Severe weather Apr 5th

[RL3AO]

Small but very significant difference in the low-level wind direction across NE Alabama.

GFS is more southwesterly


NAM is more SSW'rly/southerly


That 30 degrees of "backing" (winds shifted counter-clockwise near surface) could be the main difference between severe storms and violent tornadoes.

[EF-5bigj]

Ahhh I see why they are saying Alabama and Georgia for the violent tornado risk.

[Alyono]

Tomorrow looks very impressive. Wouldn't be surprised to see a high risk eventually. I'm not sure about the April 27th comparisons but it looks like a serious severe weather threat tomorrow.

a scaled down version of 4/27 perhaps.

Although some of the high res models are indicating a major outbreak north of the deep south. More like a 4/3/74 type event (albeit, probably a scaled down version of that as well

[EF-5bigj]

I think it will be worse in some areas but not as bad in others.

[WeatherGuesser]

Weird update, mostly off FL, but expanded up through central TN into KY.

[EF-5bigj]

I've been moved into the slight risk with this update.

[Tireman4]

Received an email and text this morning, Faulkner University in Montgomery, Alabama is now closed today due to the threat of severe weather.

[cycloneye]

Mesoscale Discussion 0438
NWS Storm Prediction Center Norman OK
0615 AM CDT Wed Apr 05 2017

Areas affected...Alabama/western Georgia and into the Florida
Panhandle

Concerning...Severe Thunderstorm Watch 123...

Valid 051115Z - 051245Z

The severe weather threat for Severe Thunderstorm Watch 123
continues.

SUMMARY...Strong/locally severe storms continue across much of
Alabama and into western Georgia and vicinity at this time. Hail,
and perhaps locally damaging winds, remain the primary risk in the
short term, though wind and tornado risk will gradually increase
this morning (eventually requiring tornado watch issuance).

DISCUSSION...Latest radar loop shows scattered strong/locally severe
storms ongoing across WW 123 at this time, with the strongest storms
existing within a cluster east of Birmingham moving eastward toward
northwest Georgia. These storms are ongoing along the leading edge
of the low-level moisture return and likely remain slightly elevated
-- with large hail the primary risk along with the possibility of a
few stronger gusts.

Meanwhile, south and west of the stronger convection, isolated
showers/thunderstorms continue to increase, ahead of the advancing
upper system and associated cold front where an increasingly
moist/unstable airmass resides. As this trend continues, eventual
development of surface-based supercells is expected; given the
scheduled 13z expiration of WW 123, a new (likely to be) tornado
watch will be required.

..Goss.. 04/05/2017


ATTN...WFO...FFC...TAE...BMX...MOB...

[Hypercane_Kyle]

TOR Warning heading into Atlanta. Rotation appears pretty broad.

[Alyono]

SPC kept moderate. Does not sound like a high risk will be issued today. This from their latest discussion. Almost like they are tempering down only calling for a few long tornadoes

Long, straight hodographs will
characterize the wind profiles, with only modest low-level hodograph
curvature expected along a branch of the 40-50 kt southwesterly
low-level jet across GA. Still, the strong buoyancy and effective
SRH in excess of 200 m2/s2 will be sufficient for the risk of a few
strong tornadoes mainly across eastern AL, GA and west central SC
through the afternoon/evening.

[Hypercane_Kyle]

Tor:con up to an 8 for the general Atlanta area.

[Tireman4]

From Peachtree City NWS. ( They do forecasts for Atlanta)

000
FXUS62 KFFC 051139
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
739 AM EDT Wed Apr 5 2017



.PREV DISCUSSION... /Issued 348 AM EDT Wed Apr 5 2017/

SHORT TERM /Today through Thursday/...
Severe weather is expected across much of Georgia today. Be ready
to execute your severe weather plan in case a Severe Thunderstorm
Warning or Tornado Warning is issued for your location. Keep a
way to receive weather warnings nearby - such as a NOAA weather
radio or your smart phone. Please stay weather aware today, and
stay safe out there.

