent aided by right entrance region jet dynamics
will continue to support expansion of the precip shield overnight.
The majority of the precip is falling as anafrontal snow with
temps well below freezing in the wake of the arctic cold front.

For the rest of tonight, the main update to the forecast was to
adjust the timing of the precip. The 00z JAN sounding revealed a
dry airmass still in place with the better moisture over portions
of Arkansas. Precip has also been slower to propagate into the
Delta and the latest hi-res guidance has latched on to the slower
timing as well. Latest surface obs also indicate that a brief mix
of snow and rain will be likely at the onset before quickly
transitioning over to all snow. Overall, QPF values have not
changed much and therefore left the snow totals and all winter
weather products unchanged. However, there have been some
indications that the highest snow totals could end up just to our
north and west where the best moisture depth is juxtaposed with
sufficient omega in a relatively deep dendritic growth zone and
snow ratios upwards of 12:1. With that behind said though, its
way too early in the event to consider adjusting any snow amounts
(up or down) and will instead pay close attention to the trends
overnight. Regardless of how much snow falls, any accumulations
will result in hazardous travel conditions with temps remaining
below freezing. /TW/

Prior discussion below:

Through Tuesday night: An Arctic front will surge southward across
the region overnight, bringing an increasingly dry and
dangerously cold airmass behind it. Ahead of the front,
temperatures have risen into the 50s in most locales, though
dewpoints were only in the 20s across most of the area. A sharp
mid/upper trough will lag behind the low level surge of cold air.
Considerable mid level moisture has already begun to surge across
the ArkLaTex and Mid South ahead of this trough, as depicted by
latest RAP PW analysis and the GOES-16 TPW product. Later on
tonight, the atmosphere will begin to saturate down through the
lower levels as well, allowing precipitation to develop across the
Delta. In the far northern part of the area, this will likely
begin as snow and remain snow throughout, but in areas farther
south across NE Louisiana/W Mississippi, there has been more of a
model trend toward a brief period of light rain at the onset this
evening. However, that should change over to snow fairly quickly
overnight as wetbulbing and CAA cool the column. Light snow will
begin to reach the Natchez Trace corridor by morning, then
southeast Mississippi during the afternoon. There may be light
rain or light sleet at the onset across South MS before a
transition to light snow.

Generally, expectations for accumulations have not changed
significantly from the previous forecast. The ensemble guidance we
have favored for snowfall amounts has remained fairly consistent,
and with this being a relatively dry snow, ratios greater than
10:1 are possible. 2-3" is still expected across the Delta, with
1-2" northwest of the Trace, and less than 1" southeast of the
Trace. For the Pine Belt, less than 1/2" is expected. With the
majority of this snow occurring with temperatures falling into the
20s, snow will begin to accumulate on roads (especially bridges
and overpasses) much more quickly, so travel impacts will be high
in spite of the (relatively) light accumulations. A Winter
Storm Warning remains in effect for the Delta, where significant
travel issues are possible, and a Winter Weather Advisory has
been posted across the remainder of the area. In an attempt to
speak to impacts, we are going to add a "significant" threat area
to the HWO/graphics for the Winter Storm Warning area to highlight
the potentially significant travel impacts related to the snow.
With this being a drier snow, utility impacts are much less likely
than they were with our December winter storm. Though they are
possible, confidence in travel impacts in the Pine Belt is lesser
than areas to the northwest. However, with light accumulations
expected and neighboring offices preferring an advisory, we
included that area for consistency/messaging sake.

