Special Weather Statement, NWS Atlanta, GA

Area Forecast Discussion...Updated for Aviation
National Weather Service Peachtree City GA
100 AM EST Wed Nov 30 2016

.UPDATE...
Updated the forecast to add the Tornado Watch for portions of NW
GA.

&&

.PREV DISCUSSION... /Issued 620 PM EST Tue Nov 29 2016/

UPDATE...
Have made a few minor tweaks to the ongoing forecast. The trend
for the last few days has been a slower onset to the leading edge
of the precip...have chosen to go this way again for
overnight/tomorrow. Most of the hi-res models support this idea.
The only other tweaks were to the hourly temp/dewpoint grids.

PREV DISCUSSION... /Issued 217 PM EST Tue Nov 29 2016/

SHORT TERM /Tonight through Wednesday Night/...
The forecast area is currently in a lull between this morning's
widespread rainfall and the next round of active weather expected by
tomorrow. A warm, moist airmass will continue to filter northward
into the area overnight as a warm front pushes northward into
Tennessee, and a cold front currently over the Ark-La-Tex region
will continue progressing eastward overnight. Showers and
thunderstorms will begin to develop in earnest in the lower
Mississippi Valley later this evening into tonight and move eastward
ahead of the aforementioned cold front. A favorable setup for severe
thunderstorms will exist in the states to our west, where ample
shear and adequate instability will be in place.

Gusty southerly winds can again be expected in the higher elevations
of the north Georgia mountains tonight into Wednesday morning as a
strong LLJ is in place. However, wind gusts are not expected to be
as intense and as widespread as last night. Only the highest peaks
are forecast to experience gusts of up to 30 to 35 mph. Due to the
more isolated nature of these stronger gusts, opted not to issue any
wind hazard products at this time.

By late tonight into early Wednesday morning, expect ongoing
convection to meld into a line as it progresses eastward toward
Georgia. Model guidance has trended a bit slower on the arrival of
this activity in northwest Georgia, favoring an arrival more towards
sunrise on Wednesday in these areas. There will be the threat for at
least isolated severe activity when the activity reaches Georgia.
Though instability will be diminished here as compared to areas
farther west (CAPE values peak around or just above 500 J/Kg) and
the best dynamics will become displaced from the convection, plenty
of shear/helicity will maintain a threat for some damaging wind
gusts. There will be a gradual reduction in overall severe threat as
storms move into eastern portions of our area later on Wednesday as
instability wanes even more by Wednesday evening.

Rain will exit the far southeastern portions of our forecast area
overnight Wednesday night, and drier and more temperate fall
temperatures will follow.

RW

LONG TERM /Thursday through Tuesday/...
Only tweaks to the long term based on the latest guidance.
Next rain event later this weekend and next week.

BDL

PREVIOUS DISCUSSION...
Surface cold front will be pushing thru the SE portion of the
forecast area at the start of the long-term period. This will keep a
high-end chance of POPs going across most of central Ga...with CAA
and drier airmass filtering into N Ga in the wake of the front.
Although deep-layer shear will be strong...lack of appreciable
instability due to meager lapse rates / despite moist boundary
layer/ will minimize any strong/severe potential as this system
exits. Most thunder activity will have diminished with moderate
rain showers seeming most likely. All precip will clear the
forecast area by Thursday morning as frontal system finally clears
the CWA.

Tranquil weather will persist Thursday through Friday under sfc high
pressure influence and CAA regime. Slightly enhanced winds just
above the sfc on Thursday could lead to breezy conditions with
daytime mixing...but does not look to be as a big of a threat as the
last several post-frontal set-ups with pressure gradient not quite
as tight.

Evaluation of ECMWF/GEFS/GEM ensemble data seem to be coming to
terms in regards to our next system/rain chance. By early
Saturday...a digging trough across the intermountain west will
become a closed low over S Arizona/N Mexico...helping pump deep
layer moisture across the SE as it taps into subtropical maritime air
and flow becomes more SW in the mid-levels. Right now...prefer the
GEFS/GEM evolution over ECMWF...which argues for slower
progression of the closed low into an open wave as it migrates
east. A steady stream of precip seems likely to move into the
local area beginning late Saturday. As we go into Sunday...
overrunning atop a more in-situ type sfc wedge will likely lead to
a chilly rain going through late Monday. Though model
discrepancies arise by Tuesday...sfc low development off east TX
coast as closed mid-level low transitions to open wave could bring
another round of precip to the area thru the remainder of the
long-term...should GFS data verify.

