Area Forecast Discussion
Issued by NWS Jackson, MS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41
000
FXUS64 KJAN 251540 AAA
AFDJAN

Area Forecast Discussion...Updated
National Weather Service Jackson MS
1040 AM CDT MON JUL 25 2016

.UPDATE...A somewhat deep inverted trough is progressing slowly
westward through the northern Gulf of Mexico today and the 12Z JAN
sounding reveals slightly drier air has worked into at least the
northern two-thirds of the region on the north side of the feature.
Latest HiRes models are reacting to this drier air by having output
far less aggressive in terms of PoPs for the bulk of the region
through this afternoon and evening. However, deep south to southeast
flow in the atmospheric lower levels is still anticipated through
this afternoon along and just north of the coast and this flow
regime, in concert with sufficient moisture and instability nearer
the coast, should result in northward-cascading seabreeze activity
advancing into my southern zones this afternoon. PoPs were kept in
high-end chance range down in that neck-of-the-woods for today while
elsewhere they were kept pretty low. One slight adjustment was to
extend slight chance pops a little further north into this evening
with the thought that the aforementioned boundaries coming in from
the south could activate late activity at least north to the I-20
corridor. Another adjustment was to raise highs just a bit in
northern zones in response to preponderance of latest HiRes output.
Heat indices still look to peak at least around 100 degs F for most
folks with the highest heat index values (near 105) confined to
northwestern zones where the HWO/graphics is already advertising
conditions near Heat Advisory. /BB/

&&

.AVIATION...VFR categories should prevail through much of the day.
Afternoon/early evening TSRA will again be possible but coverage
should mostly be confined to roughly KHKS/KJAN/KHBG. This could
bring some brief MVFR to IFR ceilings/vis restrictions. VFR
conditions expected outside of rain/storms. /28/

&&

.PREV DISCUSSION... /issued 453 AM CDT MON JUL 25 2016/

DISCUSSION...

Today through Tuesday night...

In the very near term, areas of fog have developed in the Pine Belt
and Delta regions and expect this to burn off fairly quickly after
sunrise. Visibilities have briefly dropped to a quarter mile at KPIB,
but fog is staying above dense category for the most part.

The upper trough discussed previously will shift westward across the
northern Gulf of Mexico in the next 24 to 48 hrs, and it is expected
to move fast enough to remain cold core in nature with very little
surface reflection noted in near term guidance. A deep very moist
airmass (precipitable water increasing to near 2.25 inches by Tuesday)
and convergent southeasterly flow will support highest mainly diurnal
convective precipitation coverage over southern/western portions of
the forecast area. Rather poor mid level lapse rates (vertical totals
generally < 26) will limit strong storm potential, but decent deep
layer southeast flow of 15-20kts and boundary collisions could
provide some extra boost for more intense updraft/downdraft cycles
resulting in 30-40 mph wind gusts along with very heavy downpours.

Meanwhile, over northeast portions of the ArkLaMiss, low level
negative theta-E advection will result in a drier and less favorable
airmass for diurnal convective activity today as precipitable water
falls to below 1.5 inches. However, expect significant moistening to
increase shower/thunderstorm chances by late Tuesday afternoon and
evening.

Will maintain the current limited heat threat graphic for the Delta
region but will extend it another day based on new guidance which
indicate slightly hotter heat indices for Tuesday afternoon. /EC/

Long Term (Wednesday through the weekend)...Greater than normal rain
chances and near normal temperatures characterize the extended
portion of the forecast.

By midweek, the upper trough traversing the northern Gulf will have
begun to lose its distinction within a broad weakness developing over
the eastern CONUS within the broad mid/upper trough. Though the upper
trough will fade, the increased moisture associated with it will be
pulled into the region during the mid/late week time frame. As a
result, shower and thunderstorm activity will likely become
increasingly ubiquitous throughout the long term period. This will
only be reinforced by increasing mid/upper troughing from the Great
Lakes into the MS Valley by the weekend.

Though it is conceivable there will be a few days during the period
with temps sneaking above normal, in general, the increased
prevalence of clouds and convection is expected to keep us closer to
seasonal normals. /DL/

AVIATION...VLIFR category fog and stratus has developed in the KHBG
area early this morning and this is expected to lift/mix out shortly
after sunrise. Otherwise, some MVFR category stratocumulus could
develop as the very moist boundary layer heats up during the mid
morning, but expect any lower ceilings to mix upward into VFR
category by around noon. Afternoon/early evening TSRA should mostly
be confined to roughly the GLH/JAN/HBG corridor with less coverage
expected as you go farther northeast. VFR conditions will prevail
this evening. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       94  74  93  75 /  22  23  33  34
Meridian      96  74  93  74 /  15  19  39  27
Vicksburg     94  74  94  75 /  28  23  33  32
Hattiesburg   93  74  90  75 /  40  22  60  40
Natchez       92  73  91  74 /  47  24  45  40
Greenville    96  76  95  76 /  26  22  19  20
Greenwood     96  75  95  75 /  15  18  20  20

&&

.JAN Watches/Warnings/Advisories...
MS...None.
LA...None.
AR...None.
&&

$$

BB/28



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.