A very vigorous storm system will impact the CWFA today. There
could be several rounds of severe thunderstorms today, so don`t
let your guard down if you experience relatively quiet conditions
for a period of time. The first round of severe weather is
currently impacting portions of southern Alabama and the Florida
panhandle. This activity is associated with a northward moving
warm front. This warm front is expected to move into SW GA early
this morning and keep moving to near the I-20 corridor by
daybreak. South of the warm front, the airmass is very unstable
and lapse rates are very steep for this time of the morning.
Reports of up to half dollar sized hail have been reported across
portions of SE AL. With this first round of thunderstorms, expect
the primary modes of severe weather to be large hail (up to 2
inches possible) and damaging wind gusts in excess of 60 MPH. An
isolated tornado cannot be ruled out either, as the front will
provide an excellent source of low level shear.

The warm front may end up settling somewhere in the vicinity of
the northern `burbs of Atlanta by mid morning. This means that
most of the CWFA will be in the warm sector for the afternoon. The
atmosphere should have enough time to recuperate from the morning
storms, and become very unstable during the peak heating of the
afternoon - especially if the clouds begin to break. All the
ingredients for severe weather will be present: strong mid and
upper level forcing, strong surface instability, plenty of deep
level shear, a 40-50kt 850mb jet, etc. This will be the time that
discreet cells ahead of the front are expected to develop and
supercells will be likely. (Prime time for tornado development.)

The actual cold front isn`t expected to move through until later
in the evening and into the overnight hours. The actual front will
provide enough focus for additional storms well into the evening
and overnight. However, the atmosphere *may* be worked over enough
by the time the front moves through that the coverage and
*possibly* severity of the storms may decrease. However, not
entirely confident on this situation - so continue to stay weather
aware even after the sun sets.

There is plenty of much cooler air behind this system and
Thursday`s will be a (relatively) cold and windy day. A Wind
Advisory will likely be needed, but don`t want to over complicate
the headlines for today.

NListemaa

LONG TERM /Thursday Night through Tuesday/...
Extended period largely overshadowed by short term severe threat.
Following the aforementioned system, wrap around moisture will
linger over the northeast Georgia mountains through Friday morning,
with the potential for some mixed precip as temperatures drop into
the low to mid 30s. For now, have limited the p-type to rain or
snow, and will need to revisit this in subsequent forecast packages.
Not expecting any accumulations at this time. Will also need to
consider issuing a Freeze Warning for this area given the expected
low temperatures.

Below normal temperatures expected Friday will slowly warm through
the weekend, with highs in the 60s on Saturday and the mid to upper
70s on Sunday with sunny skies. High pressure will hold through the
weekend and into next week, with the next system approaching late
Tuesday - a tad slower than the previous model runs. GFS and ECMWF
differ in timing by 6-12 hours, with the better activity currently
timed for Wednesday. For now have limited pops to good chance.
Temperatures will generally stay in the mid 70s to near 80 through
next week.

31

HYDROLOGY...
Widespread QPF amounts of 1.5 to 2.25 inches still look to be
handled well across middle Georgia today. Flash Flood Guidance
suggests that the area can handle these rainfall amounts, even if
they were to fall in a one to three hour time frame. WPC does have
the area outlooked for a slight risk of flash flooding, and isolated
flash flooding cannot be ruled out, particularly as storms train
over the same area, or where localized rainfall amounts are higher.
Site specific headwater forecasts are largely keeping river gage
locations at or below action stage following the precipitation
today. Modeled precipitable water values remain near seasonal
maximums, and expect high rainfall rates from efficient storms. Have
opted to issue a Flash Flood Watch mainly along the Interstate 20
corridor for the heaviest QPF axis.

AVIATION... 06Z Update... Main changes to the TAF this cycle were
to tweak the timing for the early morning shra/tsra and change
the prob group to a tempo. Several rounds of shra/tsra expected
for the afternoon. Will likely have to tweak the prevailing tsra
wording at later updates.

//ATL Confidence...12Z Update...
Medium confidence all elements.

&&

.AVIATION...
12Z Update...
Made some slight timing tweaks to the TAFS for the first round of
thunderstorms this morning. Otherwise, no major changes through
the day. After the first round of storms, there could be a lull,
but do expect convective activity to develop again during the
early afternoon. This activity could linger into the early evening
hours. Winds are currently flirting with due south, but do
expected them to switch to the SW by mid morning.