Kovacik

HYDROLOGY...
One product of this weather system that most of us will happily
welcome is the additional beneficial rainfall. The highest
additional rainfall totals are expected across very parched far
north Georgia, where additional rainfall amounts over 1.5 inches
will be possible. Forecast rainfall amounts gradually taper farther
to the south and east as the overall convective intensity will
diminish by the time it reaches these areas.

RW

AVIATION...
06Z Update...
Showers and a few severe thunderstorms training across nw GA and
should stay north of the taf sites during the night. Showers and
thunderstorms drifting south across the forecast area beginning
after sunrise today and continuing into the afternoon. Cold front
approaching KATL around 18z. A few storms possibly severe today.
Front should be just south of the taf sites by around 00z Thursday.
Winds remainder of tonight varying 170-200 8 to 10kt with a few
gusts...becoming more southwest and gusty after 14z. Areas of ifr
through 14z then some improvement into mvfr and occasional vfr.

41

//ATL Confidence...06Z Update...
Medium confidence all elements.

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          63  71  42  60 /  50  80  30   0
Atlanta         64  69  42  57 /  50  80  20   0
Blairsville     60  64  34  53 /  80 100  20   0
Cartersville    63  66  38  56 /  70 100  10   0
Columbus        67  73  43  61 /  50  80  20   0
Gainesville     62  68  42  57 /  70  80  20   0
Macon           64  76  43  64 /  30  80  60   0
Rome            62  66  36  57 /  90 100  10   0
Peachtree City  63  69  39  58 /  50  80  20   0
Vidalia         64  80  54  66 /  20  50  60   5

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Tornado Watch until 4 AM EST Wednesday FOR THE FOLLOWING ZONES:
Catoosa...Chattooga...Dade...Walker...Whitfield.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1013 PM EST TUE NOV 29 2016

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-301200-
BALDWIN-BANKS-BARROW-BARTOW-BIBB-BLECKLEY-BUTTS-CARROLL-CATOOSA-
CHATTAHOOCHEE-CHATTOOGA-CHEROKEE-CLARKE-CLAYTON-COBB-COWETA-
CRAWFORD-CRISP-DADE-DAWSON-DEKALB-DODGE-DOOLY-DOUGLAS-EMANUEL-
FANNIN-FAYETTE-FLOYD-FORSYTH-GILMER-GLASCOCK-GORDON-GREENE-
GWINNETT-HALL-HANCOCK-HARALSON-HARRIS-HEARD-HENRY-HOUSTON-JACKSON-
JASPER-JEFFERSON-JOHNSON-JONES-LAMAR-LAURENS-LUMPKIN-MACON-
MADISON-MARION-MERIWETHER-MONROE-MONTGOMERY-MORGAN-MURRAY-
MUSCOGEE-NEWTON-NORTH FULTON-OCONEE-OGLETHORPE-PAULDING-PEACH-
PICKENS-PIKE-POLK-PULASKI-PUTNAM-ROCKDALE-SCHLEY-SOUTH FULTON-
SPALDING-STEWART-SUMTER-TALBOT-TALIAFERRO-TAYLOR-TELFAIR-TOOMBS-
TOWNS-TREUTLEN-TROUP-TWIGGS-UNION-UPSON-WALKER-WALTON-WARREN-
WASHINGTON-WEBSTER-WHEELER-WHITE-WHITFIELD-WILCOX-WILKES-
WILKINSON-
1013 PM EST TUE NOV 29 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH AND CENTRAL GEORGIA.

.DAY ONE...TONIGHT...

A LARGE COMPLEX OF THUNDERSTORMS IS EXPECTED TO IMPACT PORTIONS OF
NORTHWEST GEORGIA OVERNIGHT. A FEW OF THE STORMS COULD BE
SEVERE...WITH THE POTENTIAL TO PRODUCE DAMAGING WIND GUSTS. IN
ADDITION...A FEW LIGHTNING STRIKES WILL BE POSSIBLE ALONG WITH
SOME LOCALLY HEAVY RAINFALL. AN ISOLATED TORNADO IS NOT OUT OF THE
QUESTION. THE BEST POTENTIAL FOR ANY SEVERE WEATHER OVERNIGHT WILL
BE ALONG AND WEST OF A LINE FROM CHATTOOGAVILLE TO FORT
OGLETHORPE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY...

