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Kmlwx

2019 Mid-Atlantic Severe Wx - General Discussion

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6 minutes ago, UIWWildthing said:

Honestly, it's about time. A period of dryness would be welcome. 

I know,  but just mentioning be careful what you wish for. 

Already my garden is totally dry and top soil is very hard. It is amazing how quickly we lose ground moisture this time of year. Once-a- week rainfall would be awesome,  but 14 days in summer in a row without rainfall is not great, if you have agriculture concerns, or have a garden. etc.  Need to get my soaker hoses set up and straw or mulch the garden, it is about time shortly. Less rain has one advantage- less mosquittos - I hate them !     

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25 minutes ago, H2O said:

my hope is to keep cloud cover at a minimum, get enough instability from warming to break cap and have the lee trough that helps pop storms do its usual thing.  

you know those are all things we need every time and tend to fail on lol 

21 minutes ago, Eskimo Joe said:

Tomorrow is shaping up to be a classic severe weather outbreak for PA and NY.  You have robust surface heating combined with a dynamic front...terrain aided updrafts could produce some storms pushing classic supercells.  I wouldn't be shocked to see a DY1 Moderate risk for parts of PA and NY tomorrow if things come together in the morning.  

 if i was in Scranton, id feel pretty good about seeing some severe tomorrow. 

11 minutes ago, high risk said:

     absolutely correct that the NAM nest is not being very aggressive for tomorrow, but at the other end of the spectrum, the two ARW Hi-Res Windows have a very robust event for PA/NY and MD/DE (and maybe WV and northern VA too).    Both bring convection out of the midwest early Thursday and redevelop it east of the mountains, with some impressive radar signatures.     Not saying this will be the outcome, but it could explain some of the more "excited" forecasts.  

ahh, i hadn't looked at either one of those. i've always considered them weenie models ;) (i honestly don't know enough about them)

I'd be happy with thunder, I know our chances down here aren't nearly as good as those in PA/NY. But still has a chance to be a fun event to watch unfold, even if we don't get the goods. 

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4 minutes ago, mappy said:

you know those are all things we need every time and tend to fail on lol 

 if i was in Scranton, id feel pretty good about seeing some severe tomorrow. 

ahh, i hadn't looked at either one of those. i've always considered them weenie models ;) (i honestly don't know enough about them)

I'd be happy with thunder, I know our chances down here aren't nearly as good as those in PA/NY. But still has a chance to be a fun event to watch unfold, even if we don't get the goods. 

They certainly seemed to be before. The last year or so though they seem far more conservative a lot of times. 

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7 minutes ago, mappy said:

you know those are all things we need every time and tend to fail on lol 

 if i was in Scranton, id feel pretty good about seeing some severe tomorrow. 

ahh, i hadn't looked at either one of those. i've always considered them weenie models ;) (i honestly don't know enough about them)

I'd be happy with thunder, I know our chances down here aren't nearly as good as those in PA/NY. But still has a chance to be a fun event to watch unfold, even if we don't get the goods. 

Cue the old adages:

ARW = Always Really Wet or Always Really Wild

NMM = Not Much Moisture

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27 minutes ago, mappy said:

 

ahh, i hadn't looked at either one of those. i've always considered them weenie models ;) (i honestly don't know enough about them

         

            :D              The ARW2 in particular is a very good model.     It's effectively the same configuration as the very popular and quite skillful NSSL-WRF.

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Just now, high risk said:

         

            :D              The ARW2 in particular is a very good model.     It's effectively the same configuration as the very popular and quite skillful NSSL-WRF.

can you provide me with a good link for it? i haven't looked around to see if the paid sites have them or not. appreciate your insight, as always! 

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2 minutes ago, mappy said:

can you provide me with a good link for it? i haven't looked around to see if the paid sites have them or not. appreciate your insight, as always! 

        you're most welcome.    Tropical Tidbits has nice displays - it's listed in the mesoscale section as WRF-ARW2.      Pivotal Weather has it as HRW WRF-NSSL.

