Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 240933
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
433 AM CDT SUN JUL 24 2016

.SHORT TERM...

Today through Tuesday morning...

Upper ridge that has brought us the heat to the region has finally
begun to really break down over the past few days. Water vapor and
00Z upper analysis shows the upper low spinning over the ArkLaMiss
Delta as it swings around the eastern periphery of the 594-595dm
upper ridge situated over western Texas into the desert southwest
CONUS. Overall increased isentropic lift from the nearby shortwave
aloft in conjunction with above 2 inch PW`s will help spark
widespread convection this afternoon, mainly in the west and
southwest. Some convection could develop early before 15Z in the
southwest and spreading to the north and east early this afternoon,
which is indicated in the hi-res HRRR/ARW/NMM and global models. Due
to meager lapse rates, some not expecting much in the way of strong
to severe storms but could not rule out some gusty winds and heavy
downpours today. There is some uncertainty on how high temperatures
will reach in the Delta due to more widespread convection, but the
best coverage of storms is still expected in the west-southwest. Due
to that and highs reaching in the low to mid 90s and dewpoints not
mixing much this afternoon, heat indices could top out above 105
degrees, which will increase heat stress issues. Went ahead and
issued a heat advisory along and northwest of a line from Richland
Parish in Louisiana to Leflore County in Mississippi. Graphics/HWO
will be updated accordingly.

As the upper low shifts to the west on Tuesday, shortwave ridging
will help bring in some slightly drier air in the east, which could
help temperatures to be slightly warmer in the east to northeast.
Along the shortwave ridging a TUTT low currently spinning over
southern Florida will move to the northwest along the shortwave
ridge up towards the Gulf Coast. This TUTT will move along the Gulf
Coast to near the Mississippi coast around 18-21Z Monday. This in
addition to increased isentropic lift/moisture convergence ahead of
the disturbance will help spark the best coverage of showers and
storms over the southern and western portions of the region, mainly
in the mid-late afternoon hours. Highs will be a touch warmer in the
Delta and with PW`s still near 2 inches, mixing will be limited.
Heat stress issues could still be some of a concern with heat indices
approaching 105 degrees. Kept the limited for the same area in the
HWO/graphics for Monday. Lows will be still warm the next few nights
mainly in the mid 70s due to clouds and high moisture around. /DC/

.LONG TERM...

Tuesday into next weekend...

Heat and humidity looks to continue through the long term period,
but likely at levels a little reduced from what has been the case the
last handful of days. Still may have to deal with a few spots on a
day or two that may flirt with heat advisory criteria although
potential for this occurrence is too low to highlight in the
HWO/graphics at this point. A lot will depend on the ultimate
coverage of afternoon showers and storms each afternoon and this is a
variable hard to pinpoint with extreme accuracy in the summer more
than several days into the future.

However, we can say with decent confidence that rainfall through the
long term period for most of the region should be at or above normal
levels for the calendar date. The primary driver of the boosted
rainfall will be a nearby weakness in the insipid, nasty, and
sprawling subtropical ridge. A TUTT (tropical upper tropospheric
trough) low now coming into the FL Peninsula should move into a
position by Tuesday near the Sabine River, and subsequently evolve
into said ridge weakness that persists for many days. The GFS and
its ensembles seems to be a little further east setting up this
weakness in comparison to the latest operational European model and,
therefore, the GFS appears the wetter of the two models. If the
latest Euro is indeed more correct with positioning then our
official forecast could be a bit optimistically wet and not quite
warm enough (and such a result could yield another brush with heat
advisories, as mentioned above). But, for now, the GFS member
solutions represent latest overall model consensus a little better
and is represented more in the official forecast. Considering the
mentioned ridge weakness will likely be setting up at least a little
west of our region expect best overall chances of rain to exists in
southern and western zones of the Arklamiss region. /BB/

&&

.AVIATION...MVFR visibilities are currently ongoing at KHKS and could
develop at most TAF sites, with some IFR ceilings and brief MVFR/IFR
visibilities expected at KGWO/KGTR between 24/10-13Z before fog and
stratus will lift after 24/14Z. Expect VFR conditions early this
afternoon before some increased chances of showers and storms and
VCTS are possible in the southwest near KHKS/KJAN around 24/16-17Z
and after 24/18Z elsewhere. Winds will be predominately from the
south-southwest around 5-7kts. /DC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       75  93  74  92 /  18  28  21  40
Meridian      73  93  73  94 /  15  23  20  34
Vicksburg     75  93  74  92 /  20  30  23  43
Hattiesburg   74  90  74  89 /  22  47  22  60
Natchez       74  91  74  90 /  24  49  24  55
Greenville    76  93  75  94 /  21  29  21  27
Greenwood     75  94  74  93 /  17  23  21  26

&&

.JAN Watches/Warnings/Advisories...
MS...Heat Advisory until 7 PM CDT this evening for MSZ018-019-025-034-
     035-040-041.

LA...Heat Advisory until 7 PM CDT this evening for LAZ007>009-015.

AR...Heat Advisory until 7 PM CDT this evening for ARZ074-075.

&&

$$

DC/BB/DC


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