Office: JAN
FXUS64 KJAN 231005
AFDJAN
Area Forecast Discussion
National Weather Service Jackson MS
505 AM CDT Sun Sep 23 2018
.UPDATE...
Updated for 12Z aviation discussion
&&
.AVIATION...
12Z TAF discussion:
Primary aviation hazards for early this morning will be LIFR/IFR
ceilings in the GLH/GWO area and MVFR ceilings in the GTR area.
Ceilings will be slow to mix upward in the GLH area and they may
not improve above MVFR category in the afternoon. Otherwise,
concerns will shift this afternoon to the potential for short-
lived vsby/cig reductions due to scattered/numerous SHRA/TSRA
activity, especially in the GLH/GWO area. Expect convection to
diminish this evening with lowering ceilings becoming the primary
concern late tonight once again. /EC/
&&
.DISCUSSION...
Today through Tonight:
The primary weather concern in the near term will be the threat for
locally heavy rainfall and minor flooding over mainly northwest
portions of the ArkLaMiss from mid/late afternoon into early this
evening. A quasi stationary front over northwest portions of the
forecast area should help to focus new convective development later
this afternoon as a weak shortwave trough moves slowly across the
region. The deep layer lift and moisture convergence in the 2+
inch precipitable water airmass characterized by thin CAPE
profiles will support some training of efficient heavy rain
producing showers and isolated thunderstorms, and we have
included a mention of a limited flooding threat in the
HWO/graphics. Confidence on the onset of the heavy rainfall threat
is not high, and some CAM guidance delay it until well into the
afternoon.
Otherwise, poor lapse rates will continue to mitigate the risk for
severe storms. Locations farther east of the flood threat area will
be under greater influence from the subtropical ridge axis, at least
in short term, and this will keep rain chances lower and daytime
temperatures slightly hotter with more lower 90s expected. All
convective precipitation should diminish quickly during the mid/late
evening hours, but low end shower chances will continue through the
night over northwest portions of the ArkLaMiss in the very
moist air closer to the frontal boundary. /EC/
Monday through Saturday:
The wet pattern will continue through most of the week ahead. With
the upper-level ridge centered off to our southeast, a series of
shortwave troughs working their way east across the country will
help to reinforce a frontal boundary near our region. Model guidance
remains fairly consistent with regards to timing and placement of
features, with a slight trend toward a better push of the cold front
south into our area around the Wednesday to Thursday time frame.
Given the consistent signal for rain along the front, and given the
fact that models are indicating a more suppressed ridge for the
later half of the week, went ahead and lowered high temperatures on
Wednesday and Thursday a few degrees compared to the consensus of
models. The combination of rain-cooled air along and behind the
front could keep northern areas closer to 80 degrees during the
afternoon both days. Expect a slight rebound in temperatures for the
end of the week as the mid-level trough axis moves east of our area
and the ridge tries to build back along the Gulf Coast.
A moisture-rich airmass (PWAT values of 2.0 to 2.3 inches) along and
south of the front will support heavy rainfall rates at times
throughout the week; however, with an expected southward push of the
front, the current expectation is for rainfall amounts to be more
evenly distributed across the region. Therefore will keep a mention
of flash flooding potential out of later periods of the Hazardous
Weather Outlook for now. Heavy downpours could still cause localized
flooding any day this week, so be sure to monitor for updates to the
forecast over the next several days. /NF/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 88 70 88 72 / 49 42 66 30
Meridian 91 70 88 71 / 31 20 66 25
Vicksburg 87 71 88 72 / 68 60 66 37
Hattiesburg 89 70 88 72 / 54 23 66 23
Natchez 86 71 87 72 / 67 45 66 30
Greenville 81 69 85 71 / 74 71 67 47
Greenwood 83 70 85 72 / 69 68 66 48
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
