Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson MS
945 PM CDT Friday may 29 2015
Discussion...much of this afternoon's convection over central and
eastern portions of the County Warning Area has dissipated this evening as expected.
Over my far western zones...a line of storms has developed south of
a vortex that's currently drifting east northeast near the arklatex.
Weakening of this line is expected as it too lifts north northeast
over locales in my County Warning Area along and west of the Mississippi River.
However...until that happens...a strong to severe storm producing
damaging winds and hail can't be ruled out over the next few hours.
For the reasons stated above...i'll maintain the best probability of precipitation for
tonight over my west and northwest zones. Elsewhere across the
forecast area...other than some low stratus developing and perhaps
some patchy fog over my eastern and southern zones early Saturday
morning...locales look to remain dry overnight.
I adjusted probability of precipitation and remaining elements of the forecast to better fit
with current radar trends and observations. No other changes will
be made to the forecast on this update. /19/
Aviation...a line of storms moving north northeast over northeast
Louisiana and southeast Arkansas...could affect western taf sites
late tonight...kglh and kgwo...but there is uncertainty as to how
far east this line will push. With any thunderstorm there could be
ceiling and visibility restrictions possible to MVFR/IFR categories.
Low stratus will again develop early Saturday morning resulting in
possible MVFR/IFR ceilings...with some patchy fog possible over
mainly east and southeast Mississippi toward day break Saturday.
Again...this could result in a period of MVFR/IFR visibilties at
namely kgtr...kmei...and khbg. /19/
Previous discussion... /issued 450 PM CDT Friday may 29 2015/
Tonight through Sunday night...
A vortex and associated boundary over the arklatex moving east
toward the arklamiss late this afternoon will interact with an
instability/moisture axis (mlcape ~2000 j/kg/precip water ~1.6
inches) currently along and just west of the MS river. Stronger
forcing will help to organize thunderstorms...but relatively weak flow
and eventually nocturnal cooling will help to limit severe
potential. Having said that...a couple of strong to severe storms
and locally heavy rainfall could be a concern...mainly in upper
portions of the arklamiss Delta Region this evening. Current
scattered activity over central portions of MS will diminish with
loss of daytime heating. These storms occasionally pulse up enough
to become strong...but not expecting it to reach severe levels.
As we go into the overnight and Saturday morning...cyclonic flow
may help to keep shower/thunderstorm chances going in spite of nocturnal
cooling...especially over northwest portions of the region. A stronger
shortwave trough will be digging southward over the arklatex and
will support additional thunderstorm development from Saturday afternoon
into the evening. Have increased guidance probability of precipitation some over southeast portions
of MS Saturday afternoon as both the GFS/European model (ecmwf) push stronger moisture
convergence and high precipitable water air into the Pine belt
region in association with the weakening initial wave. Then
activity is expected to refocus again farther west Saturday night.
For Sunday...guidance consensus has gotten a little more progressive
with the second shortwave trough and this is reflected in the latest
forecast with rain chances shifted more to the east. Overall...there
is still some concern for heavy rainfall this weekend...but
confidence is reduced somewhat by the flux in model timing and
likely mesoscale influences that make picking out a specific area a
tough task so far in advance. And the severe potential could be
mitigated by considerable cloud cover/precipitation which would limit
destabilization. Will not include any mention of heavy rainfall or
severe weather in the hazard products at this point. But depending
on how activity evolves tonight...folks should monitor for more
specific hazard products Saturday morning.
In the long term...still a low confidence situation given that the
European model (ecmwf)/ecens guidance is much more progressive than the GFS/gefs with
shortwave energy/cutoff low pushing east across the Gulf Coast
states early/middle next week. /Ec/
Long term...early/middle of next week...some uncertainty is again
creeping into the long term forecast this shift due to the latest
operational European model run coming with a more progressive take
on the trough coming into the lower MS valley Sunday. Previous model
consensus was strongly in favor of this trough energy cutting off
over top of our region and swirling overhead well into next week.
Consensus still favors this solution but the mentioned Euro idea
reduces confidence and suggests some chance that prolonged above
normal rain chances might shift east of our region faster than
By Monday repositioning of the trough axis and associated axes of
moisture transport and moisture advection should fuel the highest
amount of daytime thunderstorm production east of the Natchez trace.
Some storm chances will likely persist back west into the arklamiss
Delta as well on Monday...but this Prospect could potentially change
if the Euro is correct with its latest progressive take of upper
level trough movement.
The forecast for Tuesday through Thursday could be impacted a great
deal if this trough is indeed progressive and cuts off from the jet-
level steering currents to our east. In that case afternoon shower
and storm chances could be much more limited than what the forecast
currently represents (especially west of I-55) while daytime
temperatures may trend warmer. However...as mentioned
previously...the consensus and consistent model solution of trough
energy cutting off overhead still argues for above normal rain
chances to continue well into the week with clouds and precipitation
keeping temperatures down a few degrees. Hopefully by this time tomorrow
model consensus will strengthen regarding solutions for our region
over this time frame. /Bb/
Preliminary point temps/pops...
Jackson 69 85 67 84 / 14 58 52 60
Meridian 67 86 67 85 / 14 50 44 60
Vicksburg 70 84 67 83 / 47 63 53 53
Hattiesburg 67 88 68 86 / 14 50 34 60
Natchez 70 83 67 83 / 46 59 50 58
Greenville 71 83 68 81 / 69 65 45 45
Greenwood 70 83 67 82 / 43 63 50 51