Severe Thunderstorm Warning 45, NWS Huntsville, AL

Area Forecast Discussion
National Weather Service Huntsville AL
300 PM CDT Mon Mar 27 2017

.NEAR TERM...(Tonight)
Issued at 300 PM CDT Mon Mar 27 2017

An active convective situation continued to take shape across the
Tennessee Valley this afternoon, as strong/severe thunderstorms
begin moving across far NW Alabama. As such, Severe Thunderstorm
Watch #90 is now in effect for all of our Alabama counties until
9 PM CDT; and #91 for our Tennessee Counties until 10 PM.

Atmosphere wise, high temperatures so far have warmed into the
mid/upper 70s, with average dewpoint values ranging from the mid
50s to mid 60s (higher dewpoints generally to the west). This has
resulted in surface based CAPE values up into the 2000 J/kg range.
But lower level shear values were on the low side, mainly below 150
m/s except our far NW areas (per SPC meso-analysis). A warm frontal
boundary, thanks to a strong southerly flow has moved northward to
north of the Ohio Valley. A warm front denoting this change was in
place from low pressure along the central AR/MO border. A cold front
extended SW of this low across far NE Texas.

For tonight, various mesoscale models, as well as the NAM/ECMWF/
Canadian have convection rolling in a west east manner across the
region. As noted above, some of these storms could become strong to
severe --- with large hail and damaging winds the primary threats. A
tornado or two cannot be totally ruled out in the strongest storms.

With evening cooling after dusk, instability will remain but should
become more elevated. This will overall help temper tornado
potential, but large hail and strong to damaging wind gusts threats
remain. The storms per mesoscale models have the strongest convection
mostly to the south and east of the area and/or on a weakening trend
after midnight. Night low temperatures should fall to around 60.

.SHORT TERM...(Tuesday through Wednesday)
Issued at 300 PM CDT Mon Mar 27 2017

Isolated to scattered thunderstorms remain possible over areas south
and east of the NW Alabama Quad Cities Tuesday morning. These storms
will end from NW to SE as a cold front moves across the region during
the day. Another mild to warm spring day is forecast with highs
warming into the low/mid 70s. The above noted frontal boundary will
become stationary; oriented west to east south of the area later
Tuesday and Tuesday night. Slightly cooler and drier air filtering in
from the NW will produce lows into the lower/mid 50s. There could be
patchy fog formation late Tuesday night, mainly within and near wind
sheltered areas and locations that were affected by recent heavy
rainfall.

Wednesday, the boundary south of the area will return northward as a
warm front, and bring a slight chance of showers/thunderstorms in
the afternoon. Given limited amounts and timing of instability, did
not continue rain chances into Wednesday night. The frontal boundary
will move ever so further north during the night-time, setting up
another busy day convective wise on Thursday...

.LONG TERM...(Wednesday night through Sunday)
Issued at 300 PM CDT Mon Mar 27 2017

Models continue to diverge a bit concerning the eastward progression
of the storm system moving from Kansas/Oklahoma towards the
Tennessee Valley on Thursday. Based on the strong ridge it is moving
into over the Great Lakes region into the Mid-Atlantic region, think
the slower solution is more likely. Thus kept precipitation chances
isolated east of I-65 early on Thursday. West of I-65 enough forcing
and low-level moisture convergence should be in place in northwestern
Alabama for widespread shower and thunderstorm development.

Models diverge a bit concerning how far north the surface low and
thus how far north the warm front with this system sets up. This
would affect the amount of instability in place along and ahead of
the approaches storm system. Models are in fairly good agreement that
surface based instability around 500 J/kg is in place in the
morning. Along with 40 to 50 knots of Bulk Shear in place and some
low level turning of winds, severe storms producing damaging winds
are possible. These parameters continue and spread slowly east into
the late afternoon hours ahead of the system near and west of I- 65.
Surface based instability climbs to between 1000 and 1500 J/KG in
models (maybe a bit higher depending on how far north the warm front
makes it). Morning precipitation should keep the best instability in
place near and east of I-65. This would enhance damaging wind
potential and tornado potential as the afternoon would progress in
those areas. Luckily, low level helicity values forecast at this time
do suggest any tornadoes that develop would be fairly weak in
nature. As even stronger forcing moves into northern Alabama ahead of
a fairly strong cold front, strong to severe storms could last into
the early evening hours. However, by midnight the atmosphere should
be too worked over by precipitation to produce more than ordinary
showers and thunderstorms. Models diverge how quickly showers push
east of the area on Friday. Forecast models indicate a blend of this
timing and leans towards the later exiting time into Georgia late
Friday afternoon.