//ATL Confidence...12Z Update...
Medium confidence all elements.



&&

.PRELIMINARY POINT TEMPS/POPS...
Athens 73 50 57 41 / 80 60 20 5
Atlanta 73 48 56 42 / 80 60 20 5
Blairsville 67 44 49 34 / 70 60 40 30
Cartersville 75 48 55 41 / 70 60 30 10
Columbus 78 51 63 45 / 80 60 10 0
Gainesville 71 47 53 40 / 80 60 30 10
Macon 78 51 62 43 / 80 70 10 0
Rome 77 48 56 41 / 70 60 30 5
Peachtree City 74 49 58 41 / 80 60 20 0
Vidalia 82 54 64 45 / 80 70 10 0

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through late tonight for the following zones:
Baldwin...Barrow...Bibb...Butts...Carroll...Clarke...Clayton...
Cobb...Coweta...Crawford...DeKalb...Douglas...Fayette...
Glascock...Greene...Gwinnett...Hancock...Haralson...Harris...
Heard...Henry...Jackson...Jasper...Jones...Lamar...Madison...
Meriwether...Monroe...Morgan...Muscogee...Newton...North
Fulton...Oconee...Oglethorpe...Paulding...Pike...Polk...Putnam...
Rockdale...South Fulton...Spalding...Talbot...Taliaferro...
Troup...Upson...Walton...Warren...Wilkes.

Severe Thunderstorm Watch until 9 AM EDT this morning for the
following zones: Bibb...Butts...Carroll...Chattahoochee...
Clayton...Cobb...Coweta...Crawford...Crisp...DeKalb...Dooly...
Douglas...Fayette...Haralson...Harris...Heard...Henry...
Houston...Lamar...Macon...Marion...Meriwether...Monroe...
Muscogee...North Fulton...Paulding...Peach...Pike...Pulaski...
Rockdale...Schley...South Fulton...Spalding...Stewart...Sumter...
Talbot...Taylor...Troup...Upson...Webster...Wilcox.

&&

$$

[Alyono]

BS flag on the high res models!

They have failed to initialize the morning convection properly. They are showing no storms when the radar is lit up like a Christmas tree

This has a significant bust potential now. The morning convection may have stabilized things far more than the models are indicating

[Ntxw]

BS flag on the high res models!

They have failed to initialize the morning convection properly. They are showing no storms when the radar is lit up like a Christmas tree

This has a significant bust potential now. The morning convection may have stabilized things far more than the models are indicating

A couple of radars are down this morning, there is a blind spot near montgomery and from the Tallahassee radars to add into the complicated mix.

[Alyono]

BS flag on the high res models!

They have failed to initialize the morning convection properly. They are showing no storms when the radar is lit up like a Christmas tree

This has a significant bust potential now. The morning convection may have stabilized things far more than the models are indicating

A couple of radars are down this morning, there is a blind spot near montgomery and from the Tallahassee radars to add into the complicated mix.

think that's why.

Cannot rely upon the high res models today since radar makes up such a large amount of the initialization. If they cannot get the more stabilized atmosphere due to the morning convection correct, they are toast this afternoon and evening

[Hypercane_Kyle]

SPC still considering a high-risk upgrade. Very hard call, especially considering the terrible initialization.

DISCUSSION...GPS PW data are exhibiting a low bias by at least 0.5
inch from parts of AL into GA, which has influenced initialization
of the latest numerical weather prediction guidance. Per
coordination with the Weather Prediction Center, it appears that
related initialization is causing substantial dry biases in model
guidance -- extended through the Day 1 forecast period. With an
inland influx of rich moisture feeding ongoing intense supercells in
southern AL (with dewpoints into the middle 70s), and the
around-16.6-g/kg mean mixing ratio per LIX 12Z sounding, and around
1.5-inch PW per Atlanta and Birmingham 12Z soundings, it is evident
that rich moisture and related strong buoyancy does indeed extend
inland. As such, observational data and previous model runs will
play a major role in the consideration for a High Risk upgrade, as
the dry bias has influenced the latest model guidance. While an
Outlook upgrade is possible, it is not certain.

