U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 250536 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1236 am CDT Sat Oct 25 2014 


Valid 251200z - 261200z 


..there is a marginal risk of severe thunderstorms across parts of northern California and 
southwest Oregon... 


... 
Scattered thunderstorms are expected to develop across northern 
California into southwest Oregon Saturday afternoon. A few storms 
may become capable of producing a weak/brief tornado across this 
region. Scattered thunderstorms will also develop across upstate 
New York into portions of northern New England. 


..Pacific coast... 


Late evening satellite imagery depicts a well-defined middle-level 
circulation off the northern California coast...centered near 39n/130w. This 
feature is lifting northeastward toward the Oregon coast and should move 
inland after 18z as 80-100kt 500mb speed maximum translates into eastern 
Oregon and weakens. Latest guidance suggests 12hr middle-level height 
falls on the order of 150m should spread across western Oregon into Washington 
during the day. While strongest large-scale forcing is expected to 
focus north of marginal risk region...southern extent of low-level 
convergence should extend into northern California where shear profiles will be 
more than adequate for sustaining organized updrafts. Primary 
negatives across this region will be modest lapse rates/meager 
buoyancy which should negate updraft intensity. Forecast soundings 
across northern California/southwestern Oregon suggest surface-based convection is possible 
and longer-lived updrafts could rotate...perhaps even briefly 
producing a few weak tornadoes. 


..nern u... 


Focused area of ascent within exit region of strong middle-level jet 
will spread into upstate New York after 18z. While moisture is quite 
sparse across this region...and 50f+ surface dew points remain 600mi 
upstream over WI...scattered convection is expected to develop along cold 
front during the late afternoon as lapse rates steepen within 
cooling middle-level profile. Forecast soundings across upstate New York 
suggest surface-based convection is likely despite the expected cool surface 
temperatures. In fact...cloud heights could exceed 6km and 
graupel/small hail may accompany much of this activity. Given the 
expected steep low-level lapse rates gusty winds may also occur with 
this convection. 


.Darrow/Dean.. 10/25/2014 






Mesoscale Discussion


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sels mesoscale discussion 
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