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Just now, high risk said:

        you're most welcome.    Tropical Tidbits has nice displays - it's listed in the mesoscale section as WRF-ARW2.      Pivotal Weather has it as HRW WRF-NSSL.

thank you! 

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While its solution verbatim kinda screws some of this area, add the HRRR to the list of runs (all ARW, fwiw) which are much more widespread and further south with convection tomorrow than the NMMB runs.

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8 minutes ago, yoda said:

1730 SPC OTLK moves the SLGT and ENH risk south some compared to earlier Day 2

includes Baltimore and Frederick now

MD_swody2 (1).png

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6 minutes ago, Kmlwx said:

Can I come watch a wedge pass by from Mappyville?

Sure can! Ill be home :) 

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SPC Disco from the 1730 OTLK

Quote
Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1220 PM CDT Wed May 22 2019

   Valid 231200Z - 241200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE OH
   VALLEY/MIDDLE ATLANTIC AND SOUTHERN/CENTRAL PLAINS...

   ...SUMMARY...
   Severe storms with large hail, damaging wind and tornadoes will be
   possible over a part of the central and southern Plains Thursday.
   Other severe storms with a threat for mainly damaging wind and large
   hail are expected from a portion of the Ohio Valley into the
   northern Middle Atlantic.

   ...Upper OH Valley/Northern Middle Atlantic...

   Central US short-wave trough is forecast to eject northeast across
   the Great Lakes and flatten the eastern ridge as 80kt 500mb speed
   max translates across Lake Erie. This feature is expected to aid
   early-morning convection across the OH Valley which will propagate
   into eastern OH/western PA by 18z. Depending on the evolution of
   this convection it appears environmental shear will become favorable
   for sustaining fast-moving organized updrafts. Latest model guidance
   suggests upward-evolving thunderstorms by early afternoon within
   strengthening westerly flow regime. Boundary-layer heating is
   expected to be maximized from south-central PA, south along the lee
   of the central Appalachians. If a cold pool develops early, severe
   thunderstorms should initiate along the
   eastern-southern-southwestern flank of this activity then
   spread/develop east-southeast toward the Delmarva. Several CAMs
   solutions support this scenario and will extend higher severe probs
   into northern MD to account for the more southeast propagational
   component. Damaging winds, and some hail, are expected with
   convection as it spreads across eastern OH/PA toward northern MD by
   late afternoon.

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LWX's afternoon AFD re tomorrow from 2:30PM

The warm front will pass through the area Thursday morning. A
couple showers and perhaps even an isolated thunderstorm may
accompany the frontal passage, but again coverage will be
isolated to widely scattered.

A west to southwest flow behind the boundary will usher in
noticeably warmer and more humid conditions. Max temps will top
off well into the 80s for most areas, and a few locations may
even approach 90 degrees. Dewpoints should rise into the 60s for
most areas, making it feel more uncomfortable as well.

Still keeping a close eye on the potential for severe
thunderstorms Thursday afternoon and evening. The warmer and
more humid conditions will lead to an unstable atmosphere. The
12z HREF forecasts mean SBCAPE to be about 1-2KJ/KG across most
of the area with locally higher amounts east of the Blue Ridge
Mountains (where dewpoints will be a bit higher east of a
pressure trough). Deep layer shear will most likely be around 40
to 50 knots, which is plenty to support the threat of severe
thunderstorms. Latest guidance has come into better agreement
that an MCS will track across the Midwest tonight and then
toward our area Thursday morning. The system will likely pass
through our area Thursday afternoon and evening, and with the
moderate instability and shear in place...the threat for severe
thunderstorms is elevated with damaging winds being the
primary threat along with large hail. Confidence is still low on
exactly how this will play out because it will be highly
dependent on the strength of the MCS, which has not developed
yet. If the MCS holds together and tracks through our area, then
the threat for severe thunderstorms will be enhanced. However,
if the MCS dissipates before reaching our area, then popup
thunderstorms will still pose a threat for severe weather but it
will be more isolated. Latest thinking is that the best chance
for more enhanced severe weather will be across our northern and
perhaps even central areas...where height falls are more
noticeable and there will be less of an impact from downsloping
low-level westerly flow.

