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4/6 Strong April Storm Discussion & Observations


bluewave

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32 minutes ago, bluewave said:

Models are indicating that the 4/6 storm could be one of the strongest for the month of April during the 2010's so far. The Euro rapidly deepens the low near 980 mb as the trough goes negative tilt and cuts off. Pressures that low would approach about -4.5 sd below normal for April crossing PA into NY. The potential is there for heavy rains and strong winds. That fact that such a strong storm will be the 3rd in a series of wet storms in just one week raises the flash flood potential. Winds could also gust to 50 mph or higher.

 

 

ecmwf_mslp_sig_east3_16.thumb.png.43d20bc0d130911db8d1ce9541d3cf44.png

That's the major flood threat for far upstate and New England that's been on the table. Snow pack is well above normal in the adriondaks, greens and whites.

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2 minutes ago, LongBeachSurfFreak said:

That's the major flood threat for far upstate and New England that's been on the table. Snow pack is well above normal in the adriondaks, greens and whites.

with that track, you'd see strong SE winds bringing into warm maritime air and heavy rains for a period time....snow would quickly melt with those conditions.

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11 hours ago, bluewave said:

Models are indicating that the 4/6 storm could be one of the strongest for the month of April during the 2010's so far. The Euro rapidly deepens the low near 980 mb as the trough goes negative tilt and cuts off. Pressures that low would approach about -4.5 sd below normal for April crossing PA into NY. The potential is there for heavy rains and strong winds. That fact that such a strong storm will be the 3rd in a series of wet storms in just one week raises the flash flood potential. Winds could also gust to 50 mph or higher.

 

 

ecmwf_mslp_sig_east3_16.thumb.png.43d20bc0d130911db8d1ce9541d3cf44.png

the 4/6-4/10 period is notorious for big storms (whether they be snow or rain.)  With this storm looks like there will be accumulating snow from Chicago to Grand Rapids to Cleveland to Buffalo and from the mountains of PA down through W VA and NC down to north GA.  And a widespread frost from TN to PA for this weekend.

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The 00z GGEM goes from 990mb to 982mb in six hours while the SLP tracks through Eastern PA on Thursday afternoon. The 06z GFS tracks the surface low much further NW as it occludes the SLP quicker while the 00z EMWF is more like the GGEM. The 00z UKMET splits the difference, with a 983mb low tracking from Central PA towards Elmira. 

Bottom line is, unless the ULL closes off further Southeast we're looking at another quick hitting system that's probably in and out in less than 12 hours. We need something more like the NAVGEM track to extend the impact of the system.

navgem_mslp_pcpn_neus_11.png

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16 minutes ago, Brian5671 said:

Unusual track here.   Guess that's what happens when the trough is negative and the system is captured.

It's all about how quickly the trough goes negative and closes off. I wish this was able to dig further Southeast before closing off as that would have prolonged the event here. You can see here why the GGEM ends up further East than the GFS.

gfs_z500_vort_us_11.png

gem_z500_vort_us_12.png

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2 minutes ago, Brian5671 said:

Wow-how often do you see a 985 low over Harrisburg?    Mid-day models give the forum b/w 1 and 1.5 inches of rain from this system.   Weekend looks decent.

Don't pay too much attention to the QPF, especially on the globals.

The setup at H5 is explosive. It's just a matter of whether or not we get into the strongest dynamics or if that ends up closer to E PA.

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16 minutes ago, NJwx85 said:

Don't pay too much attention to the QPF, especially on the globals.

The setup at H5 is explosive. It's just a matter of whether or not we get into the strongest dynamics or if that ends up closer to E PA.

I agree-the track needs to be a bit closer to us-if it's that far west as shown on the GFS we won't get that much....Euro will likely have a better idea. How was the UKMET?   

 

Edit:  UKIE is a bit east with the low and stronger.

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This system is forecasted to bring quite the severe weather outbreak to portions of the Southeast tomorrow. SPC has a large area of moderate risk and noted potential upgrade to high risk in later outlooks. That threat should continue Northeastward into Thursday as SPC has Southern NJ and the Mid-Atlantic in a slight risk. Based on the trajectory of the convection, it seems plausible that whatever does develop further South will ultimately end up over our region on Thursday. Here is a snippet from the SPC day 3 outlook. The main threat up here would be heavy rains resulting from numerous thunderstorms and strong convection.

 ...Mid Atlantic Coast region...
   As the exit region of a cyclonic 90-100+ kt 500 mb jet streak noses
   across the region early Thursday, models indicate renewed surface
   cyclogenesis will take place to the east of the central
   Appalachians, with rapid deepening and occlusion probable as the low
   center tracks north northeastward out of northern Virginia.  Prior
   to the frontal passage, coinciding strengthening of southerly 850 mb
   flow in excess of 50 kt is forecast within the warm sector, along
   with at least a narrow corridor of substantive boundary layer
   moistening (mainly near/east of the Interstate 95 corridor of
   eastern Virginia into northeastern North Carolina.  In the presence
   of strong forcing for ascent this is expected to contribute to
   sufficient destabilization to support vigorous thunderstorm
   development.  This may include discrete supercells capable of
   producing tornadoes, given the strength of the wind fields and
   shear.  Considerable wind damage potential may evolve with any
   upscale growing convection, however the impact of the cooler more
   stable marine layer near/across the Chesapeake remains unclear as
   activity attempts to spread northward into/through the Delmarva
   Peninsula.
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