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May Discobs 2022

George BM

By George BM,
in Mid Atlantic

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NorthArlington101
NorthArlington101

Tough weather to graduate in, but it happened! Looking forward to my obs getting back to being consistently from Arlington.

H2O
H2O

Never get sick of these

nw baltimore wx
nw baltimore wx

Who needs heat?

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CAPE

CAPE

Posted
Posted

Impressive wave break on the GFS would set up a blocked flow with a possible cutoff low. With a E to NE flow off the cold Atlantic, late next weekend into early the following week could potentially be a chilly/gloomy period. CMC with a similar idea.

gfs_z500a_namer_34.png

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Redmorninglight

Redmorninglight

Posted
Posted
1 hour ago, CAPE said:

Impressive wave break on the GFS would set up a blocked flow with a possible cutoff low. With a E to NE flow off the cold Atlantic, late next weekend into early the following week could potentially be a chilly/gloomy period. CMC with a similar idea.

gfs_z500a_namer_34.png

Just looked at Euro on Windy and starting late Saturday through most of next week looks rough for our coast. 800 mi fetch with that sprawling high to the north feeding into that cut off low. Thankfully a few days before full moon to avoid higher astronomical tides. 

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yoda

yoda

Posted
Posted

Sounds like a fun night ahead for the region per the afternoon LWX AFD... also never seen thunder mentioned as being disruptive before... is that being said just because it's night time and could wake people up?

@high risk @MN Transplant 

NEAR TERM /THROUGH TONIGHT/...
As of mid afternoon, a warm front was dangling near the VA/NC
border, with a few other weak convergence or differential
heating zones noted roughly between the Blue Ridge and
Appalachian Mountains. This setup, combined with a frontal
system approaching from the west and south, will result in a
likelihood of showers and some thunderstorms for portions of the
region through tonight.

Central VA and vicinity:
A line of towering cumulus was evident in visible satellite
imagery along the Allegheny Front, and will likely evolve into a
cluster of showers and thunderstorms across west-central
Virginia through late afternoon. Any such convection should then
track generally eastward to northeastward toward the central
Shenandoah Valley and onto the piedmont before weakening as it
encounters more stable air in areas that have been shrouded by
low clouds much of the day.

Given 30 to 40 knots of flow within a few kilometers of the
surface, and surface- (or near surface) based CAPE on the order
of 1000+ J/kg, a few of these storms could become strong to
severe, and capable of gusty to damaging winds and hail.
Overall, the threat of severe weather appears to be limited
(i.e. marginal/isolated), and mainly focused on this evening.

Although forecast soundings indicate a threat for backbuilding,
forcing may be too weak and transient and the individual storm
motion too quick to allow enough heavy rainfall for flooding,
especially given the recent dry conditions in this area.

The most likely area/time period for storms is roughly from
Shenandoah Mountain to Staunton, Waynesboro, and Charlottesville
between 6pm and 10pm, with scattered showers and perhaps a few
weaker/elevated thunderstorms likely persisting much of the
night given forcing along an approaching warm front.

Western MD and vicinity:
Areas near and west of the Allegheny Front and north of
Petersburg WV will be located closer to stronger forcing from a
shortwave trough and associated surface low passing over OH/PA.
Similar to areas further south, CAPE likely becomes rooted at or
near the surface this evening, eclipsing 1000 J/kg at its peak.
Moderate shear is modest low-level curvature to the wind profile
could result in transient supercell structures, though the main
storm mode will likely be linear bands or clusters with an
associated risk for large hail, damaging wind gusts, or
possibly even an isolated tornado if supercells evolve.

Forecast soundings and low-level winds parallel to an
approaching cold front attached to the low could result in
training convection. HREF probabilities show potential for
localized 2+ inches of rainfall, which given somewhat higher
soil moisture in this area (relative to further south and east)
may result in a few isolated instances of flooding tonight.

The greatest risk area appears to be west of the Eastern
Continental Divide in Garrett County, closest to the
aforementioned trough/low. Timing wise, the threat looks to be
focused on the mid to late evening hours (8pm-midnight). East
and south of there into eastern West Virginia and western
Maryland east of the Allegheny Front, the threat may be more
isolated in nature.

Elsewhere:
Despite a strong near-surface stable layer, forecast soundings
indicate 600-1200 J/kg of CAPE aloft (lifting from ~875 mb) late
this evening. This, coupled with moderately strong warm/moist
advection overtop an approaching warm front could keep storms
going well into the overnight. The low-level stability should
preclude any gusty winds from reaching the surface, but hail
potential may linger. The low-level stable layer/temperature
inversion could also amplify the sound of thunder overnight,
making it rather disruptive. At least isolated thunderstorms are
possible for much of the night, though could end up being more
numerous at times given the strength of the approaching warm
front; nocturnal convection, however, is notoriously fickle and
hard to predict.

