Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Jackson MS
909 PM CDT Tuesday Sep 23 2014

Update...
quiet weather continues throughout arklamiss this evening. Tweaked
the hourly temperatures for the update otherwise the forecast looks to be
in very good shape. /10/

&&

Aviation...
VFR conditions will prevail through the period as strong surface
high pressure continues to prevail. Northeast winds at 5-8kts will
become easterly overnight./15/

&&

Previous discussion... /issued 247 PM CDT Tuesday Sep 23 2014/

Short term...relatively weak...odd looking middle level flow pattern
will prevail through the short term as jet stream will remain well to
the north...mainly in Canada. Weak flow pattern will be characterized
by trough over the upper MS valley and another along the East Coast.
Short wave ridge will remain sandwiched in the middle and controlling
our weather. Building ridge in the western states will keep the jet
firmly positioned to the north of the area as the aforementioned
troughs slowly fill. The forecast area will remain postioned under the
shortwave ridge through the period.

Meanwhile at the surface...large sprawling anticyclone centered over
the NE states will remain in control of our weather providing
easterly low level flow and a slow moderation in dewpoints. Other
than some passing thin cirrus topping the ridge...do not see any
cloud cover to contend with...thus mainly just a temperature
forecast.

With low level flow becoming increasingly weak...ending cool
advection will allow the sun to start working on the dry air and
maxes to start inching up through the 80s Wednesday and Thursday.
Mins looks to stay in the middle 50s for at least one more night then
will begin inching up as well with the slowly increasing dewpoints
from the east./26/

Long term...Friday through next Tuesday...the primary item of
interest in the extended will be rain chances this weekend and early
next week.

Dry conditions will dominate the beginning of the period...with
model prognosticated precipitable waters struggling to get above an inch through the end
of the work week. This will keep rain out of the County Warning Area Friday. However
changes will be occurring in the upper levels of the atmosphere...setting
up our next chance for rain. A cutoff upper low drifting over the
Central Plains will be nudged back eastward by the weekend as a
sharper trough digs across the Pacific coast.

On Saturday surface winds will remain out of the east to even
northeast...but just above the surface...winds will already be in
the process of shifting to the south...bringing about fairly rapid
moisture recovery through the day. Scattered showers will be
possible in this warm advection/isentropic ascent regime. Models
continue to show a surface low developing along the Gulf Coast
during this time frame...with the Euro showing a more well-defined
low lifting northward across the MS valley as it brings the
middle/upper level system closer to the area. Meanwhile the GFS keeps
the cutoff low farther north and west of the area...with a less
organized surface system. Both models have trended farther west with
the surface features since yesterday. With either scenario...it
seems prudent to maintain chance probability of precipitation from Saturday night through
Sunday night. There is still a bit too much uncertainty to pin down
a specific time frame for higher probability of precipitation...but locally heavy rainfall
could become a possibility at some point during this period.

By Monday...guidance continues to diverge making for continued low
forecast confidence. The GFS shows two pronounced cutoff lows over
the Continental U.S. With a stalled surface front over the southern half of the
County Warning Area...keeping rain chances around into the beginning of the next
week. The Euro depicts a broader upper trough...which the nearby
cutoff low becomes absorbed into. This allows the surface low to
lift north of our area...with surface high pressure and dry
conditions building by Tuesday. For the forecast for the end of the
period...opted to trend toward ensemble guidance which was drier
than the GFS/mex. /Dl/

&&

Preliminary point temps/pops...
Jackson 57 84 59 88 / 0 0 2 0
Meridian 53 83 56 87 / 0 0 2 0
Vicksburg 54 85 58 88 / 0 0 2 0
Hattiesburg 58 86 60 88 / 0 0 2 0
Natchez 57 83 60 86 / 0 0 2 0
Greenville 56 86 59 88 / 0 0 2 0
Greenwood 55 85 59 88 / 0 0 2 0

&&

Jan watches/warnings/advisories...
MS...none.
La...none.
Arkansas...none.
&&

$$

National Weather Service Glossary of Abbreviations