U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 231943 
Storm Prediction Center ac 231942 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0242 PM CDT Tue Jul 23 2019 

Valid 232000z - 241200z 

..there is a slight risk of severe thunderstorms across far 
southeast Virginia and the eastern Carolinas area... 

Scattered wind damage from strong gusts are most likely this 
afternoon into early evening across the eastern Carolinas. 

Little change to the ongoing outlook appears necessary at this time, 
as forecast reasoning and outlook areas laid out in the prior 
outlook remain valid. The primary adjustment has been to reshape 
the marginal and slight risk areas in the Carolinas, to reflect 
ongoing/eastward progression of convection. Otherwise, only minimal 
line adjustments have been implemented in this update. 

.Goss.. 07/23/2019 

Previous discussion... /issued 1130 am CDT Tue Jul 23 2019/ 

..Carolinas/far southeast Virginia to eastern Georgia... 
An upper trough will continue to amplify/dig southeastward with 
related mid-level cooling and a strengthening of southwesterly winds 
aloft atop a southwest/northeast-oriented front, which will continue 
to advance east-southeastward today. 

Near/ahead of the front, diabatic warming of a moist boundary layer 
with low 70s f dewpoints will result in moderate buoyancy (1500-2500 
j/kg mlcape) this afternoon. As already occurring, widespread 
thunderstorm development is expected near the front and within 
pre-frontal confluence bands. The region will be on the periphery of 
moderate mid-level southwesterlies with the southern extent of 30-35 
kt 700-mb winds remaining confined to North Carolina/southeast 
Virginia. This portion of the risk area should have the greatest 
potential for a few transient supercells, aside from organized 
linear clustering and short-duration bowing segments. While 
mid-level lapse rates will be weak, steepening low-level lapse rates 
should promote a risk for strong downdrafts and associated wind 
damage potential. 

..northern rockies... 
A minor/lead mid-level vorticity maximum near the California/Nevada 
border will be kicked north-northeastward into Idaho by evening, 
downstream of a shortwave trough that will reach the 
Washington/British Columbia border late tonight. Both of these 
features will promote episodic isolated to scattered thunderstorm 
activity. Warm/deeply mixed boundary-layer profiles will be common 
ahead of the lead impulse, promoting a risk for isolated severe wind 
gusts. In the Lee of the northern rockies across central Montana, 
greater buoyancy will exist owing to the presence of mid 50s f 
surface dew points. This might also support a risk for marginally 
severe hail, but proximity to the mid-level ridge axis may be a 
limiting factor to greater severe coverage. 

Stronger mid/upper-level shear will accompany the primary shortwave 
trough. However, thunderstorm activity with this wave should occur 
overnight amid weak elevated buoyancy. A residual dry sub-cloud 
layer could still Foster a risk of locally strong to severe gusts 
from eastern Washington to northwest Montana. 

..lower Colorado River valley... 
In the wake of an mesoscale convective system yesterday, a remnant mesoscale convective vortex continues to drift 
westward along the lower Colorado River valley at late morning. A 
belt of enhanced southeasterly mid-level winds may help to loosely 
organize late afternoon thunderstorms that can develop off the 
higher terrain in northwest Arizona. While buoyancy will be meager, 
deeply mixed thermodynamic profiles will support a risk for isolated 
severe wind gusts until just after sunset. 


Mesoscale Discussion

acus11 kwns 232000 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 231959 

Mesoscale discussion 1581 
National Weather Service Storm Prediction Center Norman OK 
0259 PM CDT Tue Jul 23 2019 

Areas affected...parts of northeastern South Carolina and eastern 
North Carolina 

Concerning...Severe Thunderstorm Watch 540... 

Valid 231959z - 232200z 

The severe weather threat for Severe Thunderstorm Watch 540 

Summary...Severe Thunderstorm Watch 540 continues. A further 
increase in thunderstorm activity is still possible through 6-7 PM, 
into and across the coastal plain, accompanied by a risk for 
potentially damaging wind gusts. 

Discussion...the surface cold front has begun to advance more 
rapidly southward through the Piedmont of North Carolina, and will 
continue to gradually overtake the axis of strongest heating within 
pre-frontal surface troughing across the Piedmont into coastal 
plain, through 6-7 PM EDT. As it does, there still appears a window 
of opportunity for further upscale convective growth, with 
consolidating and strengthening cold pools contributing to an 
acceleration into coastal areas, accompanied by a risk for 
potentially damaging winds along the gust front. 

.Kerr.. 07/23/2019 

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


Latitude...Lon 34248071 36177802 36317567 35377625 33897888 33647980