There will be a fair amount of moisture in the atmosphere, as
well, with PWs up to around 1.5" (1-2 SA above normal). That,
coupled with moisture flux into the area, could result in some
heavy downpours and perhaps an isolated instance or two of
nuisance flooding/ponding in urban or poor drainage areas.

&&

 

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MN Transplant

MN Transplant

Posted
Posted
13 minutes ago, yoda said:

Sounds like a fun night ahead for the region per the afternoon LWX AFD... also never seen thunder mentioned as being disruptive before... is that being said just because it's night time and could wake people up?

@high risk @MN Transplant 

NEAR TERM /THROUGH TONIGHT/...
As of mid afternoon, a warm front was dangling near the VA/NC
border, with a few other weak convergence or differential
heating zones noted roughly between the Blue Ridge and
Appalachian Mountains. This setup, combined with a frontal
system approaching from the west and south, will result in a
likelihood of showers and some thunderstorms for portions of the
region through tonight.

Central VA and vicinity:
A line of towering cumulus was evident in visible satellite
imagery along the Allegheny Front, and will likely evolve into a
cluster of showers and thunderstorms across west-central
Virginia through late afternoon. Any such convection should then
track generally eastward to northeastward toward the central
Shenandoah Valley and onto the piedmont before weakening as it
encounters more stable air in areas that have been shrouded by
low clouds much of the day.

Given 30 to 40 knots of flow within a few kilometers of the
surface, and surface- (or near surface) based CAPE on the order
of 1000+ J/kg, a few of these storms could become strong to
severe, and capable of gusty to damaging winds and hail.
Overall, the threat of severe weather appears to be limited
(i.e. marginal/isolated), and mainly focused on this evening.

Although forecast soundings indicate a threat for backbuilding,
forcing may be too weak and transient and the individual storm
motion too quick to allow enough heavy rainfall for flooding,
especially given the recent dry conditions in this area.

The most likely area/time period for storms is roughly from
Shenandoah Mountain to Staunton, Waynesboro, and Charlottesville
between 6pm and 10pm, with scattered showers and perhaps a few
weaker/elevated thunderstorms likely persisting much of the
night given forcing along an approaching warm front.

Western MD and vicinity:
Areas near and west of the Allegheny Front and north of
Petersburg WV will be located closer to stronger forcing from a
shortwave trough and associated surface low passing over OH/PA.
Similar to areas further south, CAPE likely becomes rooted at or
near the surface this evening, eclipsing 1000 J/kg at its peak.
Moderate shear is modest low-level curvature to the wind profile
could result in transient supercell structures, though the main
storm mode will likely be linear bands or clusters with an
associated risk for large hail, damaging wind gusts, or
possibly even an isolated tornado if supercells evolve.

Forecast soundings and low-level winds parallel to an
approaching cold front attached to the low could result in
training convection. HREF probabilities show potential for
localized 2+ inches of rainfall, which given somewhat higher
soil moisture in this area (relative to further south and east)
may result in a few isolated instances of flooding tonight.

The greatest risk area appears to be west of the Eastern
Continental Divide in Garrett County, closest to the
aforementioned trough/low. Timing wise, the threat looks to be
focused on the mid to late evening hours (8pm-midnight). East
and south of there into eastern West Virginia and western
Maryland east of the Allegheny Front, the threat may be more
isolated in nature.

Elsewhere:
Despite a strong near-surface stable layer, forecast soundings
indicate 600-1200 J/kg of CAPE aloft (lifting from ~875 mb) late
this evening. This, coupled with moderately strong warm/moist
advection overtop an approaching warm front could keep storms
going well into the overnight. The low-level stability should
preclude any gusty winds from reaching the surface, but hail
potential may linger. The low-level stable layer/temperature
inversion could also amplify the sound of thunder overnight,
making it rather disruptive. At least isolated thunderstorms are
possible for much of the night, though could end up being more
numerous at times given the strength of the approaching warm
front; nocturnal convection, however, is notoriously fickle and
hard to predict.

There will be a fair amount of moisture in the atmosphere, as
well, with PWs up to around 1.5" (1-2 SA above normal). That,
coupled with moisture flux into the area, could result in some
heavy downpours and perhaps an isolated instance or two of
nuisance flooding/ponding in urban or poor drainage areas.

&&

 

I’m guessing that they are being responsive to the recent interest in sound traveling due to the concert in DC on Sunday.

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