U.S. Severe Weather Forecast (Конвекција-преглед)

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Storm Prediction Center ac 240522 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1222 am CDT Mon Sep 24 2018 


Valid 241200z - 251200z 


..there is a marginal risk of severe thunderstorms across parts of 
the Tennessee and Ohio valleys... 


... 
Isolated severe storms are possible during the day across parts of 
the Tennessee and Ohio valleys, with a few strong storms across the 
northern High Plains and upper Mississippi Valley. 


... 
An upper trough will move from the northern and central rockies into 
the plains, with a lead wave across the Dakotas and Minnesota, and a 
secondary wave developing over Wyoming during the day. A weak surface 
trough will stretch from central Minnesota into the Central High plains by 
late afternoon, with a relatively late attempt at low-level moisture 
return ahead of the wind shift. To the east, a weaker upper 
disturbance will move from the lower MS valley toward the Ohio Valley 
during the day, with some strengthening in the low-level wind fields 
as a warm front lifts north to the Ohio River. 


..TN/Ohio valleys... 
Rain and thunderstorms are likely to be ongoing early Monday across 
western Tennessee and Kentucky in association with an area of warm advection. The 
effective warm front will lift north toward the Ohio River during the 
day, with southerly 850 mb winds on the order of 30 kt. While winds 
aloft will not be strong, upper 60s to near 70 f dewpoints and 
effective srh of 100-200 m2/s2 may support a few embedded strong 
storms capable of marginal wind gusts, possibly enhanced by 
rotation. 


..southeast Wyoming into western NE and northeast Colorado... 
Surface winds will gradually veer from northwest to easterly during 
the day, with some weak westward advection of moisture possible. 
This, along with heating, will occur beneath cold temperatures aloft 
related to the upper trough, resulting in a few hundred j/kg of 
MUCAPE. Strong speed shear with height will be present, and by late 
afternoon, isolated cells are expected to form over Wyoming. Some of 
these cells could contain hail, but the threat of severe weather 
appears low at this time due to limited instability. 


..upper MS valley... 
Substantial cooling aloft will occur through the period as a cold 
front moves from the eastern Dakotas into Minnesota during the day. The air 
mass will only be weakly unstable, and capped ahead of the front. 
However, lift along and behind the front should result in scattered 
storms by afternoon. Small hail is possible, but the severe threat 
appears low. 


.Jewell/squitieri.. 09/24/2018 


$$ 

Mesoscale Discussion


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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 212304 
nyz000-paz000-wvz000-ohz000-220100- 


Mesoscale discussion 1494 
National Weather Service Storm Prediction Center Norman OK 
0604 PM CDT Fri Sep 21 2018 


Areas affected...eastern Ohio...western and central 
Pennsylvania...western and central New York 


Concerning...Severe Thunderstorm Watch 386...387... 


Valid 212304z - 220100z 


The severe weather threat for Severe Thunderstorm Watch 386, 387 
continues. 


Summary...mainly a damaging wind threat continues with storms along 
a cold front. Gradual weakening is expected as the boundary layer 
cools, and storms begin moving into a less heated/more stable 
airmass. A wider warm sector in western/central Pennsylvania may 
allow for storms with isolated damaging wind gusts to continue east 
of Severe Thunderstorm Watch 0386, and a Severe Thunderstorm Watch 
issuance downstream may be necessary. 


Discussion...earlier semi-discrete storms have recently congealed 
into a squall line, from roc, down to lck, with the corridor of 
strongest storms (with a history damaging wind gusts) located from 
just west of bfd to phd. These storms have organized in a kinematic 
environment characterized by 50-60 knots of bulk effective shear, 
with up to 250-300 m2/s2 effective srh noted in northwest PA into 
western New York. Despite the favorable shear environment, the airmass 
downstream of the squall line (central PA to central ny) is more 
stable, with surface temperatures mainly in the low 70s, owing to a 
stratus deck which has limited insolation. 


As such, the squall line is expected to traverse a more buoyant 
airmass for the next few hours, characterized by surface 
temperatures in the lower 80s and MLCAPE up to 1000 j/kg. During 
this time, storms may continue to produce damaging wind gusts and 
perhaps exhibit transient low-level rotation (given the strong 
low-level speed shear in place). Thereafter, a weakening trend is 
expected given the cooler temperatures to the east and the 
cooling/decoupling of the boundary layer overall. 


The buoyant warm sector between the ongoing squall line and a more 
stable airmass to the east is narrower in New York as opposed to 
western and central Pennsylvania. Storms may continue past the 
eastern bounds of Severe Thunderstorm Watch 0386 with at least an 
isolated damaging wind threat and an additional Severe Thunderstorm 
Watch issuance may become necessary in a few more hours. 


.Squitieri/grams.. 09/21/2018 


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


Attention...WFO...btv...aly...bgm...buf...ctp...pbz...cle... 


Latitude...Lon 40098211 40668190 41428057 42487904 43337784 43817645 
44247538 43967495 43417492 42097615 41227696 40377816 
39947927 39978099 40098211