Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Jackson MS
1000 PM CDT sun Apr 20 2014

Update...only a few high thin clouds were being observed on
satellite imagery this evening and thicker cloud cover from the west
is expected to come in a little slower...toward morning. Hi-res
models only suggest very light precipitation over our northwest most zones
before sunrise so have decreased probability of precipitation tonight over the Delta but will
include mention of isolated sprinkles over the northwest close to
sunrise. Temperatures were on track. /22/


Aviation...VFR conditions were being observed this evening at all
sites and will continue through 09z. After 09z patchy fog will once again
be possible for taf sites...mainly central and S as thicker middle level
cloud cover over the northwest should inhibit fog development there. The
patchy fog will lift by 14z. Near calm winds tonight will become
southerly at 7-10kts Monday. /17/


Previous discussion... /issued 304 PM CDT sun Apr 20 2014/

Discussion...short term (tonight through Tuesday night)...shortwave
upper ridging extends across the lower Mississippi Valley today as a
surface high pressure axis extends across the Tennessee Valley to
the northern Gulf Coast. The upper ridging will be supplanted on
Monday into Tuesday by a deepening upper trough over the eastern
Continental U.S.. as this trough will be much sharper over the Great Lakes and
more subtle farther south...the associated surface boundary will get
less of a push and end up more west-to-east oriented as it
approaches our area.

Shower activity will be possible across the Delta by early tomorrow
morning as an initial shortwave pushes across the midsouth...with
isolated/scattered activity remaining possible generally north of
I-20 through the day. Instability will be sufficient for some
thunderstorms as well...mainly during the afternoon hours.

The surface front will reach the Delta on Tuesday morning...bringing
the best chance for rain Monday night into Tuesday. Opted to go with
a blend of mav and European model (ecmwf) probability of precipitation...which came out to about 40-50 percent
for most locations. Instability will again be sufficient for thunder
on Tuesday. Bulk shear magnitudes on the order of 15-20 knots will
not be supportive of well-organized severe weather is
not expected to be an issue. The front is expected to clear the County Warning Area
by sunset...with precipitation quickly tapering off by the evening. /Dl/

Long term (wednesday through next weekend)...temperatures Wednesday
will be around seasonal behind the cold front...but southerly flow
quickly building in by Wednesday night into Thursday will usher in a
warming trend...possibly lasting into next weekend. The one wildcard
will be a frontal system centered well to the north which could drag
a front into The Heart of the region around Friday. Model consensus
has been trending further north with this system and its southward
frontal progression before stall. With the latter in mind the
potential for considerable impact from this system is not very high
at present...even considering daytime instability late this week
could be running somewhat high due to increasing warmth and low level
Gulf moisture. The big inhibiting factor for significant storms in
our region in such a scenario would be thermal middle layer capping
keeping a lid on robust convective development in the absence of
considerable atmospheric lift (which should be to our north).

Models are also coming around to early next week being a time period
to watch in terms of truly active weather as copious Pacific jet
stream energy pours efficiently across the Continental U.S. From west to east.
Any associated disturbances in this potential flow regime eventually
coming across the lower MS valley should likely have some
instability to work with. /Bb/


Preliminary point temps/pops...
Jackson 53 79 59 80 / 9 17 29 39
Meridian 49 79 57 81 / 6 13 22 47
Vicksburg 54 80 59 81 / 11 19 36 32
Hattiesburg 55 79 59 83 / 4 12 11 41
Natchez 55 79 59 80 / 7 16 15 39
Greenville 57 78 60 79 / 13 31 50 20
Greenwood 55 79 60 80 / 11 28 42 25


Jan watches/warnings/advisories...