U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 231607 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1107 am CDT Tue Oct 23 2018 


Valid 231630z - 241200z 


..there is a marginal risk of severe thunderstorms across parts of 
the southwest... 


... 
A few storms could produce marginally severe hail and strong wind 
gusts across southeastern Arizona and vicinity this 
afternoon/evening. 


Earlier thoughts regarding severe probabilities across the Continental U.S. 
Remain. No appreciable changes are warranted to 13z outlook. 


... 


Latest water-vapor imagery depicts a well-defined upper vort over 
the northern Baja Peninsula moving east in line with earlier model 
guidance. This feature is forecast to shift across northern Mexico, 
just south of the international border. While large-scale forcing 
for ascent is expected to remain somewhat weak across southern AZ, 
boundary-layer heating will contribute to meaningful buoyancy as 
low-level lapse rates steepen beneath the upper trough. Ongoing 
convection that currently extends from southwest of dug into 
southwest nm is expected to shift east as the upper trough moves 
inland. In the wake of this activity any convection that evolves 
later today will do so within a weaker sheared environment. While 
scattered robust convection may ultimately evolve, modulated by 
surface heating, gusty winds and marginally severe hail are the 
primary risks given the weakening shear. 


... 


Strong boundary-layer heating across portions of central New York are 
contributing to steep low-level lapse rates north of strong 
mid-level jet that extends across northern PA. Forecast soundings 
suggest convective temperatures will be breached early in the day 
ahead of the short-wave trough that will eject into the Hudson 
Valley by 24/00z. While seasonally low precipitable water values are noted across 
the lower Hudson Valley into southern New England, steep lapse rates 
will contribute to convection attaining heights necessary for 
lightning discharge. At this time, given the forecast low-level 
shear, it appears updrafts should be too limited for any meaningful 
threat of severe. 


.Darrow.. 10/23/2018 


$$ 

Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 231805 
nmz000-azz000-232000- 


Mesoscale discussion 1592 
National Weather Service Storm Prediction Center Norman OK 
0105 PM CDT Tue Oct 23 2018 


Areas affected...portions of center into Southeast Arizona and extreme 
southwest nm 


Concerning...severe potential...watch unlikely 


Valid 231805z - 232000z 


Probability of watch issuance...5 percent 


Summary...a few strong storms may produce hail and gusty winds 
across parts of central into Southeast Arizona and perhaps extreme 
southwest nm. Overall threat will remain limited and a watch is not 
expected. 


Discussion...isolated convection will continue to become 
increasingly surface based this afternoon as a modestly moist 
airmass continues to destabilize. Cloud cover across parts of the 
area has limited instability with north and eastward extent. 
However, rap forecast soundings still indicate steep midlevel lapse 
rates with adequate deep layer shear profiles to support some threat 
for hail. Where clearing has been more prevalent, greater 
instability may help to overcome rather poor 0-3km shear profile. As 
such, stronger cells may produce hail and gusty winds. Overall 
threat will remain marginal as deep layer shear lessens with time 
across the region, leading to largely disorganized convection and/or 
brief stronger updrafts. 


.Leitman/Darrow.. 10/23/2018 


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


Attention...WFO...epz...twc...fgz...psr... 


Latitude...Lon 31301103 31531173 33401209 34071242 34471234 34741187 
34801121 34631049 34271006 32960919 32420870 31910828 
31320812 31320848 31300888 31320929 31301103