Area forecast discussion...updated
National Weather Service Jackson MS
927 PM CDT Sat may 18 2013
Update...
looks like the cap managed to hold off any storms that had the
potential of forming this afternoon. A quiet and humid night will
therefore prevail. Fog chances in the morning hours are pretty good,
especially south and east of the Natchez trace, as the southerly low
level flow will be pretty light during those cool hours of the
morning. Took out the slight chance probability of precipitation in the northeast for
tonight and adjusted the hourly temperatures for the update. /10/
&&
Aviation...
the primary aviation concern for later tonight into Saturday morning
will be another episode of MVFR/IFR category stratus impacting most
taf sites in southerly low-level flow...and potentially fog as well
as boundary layer winds are expected to be lighter. Expect any fog to
dissipate by middle morning with ceilings breaking up or lifting into
VFR category shortly thereafter in the strong may sunshine. /Ec/
&&
Previous discussion... /issued 414 PM CDT Sat may 18 2013/
Short term...
Saturday evening through Tuesday morning...
Temperatures have warmed nicely this afternoon as ridging begins to
build into the region. Clouds are finally clearing in the northeast
but a thermal gradient is evident. There is still a chance there
could be some development of storms late today into tonight in the
northeast. If any can develop...good instability and lapse rates will
favor strong storms capable of small hail and gusty winds. Upper and
surface ridging will begin to build into the region tonight. Mav
guidance overnight tonight looked good. Just bumped up lows slightly
in the west due to some clouds moving in overnight. Temperatures will
fall into the middle to upper 60s and with high low level
moisture...strongly capped and dry middle levels and light low level
flow...there is a good possibility of some low stratus and
patchy/areas of fog overnight tonight between 10-15z for most of the
region. Sref probs and lvori values are highest in southeast
Mississippi. Thus introduced patchy fog for areas southeast of the
northwest Delta...with areas of fog in far southeast Mississippi.
Upper ridging will continually move into the region as a strong and
deep longwave trough moves through the central/upper plains. The
region will stay capped and low stratus/fog will hang into the early
morning hours before mixing out. Temperatures will be above normal
as 500 mb heights increase and temperatures aloft increase slightly.
Temperatures on Sunday will warm into the upper 80s to near 90
degrees. Mav temperatures look good for temperatures on Sunday.
Shortwave ridge axis will gradually build to the east overnight on
Sunday...leading to weak isentropic lift and middle to high level
clouds in the region. Mav temperature look good Sunday night. There
will again be the potential for some patchy to areas of fog in the
south and southeast due to strongly capped environment and light low
level flow but decided to hold off for now to introduce fog Sunday
night as there could be more low stratus than fog as low level flow
is slightly stronger. Temperatures will again be very warm and humid
Monday afternoon as upper ridge will be situated to the southeast
and increasing southerly flow increases precipitable waters near 1.3-1.5 inches.
Strong capping and increasing low level flow will lead to low
stratus again on Monday night into Tuesday morning. Went close to
mav on temperatures Tuesday night. Strong upper trough and surface
low pressure will gradually propagate to the east/northeast over the
central to High Plains and drag a cold front towards the region. The
cold front should be situated northwest of the region on Monday
morning to Tuesday. Decided to hold off on probability of precipitation until after 12z
Tuesday. However...Euro has sped up slightly in the forward
progression of the cold front bringing the cold front near the
northwest Delta late Tuesday afternoon. This will need to be
monitored for later updates. Rest of the forecast is on track and
relevant portion of long term discussion is attached. /DC/
Long term...
Tuesday afternoon into next weekend...
By Tuesday precipitable waters in the west are expected to exceed an inch
and a half with a weaker cap in place. Daytime heating should lead
to scattered mainly afternoon and evening convection. Thermodynamic
parameters indicate potential for a few strong storms over the Delta
Region. The GFS and European model (ecmwf) agree that the cold front will move into
our western zones Wednesday and that the closed low will open up
into a weakening trough as it moves across our region but they
differ significantly on timing and progression of the cold front.
The GFS brings the cold front through our County Warning Area by Thursday morning
while the European model (ecmwf) stalls the front and dissipates it by Thursday
morning. Either way strong to severe storms look possible over the
western portions of the area again Wednesday. Have leaned toward
the GFS this forecast and will result in cooler and drier weather for
Thursday and Friday. Both GFS and European model (ecmwf) show a second closed low
developing over the Ohio Valley Friday resulting in an Omega block
with the ridge over the central Continental U.S. Going into next weekend. This
would result in continued northwest flow aloft over our region and
cooler than normal temperatures into next weekend. /22/
&&
Preliminary point temps/pops...
Jackson 67 89 70 89 / 2 4 4 8
Meridian 67 88 68 91 / 3 6 4 7
Vicksburg 67 89 70 89 / 2 4 5 9
Hattiesburg 68 89 70 90 / 3 3 4 9
Natchez 68 88 71 87 / 2 5 4 10
Greenville 69 89 71 89 / 2 6 6 9
Greenwood 69 90 70 89 / 2 6 6 9
&&
Jan watches/warnings/advisories...
MS...none.
La...none.
Arkansas...none.
&&
$$
