Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson MS
348 am CST Tuesday Dec 10 2013
Short term...today through Wednesday night...a much drier forecast
is in store for the short term with no winter weather concerns but
below normal temperatures will continue. Evening rainfall is very
quickly exiting the County Warning Area this morning. Temperatures overnight have
remained just above freezing. This has greatly limited any freezing
rain for the County Warning Area this evening and overnight. Subsidence on the
backside of this rain has dried out conditions quickly with the
upper trough continuing to push into and through the region this
morning. Satellite imagery is starting to show some breaks in cloud
cover and this should continue to erode fairly quickly through the
morning hours with clear skies by noon...which should come as a
welcome sight to many. While sites in the Delta have not dropped
below freezing...with clearing on the way...there is still some time
this morning for readings to drop below freezing.
1030mb surface high located over Texas will make its way across the
region today. Despite the clearing and sunny skies expected for
today...temperatures will continue to be on the cool side with
readings mainly in the 40s across the County Warning Area. Some locations in the
south/southeastern part of the County Warning Area may reach around 50 degrees. As
the surface high moves into the lower Appalachians...the upper flow
becomes a bit more zonal through Wednesday morning. Clear skies and
light winds should provide good radiational cooling for tonight
bringing the arklamiss low temperatures in the 20s. The GFS...and to
a lesser extent the NAM...shows maybe some potential for high
clouds/moisture which may limit lows a tad but shouldnt have too
much of an impact.
Wednesday will be a dry and sunny day as well. After a cool start to
the day temperatures will warm up decently with readings in the 50s
for all locations. Another Canadian 1040mb surface high will slide down
west of The Rockies and move into our region by late Wednesday into
Wednesday night behind a dry frontal boundary. This will bring a
reinforcing shot of cooler air to the region. As the surface high becomes
centered over the bootheel of Missouri...we will be under a
tightened pressure gradient on the south side. This will bring
breezy conditions to the region for Wednesday night. With the
additional cooler air moving in...overnight lows will be on the chilly
side in the 20s and some 30s...but with the increased winds from the
tightened pressure gradient...temperatures likely wont dip as much
as could be possible with this airmass and clear skies. /28/
Long term...Thursday through Tuesday...global forecast models continue
to be in good agreement on the overall pattern through the long term
and continues to show much better than average consensus on timing of the
next system that will bring precipitation to the region.
Thursday will be quiet with the forecast focus being on temperatures. Cold air advection will
continue as NE low level flow persists. High temperatures will continue to
be below average (5-10 f) which is supported by the majority of the temperature
guidance. The GFS continues to be on the warmer side and have
trimmed 2-4 degrees off those values. Low Thursday night will be tricky as
initially the cool/dry airmass will allow for a quick cool down.
However...increasing high level clouds will likely limiting cooling
by middle/late evening with temperatures more steady after that. Raw guidance along
with ensemble data support a slightly warmer option and I have
followed those solution and raised the GFS guidance by a couple degrees.
For Friday...clouds will continue to lower and thicken as the next
system approaches. Strong isentropic ascent will be increasing early
in the period through the 305-320k layers. These clouds (lift) will
eventually bring precipitation but will also limit warming during the day.
GFS guidance continues to struggle with highs this period and I have
continued the trend of cutting temperatures quite a bit (5-10 f). As for
precipitation...the trend continues to show a slightly faster evolution.
Nearly all the guidance now shows some light precipitation occurring by the
afternoon timeframe. Due to this...have followed the higher guidance
probability of precipitation with some increase in those values across the west/northwest third.
Strong model agreement exists in the Friday night period being the main
period for widespread precipitation. Due to this high confidence...
increased probability of precipitation to 90%. For the most part...this will be a widespread
rain event with the potential for totals between 1-2 inches. High
deep moisture (pws 1.5-1.7 in) looks to get tapped and throw in some
convective elements...precipitation could be on the efficient side.
Additionally...both the GFS/Euro have trended a tad more north with the
best height falls which is resulting in a slightly more northward
track of a broad surface low. If this trend continues/holds...then that
opens a small door to push lower 60s dewpoints up to the Highway 84
corridor. Any instability that can be generated will be on the low
side...but it may be enough when combined with the strong forcing
and high shear. If certain ingredients combine...then some risk for
strong/severe storms may develop. At this time...this is just something
I wanted to bring attention to and will not mention in any official
For Sat-Sat night...looks like some lingering precipitation will exist and
continued with the chance probability of precipitation with some increase to guidance values
across the southeast. Temperatures will be tricky and have used a blend of the
GFS/GFS ensemble to cover highs as clouds/cold air advection will exist.
For sun-Tue...quiet weather looks to return. Guidance temperatures looked
reasonable and have followed. Overall...below average conditions look to
Aviation...widespread IFR and some MVFR conditions prevailing this
morning as low stratus continues in the wake of evening rainfall.
Evidence of this stratus breaking up has been shown on satellite
imagery and this will continue through the morning. Sky clear conditions
should likely occur by noon for all sites. Once this occurs...VFR
conditions will prevail for the next 24 to 48 hours as high pressure
will remain in control of the weather. North to northeast winds will
continue today around 10kts before speeds diminish to around 3kts or
less after sunset. /28/
Preliminary point temps/pops...
Jackson 45 28 55 30 / 0 0 0 0
Meridian 48 25 58 27 / 0 0 0 0
Vicksburg 45 28 54 27 / 0 0 0 0
Hattiesburg 50 29 58 33 / 0 0 0 0
Natchez 46 28 55 30 / 0 0 0 0
Greenville 41 27 48 27 / 0 0 0 0
Greenwood 42 25 53 25 / 0 0 0 0