U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 041258 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0758 am CDT Sat Jul 04 2015 


Valid 041300z - 051200z 


..there is a slight risk of severe thunderstorms over parts of the northern and Central 
Plains... 


..there is a slight risk of severe thunderstorms over parts of the central Gulf 
CST states... 


..there is a marginal risk of severe thunderstorms from the northern High Plains to the 
Southern Plains and from the lower MS valley to the Carolina CST... 


..there is a marginal risk of severe thunderstorms over parts of the Great Basin... 


... 
a few severe storms with large hail...damaging winds...and possibly 
a tornado are expected over parts of the northern and Central Plains 
late this afternoon and evening. Storms capable of locally damaging 
wind and heavy rain are expected over central Gulf Coast states. 
More isolated strong to severe storms will affect the Southern 
Plains...Georgia...the Carolinas...and the Great Basin. 


..synoptic setup... 
Great Basin/southern rockies ridge/eastern U.S. Trough pattern will prevail 
through sun. Moderate westerly flow with several embedded disturbances 
will continue over the northern rockies and northern/Central Plains...on NE side of 
the ridge. One notable disturbance within the eastern trough...now 
entering northwest Arkansas...will track east across the lower MS/lower Tennessee valleys 
tonight/early sun...while several weaker impulses precede it across the 
southern Appalachians/Carolinas. 


Very moist air /pw 1.75-2.00 inches/ will persist from the Southern Plains 
east/NE to the middle/S Atlantic CST. Sufficient moisture for storms also 
will be present over the central and northern plains...where precipitable water will remain 
at or above 1.25 inches. 


..cntrl Gulf CST states to Carolina CST this afternoon... 
Morning radiosonde observation and vwp data Sample seasonably strong /30-40 knots/ west-southwesterly 
middle-level flow over region...associated in part with Arkansas upper impulse. 
Combination of modest surface heating...increasing large-scale ascent 
with upper disturbance...and hi precipitable water may Foster development of 
occasional bowing segments this afternoon with a risk for locally damaging 
wind...mainly with new storms forming along and S of existing west-east 
outflow boundary that at this time extends from far northern la to west central Georgia. 
More isolated strong gusts may persist into tonight as embedded bowing 
segments continue east into GA/SC. Farther east...a more conditional risk 
for locally damaging wind may evolve over parts of SC and eastern NC this 
afternoon...where convergence will be limited but somewhat stronger 
heating will occur beneath lingering axis of stronger flow 
associated with surface wave/upper impulse departing the NC CST. 


..nrn/Central Plains this afternoon into tonight... 
Strong heating amidst ample moisture will promote substantial 
destabilization today along and ahead of Lee trough over the 
northern/Central High plains. More modest destabilization is expected over 
the northern High Plains...along weak cold front associated with western Canada 
upper low. 


A few storms may form toward midday...associated with lead upper 
impulse now over the western Dakotas. Additional development should 
occur later this afternoon southward across western Nebraska into northwest Kansas...with secondary 
disturbance tracking southeastward from Montana. Storms also may form near the 
Black Hills...and along the cold front in northern/eastern Montana. Some of the 
Dakotas/neb/NW Kansas convection may evolve into discrete supercells 
capable of large hail...damaging winds...and a 
tornado or two. The Dakotas/neb/KS activity should merge into one or 
two small mcss that persist into early sun. 


..srn plains this aftn/eve... 
Weak northwest/southeast front and related convective outflow boundaries will once 
again serve to focus afternoon/evening storm development over parts of OK and 
Texas. Large-scale forcing for ascent will remain weak...and the 850 mb 
flow slightly divergent. Nevertheless...presence of very 
moist/unstable low-level air beneath relatively cool middle-level 
temperatures...and modest but vertically-veering wind 
profiles...will yield an environment conditionally favorable for 
isolated to perhaps widely scattered strong updrafts. A supercell or two could 
form and...given strength of buoyancy...these would be capable of 
severe hail/wind. 


..grt basin this aftn/eve... 
Surface heating and ascent associated with an impulse moving north-northwest around 
western side of upper ridge should yield fairly widespread diurnal storms 
over much of central and northern Nevada. Coupled with steep low to middle-level 
lapse rates...isolated strong to severe wind gusts and/or small hail may 
occur as the activity organizes into small...nwd-moving clusters. 


.Corfidi/marsh.. 07/04/2015 

Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 032236 
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Mesoscale discussion 1293 
National Weather Service Storm Prediction Center Norman OK 
0536 PM CDT Friday Jul 03 2015 


Areas affected...portions of central MS...central Alabama...and far west-central 
Georgia 


Concerning...severe potential...watch possible 


Valid 032236z - 040000z 


Probability of watch issuance...40 percent 


Summary...isolated strong to damaging wind gusts remain possible 
through the early evening. Large hail may also occur with any 
discrete storms. Depending on storm coverage and intensity over the 
next several hours...ww issuance is possible. 


Discussion...a convectively reinforced outflow boundary currently 
bisects the mesoscale discussion area from west to east...lying roughly across central MS 
into central Alabama. A warm...moist airmass remains in place over the 
region...with temperatures generally in the lower to middle 80s and 
dewpoints in the lower 70s to middle 70s contributing to MLCAPE of 
1500-2500 j/kg per rap mesoanalysis. Enhanced middle-level flow of 
35-45 knots present on area vwps suggests convection developing along 
the outflow boundary may acquire sufficient organization to support 
mulitcell and occasional supercell structures. Once such supercell 
that has moved from Bibb into Chilton County Alabama has produced large 
hail up to 1.50 inch in diameter. 


Another cluster of thunderstorms moving eastward over west-central MS may be 
associated with a remnant mesoscale convective vortex from convection last night in OK. 
Given sufficient effective bulk shear of 35-40 knots...this activity 
may pose more of a strong/damaging wind threat as it continues 
moving over central MS with time. If the activity along the remnant 
outflow boundary and/or the cluster of storms in west-central MS increase 
in coverage and intensity over the next several hours...then a 
Severe Thunderstorm Watch may be needed. 


.Gleason/Thompson.. 07/03/2015 


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


Attention...WFO...ffc...tae...bmx...mob...Meg...Jan... 


Latitude...Lon 32759105 33399101 33789043 33698828 33528628 33408514 
31968469 31778518 31908768 32239027 32759105