U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 020517 
Storm Prediction Center ac 020515 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1215 am CDT Tuesday Sep 02 2014 

Valid 021200z - 031200z 

..there is a slight risk of severe thunderstorms from parts of New York to Kentucky... 

strong to isolated severe storms...primarily producing damaging 
winds...are possible from the northern Appalachians southwest to the 
middle-south today. Marginally severe hail may occur tonight over parts 
of Kansas...western Missouri and northern Oklahoma. 

A shortwave trough...currently moving southeastward through Nebraska per 
satellite imagery...will remain progressive today tracking east-northeastward 
through the southern Great Lakes and Ohio Valley...reaching New York by 03/00z. 
In the wake of this trough...a zonal flow pattern will develop will 
develop across most of the Continental U.S.. at the surface...a weak cold 
front will shift east in tandem with the shortwave trough. 
Meanwhile...the trailing portion of this front should tend to be 
quasi-stationary near the Ozark Plateau westward into northern OK...and then 
advance northward as a warm front tonight. 

..nrn Appalachians to the mid-south... 
Scattered convection should be ongoing at 12z from parts of 
central/eastern OK east-northeastward through the Ozark Plateau to Indiana and Ohio. 
This activity is expected to be displaced southward from the cold front 
and supported by weak height falls ahead of the Nebraska trough and 
within weak low-level warm air advection along a 30-40 knots west-southwesterly low level jet. This activity 
is not expected to be severe...but concern remains for associated 
extensive clouds limiting downstream destabilization. Despite poor 
700-500-mb lapse rates...some surface heating within a rather moist 
environment /pw to around 1.75 inches/ should result in moderate 
instability primarily from southern Ohio/WV westward to the Ozark Plateau. 
Instability should tend to be more marginal with northeastward extent. A 
strong belt of midlevel flow accompanying the progressive trough 
will overspread this region...with 700-mb winds up to 40 knots and 
500-mb winds of 50-60 knots extending from the middle-upper Ohio Valley to 
New York. This and weak height falls with this trough should support an 
increase in convective intensity as renewed development occurs along 
convective outflow/differential heating corridors by late morning 
through the afternoon. This activity should organize into line 
segments/clusters that could yield at least isolated damaging 
winds...maintaining a slight risk from central/eastern Kentucky and southern Ohio to 
southern New York. Bulk shear will be progressively weaker with southern and western 
extent...limiting the risk for organized storms into the mid-south. 

..central and eastern Kansas/western MO to northern OK... 
Low-level warm air advection will increase Tuesday tonight as a relatively diffuse 
warm front advances north and a southerly low level jet strengthens from the Southern 
Plains into Kansas. Isolated to scattered elevated convection should 
develop along the periphery of a gradually eastward-expanding High Plains 
elevated mixed layer. Westerlies within the cloud-bearing layer should 
weaken late in the period...suggesting mainly a multicell storm 
Mode. The forecast for moderate instability should result in some 
threat for marginally severe hail. 

.Peters/Dean.. 09/02/2014 

Mesoscale Discussion

acus11 kwns 020146 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 020145 

Mesoscale discussion 1661 
National Weather Service Storm Prediction Center Norman OK 
0845 PM CDT Monday Sep 01 2014 

Areas affected...north central/northestern OK...and southeastern Kansas into southwestern MO 

Concerning...Severe Thunderstorm Watch 486...487... 

Valid 020145z - 020315z 

The severe weather threat for Severe Thunderstorm Watch 

Summary...potentially damaging wind gusts...frequent cloud to ground 
lightning and heavy rainfall are expected to become the primary 
convective hazards within the next hour or so. A new severe weather 
watch...or extension in time of ww 486...probably will be needed by 

Discussion...a considerable increase in the number of 
storms/convective coverage has been underway during the past hour or 
so. This appears generally in response to large-scale ascent 
associated with a band of enhanced convergence and warm 
advection...based roughly around 850 mb. Forcing for ascent could 
still increase some with modest strengthening of the southerly 
low-level jet /30-35 knots at 850 mb/ through the 03-05z time 
frame...likely providing the focus for strongest storm development 
near the Kansas/Oklahoma border area...between Bartlesville and 
Joplin. Aided by inflow of seasonably high moisture content 
air...with sizable cape beneath lingering modestly steep middle-level 
lapse rates...the evolution of a small but increasingly organized 
convective system appears possible in the presence of strong 
vertical shear. Heavy precipitation loading and downward Transfer 
of momentum associated with 30 knots deep layer westerly mean flow will 
contribute to increasing potential for downbursts and surface gusts 
at least approaching...if not exceeding...severe limits. 

.Kerr.. 09/02/2014 

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


Latitude...Lon 37849524 37849324 36869295 36659496 36379654 36169748 
36399803 37069754 37849524