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June 25-27 severe and heavy rain


Ian

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NAM look at 500mb and sfc is pretty classic tornado event.. even has a lee low pop and ride the apps. We won't need a ton of instability in this setup.. 1000+ would do. ~1500-2000 prob better.

I'm starting to get excited. But plenty of time for it to trend badly.

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NAM look at 500mb and sfc is pretty classic tornado event.. even has a lee low pop and ride the apps. We won't need a ton of instability in this setup.. 1000+ would do. ~1500-2000 prob better. 

I do have my doubts about the CAD and cloud cover clearing out. It's taking a similar track to Frances, but NE water temps are a lot colder at this time of year so the ENE flow could be a problem. I like the setup for SE Virginia and NC though.

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I do have my doubts about the CAD and cloud cover clearing out. It's taking a similar track to Frances, but NE water temps are a lot colder at this time of year so the ENE flow could be a problem. I like the setup for SE Virginia and NC though.

Verbatim, flow is S/SE and we're definitely in the warm sector..no northerly component to the streamflow. Only thing I'm worried about is cloud cover/progression of the warm front.

That said, insolation is at it's seasonal peak now, so if we do get warm sectored, we should destabilize at least somewhat.

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Verbatim, flow is S/SE and we're definitely in the warm sector..no northerly component to the streamflow. Only thing I'm worried about is cloud cover/progression of the warm front.

That said, insolation is at it's seasonal peak now, so if we do get warm sectored, we should destabilize at least somewhat.

Yeah but models tend to under do surface CAD, so there's a possibility of a stubborn inversion layer further south than shown.

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Flash flood watch just issued.

 

 

 

FLOOD WATCH
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
420 AM EDT FRI JUN 26 2015


(snip)
420 AM EDT FRI JUN 26 2015

...FLASH FLOOD WATCH IN EFFECT FROM LATE TONIGHT THROUGH LATE
SATURDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* FLASH FLOOD WATCH FOR PORTIONS OF MARYLAND...THE THE DISTRICT
  OF COLUMBIA...VIRGINIA AND NORTHEAST WEST VIRGINIA...INCLUDING
  THE FOLLOWING AREAS...IN MARYLAND...ANNE ARUNDEL...CARROLL...
  CENTRAL AND EASTERN ALLEGANY...CENTRAL AND SOUTHEAST HOWARD...
  CENTRAL AND SOUTHEAST MONTGOMERY...CHARLES...EXTREME WESTERN
  ALLEGANY...FREDERICK...NORTHERN BALTIMORE...NORTHWEST
  HARFORD...NORTHWEST HOWARD...NORTHWEST MONTGOMERY...PRINCE
  GEORGES...SOUTHEAST HARFORD...SOUTHERN BALTIMORE AND
  WASHINGTON. THE DISTRICT OF COLUMBIA. IN VIRGINIA...
  ALBEMARLE...ARLINGTON/FALLS CHURCH/ALEXANDRIA...AUGUSTA...
  CENTRAL VA BLUE RIDGE...CLARKE...CULPEPER...EASTERN HIGHLAND...
   EASTERN LOUDOUN...FAIRFAX...FREDERICK...GREENE...MADISON...
  NELSON...NORTHERN FAUQUIER...NORTHERN VA BLUE RIDGE...ORANGE...
   PAGE...PRINCE WILLIAM/MANASSAS/MANASSAS PARK...RAPPAHANNOCK...
   ROCKINGHAM...SHENANDOAH...SOUTHERN FAUQUIER...SPOTSYLVANIA...
  STAFFORD...WARREN...WESTERN HIGHLAND AND WESTERN LOUDOUN. IN
  NORTHEAST WEST VIRGINIA...BERKELEY...EASTERN GRANT...EASTERN
  MINERAL...EASTERN PENDLETON...HAMPSHIRE...HARDY...JEFFERSON...
  MORGAN...WESTERN GRANT...WESTERN MINERAL AND WESTERN
  PENDLETON.

* FROM LATE TONIGHT THROUGH LATE SATURDAY NIGHT

* LOW PRESSURE IS EXPECTED TO INTENSIFY OVER THE OHIO VALLEY
  TONIGHT AND MOVE INTO SOUTHWESTERN NEW YORK BY SUNDAY MORNING.
  AS IT DOES SO...A WARM FRONT WILL LIFT THROUGH SOUTHERN AND
  CENTRAL VIRGINIA SATURDAY AND SATURDAY NIGHT WITH HEAVY RAINS
  DEVELOPING LATE TONIGHT INTO SATURDAY MORNING ACROSS THE
  SHENANDOAH VALLEY AND SPREADING NORTHEAST ACROSS THE REST OF THE
  AREA SATURDAY MORNING. RAINS...HEAVY AT TIMES WITH EMBEDDED
  THUNDERSTORMS ARE EXPECTED SATURDAY INTO SATURDAY EVENING WITH
  ONE TO THREE INCHES OF RAIN LIKELY BY THE TIME A COLD FRONT
  CLEARS THE AREA LATE SATURDAY NIGHT.

