Convective Outlook

SPC 1730Z Day 2 Outlook
Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1206 PM CDT Mon Jul 22 2019

Valid 231200Z - 241200Z


Numerous thunderstorms with a few damaging wind gusts are possible
Tuesday mainly across the central and eastern Carolinas.

An upper high will be centered over the Four Corners states, with a
ridge extending north across WY and MT. Northern portions of this
ridge will break down Tuesday night as a shortwave trough moves
across ID and MT, and this feature will also support thunderstorms
through evening.

To the east, a deep upper trough will approach the Appalachians with
cooling aloft and substantial southerly winds. A cold front will
slowly move across eastern VA and the Carolinas, where a moist and
unstable air mass will support numerous daytime thunderstorms, some
producing strong wind gusts.

...Eastern NC/SC and extreme southeast VA...
A very moist air mass with mid 70s F dewpoints will exist ahead of
the cold front, and heating will lead to MUCAPE in excess of 2000
J/kg prior to frontal passage. Substantial lift along the front will
lead to early afternoon development, with numerous storms expected
from southeast VA across the Carolinas. Storms may be cellular at
first, but deep-layer shear and mean winds will be oriented parallel
to the front. The result should be merging outflows, with linear
structures advancing east throughout the day. Shear will be weak,
but numerous storms with substantial outflow will create
opportunities for marginally severe but locally damaging wind gusts.

...Southwest into central MT...
Batches of storms are likely to develop near the ID/MT border during
the afternoon with the upper disturbance which will eventually
flatten the ridge. A steep lapse rate environment will exist, with
generally weak winds below 700 mb. This may support small hail and
gusty winds, but severe weather is generally not anticipated as
storms continue into central MT through evening.

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Updated 22 July 2019 | 12:07 pm

SPC 1630Z Day 1 Outlook
Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1135 AM CDT Mon Jul 22 2019

Valid 221630Z - 231200Z


Scattered damaging winds are possible across portions of the
Mid-Atlantic States into southern New England, as well as the
Tennessee Valley, this afternoon to early evening.

...Mid-Atlantic States to southern New England...
Additional amplification of the large-scale trough over the eastern
CONUS will contribute to a slight cooling of mid-level temperatures
and strengthening southwesterly winds aloft coincident with a
slow-southeastward-moving front across the central Appalachians
toward parts of the Mid-Atlantic region. 

The coverage of yesterday's storms across most of this region has
impacted thermodynamic profiles, with surface temperatures/dewpoints
running at least several degrees lower than this time (late
morning/midday) yesterday. As noted in the prior Outlook discussion,
12Z soundings from Sterling, Wallops, Upton, Pittsburgh, and
Wilmington OH all sampled mean mixing ratios about 2-3 g/kg lower
compared to 12Z yesterday and have weaker mid-level lapse rates.

That said, moisture will steadily recover and ample insolation is
noted at midday across the Mid-Atlantic in the lee of the
Appalachians, with MLCAPE to 1500-2000 J/kg possible (highest near
the coast). As compared to yesterday, somewhat stronger wind
profiles between 2-6km AGL will also be a factor for individual
storm longevity/organized storms. Multicells will be common and the
possibility exists for a few transient supercells from far southern
New York/northern New Jersey into southern New England. Damaging
winds will be the most common risk through the afternoon into early

...Mid-South and Tennessee Valley...
A moist air mass (70-75F surface dewpoints) remains ahead of a
southeastward-moving cold front. As morning cloud cover thins,
increasing cumuliform/thunderstorm development are expected this
afternoon, particularly downstream of a pair of residual MCVs. Wet
microbursts yielding localized wind damage will be the main risk.

While weak vertical shear will tend to limit overall organization
and risk magnitude, a somewhat more focused/organized severe risk
may exist this afternoon into early evening across western/middle
Tennessee and nearby southern Kentucky and perhaps northern portions
of Mississippi/Alabama. Enhanced winds are noted with the MCV near
the Mississippi River, with 30-40 kt west-southwesterly winds
between 4-6 km in recent (16Z) Paducah, KY WFO-88D VWP data.

...Central/southern Rockies and adjacent High Plains...
Isolated thunderstorms will develop this afternoon and remain
largely confined to the higher terrain of Wyoming/Colorado/New
Mexico, although a few storms could drift into the immediately
adjacent High Plains. A belt of modest mid-level north/northwesterly
flow aloft will persist around the Four Corners/southern Rockies
upper ridge, yielding some threat for marginally severe hail/wind.

...Southeast/south-central Arizona...
On the southern periphery of the south-central Rockies-centered
upper ridge, 15-20 kt mid-level easterlies may help loosely organize
scattered thunderstorms that develop over the higher terrain during
the late afternoon and move toward the desert floor. Hot/deeply
mixed boundary layer will support vigorous downdrafts and the
possibility of severe-caliber winds and blowing dust late this
afternoon/early evening.

..Guyer/Nauslar.. 07/22/2019

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Updated 22 July 2019 | 11:56 am