U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 190602 
Storm Prediction Center ac 190600 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0100 am CDT Mon Mar 19 2018 

Valid 191200z - 201200z 

..there is an enhanced risk of severe thunderstorms parts of 
Tennessee...northeast MS...northern Alabama...and northwest Georgia... 

..there is a slight risk of severe thunderstorms surrounding the 
enhanced risk from the Tennessee Valley to the southeast states... 

..there is a marginal risk of severe thunderstorms surrounding the 
slight risk from the middle-south and southern Kentucky to northern Florida... 

Tornadoes (some strong), very large hail, and damaging winds are 
expected across parts of middle Tennessee into northeast 
Mississippi, northern and central Alabama to western Georgia. 
Severe storms will be possible into southern Georgia and northern 

A compact closed cyclone and attendant shortwave trough will weaken 
this forecast period as this system remains progressive, reaching 
the lower Ohio and Tennessee valleys by 20/00z and into the upper 
Ohio Valley by 12z Tuesday. Meanwhile, a pair of shortwave troughs 
and accompanying midlevel jets is expected to phase across the 
Southern Plains this afternoon into the evening, with further 
amplification of this trough into the middle Mississippi Valley to 
the northwest Gulf Coast region. A surface low, attendant to the 
lead trough, will track from northeast OK to western middle 
Tennessee by late this afternoon (by 21z), with a cold front 
extending southwest through northeast MS to southern la. At 12z 
today, a warm front should extend through central Arkansas and MS into 
southern al/GA. An increase in southwesterly winds across the lower 
Mississippi and Tennessee valleys to the southeast states will 
result in a moistening warm sector as the warm front advances to the 
northeast. This boundary should extend from the surface low in 
middle Tennessee south-southeast through northern and central Alabama to 
south-central Georgia by mid-late afternoon, before advancing farther 
northeast tonight. 

..TN/northeast MS/al/northern and western Georgia... 
Elevated showers and thunderstorms are expected to be ongoing at the 
start of d1 within a zone of warm advection and strong forcing for 
ascent attendant to a strong southwesterly low-level jet and the 
lead compact shortwave trough moving through southern MO and Arkansas. As 
the deep-layer ascent spreads east into the lower Tennessee Valley 
this morning to early afternoon, the early day convection will shift 
into the mid-south, likely delineating the northwest extent of 
stronger destabilization. Surface dew points in the 60s and 
steepening lapse rates will result in moderate instability across 
the warm sector. 

New storm development is expected by mid afternoon in western middle 
Tennessee into northeast MS as the surface low and cold front reach these 
areas. This will coincide with strong forcing for ascent spreading 
across the western extent of moderate instability. Strengthening 
deep-layer winds (westerly at 50-70 kt in the 500-700-mb layer and 
southwesterly at 40-50 kt at 850 mb shifting across MS into al) this 
afternoon will prove favorable for supercells. Given effective srh 
will exceed 300-400 m2/s2, a strong tornado or two will be possible 
from parts of middle Tennessee into northeast MS, northern Alabama and northwest 
Georgia late this afternoon into the early evening, as the cold front 
advances east. The favor thermodynamics and strong bulk shear will 
support very large hail, as well. 

Farther south across central into southeast al, organized storms 
including supercells will prove favorable for all severe hazards as 
activity forms along the warm front this afternoon. 

..southern and eastern Georgia into northern Florida... 
Weak height falls across this region where the environment should 
become moderately unstable may prove favorable for thunderstorm 
development. Strengthening deep-layer westerlies across this region 
will result in favorable shear for organized storms producing all 
severe hazards into the early evening. 

.Peters/Gleason.. 03/19/2018 


Mesoscale Discussion

acus11 kwns 190714 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 190714 

Mesoscale discussion 0140 
National Weather Service Storm Prediction Center Norman OK 
0214 am CDT Mon Mar 19 2018 

Areas affected...north-Central/Northeast 
OK...south-central/southeast Kansas 

Concerning...severe potential...watch unlikely 

Valid 190714z - 190915z 

Probability of watch issuance...20 percent 

Summary...isolated hail possible for the next several hours across 
portions of north-Central/Northeast OK and south-central/southeast 

Discussion...strong forcing for ascent and continued warm-air 
advection across the frontal zone have contributed to a persistence 
of the elevated convection ongoing across north-central OK and 
south-central/southeast Kansas during the past several hours. In fact, 
regional radar imagery has shown an increase in coverage over the 
past hour, likely a result of continued forcing for ascent as the 
system shifts eastward into better moisture. 

Steep mid-level lapse rates still exist across much of the region 
and recent mesoanalysis estimated MUCAPE is around 1000 j/kg. Strong 
vertical shear is also in place, with VAD wind profiles from inx 
sampling over 60 kt of 0-6 km bulk shear and mesoanalysis estimating 
effective bulk shear around 40 to 50 kt. This type of environment 
supports hail, particularly in new, more cellular development. 
General expectation is for these storms to persist, gradually 
shifting eastward over the next few hours, with occasional instances 
of hail possible. 

.Mosier.. 03/19/2018 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 36389808 36979894 37759787 37929528 36959458 36629547