Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Jackson MS
918 am CDT Thursday Apr 17 2014
Update...clouds will continue to increase today ahead of a shortwave
trough that will swing across the region tonight into tomorrow.
Temperatures were off to a slightly warmer start than originally
anticipated...but it appears afternoon highs will be in good shape
with no major adjustments needed. /Bk/
Previous discussion... /issued 339 am CDT Thursday Apr 17 2014/
Short term...today through Friday night...
the primary concerns will be only some shower chances for tonight through
Friday as well as temperatures.
Latest satellite imagery shows a complicated split flow pattern of
the northern and southern streams over the Continental U.S. Early this morning.
The southern stream was trying to push in some stratus toward the region
from the coastal areas. On the surface high pressure was prevalent
across the region under an unseasonable cool airmass with temperatures in
the 40s. A short wave was approaching from the plains along with a
short wave off the southeast Texas coast.
For today into tonight...expect dry weather across the region for
today as moisture builds into the arklamiss as the northwest Gulf
shortwave approaches. This will increase clouds during the day into
tonight. Model sounding shows that the area will be rather cap with
some limited instability near the surface. So will opt for showers
for tonight as moisture convergence and lift increases some with precipitable waters
around 1.1 to 1.3 inches. This was noted by the local and National
WRF models...which does not show much coverage. So with this in mind
kept close to MOS chance probability of precipitation. With midlevel drying quantitative precipitation forecast amounts will
be on the light side of under a half inch in general. Temperatures
will be a little milder with highs in the upper 60s to around 70.
Lows tonight will be from the lower to middle 50s.
For Friday into Friday night...the short wave coming from the plains
will combine with the Gulf short wave which will continue our
chances of showers mainly for Friday morning before ending in the
east by Friday evening. The system will develop into a decent short
wave trough before becoming a closed system east of the County Warning Area. National
WRF and model guidance shows that most of the shower development
will be east of the region. Expect dry conditions to return to the
region for Friday night as shortwave ridging builds in from the
west. Highs for Friday will be more Spring like with highs from the
lower to middle 70s. Lows for Friday night will be a little cooler
with readings ranging from the middle 40s east to the lower 50s west.
As far as temperatures are concern stuck generally close to mav and gmos
guidance. As for probability of precipitation made slight adjustments to mav and gmos
Long term...Saturday through next Wednesday...
nice Easter weekend expected but rain and general tstorm chances
will be on the rise Monday morning, peak Tuesday morning/aftn, and
taper down Tuesday evening. Temperatures will be at or slightly
above normal through the period.
Forecast confidence has increased over previous runs with model suite
converging on overall split flow pattern evolution in the medium to
long range time frame. Easter weekend will feature a progressive 500 mb
Omega block pattern over the southern Continental U.S. With the region nuzzled in
the shortwave ridging Saturday and transition to SW flow with an
approaching trough across the Southern Plains by late Sunday. Top-down
moisturizing will be delayed from previous forecast Sunday and thus
slowed timing of initial rain development until early Monday morning
given run-to-run consistency of ec and with GFS agreement.
Main active period will start Monday afternoon through Tuesday afternoon as a
once phased northern/southern stream 500 mb shortwave trough across the Southern Plains
decouples over the middle MS valley while precipitable waters climb towards 1.3-1.5".
Combination of weak qg lift from southern branch split overtop slightly
unstable airmass /500-1000 j/kg SBCAPE/ Monday afternoon should help
scattered showers/thunderstorms develop mainly across north and central
areas of the arklamiss. Instability will wane into the evening but
with middle level forcing lingering, showers will likely continue
through the overnight. Instability /750-1500 j/kg SBCAPE/ will
return with diabatic heating Tuesday afternoon ahead of a weak boundary
as the positive tilted trough slowly shifts east into Alabama. This
pattern should lead to increased coverage of general thunderstorms Tuesday
afternoon but shear/vertical totals look meager at best to support
anything more robust at this time. Also, widespread heavy rain is
not likely with this set-up and will continue to allow for swollen
rivers to fall. Upper ridging will build back in by Wednesday
morning with a warming trend expected into middle next week. /Allen/
Aviation...VFR conditions will continue across the majority of the
region through the daytime hours...but ceilings will gradually fall from
south to north through the day...becoming MVFR by this evening
around hbg and during the evening/overnight at sites farther north.
Rain showers will become prevalent around hbg/mei and possibly Jan/hks...
with the greatest chance between 06z-12z. IFR ceilings will be possible
in the areas affected by rain. Farther north...only isolated rain showers
are expected with ceilings generally expected to remain in the MVFR
Preliminary point temps/pops...
Jackson 69 54 74 50 / 4 30 21 3
Meridian 68 51 72 46 / 4 33 27 6
Vicksburg 69 54 76 51 / 4 26 21 3
Hattiesburg 69 54 74 50 / 5 41 28 4
Natchez 68 54 76 52 / 5 28 20 5
Greenville 70 53 75 52 / 4 18 16 3
Greenwood 71 53 74 50 / 4 19 16 4