Severe Thunderstorm Warning 351, NWS Jackson, MS

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
645 AM CDT Sat Oct 26 2019

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
Flight categories are in the MVFR/IFR range at most sites this
morning, mostly due to low stratus. Visibilities are also reduced
in some areas due to RA/TS. Rain will end from southwest to
northeast through the morning to early afternoon hours as a storm
system moves across the area. Ahead of it, E/SE winds may be gusty
at times with brief gusts to 35-40 kt possible. Isolated severe
storms are also possible this morning. Conditions will improve to
MVFR, and possibly to VFR, this afternoon. However, ceilings are
expected to lower again overnight, with some fog development
possible. /DL/

&&

.DISCUSSION...

Through tonight: The surface low formerly known as Olga has moved
into southeastern Louisiana early this morning and continues
northward toward Mississippi. To the north of the system,
frontogenesis is ongoing roughly along the MS River, with westerly
surface wind and 50s dewpoints observed across most of North LA.
Meanwhile, to the east of the developing front, lower 70s
dewpoints have surged into southeast Mississippi, allowing surface
based instability to slowly increase overnight. As the low
continues to lift northward along the front, a broken line of
convection is expected to develop along the front and surge
northeastward through the morning hours. Given the highly sheared
environment and potential for a sufficiency of instability, a few
damaging wind gusts are possible along the line and tornadoes will
be possible as well. A marginal severe weather outlook is being
highlighted in the HWO/graphical products.

With the surface low deepening as it lifts north of our area, a
brief period of strong gradient winds are also likely to occur just
ahead of the front. Particularly with the ground already being
saturated, a few gusts in the 30-40 mph range could easily knock
down some trees. We have added a limited gradient wind threat to the
HWO/graphics to highlight this potential.

And lest we not forget the flash flood threat. Through 7z, MRMS
gauge bias corrected 24 hour rainfall totals indicate a large swath
of east MS has already received 3-5" of rain, while farther west
totals are closer to the 1-3" range. With an additional 1-2"/locally
higher expected, flash flooding remains a threat in bands of heavier
rain/higher rain rates until the front clears the area. The Flash
Flood Watch has been continued with no modification (though some of
the western portion of the watch could probably be canceled early
as rain clears later this morning.)

The bulk of the rain will be east of the area by this afternoon.
Clouds will linger across most of the area into tonight, and with
only modest cold advection behind the front, low temperatures will
still be near normal for this time of year. Due to the light flow
behind the front and continued low dewpoint depressions, patchy fog
will become possible if any clearing is able to occur. /DL/

Sunday through Friday night: While the overall upper level pattern
across North America will remain extremely amplified during the
long range, we expect a stretch of quiet weather to prevail
Sunday through Tuesday as weak surface high pressure covers the
ArkLaMiss region. Generally dry weather with seasonable
temperatures can be expected in this period.

Global models have come into better agreement on the approach of
a powerful upper level trough as we go into mid week, but with the
ensemble guidance continuing to trend slower overall, don't be
surprised if timing slows even further with the next system and
eventual frontal passage. As it stands, rapid moisture transport
should occur over the forecast area by Tues night into Wednesday
as backing upper level winds allow the tropical moisture
connection observed in recent weeks to make a return. It appears
convective instability and general lift associated with
increasingly favorable upper jet dynamics will support
considerable coverage of shower/thunderstorm activity, but
confidence is somewhat low concerning the exact location of any
convective systems at this point. Given the anomalous moisture and
antecedent conditions following the current flood event, it is
likely that an additional heavy rain/flooding threat will develop
by Wed night/Thurs as a strong cold front approaches. Will hold
off for now on any mention of this in the HWO with global models
still in flux and timing in doubt.

Assuming the cold front pushes through by Thursday/Friday, would
expect much colder air to surge into the ArkLaMiss region with the
potential for the first freezing temperatures of the season over
at least northern portions of the area. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       69  50  70  51 / 100   1   1   0
Meridian      75  51  70  51 / 100   5   1   0
Vicksburg     63  49  71  50 /  75   1   1   0
Hattiesburg   73  50  71  51 / 100   3   1   0
Natchez       62  48  71  50 /  49   1   1   0
Greenville    61  48  69  50 /  91   1   2   0
Greenwood     70  50  69  51 / 100   1   2   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Flash Flood Watch until 1 PM CDT this afternoon for MSZ018-019-
     025>066-072>074.

     Wind Advisory until 1 PM CDT this afternoon for MSZ025>033-
     036>039-042>046-048>052-054>058-062>066-072>074.

LA...Flash Flood Watch until 1 PM CDT this afternoon for LAZ007>009-
     015-016-023>026.

AR...Flash Flood Watch until 1 PM CDT this afternoon for ARZ074-075.

&&

DL/EC

Hazardous Weather Outlook...UPDATED
National Weather Service Jackson MS
516 AM CDT Sat Oct 26 2019

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-034-035-040-041-
047-053-059>061-271030-
Ashley-Chicot-Morehouse-West Carroll-East Carroll-Richland-
Madison LA-Franklin LA-Catahoula-Tensas-Concordia-Bolivar-
Sunflower-Washington-Humphreys-Issaquena-Sharkey-Warren-Claiborne-
Jefferson-Adams-Franklin MS-
516 AM CDT Sat Oct 26 2019

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

.DAY ONE...Today and Tonight

FLOODING
THREAT...Elevated
TIMING...Through mid-morning

Areas of flash flooding are likely through around mid-morning.
Additional rainfall amounts of 1 to 2 inches of rain are expected,
with locally higher amounts possible.

