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Area forecast discussion...updated 
National Weather Service Jackson MS
1118 am CDT Sat Apr 25 2015

Update...newly issued Severe Thunderstorm Watch is now in effect for
my southernmost counties generally east of I-55. This is thanks to
another complex of showers and storms currently moving across south
central Louisiana and tracking to the east/northeast. It is in this
area where the airmass has been virtually untouched by last nights
storms and some outflow boundary likely has been layed out over the
region. Short term guidance indicates that there is plenty of lapse
rate down in this region with vertical totals around 28-30c. While
lower level shear isnt huge...deep layer shear is sufficient for
organized storms that could bring some damaging wind gusts. Severe
thunderstorm warnings have already gone out to our south where the
strongest...most organized convection currently is and is not out of
the question for this to move into my southeastern counties through
the early afternoon hours as daytime heating helps contribute to
making the atmosphere more unstable. Current limited outlook in the severe weather potential statement
and graphics appear reasonable. The hrrr again seems to handle the
ongoing activity well this morning and shows a few better convective
cells in my far south through the early afternoon before exiting
before 00z. Further north...the atmosphere...while still moist...is
more stable from overnight convection and should be limited in the
amount of storm activity we see. Going forecast handles much of this
well and only increased probability of precipitation in the south where rain appears
imminent. /28/



&&

Aviation...very moist lower levels are keeping plenty of IFR
category stratus around this morning...but heating should mix ceilings
up into VFR category this afternoon through the evening and bring
the potential for isolated thunderstorms and rain containing hail and damaging wind
gusts. The exception will be in the hbg/pib area where a convective
complex over southern/central la will move east and bring thunderstorms and rain and lower
ceilings/visibility during the early/middle afternoon. Late tonight through early
Sunday morning...IFR/LIFR category stratus will redevelop mainly
along/S of the tvr-Jan-mei corridor. The shallow moist layer should
mix out quickly by middle morning. /Ec/



&&

Previous discussion... /issued 500 am CDT Sat Apr 25 2015/

Short term...today through Sunday night...it has been an active
night...especially north of Interstate twenty...as residents of the
lower MS valley have had to deal with a bowing line of thunderstorms
with pockets of very strong winds. There was also a handful of radar
and reported damage signatures suggestive of brief tornadoes
spinning up with some of the bowing line segments...but we will have
to wait until later today to start survey efforts which may or may
not confirm tornado touchdowns. As I write the tail end of this line
of thunderstorms is about to exit into Alabama with a remnant
outflow boundary slowly sinking south toward the Highway 84
corridor. Tornado Watch number 106 still in effect for a few
counties in east central MS will likely be cancelled very shortly
after aforementioned line entirely clears to the east.

Despite the bulk of storms exiting early this morning the forecast
for our region today will be tricky owing to the fact that the
southern fringe of a southern stream disturbance still has to pass
through the area before evening. Winds throughout the atmosphere
will be gradually veering through the day...which in general will
have the effect of lowering moisture levels (although maybe not
right at the surface). Best moisture depth and usable instability
(which could be quite impressive considering cold temperatures aloft) will
reside south of I-20 with the lingering effect of the baroclinic
zone left in the wake of overnight storms perhaps acting as a
trigger for convective initiation in those parts. Any deep
convection that gets going in the unstable and sheared environment
will potentially be trouble and Worth of keeping a mention of severe
potential in southern zones for primarily the risk of damaging winds
and hail. Further north the drying middle layers of the atmosphere will
be a considerable hindrance to deep...vigorous...convection and it
is most likely those areas will remain dry later today. However...it
is Worth noting a one or two hires model runs has produced a stray
potent storm across the north despite the moisture deficiencies so
it is an aspect of the forecast that will have to be monitored
closely throughout the day.

Expect all lingering late afternoon convection to die in the early
evening with dry weather overnight. The actual cold front will still
remain off to our north so temperatures will generally remain quite
mild.

On Sunday higher clouds will begin increasing later in the day with
the cold front trailing the current system finally coming into
northern zones in the afternoon. But even with the arrival of this
front temperatures should peak well up into the 80s in most areas
(which should probably make for the warmest day of the year so far).
Some locations along and south of the Highway 84 corridor could even
manage to hit the 90 degree mark.

On Sunday night another southern stream disturbance moving into the
plains will begin trying to initiate moisture return up into our
southern zones near the incoming front (which should stall by later
in the night). A few outlying model solutions depict decaying storm
clusters riding southeast from the Red River valley toward our
region before daybreak Monday along this baroclinic zone. Probability of precipitation kept
at no more than 20 percent though considering the consensus solution
is to remain mostly dry until at least the daytime Monday. /Bb/

Long term...Monday through Friday...main focus in the extended is
on rain chances during the first half of the week.

To begin the new work week the upper level pattern will feature
broad troughing over much of the central and eastern Continental U.S. With
ridging along the Pacific coast. A closed off middle/upper low will
track slowly from the Texas Panhandle Monday into the middle MS valley by
Wednesday. With the trough digging rather far to the south...the
surface low will also follow a more southerly path than recent
systems...developing close to the coast during the day Monday and
tracking to the north central Gulf off the MS/Alabama coast by Tuesday
night.

As disturbances pinwheel around the upper low...showers will spread
back into the area Monday into Monday night ahead of the system.
Even better rain chances look to exist Monday night overnight into
Tuesday as an inverted trough extending northward from the surface
cyclone shifts across the forecast area. As we remain on the north
side of the low track...surface based instability will be very
limited though thunder will remain possible thanks to elevated
instability and respectable deep layer shear. As mentioned in
previous discussions there is some potential for coastal convection
to limit activity across our area during a portion of this time
frame.

Precipitation will taper off Wednesday as the system shifts east of the
area. As the upper trough shifts to the Atlantic Seaboard...guidance
shows good agreement on upper ridging building across the remainder
of the country...with a broad surface high building over our area
bringing dry weather through the end of the week. /Dl/

&&

Preliminary point temps/pops...
Jackson 85 67 88 61 / 37 11 6 15
Meridian 83 66 87 59 / 43 13 6 12
Vicksburg 85 66 87 62 / 34 10 7 19
Hattiesburg 85 68 90 65 / 96 11 6 15
Natchez 85 67 87 64 / 95 8 5 19
Greenville 85 63 82 58 / 14 7 7 19
Greenwood 85 62 83 56 / 14 9 6 14

&&

Jan watches/warnings/advisories...
MS...none.
La...none.
Arkansas...none.
&&

$$

28/ec/bb/dl

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