U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 201957 
Storm Prediction Center ac 201956 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0156 PM CST Tue Nov 20 2018 

Valid 202000z - 211200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are possible today across the Florida 
Peninsula, and late tonight in the vicinity of southern New Mexico 
and far West Texas. 

The only change to the previous outlook was to adjust the Florida 
thunderstorm area based on the current position of the front. 
Otherwise, the previous outlook reasoning remains valid. 

.Bunting.. 11/20/2018 

Previous discussion... /issued 1015 am CST Tue Nov 20 2018/ 

..Florida Peninsula... 
A low-amplitude shortwave trough over the northeastern Gulf of 
Mexico will continue eastward across North Florida today. A relatively 
moist/modestly unstable air mass exists along and south of a 
slow-moving front. A couple of strong/more organized storms may 
occur today, such as recently (~1545z) along the Florida East Coast, 
especially near the front in the presence of relatively strong 
deep-layer shear. However, it seems likely that weak winds in the 
lower troposphere, along with weak mid-level lapse rates and 
weakening low-level convergence, will keep severe-weather potential 
at a minimum. The thunderstorm threat across Florida is generally 
expected to diminish by mid/late evening. 

..far West Texas/southeast New Mexico tonight... 
A southern-stream shortwave trough over northern baja will continue 
to move eastward toward far West Texas by early Wednesday. Some 
low/mid-level moistening is expected in the zone of ascent preceding 
this trough as it reaches far West Texas/southern nm tonight. Weak 
buoyancy rooted near or just above 700 mb will be possible 
overnight, when a few lightning flashes may occur with the weak 
elevated convection. 


Mesoscale Discussion

acus11 kwns 160857 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 160856 

Mesoscale discussion 1652 
National Weather Service Storm Prediction Center Norman OK 
0256 am CST Fri Nov 16 2018 

Areas affected...portions of the mid-Atlantic and New England 

Concerning...heavy snow 

Valid 160856z - 161500z 

Summary...one area of heavy snow with rates in excess of 1 inch per 
hour will develop northeastward across northern New England this 
morning. Another area of moderate to locally heavy snow, with rates 
up to 1 inch per hour, will move across eastern PA into southern New 

Discussion...within large-scale upper troughing encompassing much of 
the central and eastern conus, a compact shortwave trough will 
continue moving quickly northeastward over the mid-Atlantic and New 
England regions this morning. A deepening surface low associated 
with this shortwave trough will likewise develop northeastward along 
the coast of southern New England. A band of moderate to heavy snow 
is occurring over western/northern NY, attendant to strong forcing 
for ascent and a mid-level deformation zone immediately ahead of the 
shortwave trough. Snowfall rates in excess of 1 inch per hour will 
likely continue for at least the next several hours as this band 
develops into northern New England. 

Across parts of central/eastern PA, northern NJ, southern NY, and 
southern New England, a mix of snow, sleet, and freezing rain have 
all been observed recently as strong low-level warm air advection 
has allowed for at least some melting of hydrometeors. However, a 
quick transition back to mainly snow is likely from west to east 
this morning as cold mid/upper-level temperatures embedded within 
the core of the shortwave trough overspread these areas. Forecast 
soundings from the NAM and rap both suggest that there will be 
sufficient wrap-around moisture remaining within the dendritic 
growth zone and steepening mid-level lapse rates to support moderate 
to locally heavy snow for a couple of hours. Snowfall rates up to 1 
inch per hour may occur. This scenario is well supported by recent 
high-resolution guidance, including most href members. A rapid 
decrease in snowfall intensity/coverage will likely be noted from 
west to east through the morning, as strong subsidence and mid-level 
drying behind the shortwave trough passage suppress precipitation 

.Gleason.. 11/16/2018 

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


Latitude...Lon 43667018 42917138 42457230 41937334 40907478 40407593 
40217652 40257704 41037762 41687752 43387669 44457594 
45047489 45087164 45387140 45447091 45837051 46087035 
46257028 46417018 46566969 46536828 46286771 45706771 
45216802 44626873 43996958 43667018