[Bunkertor]

The Masters Golf tournament in GA has suspended the game ( practicing round )

[Bunkertor]

Btw: Do we see something like a "fake" dryline in the AL/GA setup ?

[cycloneye]

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1129 AM CDT Wed Apr 05 2017

Valid 051630Z - 061200Z

...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
CENTRAL AND SOUTHERN GEORGIA INTO CENTRAL SOUTH CAROLINA...

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
HIGH FROM PORTIONS OF SOUTH CAROLINA TO GEORGIA AND ALABAMA AND THEN
NORTHWARD INTO SOUTH-CENTRAL KENTUCKY...

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
MODERATE FROM PORTIONS OF THE OHIO VALLEY REGION TO THE SOUTHEAST
STATES AND MID-ATLANTIC...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED FROM PORTIONS OF THE LOWER GREAT LAKES REGION TO THE
SOUTHEAST STATES AND MID-ATLANTIC...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE EASTERN STATES...

...SUMMARY...
An outbreak of severe thunderstorms is expected from portions of the
Southeast States to the Ohio Valley region and eastward to the
Mid-Atlantic. Significant tornadoes will be possible, especially
from parts of central and southern Georgia into South Carolina, and
also from parts of eastern Alabama into south-central Kentucky. In
addition, very large hail, and damaging wind gusts are expected.

...Portions of the Southeast States to the Ohio Valley region and
the Mid-Atlantic...
Ongoing semi-discrete supercells and supercell clusters are
developing northeastward from parts of the central/eastern Gulf
Coast into southern GA. This activity resides well ahead of a
shortwave trough across the South-Central States and is evolving
within a broad, moistening open warm sector. With observational data
suggesting dewpoints in the lower 70s developing northward ahead of
this activity, supporting MLCAPE around 2000-3000 J/kg aided by
warm-sector insolation steepening low-level lapse rates beneath a
residual EML plume, and given the ongoing semi-discrete nature to
rotating updrafts developing as far south as the central Gulf Coast
vicinity, there is increasing confidence that long-track supercells
will be likely. Furthermore, with maturing midlevel mesocyclones
already evident, and low-level SRH around 200-300 m2/s2 aiding the
development of low-level mesocyclones amid the increasing low-level
theta-e, confidence has increased in higher coverage of tornado
potential -- including significant tornado potential -- across the
now-upgraded High Risk area. This activity will spread across the
High Risk area into the evening hours, as vertical wind profiles
further strengthen with the approaching midlevel trough and 700-mb
flow increasing over 50 kt. Observational trends and previous model
guidance are the primary supporters of this High Risk upgrade, as
opposed to the most recent model guidance which suggests a dry bias
in thermodynamic profiles -- Reference Mesoscale Discussion 440.
Outflow from ongoing convection from north GA to western SC serves
as a northern bound to the greatest severe potential.

Furthermore, confidence has increased that substantial severe risk
including tornado potential will develop through parts of the
Mid-Atlantic region into the overnight hours amid strong low-level
and deep shear, and a moistening boundary layer. As a result, severe
probabilities have been increased across parts of the Mid-Atlantic.
Also, severe storms are expected to spread across parts of the Gulf
Coast vicinity into the evening/overnight hours -- affecting parts
of north/central FL with tornado potential.

Farther to the west, a somewhat separate area of severe storm
development will be likely from parts of the Ohio Valley region to
the Tennessee Valley and vicinity in association with the primary
midlevel vorticity maximum and related low-level baroclinic zone
this afternoon. Strong low-level SRH in the destabilizing warm
sector -- enhanced near the surface low tracking from parts of IL
into OH -- will support organized, rotating updrafts. All severe
hazards -- including significant hail and tornadoes -- will be
possible from this afternoon into the evening.

..Cohen.. 04/05/2017

[psyclone]

High risk for portions of central GA across the Savannah river to near Columbia SC. the other 2 high risks this year were underperformers but based on what's already going on this one may be legit. Looks bad and protracted, especially with the clearing back to the west.