Flash Flood Warning 98, NWS Jackson, MS

Area Forecast Discussion
National Weather Service Jackson MS
1233 AM CDT Sun Sep 13 2020

.UPDATE...
Updated for 06Z aviation discussion

&&

.AVIATION...
06Z TAF discussion:
The day's convection is still trying to wind down and so some
scattered showers are affecting a couple TAF sites currently. This
will come to an end soon though as storm coverage is lessening.
MVFR/IFR ceilings are likely to develop around dawn this morning.
Showers and tstorms will develop early today with some sites
seeing convection before 18Z. /10/

&&

.DISCUSSION...
There was considerable rain coverage from westward-moving bands
of convection this afternoon in association with a tropical wave
moving across the northwestern Gulf (not to be confused with
Sally). Meanwhile, a stalling front extends from the Midwest into
the southern Plains, with associated convection moving eastward
into the Mid South and Mississippi River Valley this afternoon.
This activity converged over central Mississippi early this
evening, with a corridor of stalled convection now extending
roughly along the Big Black River. Though much of the convection
associated with the tropical wave was more diurnal in nature and
has since fallen apart, persisting low level convergence ahead of
the surface front overnight along with subtle upper diffluence
and forcing will keep scattered showers and a few storms going
mainly north of the Natchez Trace. The inherited forecast had a
decent handle on this, so only minor tweaks were made to adjust to
current trends. /DL/

Prior discussion below:

Tonight and Sunday:  Scattered to numerous coverage of showers and
thunderstorms were noted on local radars this afternoon. This
activity will gradually diminish this evening with the loss of
daytime heating but the chance for rain will likely continue tonight
in our west as a quasi-stationary boundary tries to edge into our
CWA. Tropical Storm Sally formed in the eastern Gulf of Mexico
earlier this afternoon and will slowly move our way through Sunday.
Meanwhile, the closed low over the upper Mississippi valley this
afternoon will continue tracking to the northeast across the Great
Lakes region tonight while weakening. This departing shortwave
trough will help the old quasi-stationary frontal boundary just to
our northwest to drift southeast into our CWA later tonight and
Sunday. This boundary will become the focus for convection Sunday
especially during prime heating. Otherwise, warmer than normal
temperatures will continue tonight thanks to our tropical airmass.
High temperatures will continue above normal the southeast half of
our CWA while temperatures are held closer to normal in our
northwest due to the greater rain chances and associated cloud
cover. /22/

Sunday night through Friday night: Primary weather concerns in
the longer term forecast are associated with Tropical Storm Sally.
The official NHC forecast strengthens Sally into a hurricane
before making landfall somewhere along the central Gulf Coast
early Tuesday. With guidance generally trending stronger with
Sally and showing a greater chance for intensification as it
approaches land, am a little more concerned for tropical cyclone
impacts extending into the ArkLaMiss region, especially for heavy
rain and wind in the Tues-Wed time frame over the Pine Belt
region. One of the complicating factors will be with motion as
steering currents will likely become very weak and the system
could slow down once near the coast or inland. Given the potential
for a slow-moving tropical system, will go ahead and post a
limited flooding graphic. If trends continue, both rainfall/wind
threats will need to be highlighted more, and we may ultimately
need to issue tropical storm watch/warning for southeast portions
of the area. Going later into the week, an upper level trough in
the westerlies will likely approach and help to send the remnants
of "Sally" out of the area, and this would bring an end to the
heavy rain threat. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       73  89  73  89 /  40  55   4  56
Meridian      73  90  73  88 /  18  33   8  63
Vicksburg     74  89  73  91 /  52  65   3  40
Hattiesburg   72  92  73  88 /  22  39   9  68
Natchez       73  89  73  90 /  35  61   5  44
Greenville    73  86  71  88 /  57  66   3  33
Greenwood     72  87  70  90 /  60  69   3  40

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&

Hazardous Weather Outlook
National Weather Service Jackson MS
521 PM CDT Sat Sep 12 2020

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
132230-
Ashley-Chicot-Morehouse-West Carroll-East Carroll-Richland-
Madison LA-Franklin LA-Catahoula-Tensas-Concordia-Bolivar-
Sunflower-Leflore-Grenada-Carroll-Montgomery-Webster-Clay-Lowndes-
Choctaw-Oktibbeha-Washington-Humphreys-Holmes-Attala-Winston-
Noxubee-Issaquena-Sharkey-Yazoo-Madison MS-Leake-Neshoba-Kemper-
Warren-Hinds-Rankin-Scott-Newton-Lauderdale-Claiborne-Copiah-
Simpson-Smith-Jasper-Clarke-Jefferson-Adams-Franklin MS-Lincoln-
Lawrence-Jefferson Davis-Covington-Jones-Marion-Lamar-Forrest-
521 PM CDT Sat Sep 12 2020

This hazardous weather outlook is for portions of southeast
Arkansas, northeast Louisiana, central Mississippi, north central
Mississippi, and south central Mississippi.

.DAY ONE...Tonight and Sunday

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Sunday night through Friday

Based on the forecast track for Tropical Storm Sally, the threat
for heavy rainfall and localized flash flooding may increase for
southeast portions of the ArkLaMiss region next week. This will
especially be the case during the Tuesday through Thursday time
frame along and southeast of a line from Monticello to Mendenhall
to Meridian in Mississippi. Rainfall of 3 to 6 inches with locally
heavier amounts will be possible in this area, but monitor for
updates as the forecast will likely change.

(https://www.weather.gov/images/jan/graphicast/1.png)

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations is not expected through next Friday.

21

&&

...HAZARD LEGEND...

No short term hazards expected.

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