In most areas, temperatures will fall during the daytime hours
tomorrow, with highs occurring in the morning. By noon, we`re
expecting low to mid 20s northwest of the Trace, with teens
already sneaking into the upper Delta. Snow will taper off in the
northwest by early afternoon, central by late afternoon, and
southeast by mid evening, followed by a night of dangerous cold.
As a result, much of that which falls tomorrow will stick around
overnight and into the day Wednesday, so even with snow ending on
Tuesday, travel issues could persist well into Wednesday. As cold
advection continues Tuesday night, snow cover may impact
temperatures. Though we are currently advertising lows in the
teens areawide, some single digit readings aren`t out of the
question in the areas that receive the most snow. This, along with
a steady northerly breeze will result in wind chills falling into
the single digits to near zero at times. A Hard Freeze Warning
and Wind Chill Advisory have been posted to address those
concerns, which are also going to be quite impactful. More details
on this below.../DL/

Wednesday through the weekend:

After a brief respite from the cold on Monday, the ArkLaMiss will
plunge back into the deep freeze yet again for a few days mid-week.
Strong arctic high pressure will barrel south into the region by
Wednesday morning, resulting in frigid conditions. Wind chills early
Wednesday will be in the single digits across most of the ArkLaMiss
region, with the worst wind chills being north of I-20. It is in
this area where we could see wind chills of zero to five degrees. A
Wind Chill Advisory is in effect through mid-morning Wednesday,
before conditions should improve, though still chilly. Hard freeze
conditions will continue through Wednesday and Wednesday night as
highs will struggle to rise above freezing across most of the
ArkLaMiss. The Pine Belt may see highs above freezing on Wednesday
but this will be very brief and temperatures will plunge back into
the teens overnight as the cold dome of high pressure settles over
the region. A Hard Freeze Warning, which will  be in effect Tuesday
morning, will continue until Thursday late morning as temperatures
are expected to finally rise above freezing by then.

High pressure will dominate the weather pattern through the
remainder of the week into the early portion of the weekend. This
will leave dry conditions in place across the area. Temperatures
will slowly moderate through the rest of the week and highs will
eventually return to the 40s and 50s by Friday and southerly flow

The bright spot of the extended forecast comes this weekend as
temperatures will reach into the 60s for both Saturday and Sunday,
and some locales in the southern part of the forecast area may even
flirt with 70 degrees! This comes ahead of a developing shortwave
trough across Colorado, which will swing east into the Mid-
Mississippi Valley region by later Sunday. This will bring another
front to our region but also some rain and possibly storms as well
starting Saturday and especially for Sunday. /28/


Jackson       28  15  32  16 /  75   5   0   0
Meridian      32  15  33  15 /  56  28   0   0
Vicksburg     28  15  31  14 /  80   3   0   0
Hattiesburg   37  18  37  17 /  20  44   0   0
Natchez       29  16  32  16 /  73   5   0   0
Greenville    23  13  27  14 /  76   2   0   0
Greenwood     25  12  28  13 /  78   2   0   0


MS...Hard Freeze Warning from 6 AM this morning to noon CST Thursday
     for MSZ018-019-025>057-059>064.

     Winter Weather Advisory until 6 PM CST this evening for

     Wind Chill Advisory from 6 PM this evening to 10 AM CST
     Wednesday for MSZ018-019-025>066-072>074.

     Winter Storm Warning until 3 PM CST this afternoon for MSZ018-

     Hard Freeze Warning from noon today to noon CST Thursday for

     Winter Weather Advisory from 9 AM this morning to midnight CST
     tonight for MSZ051-052-055>058-061>066-072>074.

LA...Hard Freeze Warning from 6 AM this morning to noon CST Thursday
     for LAZ007>009-015-016-023>026.

     Winter Weather Advisory until 6 PM CST this evening for LAZ008-

     Wind Chill Advisory from 6 PM this evening to 10 AM CST
     Wednesday for LAZ007>009-015-016-023>026.

     Winter Storm Warning until 3 PM CST this afternoon for LAZ007.

AR...Hard Freeze Warning from 6 AM this morning to noon CST Thursday
     for ARZ074-075.

     Wind Chill Advisory from 6 PM this evening to 10 AM CST
     Wednesday for ARZ074-075.

     Winter Storm Warning until 3 PM CST this afternoon for ARZ074-



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