Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson MS
1030 am CDT sun Sep 21 2014
Discussion...a cold front currently dropping south through the middle-
south region this morning will continue its southward trek and
eventually enter the northern portion of the forecast area late this
afternoon. This front is expected to bring some scattered showers...
and perhaps a thunderstorm or two...to the region as it pushes into
and through the arklamiss late today and overnight. Until then..look
for continued hot and humid conditions today as highs climb into the
low and middle 90s. Clouds will also increase across the area through
the course of the day thanks to warming and the approaching front.
The better rain chances for today look to exist over locales north of
Interstate 20...with the best rain chances across the Highway 82
corridor late this afternoon.
Other than some minor tweaks to the hourly grids as a result of
current trends...the current forecast looks good and no major
changes will be made on this update. /19/
Aviation...VFR conds prevail late this morning and are expected to
continue. A cool front will approach the region from the north and
isolated/scattered rain showers are expected after 18z with best coverage near
kglh/kgwo/kgtr. Have placed vcsh in those respective tafs for now
and will monitor for direct inclusion if needed after 00z as front
moves through and winds turn north. A few showers could linger
overnight towards kjan but confidence is low and have kept out for
Previous discussion... /issued 409 am CDT sun Sep 21 2014/...
Today through Monday...
One last day with above normal temperatures today as a cool front
will sweep through the region this evening into Monday bringing near
to slightly below normal readings Monday and especially by Tuesday
morning. Isolated/scattered showers and a few rumbles of thunder
expected with frontal passage but overall coverage/scope will be
Water vapor imagery depicts potent trough digging down across the
Great Lakes region and a frontal zone located across central MO
towards the Ohio River basin. This front won't reach the region
until this evening, leaving one more above normal temperature day.
Given overall raw model suite of 925mb temperatures and prognosticated bufr
soundings feel mavmos may be 1-2f warm and blended it with cooler
met guidance. Still, expect highs to be 4-7f degrees above normal
reaching into the 90-93f range. Based on these temperatures and resulting
instability in northwest Delta where slight moisture pooling will occur
ahead of the front this afternoon, some isolated shower activity
looks likely. Have placed 15-20% probability of precipitation for this area which was above
mavmos but in-line with hi-res and sseo output that did well with
yesterday's Delta activity.
The isolated/scattered instability induced showers will dissipate through
evening before front arrives with some light activity continuing
along the front as it enters Highway 82 corridor 7-9pm tonight. Will
carry thunder wording till 11pm and change over to showers
thereafter. Again, given late timing of front with respect to
overall poor Thermo environment, not expecting any strong storms.
Light showers will be possible along I-20 corridor by midnight with
decreasing coverage towards dawn Monday along Highway 84 corridor.
For Monday morning, dewpoints will fall into the low 50s for the
north 1/3rd but residual clouds and elevated winds due to pressure
gradient will keep temperatures up from full potential and were massaged up
to upper 50s to 60. As weak inversion breaks Monday morning and
mixing increases, surface winds could pick up quickly to 15-20 miles per hour
late morning through afternoon. This north wind mixing down in combo with
cold air advection of 925mb temperatures of 16c north to 21c south will only support surface
temperatures in the 80-86f range north to south. Region will be cloud free
Monday with no rain chances as precipitable waters fall near 0.5". Tuesday morning
temperatures will be the coolest of the season so far as low 50s north to
middle and upper 50s south under clear skies and light winds are
Tuesday through Saturday...
Dry through Thursday but rain chances begin to increase Friday and
continue Saturday. In the wake of monday's cold front...a dry airmass
with precipitable waters below a half inch will reside over the County Warning Area. A large 1027mb
surface high centered over the Ohio Valley will move northeast over
the New England states and continue to ridge back to the southwest
over our region into Friday. This will result in a northeast to east
low level flow that will limit moisture return to our region. Normal
highs run near 85 degrees Tuesday and under mostly sunny skies and a
drier airmass... afternoon highs will be near normal. Normal lows are
near 60 degrees at most sites. Decent radiational cooling will allow
temperatures to cool rapidly Tuesday evening but Wednesday morning
lows will not be as cold as Tuesday morning. Still...most sites will
bottom out below normal in the upper 50s Wednesday morning. A slow
moderation in temperatures and moisture is expected Wednesday and
Thursday but precipitable waters will be back above an inch areawide by Thursday
afternoon. Ridging aloft will amplify over over the eastern Continental U.S.
While troughing aloft deepens over the western Continental U.S. Thursday and
Friday. This pattern will be progressive and shift east through the
weekend. The approach of the upper level trough will lead to an
increase in deep moisture and rain chances by Saturday. Thursday will
be dry but a slight chance of afternoon and early evening storms is
expected in our south Friday. Isolated to scattered coverage of
mainly afternoon and evening storms is expected areawide Saturday.
Preliminary point temps/pops...
Jackson 91 64 84 55 / 10 16 4 0
Meridian 92 64 85 52 / 9 16 7 0
Vicksburg 92 62 83 53 / 10 16 3 0
Hattiesburg 92 68 86 57 / 7 16 14 0
Natchez 91 68 84 57 / 7 16 8 0
Greenville 92 61 81 52 / 23 20 0 0
Greenwood 92 60 81 52 / 23 20 0 0