U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 040556 
Storm Prediction Center ac 040554 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1254 am CDT Friday Sep 04 2015 

Valid 041200z - 051200z 

..there is a slight risk of severe thunderstorms over portions of eastern North 
Dakota/northwest Minnesota... 

..there is a marginal risk of severe thunderstorms surrounding the slight risk 
over portions of central/eastern North Dakota...northeast South 
Dakota and western/central Minnesota... 

Isolated to widely scattered severe thunderstorms will be possible 
Friday afternoon and evening across portions of eastern North 
Dakota...northeast South Dakota and western Minnesota. Large hail 
and damaging winds will be the main threats. 

A seasonably strong/slightly amplifying upper-level trough over the 
Pacific northwest will move little Friday as an upper-level ridge 
extends from the Southern Plains into the Great Lakes. An impulse 
within the southwesterly middle-level flow over the central/northern 
High Plains Friday morning will lift northeast across the 
Dakotas/Minnesota during the afternoon/evening. A frontal boundary 
will extend from North Dakota southwest across northern Wyoming late 
Friday afternoon...with another quasi-stationary front from 
southern/central Minnesota east into the Ohio Valley. 

..portions of the Dakotas/Minnesota... 
Surface dew points in the upper 60s/lower 70s will be present across 
the upper Midwest/northern plains on Friday. Despite morning 
clouds/scattered storms...diurnal heating and a plume of steep 
middle-level lapse rates will lead to areas of moderate-strong 
surface-based instability by afternoon across central/eastern 
portions of the Dakotas eastward into Minnesota. Low-middle level wind 
fields will increase somewhat with the approach of the upper-level 
impulse during the afternoon/evening...resulting in sufficient 
deep-layer shear /35-40 kts/ across the slight risk area for storm 
organization. Expect isolated to widely scattered thunderstorms to 
develop by late afternoon across eastern North Dakota and move 
northeast during the evening. With adequate deep shear for updraft 
rotation...large hail and damaging gusts will be possible with the 
more discrete storms. Storms may tend to develop into clusters with 
time posing a continued severe risk mainly in the form of damaging 

..eastern Montana/northwest North Dakota late Friday night... 
Some signal exists in latest guidance regarding the potential for 
strong storms in the 06z-12z Sat time frame over portions of eastern 
Montana/northwest North Dakota...where developing warm advection and 
an approaching impulse within southwesterly middle-level flow could 
provide sufficient large-scale forcing for ascent to aid in 
thunderstorm development. Considered a westward extension of the 
marginal/5 percent severe probabilities...however with questions on 
timing and magnitude of elevated instability/thunderstorm 
intensity...opted to defer to later outlooks in this area. 

.Bunting/Cook.. 09/04/2015 

Mesoscale Discussion

acus11 kwns 021935 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 021935 

Mesoscale discussion 1757 
National Weather Service Storm Prediction Center Norman OK 
0235 PM CDT Wednesday Sep 02 2015 

Areas affected...eastern WV...Maryland Panhandle...cntrl/ern Virginia 

Concerning...severe potential...watch unlikely 

Valid 021935z - 022100z 

Probability of watch issuance...5 percent 

Summary...scattered thunderstorms are expected to persist through the 
afternoon with the low potential for some damaging wind gusts and 
hail. Minimal severe coverage and a generally marginal threat will 
preclude the need for a ww. 

Discussion...regional radar imagery shows gradually increasing thunderstorm 
coverage ahead of a weak upper low currently moving across central WV 
and into northern Virginia. Middle-level lapses rates are poor -- less than 6 degree 
c per km based on the recent mesoanalysis -- but warm surface 
conditions and good low level moisture /upper 60s dewpoints/ are 
contributing to airmass destabilization. Latest mesoanalysis 
estimates MLCAPE over 1000 j/kg for much of the region. A very 
modest increase in middle-level winds is possible as the low moves 
through but even with this increase shear is expected to remain weak 
across the area. This lack of shear will preclude storm organization 
and temper the overall severe threat. Precipitation loading within 
the stronger updrafts resulting from storm mergers and/or quick 
development on outflow boundaries may result some localized damaging 
winds with some hail also possible with the strongest updrafts. 

.Mosier/Thompson.. 09/02/2015 

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


Latitude...Lon 37887996 38518005 39127981 39457941 39647919 39717888 
39727793 39697775 39477730 39357718 38297645 37747630 
37217656 36887697 36657745 36697826 36847902 37487970