High pressure builds into the Tennessee Valley behind the front
Saturday night into Sunday, as another storm system develops
somewhere over southwestern Texas or Oklahoma. The surface high
should keep forcing and better moisture advection to our west in
Mississippi until Sunday evening. This should also keep highs and
lows cooler (highs in the upper 60s to lower 70s/lows in the upper
40s to lower 50s) Friday night through Sunday. By Sunday evening
into Monday, these parameters should become stronger over northern
Alabama and Southern Middle Tennessee. At this time, this system
does not look as unstable as previous systems. Strong storms look
possible, but surface based instability does not looks as good. Rain
chances really pick up Monday into Monday night as this systems
pushes east through the area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1242 PM CDT Mon Mar 27 2017

Scattered to numerous showers/thunderstorms will affect the area
this afternoon and evening. Some of the storms could become strong to
severe in intensity, with large hail, damaging winds, and a tornado
or two possible (the strongest storms occur in areas west of I-65).
Started prevailing convection at KMSL at 27/1900Z and KHSV an hour
later, with erratic wind gusts and lowered CIG/VIS values into MVFR.
Even lower minimums are possible in the strongest showers/storms.
Shower activity should wind down as the activity progresses in a NW-
SE manner this evening. Winds should remain high enough to keep fog
formation minimized late tonight.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

NEAR TERM...RSB
SHORT TERM...RSB
LONG TERM...KTW
AVIATION...RSB

For more information please visit our website
at weather.gov/huntsville.

Hazardous Weather Outlook
National Weather Service Huntsville AL
316 PM CDT Mon Mar 27 2017

ALZ001>010-016-TNZ076-096-097-281130-
Lauderdale-Colbert-Franklin AL-Lawrence-Limestone-Madison-Morgan-
Marshall-Jackson-De Kalb-Cullman-Moore-Lincoln-Franklin TN-
316 PM CDT Mon Mar 27 2017

This Hazardous Weather Outlook is for north Alabama and portions of
southern middle Tennessee.

.DAY ONE...Tonight...

Scattered to numerous thunderstorms will continue to develop into the
evening hours in response to a passing upper level disturbance. Some
of these storms may be strong to severe in nature this afternoon and
this evening, and will be capable of producing large hail and
damaging winds. A low tornado threat cannot be ruled as well. The
threat for strong to severe thunderstorms will then come to an end
around midnight.

Scattered thunderstorms will continue overnight, but should remain
below severe limits producing gusty winds and heavy downpours.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday...

A few lingering thunderstorms are possible Tuesday morning as a cold
front moves eastward across the outlook area.

Another storm system approaching from the west may bring additional
thunderstorms to the outlook area Thursday into Friday. Some storms
may be strong to severe but the exact details and timing remain
uncertain at this point.

.SPOTTER CALL TO ACTION STATEMENT...

Activation of storm spotters and emergency management personnel is
likely this afternoon and evening.

20

Special Weather Statement
National Weather Service Huntsville AL
302 PM CDT MON MAR 27 2017

ALZ001-272030-
Lauderdale AL-
302 PM CDT MON MAR 27 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN LAUDERDALE COUNTY
UNTIL 330 PM CDT...

At 302 PM CDT, Doppler radar was tracking a strong thunderstorm near
Killen, or 12 miles northeast of Florence, moving northeast at 30
mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Killen, Lexington, St. Joseph, Anderson, Green Hill, Center Star,
Kingtown and Whitehead.

LAT...LON 3500 8724 3500 8721 3493 8721 3481 8749
      3483 8752 3483 8757 3497 8764 3501 8756
TIME...MOT...LOC 2002Z 244DEG 28KT 3492 8752

15

Special Weather Statement
National Weather Service Huntsville AL
304 PM CDT MON MAR 27 2017

ALZ009-272045-
Jackson AL-
304 PM CDT MON MAR 27 2017

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL JACKSON COUNTY UNTIL 345
PM CDT...

At 304 PM CDT, Doppler radar was tracking a strong thunderstorm near
Grant, or 9 miles southwest of Scottsboro, moving northeast at 30
mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Scottsboro, Stevenson, Hollywood, Skyline, Section, Hytop, Langston,
Martintown, Lim Rock and Fackler.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3447 8605 3446 8608 3451 8610 3452 8610
      3453 8611 3453 8613 3452 8614 3455 8615
      3460 8615 3460 8625 3491 8610 3484 8577
TIME...MOT...LOC 2004Z 205DEG 28KT 3456 8614

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Special Weather Statement
National Weather Service Huntsville AL
309 PM CDT MON MAR 27 2017

ALZ006-008-272045-
Marshall AL-Madison AL-
309 PM CDT MON MAR 27 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN MARSHALL AND
SOUTHEASTERN MADISON COUNTIES UNTIL 345 PM CDT...

