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Area forecast discussion...update 
National Weather Service Jackson MS
855 PM CDT sun may 24 2015

Update...first off...wanted to confirm that Tornado Watch #204 has
indeed expired for all of our coverage region. It was locally
extended for some locations to our south by the New Orleans
office...which resulted in some confusion.

But despite the watch expiring for our region the potential for
locally heavy rain...thunderstorms and even a lingering potential
for a stray severe storm will remain well into tonight. Current
analysis reveals impressive northward Gulf moisture transport up
(and a little to the east of) the MS river axis with a slow moving
upper level trough axis moving into the lower MS valley.
Precipitable water values in excess of 1.75 inches (very high for
the date) are coincident with this moisture transport axis and the
juxtaposition of moisture...lift...and instability will bring
potential for training thunderstorms well into tonight across The
Heart of our region. Shear levels are such that even with MLCAPE
values under 1000 j/kg a stray severe storm cannot be ruled out and
indeed many storms will contain wind gusts up to 45 miles per hour.
Fortunately...latest hrrr hires output suggests axis of heaviest
rain (and moisture transport) associated with said trough will
advance slowly through the region overnight and will likely be
exiting to the east by daybreak. If this axis were expected to stall
the potential for heavy rain issues overnight would go way up...but
even with that not anticipated there is still some possibility of
flash flooding (which was mentioned in the updated hwo). /Bb/

&&

Aviation...VFR to MVFR conditions and occasionally gusty south to
southeast winds are expected through tomorrow morning although there
will be scattered to numerous showers and storms moving from south
to north through tonight and some of these storms will bring brief
potential for ceilings and visible restriction IFR or worse. Expect
additional numerous storms tomorrow (especially late) with of course
potential hazards for exclusively VFR traffic. /Bb/

&&

Previous discussion... /issued 437 PM CDT sun may 24 2015/

Discussion...
short term...showers and storms have become more widespread across
the area with daytime heating and aided by broad upper troughing over
the western 2/3rds of the country and a middle level shortwave passing
through the Red River valley. While convection hasn't been
particularly deep so far today...some of the storms have still been
efficient wind producers. Tornado Watch 204 has been posted for all
of our la parishes/Arkansas counties and portions of west/central MS.
However the overall tornado threat appears to be on the low end...
especially with eastward extent. Latest Storm Prediction Center mesoanalysis shows
rather marginal srh and middle level lapse rates across most of the
County Warning Area...with neither expected to substantially increase over the next
few hours per Storm Prediction Center sseo/recent rap runs. Bufr sounding analysis/vwps
are mostly unidirectional. However deep layer/effective bulk shear is
increasing over much of the Delta...so there is greater concern for
potential damaging winds through the remainder of the afternoon into
the evening.

Even as the shortwave pulls away from the region...scattered
convection will remain possible overnight into Monday as middle/upper
flow will be nearly meridional thus not giving activity much of an
eastward push out of our area. Another middle level shortwave will swing
across the Lower Plains/MS valley Monday night into early Tuesday.
Best potential for severe weather including some possibility for a
tornado or two would be across the Delta...where the best overlay of
stronger deep layer shear and helicity is prognosticated. Similarly we may
some convection become reinvigorated farther east across a larger
portion of the County Warning Area during the daytime Tuesday as stronger forcing
spreads eastward.

Locally heavy rainfall will be possible this afternoon and evening
especially over the western half of the area as precipitable waters increase to
around 1 3/4 inch. It appears widespread amounts will be low enough
to preclude a notable flood threat over the next 24 hours. However
flooding could become a greater concern Monday into Tuesday as the
atmosphere remains very moist (pwats increasing to around 2 in) and
the ground will have become more saturated due to rain from
today/tonight. /Dl/

Long term...as we go into the rest of the period we will see some
height rises as we go toward a more diurnal driven regime for mainly
afternoon and early evening convection. The mean ridge will fluctuate
some during the rest of the period./17/

&&

Preliminary point temps/pops...
Jackson 71 81 70 81 / 87 62 46 76
Meridian 69 80 69 80 / 46 63 40 79
Vicksburg 71 84 71 81 / 95 60 67 79
Hattiesburg 71 81 71 82 / 62 71 42 73
Natchez 71 84 71 81 / 90 66 66 77
Greenville 70 83 70 80 / 89 69 74 78
Greenwood 71 83 70 79 / 92 66 58 79

&&

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

$$

Bb/dl/17

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