STORM2K

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1251 AM CDT Sun May 19 2019

Valid 201200Z - 211200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE
EASTERN TX PANHANDLE...NORTHWEST TX...AND WESTERN/CENTRAL OK...

...SUMMARY...
Severe thunderstorms capable of all severe hazards, including strong
tornadoes, are expected across portions of the southern Plains on
Monday.

...SIGNIFICANT SEVERE WEATHER EVENT POSSIBLE ACROSS THE SOUTHERN
PLAINS ON MONDAY...

...Synopsis...
A strong shortwave trough is expected to move through the base of
mean western CONUS troughing, ejecting through the southern High
Plains late Monday night/early Tuesday morning. Recent guidance has
trended slower with the progression of shortwave trough. Strong
southwesterly flow aloft (i.e. 70-80 kt at 500 mb) will spread
across the southern and central Plains ahead of the approaching
shortwave trough. These winds aloft will strengthen as the shortwave
trough moves through, likely reaching 100 kt at 500 mb by early
Tuesday morning. Surface pattern will feature a deepening lee low
over southeast CO with a warm front initially extending
southeastward from this low across the eastern TX Panhandle to the
TX/OK border, and a dryline extending southward through the Permian
Basin.

Farther northeast, a pair of shortwave troughs will move from the
upper Great Lakes through the Northeast/Quebec. The more northerly
lead wave will move through Quebec during the first half of the
period while the more southerly wave in its wake moves across the
Northeast during the second half of the period. At the surface, low
associated with the lead wave will take a similar path across Quebec
while an attendant cold front sweeps across the Northeast.

...Southern/Central Plains...
A warm front near the Red River at 12Z Monday is expected to move
northward throughout the day amidst strong moisture advection.
Dewpoints south of the front will be in upper 60s/low 70s, resulting
in the development of moderate to strong instability within the warm
sector. Northward progression of the warm front may be mitigated
somewhat by the numerous warm-air advection showers and
thunderstorms expected north of this boundary (i.e. western/central
KS/OK border vicinity). Severe hail will be possible with this
elevated activity north of the warm front while the more significant
severe threat is expected along and south of the front.

Large-scale forcing for ascent is expected to be negligible until
after 00Z, resulting in some uncertainty regarding the primary
mechanism for convective initiation within the warm sector. One
mechanism will be the dryline, which could act to initiate multiple
rounds of storms over the TX Panhandle before it surges eastward
after 00Z. Another forcing mechanism will be warm advection, where
storms would initially be elevated but could become more
surface-based as intensity increases. Both of these mechanisms
suggest a predominantly discrete mode, although the warm advection
mechanism leaves some uncertainty where the most favored region for
initiation would be.

Overall kinematic environment across much of the region is very
impressive. 70+ kt of southwesterly 500 mb flow will gradually
spread eastward/northward across the TX Panhandle and into OK and
KS. At same time, a strong and persistent low-level jet will be in
place, with 40+ kt at 850 mb throughout the period. Surface winds
within the warm sector will likely be southeasterly at 15 to 20 kt.
All of these factors result in large, looping hodographs favorable
for discrete supercells capable of all severe hazards, including
significant tornadoes.

As the shortwave ejects out later in the period, linear MCS
development is anticipated. Wind profiles remain strong and this MCS
will likely be well-organized, resulting in a second round of severe
thunderstorms Monday night into Tuesday morning.

...Northeast...
Thunderstorms are expected to develop along and ahead of a cold
front progressing across the region. Favorable low-level moisture, a
well-mixed boundary layer, and strong unidirectional wind fields
will result in the potential for a few strong to severe storms. A
multicell mode is favored with damaging wind gusts as the primary
severe threat.

...MAXIMUM RISK BY HAZARD...
Tornado: 15% SIG - Moderate
Wind: 45% - Enhanced
Hail: 30% SIG - Enhanced

..Mosier.. 05/19/2019

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 PM CDT Sun May 19 2019

Valid 201200Z - 211200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM NORTHWEST
TEXAS INTO CENTRAL OKLAHOMA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN
NEW YORK INTO SOUTHERN NEW ENGLAND...