At 309 PM CDT, Doppler radar was tracking a strong thunderstorm near
Morgan City, or near Arab, moving northeast at 40 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Southern Huntsville, Arab, Owens Cross Roads, Union Grove, Hampton
Cove, Eddy and Hebron.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3434 8658 3446 8657 3472 8649 3464 8636
      3463 8636 3461 8633 3460 8632 3460 8629
      3459 8627 3431 8652
TIME...MOT...LOC 2009Z 211DEG 35KT 3441 8655

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PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE HUNTSVILLE AL
342 PM CDT MON MAR 27 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0230 PM     HAIL             3 N FLORENCE            34.85N 87.68W
03/27/2017  M0.75 INCH       LAUDERDALE         AL   EMERGENCY MNGR

            DIME SIZED HAIL ON PATSY DRIVE IN FORREST HILLS
            SUBDIVISION IN FLORENCE.

0235 PM     HAIL             3 N FLORENCE            34.85N 87.68W
03/27/2017  M0.88 INCH       LAUDERDALE         AL   EMERGENCY MNGR

            NICKEL HAIL ON PATSY DRIVE IN FORREST HILLS SUBDIVISION
            IN FLORENCE.

0241 PM     HAIL             4 SSW GUNTERSVILLE      34.31N 86.32W
03/27/2017  M1.25 INCH       MARSHALL           AL   TRAINED SPOTTER

            BETWEEN QUARTER AND HALF DOLLAR SIZE HAIL ON SPRING CREEK
            DRIVE IN GUNTERSVILLE.

0241 PM     HAIL             1 SE GUNTERSVILLE       34.35N 86.28W
03/27/2017  M1.75 INCH       MARSHALL           AL   BROADCAST MEDIA

            GOLFBALL HAIL ON THE EAST SIDE OF GUNTERSVILLE.

0336 PM     FUNNEL CLOUD     5 SSW BELGREEN          34.41N 87.90W
03/27/2017                   FRANKLIN           AL   CO-OP OBSERVER

            WALL CLOUD SPOTTED WITH FUNNEL CLOUD TRYING TO LOWER.
            REPORT RELAYED BY NWS BMX COOP OBSERVER.

&&

12

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE HUNTSVILLE AL
347 PM CDT MON MAR 27 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0230 PM     HAIL             3 N FLORENCE            34.85N 87.68W
03/27/2017  M0.75 INCH       LAUDERDALE         AL   EMERGENCY MNGR

            DIME SIZED HAIL ON PATSY DRIVE IN FORREST HILLS
            SUBDIVISION IN FLORENCE.

0235 PM     HAIL             3 N FLORENCE            34.85N 87.68W
03/27/2017  M0.88 INCH       LAUDERDALE         AL   EMERGENCY MNGR

            NICKEL HAIL ON PATSY DRIVE IN FORREST HILLS SUBDIVISION
            IN FLORENCE.

0241 PM     HAIL             4 SSW GUNTERSVILLE      34.31N 86.32W
03/27/2017  M1.25 INCH       MARSHALL           AL   TRAINED SPOTTER

            BETWEEN QUARTER AND HALF DOLLAR SIZE HAIL ON SPRING CREEK
            DRIVE IN GUNTERSVILLE.

0241 PM     HAIL             1 SE GUNTERSVILLE       34.35N 86.28W
03/27/2017  M1.75 INCH       MARSHALL           AL   BROADCAST MEDIA

            GOLFBALL HAIL ON THE EAST SIDE OF GUNTERSVILLE.

0336 PM     FUNNEL CLOUD     5 SSW BELGREEN          34.41N 87.90W
03/27/2017                   FRANKLIN           AL   CO-OP OBSERVER

            WALL CLOUD SPOTTED WITH FUNNEL CLOUD TRYING TO LOWER.
            REPORT RELAYED BY NWS BMX COOP OBSERVER.

0345 PM     HAIL             1 S BELGREEN            34.47N 87.87W
03/27/2017  M1.00 INCH       FRANKLIN           AL   EMERGENCY MNGR

            QUARTER HAIL MEASURED AT THE FRANKLIN COUNTY EOC IN
            BELGREEN

&&

12

Special Weather Statement
National Weather Service Huntsville AL
352 PM CDT MON MAR 27 2017

ALZ005-272115-
Limestone AL-
352 PM CDT MON MAR 27 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN LIMESTONE COUNTY UNTIL
415 PM CDT...

At 351 PM CDT, Doppler radar was tracking a strong thunderstorm 9
miles north of Athens, moving east at 40 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Ardmore, Elkmont, Lester, Cartwright, Mt Rozell, Cairo, Holland Gin
and Leggtown.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3499 8678 3485 8678 3486 8717 3500 8716
TIME...MOT...LOC 2051Z 259DEG 36KT 3494 8702

73