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Area forecast discussion...updated
National Weather Service Jackson MS
608 am CDT Thu Jun 21 2018

updated for 12z aviation discussion


12z taf discussion:
MVFR cigs and scattered thunderstorms and rain wl cont through 15z across the Highway 82
corridor taf sites. VFR conds wl cont south of Highway 82. After 15z
widespread thunderstorms and rain coverage is expected to develop today. This
activity will become isold this evening cntrl and south but
scattered to numerous thunderstorms and rain coverage will continue across the
northern taf sites tonight. Away from thunderstorms and rain activity VFR conds wl
prevail. /22/


today and tonight: early morning water vapor imagery/rap analysis
showed the circulation around a closed low spinning over northwest
Missouri and southwest Iowa. Also noted was a second weaker closed
low spinning over southern Texas. This low over Texas will continue
to help send anomalously high pwats in excess of two and a quarter
inches northeastward ahead of the larger upper level low that will
track east southeast across the mid Mississippi Valley through
tonight. This will support the training of storms will locally heavy
rainfall potential across our County Warning Area today and tonight. Local radars
were already lit up early this morning with thunderstorms with heavy
rainfall training northeast across portions of the Delta Region. As
troughing aloft associated with the upper level low increases over
our region today more widespread development of thunderstorm
activity is expected with daytime heating gradually shifting
southeast through our County Warning Area. Extensive cloud cover and rain will work
to limit heating holding many locations in the mid to upper 80s.
This will still result in enough instability combined with
increasing wind shear that a few severe storms with damaging winds
will be possible. A marginal risk of severe storms has been
outlooked for the area north of Interstate 20. In this same area the
greatest potential for locally heavy rainfall will also exist so a
limited flooding threat will also be mentioned in our severe weather potential statement. Much of
the convective activity will wain this evening with the loss of
daytime heating but a cold front will be dropping into northern
Mississippi toward midnight. Some of the guidance suggests an mesoscale convective system
may develop along the front and drop across our northeast zones
before sunrise. Thus, rain chances will increase after midnight
across the Highway 82 corridor and spread south to Interstate 20 by
daybreak. /22/

Friday: by daybreak on Friday, a cutoff mid/upper low will be
swinging across the mid Mississippi River valley with an associated
cold front stalling across the upper arklamiss Delta. As multiple
upper disturbances pivot around this upper low, a couple rounds of
storms are possible throughout both Friday and Friday night
especially over the northern 2/3rd of the area. Some guidance
suggests storms could be ongoing as early as daybreak in the north.
With northwesterly deep layer shear increasing to 40-50 kt and
steepening mid level lapse rates, some of these storms could be
severe. Damaging wind gusts will be the main threat, but marginally
severe hail is also possible. With the moisture rich environment in
place across the area, there is also a threat for locally heavy
rainfall, though it is a bit too soon to target a specific area for
mention in the severe weather potential statement on Friday.

Saturday and sunday: the surface front will retreat back to the
north and weaken as the upper low pulls northeastward. Surface
ridging will build in from the south/east with strengthening mid
level ridging putting more of a cap on convection in spite of the
lingering moist airmass. We'll have to keep a close eye just to the
north, however, as there are still signs a convective complex could
clip the northern part of the County Warning Area. With less clouds/rain around, it
will be warmer, and with humid conditions continuing, excessive heat
will become more of a concern on Saturday. Heat indices will begin
to approach 105 in some areas, and thus we'll add mention of limited
heat concerns to the severe weather potential statement for Saturday for much of the area, with the
chance this will need to be expanded to include later days/
additional areas.

Monday through wednesday: by next week, the surface ridge will begin
to lose its grip over the area. Now on the periphery of the ridge
and with high deep layer moisture remaining, rain coverage will
likely increase again next work week. Outside of the rain, excessive
heat could still present issues, though with the uncertainty with
regards to clouds/rain disrupting heating, it is too soon to
advertise this threat in the severe weather potential statement. /Dl/


Preliminary point temps/pops...
Jackson 87 73 91 73 / 78 8 46 27
Meridian 88 73 91 73 / 61 17 44 32
Vicksburg 88 74 92 74 / 76 8 42 25
Hattiesburg 89 73 92 73 / 66 20 22 13
Natchez 87 74 92 73 / 78 11 25 15
Greenville 88 73 89 73 / 57 32 65 40
Greenwood 86 72 88 72 / 81 41 70 41


Jan watches/warnings/advisories...


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