U.S. Severe Weather Forecast (Sääkatsaus)

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Day Three

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Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1028 am CST Wed Mar 01 2017 


Valid 011630z - 021200z 


..there is an enhanced risk of severe thunderstorms from portions 
of northeast MS...northern Alabama...and southern Tennessee northeastward to the 
mid-Atlantic... 


..there is a slight risk of severe thunderstorms surrounding the 
enhanced from parts of the lower MS valley to southern New 
England... 


..there is a marginal risk of severe thunderstorms surrounding the 
slight across portions of the eastern states... 


... 
Severe thunderstorms with damaging winds are expected from portions 
of the southeast to the mid Atlantic region and parts of southern 
New England. Damaging winds will be likely, and the risk for 
tornadoes will exist particularly from parts of northeast 
Mississippi to portions of north Georgia and vicinity. 


..portions of the southeast to the mid-Atlantic region and southern 
New England... 


An extensive belt of strong mid/high-level flow across the southern 
and eastern states will maintain strong deep shear over a moist and 
diurnally destabilizing warm sector across the area. A squall line 
from middle Tennessee toward the central Appalachians will likely spread 
across the adjacent Piedmont during the next several hours. 
Re-intensification of this activity is expected, owing to the 
presence of adequate moisture return (upper 50s to lower 60s 
dewpoints) amidst surface heating and relatively steep midlevel 
lapse rates. Swaths of damaging wind gusts will be likely as this 
activity spreads toward the coastal plain through the evening. A 
couple of tornadoes will be possible. Severe-wind probabilities have 
been increased eastward across the Piedmont area. 


More separated updrafts/discrete convection are evolving across 
parts of the lower MS valley, at the southern end of a zone of 
stronger deep ascent. As this activity spreads eastward toward parts 
of the southern Appalachians and vicinity, it will intercept a 
relatively more moist boundary layer supporting stronger instability 
further aided by steep midlevel lapse rates (around 8.5 c/km in the 
700-500-mb layer per the 12z Jackson sounding). With 250-350 m2/s2 
of effective srh associated with modestly curved though long 
hodographs, tornado probabilities have been increased in this area. 


With northward extent across the east (i.E., Toward southern New 
England and vicinity), weaker instability will exist owing to more 
widespread cloud coverage amidst an antecedent cooler/drier boundary 
layer. However, strong vertical shear profiles will support a 
conditional severe risk. 


Modest destabilization may take place around the upper Ohio Valley 
and eastern Great Lakes area amidst recycled moisture ahead of the 
primary cold front, perhaps supporting a band of strongly forced 
convection spreading eastward from the late afternoon through the 
evening. Locally damaging wind gusts may accompany this activity. 


.Cohen.. 03/01/2017 


$$ 

Mesoscale Discussion


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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 011950 
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Mesoscale discussion 0246 
National Weather Service Storm Prediction Center Norman OK 
0150 PM CST Wed Mar 01 2017 


Areas affected...NJ...southeastern PA...the Delmarva Peninsula...and 
southeastern Virginia 


Concerning...Severe Thunderstorm Watch 58... 


Valid 011950z - 012045z 


The severe weather threat for Severe Thunderstorm Watch 58 
continues. 


Summary...a widespread damaging wind threat will continue across 
Severe Thunderstorm Watch 58 with a line of thunderstorms. 


Discussion...a line of shallow convection with occasional embedded 
lightning strikes has produced numerous measured severe wind gusts 
in addition to trees down/damage reports across VA, MD, and District of Columbia over 
the past several hours. This line is moving quickly eastward around 
60 mph, and it will continue to pose a widespread damaging wind risk 
across the Delmarva Peninsula and New Jersey until it moves offshore. Across 
southeastern VA, the line has not regenerated, possibly due to 
slightly stronger capping in the 850-700 mb layer compared to 
locations farther north. Regardless, a conditional damaging wind 
threat exists across southeastern Virginia. Across central/northern New Jersey 
into far southern NY, the atmosphere remains only weakly unstable, 
and the Prospect for an appreciable wind threat north of the current 
Severe Thunderstorm Watch remains unclear. 


.Gleason.. 03/01/2017 


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


Attention...WFO...okx...phi...akq...lwx... 


Latitude...Lon 37157797 38187655 38977620 40607568 40957502 40737403 
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