...SUMMARY...
Severe thunderstorms capable of all severe hazards, including strong
tornadoes, are expected across portions of the southern Plains on
Monday.

...SIGNIFICANT SEVERE WEATHER EVENT POSSIBLE ACROSS THE SOUTHERN
PLAINS ON MONDAY...

...Southern Plains...
A complicated, yet potentially higher-end severe weather scenario
will unfold across the southern Plains throughout the forecast
period. Height falls associated with an approaching longwave trough
centered over Arizona will overlie a strong surface dryline along
the New Mexico/Texas border, resulting in a north-south oriented
band of storms in that area around 12Z or so. These storms will
migrate northeastward and contain a threat for hail and damaging
wind gusts throughout the morning due to steep mid-level lapse rates
and supercellular wind profiles. A tornado threat may also exist on
the southern end of this activity - especially where convection can
become surface-based and remain discrete amidst with slightly higher
boundary layer moisture (i.e., upper 60s to 70s dewpoints).

The evolution of this early morning complex will impact the severe
risk in downstream areas of Oklahoma and northwest Texas through the
afternoon and evening. A variety of operational models and CAMS
suggest that some portions of this MCS will interact with the
northward-moving surface warm front and possibly retard its movement
into northern portions of the outlook area (near the OK/KS border
area). Meanwhile, most model solutions suggest the development of
isolated convection out ahead of any ongoing MCS activity - with
this risk most evident across portions of southwestern Oklahoma and
vicinity. These storms are expected to reside in a environmental
parameter space supportive of all severe hazards, including
significant hail and strong tornadoes, and this risk should be
maximized as long as discrete, cellular convection can persist
through the forecast period. This risk will become further enhanced
by an increasingly strong low-level jet across the region during the
early evening should storms maintain a relatively discrete mode.

Farther downstream across eastern Oklahoma and vicinity, uncertainty
remains regarding specific positioning of the warm front, although
most model solutions persist in developing convection across the
region via either an upstream MCS moving into the region and/or
isolated convection forming along and south of the front. The
potential for isolated convection is plausible given surface
heating, weak mid-level inhibition, and broadly confluent
warm-sector low-level flow - even in the absence of any forcing for
ascent aloft. The environment along and south of any warm front or
convective outflow will support all severe hazards, including strong
tornadoes. The inherited risk areas have been expanded eastward
into western Arkansas to account for severe potential in those
areas.

North of the warm front (across Kansas and vicinity), steep
mid-level lapse rates and strong vertical shear will support
primarily elevated storms with a threat of large hail. Steep
mid-level lapse rates will also exist in portions of Colorado,
although the development of any substantial surface-based
instability will depend on convective evolution across the Texas
Panhandle and vicinity. Storms in that area will have at least a
threat for large hail.

Late in the forecast period (after about 06Z Tuesday), an ejecting
mid-level trough over the Four Corners vicinity will take on a
negative tilt while moving toward the High Plains. Sustained
low-level advection across the warm sector (and resultant moderate
instability) should result in development of another line of storms
across the Texas South Plains/Panhandle vicinity. These storms
should reach the I-35 corridor of Oklahoma and north Texas by the
end of the forecast period, with damaging wind and isolated
tornadoes remaining possible.

...Mid-Atlantic and Northeast...
Surface heating ahead of an approaching cold front near the
Appalachians will result in steepening low-level lapse rates and
weak instability. Mid-level lapse rates will be relatively poor,
although the glancing influence of an approaching wave over the
eastern Great Lakes will result in development of a few convective
cells along and ahead of the front. Strong flow aloft and downward
transport of that momentum near storms will result in a few damaging
wind gusts. This risk should wane with eastward extent in response
to nocturnal stabilization.

...MAXIMUM RISK BY HAZARD...
Tornado: 15% SIG - Moderate
Wind: 45% - Enhanced
Hail: 30% SIG - Enhanced

..Cook.. 05/19/2019