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

.DAYS TWO THROUGH SEVEN...Sunday through Friday

The probability for widespread hazardous weather is low.

.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.

MSZ026>033-036>039-042>046-048>052-054>058-062>066-072>074-271030-
Grenada-Carroll-Montgomery-Webster-Clay-Lowndes-Choctaw-Oktibbeha-
Holmes-Attala-Winston-Noxubee-Yazoo-Madison MS-Leake-Neshoba-
Kemper-Hinds-Rankin-Scott-Newton-Lauderdale-Copiah-Simpson-Smith-
Jasper-Clarke-Lincoln-Lawrence-Jefferson Davis-Covington-Jones-
Marion-Lamar-Forrest-
516 AM CDT Sat Oct 26 2019

This hazardous weather outlook is for portions of central
and eastern Mississippi.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Marginal
TIMING...Through midday

FLOODING
THREAT...Elevated
TIMING...Through midday

NON-THUNDERSTORM WINDS
THREAT...Elevated
TIMING...Through midday

Areas of flash flooding are likely through this morning.
Additional rainfall amounts of 1 to 2 inches of rain are expected,
with locally higher amounts possible.

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

A period of gusty winds, with gusts of 35 to 45 mph, is expected
early today. With saturated soils, wind gusts will likely down
some trees. High profile vehicles should exercise caution.

(https://www.weather.gov/images/jan/graphicast/2.png)

Isolated severe storms, capable of producing damaging wind gusts
and tornadoes, are possible through midday.

(https://www.weather.gov/images/jan/graphicast/3.png)

.DAYS TWO THROUGH SEVEN...Sunday through Friday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today.

MSZ025-271030-
Leflore-
516 AM CDT Sat Oct 26 2019

This hazardous weather outlook is for portions of north central
Mississippi.

.DAY ONE...Today and Tonight

FLOODING
THREAT...Elevated
TIMING...Through midday

NON-THUNDERSTORM WINDS
THREAT...Elevated
TIMING...Through midday

Areas of flash flooding are likely through this morning.
Additional rainfall amounts of 1 to 2 inches of rain are expected,
with locally higher amounts possible.

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

A period of gusty winds, with gusts of 35 to 45 mph, is expected
early today. With saturated soils, wind gusts will likely down
some trees. High profile vehicles should exercise caution.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Sunday through Friday

The probability for widespread hazardous weather is low.

.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.

DL

&&

...HAZARD LEGEND...

*FLOODING*
Extreme...Confident in significant flooding.
Significant...Significant flooding possible.
Elevated...Confident in flooding.
Limited...Flooding possible.

*SEVERE THUNDERSTORMS*
High...Significant severe thunderstorms are expected.
Moderate...Severe storms expected with significant
 severe weather possible.
Enhanced...Severe storms expected.
Slight...Severe storms possible.
Marginal...Isolated severe storms possible.

*NON-THUNDERSTORM WINDS*
Extreme...Sustained winds 50 mph or greater or wind gusts 65 mph
 or greater.
Significant...Sustained winds 40-49 mph or wind gusts 58-64 mph.
Elevated...Sustained winds 30-39 mph or wind gusts 45-57 mph.
Limited...Sustained winds 20-29 mph or wind gusts 30 to 44 mph.

...USEFUL WEATHER WEB PAGES (URLS)...

NWS JAN Home page...
   https://www.weather.gov/jan
Stay Aware, Stay Safe NWS JAN Briefing Page...
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Latest Weather Briefing...
   https://www.weather.gov/jan/weather_briefing

Tropical page...
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National Hurricane Center Home Page...
   https://www.nhc.noaa.gov/
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Follow NWS JAN on Twitter...
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...ADDITIONAL URLS FOR FLOODING ISSUES...

Current Watches and Warnings...
   https://www.weather.gov/jan/safe_HeavyRain

Observed Precipitation Images...
   https://www.weather.gov/jan/precipmaps

River Forecast Center...
   https://www.weather.gov/lmrfc/
Significant River Flood Outlook...
   https://www.wpc.ncep.noaa.gov/nationalfloodoutlook/index.html
Day 1 through 3 Excessive Rainfall...
   https://www.wpc.ncep.noaa.gov/qpf/excess_rain.shtml
Excessive Rainfall Discussion...
   https://www.wpc.ncep.noaa.gov/discussions/qpferd.html
Day 1 through 7 QPF...
   https://www.wpc.ncep.noaa.gov/qpf/qpf2.shtml
QPF Discussion...
   https://www.wpc.ncep.noaa.gov/discussions/qpfpfd.html
...ADDITIONAL URLS FOR SEVERE WEATHER ISSUES...

Storm Prediction Center (SPC)...
   https://www.spc.noaa.gov/
Meso Analysis...
   https://www.spc.noaa.gov/exper/mesoanalysis/
Day 1 through 3 Outlooks...
   https://www.spc.noaa.gov/products/outlook/
Storm Reports...
   https://www.spc.noaa.gov/climo/online/