The actual cold front will drop into our area from the north
Thursday night. Convection will dissipate overnight with the
loss of daytime heating and a downslope west to northwest flow.

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Parameters continue to look pretty impressive. But sim radar is pretty weak sauce for us on most models (even the better ones @high risk ) mentioned. Still think it could go either way. I want to get excited but that's always a losing strategy around here. On the plus side - it does look pretty certain that we'll see a good bit of sun tomorrow...that's one of the factors we sometimes don't have (often). 

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21 minutes ago, Kmlwx said:

Parameters continue to look pretty impressive. But sim radar is pretty weak sauce for us on most models (even the better ones @high risk ) mentioned. Still think it could go either way. I want to get excited but that's always a losing strategy around here. On the plus side - it does look pretty certain that we'll see a good bit of sun tomorrow...that's one of the factors we sometimes don't have (often). 

I think it will continue to look that way on sim radar until the MCS that LWX mentioned in the afternoon AFD develops 

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Interesting read from Mount Holly on the severe potential, and limiting factors:

Although showers, and possibly a thunderstorm or two, will continue to be possible in the warm sector through the morning, the main round of storms we are concerned about are storms that are expected to develop along and ahead of the pre-frontal trough late Thursday afternoon into Thursday evening. Some of these storms could be severe. Most models depict ML CAPE values near or above 1000 J/kg in the 21 to 00Z time frame along with 0-6km bulk shear values of 40 to 50 kt. Not only is this a significant amount of shear, but model soundings depict plenty of veering with height (especially within the first 3 km). This further enhances the risk that updrafts could be persistent. There are a few potential caveats. First, low/mid level clouds may not erode through the morning. This will limit diurnal heating (in anticipation that this may be the case, have gone with the cooler guidance for highs on Thursday), which would limit instability/CAPE values. Secondly, related to the first caveat, the NAM depicts a low level inversion (around 900 mb) which never fully erodes through the day (unlike the GFS which depicts this eroding between 21 and 00Z). Even if we are cooler and the inversion stays in place, I think we will continue to have at least some severe threat as lift along the trough could be enough to lift elevated parcels above the inversion. The final caveat is that remarkably, model soundings are depicting several dry (and one very dry) layers through the afternoon and evening. This means the LCL will be higher than normal, and will have an impact on the risk for wind, tornado, and heavy rain. Speaking of hazards: Damaging wind: This looks to be the primary hazard thanks to a low and mid level jet, and plenty of shear. The low level inversion mentioned above may limit how efficient the mixing is down to the surface, but the dry levels will help to increase the risk of downbursts thanks to an increased risk of dry air entrainment. Hail: Severe hail (1" in diameter or greater) is certainly possible, especially if we warm up as much as what the GFS is depicting and are able to realize the higher CAPE values. The highest threat for hail looks to be over Delmarva and far SE PA where the highest CAPE values are possible. Tornado: The veering wind profiles increase the risk for rotating updrafts. However, as mentioned above the LCL will be higher than normal which could limit the threat for tornadoes.

 

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Ok... those are some disturbing soundings the 00z NAM is tossing out at 00z and 03z FRI at KIAD... 03z FRI at KBWI and KDCA...  Yes, just a sounding, but you don't see those types of soundings around here very often

Yes, doesn't guarantee we see severe.  But still... wow @Kmlwx @high risk

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5 minutes ago, yoda said:

00z NAM sim radar brings some nastiness for the evening commute from BWI to DCA to near EZF at 21z

00z NAM NEST decides to drive through some what would appear to be supercells around 20z to 21z... then brings a pretty decent line south from PA as a finale around 03z but its fragmenting around DC at that time

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