Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 311536 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1036 AM CDT TUE MAY 31 2016

.UPDATE...Morning convection is slowly moving out of the northern
part of the CWA this morning leaving much of the region dry. Cloud
debris is helping to keep temperatures from getting too warm this
morning. Despite the fact that we are already seeing temperatures in
the upper 70s to mid 80s, readings this morning are actually about 2
to 6 degrees cooler than this time yesterday. Hi-res guidance
indicates that afternoon convection today will be mostly concentrated
in the central and eastern parts of the CWA and the higher POPs are
arranged as such. Other aspects of the forecast are in good shape and
updated products have been shipped. /28/


.AVIATION...Expect mainly VFR conditions through today and into the
evening hours. Some very isolated spots of IFR will be around this
afternoon in the midst of isolated to scattered thunderstorms. Winds
will be light today...expect around areas of storms. Patchy fog will
be possible across the south by 06z affecting mainly KHBG. The fog
will lift by 13z./17/


.PREV DISCUSSION... /issued 440 AM CDT TUE MAY 31 2016/

SHORT TERM...Today through Wednesday Night...A modest upper level
disturbance moving from the Arklatex and across the northwestern
portion of the Lower Mississippi Valley has been producing a decent
coverage of showers and thunderstorms over the Arklamiss Delta
overnight. The bulk of this short wave energy should translate north
of the region through the morning hours and the solid coverage of
showers and thunderstorms in northwestern zones should fade
gradually. However, the generally perturbed upper flow will remain
through the day over the region with a weak lower tropospheric
convergence zone (which helped initiate scattered afternoon storms
yesterday in central and western zones) migrating a little further
east. The shifting alignment of this convergence zone should spread
afternoon shower and storm chances to predominantly central and
eastern areas of Mississippi and will probably (hopefully) keep
temperatures from peaking well above levels anticipated the last few
days. Even with that expectation, maximums could still hit the mid
90s in a few spots and in these particular locales surface-based
instability will be bordering on high with atmospheric lapse rates
and other aspects of parameter space suggesting some gusty winds
risk will result from wet microburst potential. Given uncertainty on
whether this microburst potential will be high enough to yield more
than a few very isolated strong storms we will not yet mention a
limited severe risk in the HWO, but instead will defer decision to
the morning update after they get some critical clues from examining
the 12Z JAN sounding.

Expect most of the convection today to be done in the evening hours
with little suggestion in models of anything more than isolated
showers and storms hanging on in northwestern zones into the
overnight hours (i.e., no repeat of what has been going on the last
several hours in the Arklamiss Delta). Low temperatures will be mild
with maybe some patchy late night fog in Southeast Mississippi.

On Wednesday, a more considerable amount of upper trough energy will
start approaching the region from the Southern Plains as an upper
low in the Desert Southwest at least briefly phases with a
transitory disturbance in the northern branch of the jet stream. In
response, expect southerly flow to increase over the region although
Gulf moisture advection trajectories are not the best to keep a deep
feed of moisture-laden air coming up into our area from the south.
Still thinking there will be enough ingredients to spawn isolated to
scattered showers and storms during the heat of the day with the
better southerly flow helping to keep temperatures from peaking
quite as hot. The approaching trough and the associated moisture
feed alignment will just start touching far western zones late
tomorrow night, where chances of convection will linger through the
overnight. /BB/

LONG TERM...Thursday through Monday...a cooler and wetter
pattern is still expected for the long term period. A stalled cold
front will be just northwest of our CWA Thursday while a weak
southern stream closed low moves over the Southern Plains.
Downstream of this low a rather moist air mass with above normal
pwats around an inch and three quarters will reside over our region.
The close proximity of the closed low and the stalled cold front
will lead to greater rain chances Thursday with the greatest rain
chances over our northwest zones. The increased rain chances and
associated cloud cover will limit insolation and result in cooler
afternoon highs. The ECMWF and GFS agree that this closed low will
linger over the eastern half of Texas through Saturday before
weakening into an open trough Sunday. This will maintain cloud cover
and rain chances over our cwa through the weekend. The weakening
southern stream trough Sunday will be replaced over our cwa by a
deepening northern stream upper upper level trough that will
encompass the eastern CONUS. This northern stream trough will send a
cold front into our CWA Sunday. The GFS pushes this cold front to
the Gulf coast by Monday morning with cooler and drier air over our
cwa ending rain chances. The ECMWF stalls the cold front Monday just
south of interstate 20 and maintains rain chances over our cwa.
Have leaned toward the ECMWF and kept pops in for Monday but have
tended drier for Monday night. Cooler than normal afternoon highs
are expected Friday through Monday but morning lows will continue at
or above normal through the period. /22/


Jackson       92  68  90  70 /  33  21  25  22
Meridian      94  67  92  68 /  36  17  24  18
Vicksburg     91  69  90  69 /  24  23  25  25
Hattiesburg   94  68  92  69 /  40  19  20  10
Natchez       91  68  88  69 /  20  19  19  18
Greenville    91  70  89  69 /  29  26  37  34
Greenwood     92  70  90  69 /  42  21  37  29


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