(snip)

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Haven't looked at the models yet, but Ava on WBAL was talking about how its going to rain all day tomorrow. Is that really the case? Was hoping to luck out and deal with off and on showers instead of a deluge. 

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Still a question of how far north the front progresses. Some of the modeling is slow w/ the progression of the front/warm sector.

 

Probably good to bet on a failure - but as Ian said we won't need copious amounts of instability potentially. 

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I would bet against severe in Northern MD, sweet spot for Tornadoes will be from the Tidewater area west to the Blue Ridge and north to the MD/VA border, through Southern MD. Would expect Mod-Heavy Rain, Some Rumbles, and breezy conditions in Northern MD. Still definitely possible for something sub severe with the CF.

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Still a question of how far north the front progresses. Some of the modeling is slow w/ the progression of the front/warm sector.

Bet on fail and be happy with your two low rumbles of thunder.  It's been my experience that when you need to wait on the warm front to bust north and quickly clear out, it doesn't happen.  We've seen time after time when the models underestimate the speed and progression of the surface warm front and it's ability to scour out the stable, low level air mass.

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12Z NAM and hi-res counterpart are more aggressive Potomac south. Agree that Maryland will have issues with the WF not lifting enough. Lots of morning and midday rain may achor WF and/or an outflow boundary. Virginia looks sweet tomorrow!

 

Deepening low press makes less veered low level winds believable. Secondary boundary may be over Virginia, not hammered by rain, and would provide a focus for locally backed surface winds - and perhaps a tornado or two. Strength of upper level winds is pretty remarkable for this time of year. Gosh it almost looks like May in the Plains, but maybe I'm getting carried away. SPC needs to drop the ENH Day 2 this afternoon. Can't see postponing until tomorrow morning.

 

If all else fails there is certainly enough speed and directional shear for a good high wind show in spots, along with the chance of some good hail for the East Coast. Thanks for letting me live vicariously in your forum.

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I think I'm on board with the idea that areas north and east of a line from Winchester to Leesburg to DC to Chesapeake Beach will probably not see significant severe (although I won't rule it out).  The NAM and its nest both bring the warm front to roughly that line by 21z.   Big differences south of there with the NAM generally limiting sfc-based cape to 500-1500 (with some higher pockets further south), while the nest has large coverage of 2500+ along and south of the warm front including up to DC.

 

The truth will probably be somewhere in the middle.   The nest is always too high with its cape, but the NAM value is low because this type of high moisture environment with some instability is like crack to its convective scheme, and it kicks in too early tomorrow afternoon and wipes out the cape.

 

The key is how much precip will there be with the warm front in the morning.   The NAM and its nest both have a nice slug moving through northern VA/DC/central MD during the morning, but there is a sharp cutoff on its southern edge.  I suspect that the warm front's movement north will be retarded by the morning rain, so if the rain ends up a little further north, more of the area will destabilize.   The nest defnitely wants to shut off precip during the midday and afternoon hours.

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I think I'm on board with the idea that areas north and east of a line from Winchester to Leesburg to DC to Chesapeake Beach will probably not see significant severe (although I won't rule it out).  The NAM and its nest both bring the warm front to roughly that line by 21z.   Big differences south of there with the NAM generally limiting sfc-based cape to 500-1500 (with some higher pockets further south), while the nest has large coverage of 2500+ along and south of the warm front including up to DC.

 

The truth will probably be somewhere in the middle.   The nest is always too high with its cape, but the NAM value is low because this type of high moisture environment with some instability is like crack to its convective scheme, and it kicks in too early tomorrow afternoon and wipes out the cape.

 

The key is how much precip will there be with the warm front in the morning.   The NAM and its nest both have a nice slug moving through northern VA/DC/central MD during the morning, but there is a sharp cutoff on its southern edge.  I suspect that the warm front's movement north will be retarded by the morning rain, so if the rain ends up a little further north, more of the area will destabilize.   The nest defnitely wants to shut off precip during the midday and afternoon hours.

 

ugh, not what i wanted to hear. while i knew the WF would have issues getting north, was hoping it would make it further north than that and my entire day wouldn't be a washout. oh well. 

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