SPC - No watches are valid as of Mon Jul 24 06:05:02 UTC 2017

No watches are valid as of Mon Jul 24 06:05:02 UTC 2017.


SPC MD 1413

MD 1413 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN MARYLAND INTO NEW JERSEY
MD 1413 Image


Mesoscale Discussion 1413
NWS Storm Prediction Center Norman OK
1141 PM CDT Sun Jul 23 2017

Areas affected...Eastern Maryland into New Jersey

Concerning...Severe potential...Watch unlikely 

Valid 240441Z - 240645Z

Probability of Watch Issuance...20 percent

SUMMARY...Areas of storms may increase across the region, but are
expected to mainly be non-severe over land. A few strong wind gusts
appear most likely.

DISCUSSION...Modest warm advection in the low-levels is helping to
create lift, resulting in a rash of thunderstorm development from
eastern MD into southern NJ. Recently, an impressive supercell had
developed near the NJ coast and is now offshore. To the west, cells
have shown mainly weak/broad rotation at times. This corresponds
well with observed wind profiles, which show veering winds with
height, but with weak magnitude resulting in small hodographs.

Models show this general area of storms lifting east/northeastward
tonight, with perhaps some increase in storm intensity over the
ocean. A few strong wind gusts cannot be ruled out with any cells
over land, especially if they show signs of rotation, or, if they
conglomerate into larger clusters. The weak lapse rate environment,
unfavorable time of day, and modest low-level shear should keep
tornado threat minimal. However, trends will continue to be
monitored.

..Jewell/Weiss.. 07/24/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...PHI...CTP...LWX...

LAT...LON   39297369 39157487 38897653 39057674 39537688 39937642
            40287562 40567364 40727240 40637214 40197188 39617214
            39457233 39297369 

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SPC Jul 24, 2017 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1252 AM CDT Mon Jul 24 2017

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE NORTHEAST STATES AND MID ATLANTIC AREA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE SOUTHEAST STATES...

...SUMMARY...
Isolated strong/severe storms may occur over portions of the
northern Plains vicinity, as well as across parts of the Northeast
States, Mid-Atlantic, and Mid-South.

...Synopsis...

Synoptic upper trough will continue through the Northeast U.S.
today, while an upstream trough advances through the Canadian
Prairies. A low-amplitude impulse now moving along the WY/MT border
will continue through the Dakotas and weaken. Cutoff upper low
should remain over northern CA. 

At the surface a quasi-stationary front will persist from NY to
southern New England. A cold front will move into the Middle
Atlantic area with trailing portion likely to stall over the TN
Valley.  Farther west a cold front will move through the northern
Plains in association with the Canadian shortwave trough. Warm front
will lift slowly north through the northern Plains and upper
Mississippi Valley.

...Northern Plains and Upper Mississippi Valley area...

Modified continental-polar air with dewpoints generally in the 50s
to near 60F will advect into the northern Plains beneath steep
mid-level lapse rates associated with a warm elevated-mixed layer,
contributing to destabilization. The atmosphere in this region
should become moderately unstable, but strong convective inhibition
may limit surface-based thunderstorm initiation until later this
afternoon when a few storms could form over central SD in
association with the weakening shortwave trough. Other storms might
also develop farther west within the more deeply mixed regime across
the western Dakotas and along the southeast-advancing cold front.
Given generally weak forcing aloft and moderate to strong convective
inhibition, storm coverage will probably remain isolated, but the
thermodynamic environment would support a conditional risk for
downburst winds and hail. Any storms that form during the day will
likely diminish with loss of heating. However, additional storms may
occur overnight across MN within zone of isentropic ascent north of
the warm front. Some of this activity could pose a risk for
marginally severe hail.  

...Northeast States and Mid Atlantic...

In wake of early morning convection associated with lead shortwave
trough, storms will once again develop along and ahead of the cold
front in the moist, weakly capped warm sector. Pockets of diabatic
warming will promote destabilization of the boundary layer, but the
thermodynamic environment will remain weak in most areas due in part
to poor mid-level lapse rates. Westerly unidirectional winds aloft
will reside across this region supporting 35-45 kt effective bulk
shear. A few storms might develop some mid-level updraft rotation
and evolve into bowing structures with a threat for a few locally
strong to damaging wind gusts. However, expected weak thermodynamic
environment should remain a limiting factor for a robust severe
risk. 

...Tennessee Valley area and Southeast States...

The atmosphere in this region will become moderately unstable, and
storms will likely redevelop along and south of the cold front. Weak
vertical shear will promote multicell and pulse storms. A few of the
stronger storms might produce locally strong to marginally severe
wind gusts from mid afternoon to early evening.

..Dial/Dean.. 07/24/2017

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SPC Jul 24, 2017 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook
      
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1255 AM CDT Mon Jul 24 2017

Valid 251200Z - 261200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
EASTERN DAKOTAS EAST INTO NORTHWEST WISCONSIN AND WESTERN UPPER
MICHIGAN...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK AREA AND EXTENDING AS FAR SOUTH AS NEBRASKA AND IOWA...

...SUMMARY...
Strong/locally severe thunderstorms will be possible across portions
of the north-central U.S. Tuesday.

...Synopsis...
As an upper trough across the Northeast moves east and eventually
offshore, and a second trough lingers near the West Coast, ridging
will prevail across much of the country.  During the second half of
the period, this ridging will become suppressed over the
north-central U.S., as weak short-wave troughing moving
east-northeast out of the Rockies and into the Plains phases loosely
with a low/trough crossing the Canadian Prairie.  

At the surface, a cold front -- associated with the aforementioned
Prairie/Plains upper troughing -- is forecast to move southeast
across the northern Plains, eventually extending from the upper
Mississippi Valley area southwestward across the central Plains by
late in the period.  Elsewhere, a weak/lingering front extending
from VA/NC and westward into the mid South will drift very slowly
southward, as surface high pressure shifts slowly east across the
Great Lakes into the Northeast.

...North-central states...
Daytime heating of a moistening warm sector will support substantial
diurnal destabilization, with afternoon mixed-layer CAPE values
averaging 1500 to 2500 J/kg expected to evolve near/ahead of the
advancing cold front.  Thus will likely prove sufficient, in
combination with ascent focused near the front, to allow isolated to
scattered storms to develop from the Minnesota vicinity
west-southwest along the front to the northern High Plains area.  

The strongest mid-level westerlies are forecast to remain across the
North Dakota/northern Minnesota area, though a weaker/secondary
speed max shifting out of the Rockies suggests that ample flow for
isolated/organized cells will extend as far southwest as eastern
Wyoming and into Nebraska.  As such, will maintain a broad area of
5%/MRGL risk across the north-central U.S., with greatest (SLGT
risk) probabilities focused over the eastern Dakotas/Minnesota
through the afternoon and early evening.  With time, upscale growth
of storms into one or two MCSs is possible, with risk possibly
spreading east of the upper Mississippi Valley later in the evening.
 Convection is expected to diminish overnight, due to a decrease in
instability -- both diurnally, and with eastward extent into the
upper Great Lakes area.

..Goss.. 07/24/2017

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