ADDITIONAL WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS ARE
EXPECTED ON WEDNESDAY AS A COLD FRONT MOVES THROUGH THE STATE. A
FEW OF THE STORMS COULD BECOME STRONG PRODUCING GUSTY
WINDS...LOCALLY HEAVY RAINFALL AND AN OCCASIONAL LIGHTNING
STRIKE. ISOLATED SEVERE THUNDERSTORMS WILL ALSO BE POSSIBLE. BRIEF
DAMAGING WIND GUSTS WOULD BE THE MAIN THREAT.

NO HAZARDOUS WEATHER IS EXPECTED FOR THURSDAY THROUGH SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1157 PM EST TUE NOV 29 2016

GAZ001-300530-
DADE GA-
1157 PM EST TUE NOV 29 2016

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN DADE COUNTY UNTIL 1230
AM EST...

AT 1157 PM EST...A STRONG THUNDERSTORM WAS NEAR BRIDGEPORT...MOVING
NORTHEAST AT 45 MPH.

  HAZARD...40 TO 50 MPH WIND AND HEAVY RAIN. POSSIBLE ROTATION AS
           WELL. TORNADO WARNING MAY BE NEEDED.

  IMPACT...PEOPLE OUTDOORS SHOULD SEEK SHELTER IMMEDIATELY. EXPECT
           MINOR DAMAGE TO TREE LIMBS AND BLOWING AROUND OF
           LIGHT...UNSECURED OBJECTS. MOTORISTS SHOULD SLOW DOWN AND
           BE PREPARED FOR POSSIBLE LOSS OF CONTROL DUE TO
           HYDROPLANING. ALSO...THE HEAVY RAIN MAY CAUSE TEMPORARY
           STREET FLOODING OR ROAD PONDING IN SLOW DRAINAGE AREAS.
           WHEN WATER COVERS THE ROAD...REMEMBER TO TURN AROUND
           DON'T DROWN.

SOME LOCATIONS IN THE PATH OF THIS STORM INCLUDE
TRENTON...NEW ENGLAND...COLE CITY...MORGANVILLE...WILDWOOD...HOOKER
AND STEPHENSVILLE.

LAT...LON 3498 8536 3492 8540 3485 8558 3495 8560
      3498 8560
TIME...MOT...LOC 0457Z 240DEG 49KT 3490 8575

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
205 AM EST WED NOV 30 2016

GAZ004-005-300730-
MURRAY GA-WHITFIELD GA-
205 AM EST WED NOV 30 2016

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN MURRAY AND NORTHEASTERN
WHITFIELD COUNTIES UNTIL 230 AM EST...

AT 204 AM EST...A STRONG THUNDERSTORM WAS OVER COHUTTA...OR 9 MILES
NORTHEAST OF RINGGOLD...MOVING NORTHEAST AT 45 MPH.

  HAZARD...40 TO 50 MPH WIND AND HEAVY RAIN.

  IMPACT...PEOPLE OUTDOORS SHOULD SEEK SHELTER IMMEDIATELY. EXPECT
           MINOR DAMAGE TO TREE LIMBS AND BLOWING AROUND OF
           LIGHT...UNSECURED OBJECTS. MOTORISTS SHOULD SLOW DOWN AND
           BE PREPARED FOR POSSIBLE LOSS OF CONTROL DUE TO
           HYDROPLANING. ALSO...THE HEAVY RAIN MAY CAUSE TEMPORARY
           STREET FLOODING OR ROAD PONDING IN SLOW DRAINAGE AREAS.
           WHEN WATER COVERS THE ROAD...REMEMBER TO TURN AROUND
           DON'T DROWN.

SOME LOCATIONS IN THE PATH OF THIS STORM INCLUDE
VARNELL...COHUTTA...TENNGA AND RED CLAY S.P..

A TORNADO WATCH REMAINS IN EFFECT. CONTINUE TO MONITOR NOAA WEATHER
RADIO...WEATHER.GOV OR OTHER MEDIA OUTLETS FOR FURTHER STATEMENTS OR
POSSIBLE WARNINGS ON THESE STORMS.

LAT...LON 3499 8471 3498 8471 3492 8500 3493 8501
      3494 8500 3497 8500 3497 8498 3499 8498
TIME...MOT...LOC 0704Z 245DEG 39KT 3497 8497