U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 190427 
Storm Prediction Center ac 190426 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1126 PM CDT Wed Oct 18 2017 

Valid 191200z - 201200z 

..there is a marginal risk of severe thunderstorms across southern 
New Mexico and far West Texas... 

A few thunderstorms may produce marginally severe hail or wind 
across southern New Mexico and far West Texas, including the El Paso 
vicinity, mainly during the afternoon and early evening. 

A large area of high pressure will remain over the eastern half of 
the country, with an upper ridge from the Great Lakes to the Gulf of 
Mexico. To the west, a potent, amplifying shortwave trough will 
approach the Pacific northwest by Thursday afternoon, and spread 
into the Great Basin by Friday morning. While this will bring 
precipitation and windy conditions to parts of the west, instability 
will be minimal. 

Farther east, daytime thunderstorms are expected across much of nm, 
far eastern Arizona and far west TX, aided by cool air aloft associated 
with a leading/weak shortwave trough. Weak instability and lack of 
appreciable flow aloft and shear will mitigate storm strength, but 
isolated cells could produce marginally severe hail or wind. 

..far West Texas into southern nm... 
A relative maximum in instability is expected during the late 
afternoon at peak heating time and with dewpoints into the lower 
50s. This moisture should be sufficient for a few strong storms 
given steep lapse rates aloft. While upper flow will be weak, 
westerly winds around 20 kt atop low-level southerlies will result 
in small but favorable hodographs supportive of a few longer-lived 
cells/clusters, possibly affecting the El Paso vicinity. A few cores 
could produce marginally severe hail, with strong wind gusts with 
any storm clusters. The threat should be mainly diurnal in nature, 
with little to support strong storms after sunset. 

.Jewell/Elliott.. 10/19/2017 


Mesoscale Discussion

acus11 kwns 151903 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 151903 

Mesoscale discussion 1719 
National Weather Service Storm Prediction Center Norman OK 
0203 PM CDT sun Oct 15 2017 

Areas affected...from eastern Ohio across Pennsylvania and into 
western/central New York 

Concerning...severe potential...watch possible 

Valid 151903z - 152000z 

Probability of watch issuance...40 percent 

Summary...a narrow line of low-topped showers and thunderstorms will 
develop eastward with a threat of strong to severe wind gusts this 

Discussion...multiple segments of low-topped showers and storms are 
developing from southwest Ontario into eastern Ohio along an 
intensifying cold front. The strongest area of lift currently exists 
over Canada, and this is where sporadic lightning activity is 

Surface observations show gradually warming temperatures, with 
dewpoints in the lower 60s. The deeper moist plume exists mainly 
just ahead of the front, with drier air/lower precipitable water values from the 
Appalachians into New England. Temperatures aloft are not very cold 
except for well behind the front into Michigan, leading to only weak 
cape values. In addition, much of the instability exists mainly in 
the parts of the atmosphere. 

With mean winds in excess of 40 kt in the lowest few km, these 
showers and storms along the cold front will likely Transfer 
momentum to the surface with 40-50 mph wind gusts possible, and 
perhaps an isolated severe gust. The most likely area for severe 
winds would appear to be over New York where mean wind speeds are 
strongest, and in closest proximity to the shortwave trough. In 
addition, veering winds with height and sufficient srh may result in 
embedded areas of rotation in qlcs fashion. This, however, will be 
dependent on sufficient instability being present. Ample heating 
over New York lends some confidence of this possibility. 

.Jewell/Hart.. 10/15/2017 

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


Latitude...Lon 45137382 44617383 43857421 42877523 41847651 40797811 
40338016 40308120 40628143 41138132 41808085 42798018 
43597918 43997754 44407616 44927537 45137464 45137382