U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 251626 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1126 am CDT Sat Oct 25 2014 


Valid 251630z - 261200z 


..there is a marginal risk of severe thunderstorms this afternoon from the SW 
Oregon/northwest California coasts to the northern Sacramento Valley... 


... 
Scattered showers and thunderstorms are expected to develop across 
northwestern California and southwestern Oregon from midday through 
this afternoon. A few of these may bring the risk of a weak/brief 
tornado. Thunderstorms will also develop across northern parts of 
New York and New England. 


..SW Oregon/northwest California and northern Sacramento Valley this afternoon... 
A strong midlevel shortwave trough will move inland over the Pacific northwest 
and northern California coasts today. Radar imagery has confirmed low-topped 
convection with weak rotation within the deep baroclinic zone 
approaching the northwest California/SW Oregon coast...while satellite 
imagery/lightning data show additional convection/isolated 
thunderstorms offshore. Eastward progression of the trough will bring 
cooler temperatures aloft over land and will contribute to 
destabilization as far east as the northern Sacramento Valley this 
afternoon. In tandem with the inland destabilization...vertical 
shear profiles will be favorable for rotating storms for a few hours 
before low-level flow veers and shear weakens. Since buoyancy will 
remain rather weak inland /SBCAPE of 100-300 j per kg/...the overall 
tornado risk will remain marginal. 


..nrn New York state into Vermont/New Hampshire this afternoon/evening... 
A strong shortwave trough and jet streak over the upper Great Lakes 
will translate east-southeastward to the Saint Lawrence valley this 
afternoon...along with an associated surface cold front. Steepening 
midlevel lapse rates with the approach of the shortwave trough...and 
ascent within the left exit region of the jet streak...could support 
isolated low-topped thunderstorms later this afternoon/evening with 
frontal passage. 


.Thompson/Marsh.. 10/25/2014 






Mesoscale Discussion


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acus11 kwns 151721 
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Storm Prediction Center mesoscale discussion 151720 
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Mesoscale discussion 1899 
National Weather Service Storm Prediction Center Norman OK 
1220 PM CDT Wednesday Oct 15 2014 


Areas affected...central Maryland into southeastern PA 


Concerning...severe potential...watch unlikely 


Valid 151720z - 151945z 


Probability of watch issuance...20 percent 


Summary...an isolated strong wind gust or brief/weak tornado cannot 
be ruled out with storms as they develop northward from Maryland into southeastern PA. 


Discussion...an isolated strong cell with substantial vertical 
development continues to propagate northward along a north-S oriented boundary 
which extends into PA and links with an existing front across eastern PA 
which currently separates the more moist/unstable air to the southeast. 


This particular storm has had a persistent and broad circulation 
with it...but nothing particularly strong or tight probably due to 
weak low-level buoyancy/acceleration. While deep-layer flow is 
strong above the ground...most of the shear is relegated to the 
near-surface layer and other cells away from the outflow boundary 
have shown little if any shear. Therefore...any wind/tornados threat is 
expected to be brief...short-lived and isolated...and a watch is not 
expected. 


.Jewell/corfidi.. 10/15/2014 


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


Attention...WFO...phi...ctp...lwx... 


Latitude...Lon 39157664 39007677 38987688 39067699 39267696 39617690 
40007679 40347640 40457615 40407593 40137594 39617620 
39157664