RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Fri Feb 22 07:21:02 UTC 2019.
No Mesoscale Discussions are in effect as of Fri Feb 22 07:21:02 UTC 2019.
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1148 PM CST Thu Feb 21 2019
Valid 221200Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EAST TEXAS
INTO THE LOWER MISSISSIPPI VALLEY...
...SUMMARY...
Strong thunderstorms may impact portions of the lower Mississippi
Valley this afternoon, expanding into the ArkLaTex vicinity by late
tonight, accompanied by at least some risk for severe weather.
...Synopsis...
A strong shortwave trough over the Southwest is expected to
intensify and become negatively tilted as it moves
east-northeastward towards the Southern Plains by Saturday morning.
In response, cyclogenesis is expected in the lee of the southern
Rockies, and a cold front will begin to surge eastward into portions
of West TX late tonight. Further east, a warm front will move slowly
northward during the day across portions of east TX into the lower
Mississippi Valley, with some acceleration northward into the
ArkLaTex region late tonight as the surface low deepens to the west.
...Lower MS Valley Region...
Showers and scattered thunderstorms will likely be ongoing at the
start of the period and will continue through much of the day due to
persistent warm advection north of the warm front. While rich
low-level moisture (characterized by mid-upper 60s F dewpoints) will
spread slowly northward through the day south of the boundary,
widespread cloudiness and only modest midlevel lapse rates will tend
to limit instability, with MLCAPE likely remaining in the 500-1000
J/kg range across the warm sector. With the primary upper system and
associated large-scale ascent remaining well to the west during the
day, the greatest coverage of convection is expected to remain north
of the boundary, though there will be some potential for a few
surface-based storms during the afternoon across portions of
central/southern MS and perhaps northern LA, with an attendant risk
of marginally severe hail and locally damaging wind. While a brief
tornado cannot be ruled out with any cell that interacts with the
surface boundary, the potential for substantial surface-based
development appears too limited at this time to introduce tornado
probabilities.
Elevated convection from southeast AR into northern MS may also pose
some severe risk, especially later tonight when somewhat steeper
midlevel lapse rates begin to move in from the west as the upper
trough approaches and the surface boundary gradually moves
northward.
...ArkLaTex Region Late Tonight...
As the primary shortwave moves into the southern Plains late in the
period, elevated storms may develop across portions of eastern OK/TX
into the ArkLaTex by early Saturday morning. Steep midlevel lapse
rates and sufficient effective shear will support a conditional risk
of hail and perhaps locally damaging wind with the strongest cells,
though the coverage and southward extent of deep convection across
the region prior to the end of the period at 12Z remains uncertain
at this time.
..Dean/Squitieri.. 02/22/2019
Read more
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1133 PM CST Thu Feb 21 2019
Valid 231200Z - 241200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SE
AR/NORTHERN MS TO WESTERN TN...
...SUMMARY...
Scattered severe thunderstorms are expected to form along a corridor
from the lower Mississippi Valley into portions of the Tennessee
Valley. Damaging winds and tornadoes are possible.
...Lower MS Valley to TN Valley...
Late-evening water vapor imagery depicts a well-defined upper low
near the lower CO River Valley. This feature is forecast to eject
into the southern Plains by the start of the day2 period then lift
into the Mid MS Valley by mid day Saturday as an intense 500mb speed
max translates across OK into MO. Mid-level speed max will shift
into western PA by Sunday morning. Impressive 12hr 500mb height
falls will spread across the southern High Plains into MO with the
southern extent of large-scale forcing for ascent expected to glance
the ENH Risk region.
Latest model guidance suggests this low-latitude system will induce
a lee surface low over northeast NM late Friday. Surface low should
track along the KS/OK border before ejecting northeast into
southeast IA by early evening. In response to this developing
cyclone, higher-PW air mass will surge inland as a warm front lifts
across the Arklatex ahead of a surging cold front. Latest NAM
guidance is not as aggressive with destabilization from eastern OK
into KY due to a slower advancing warm front. Have adjusted northern
severe probabilities to reflect the possibility that buoyancy, and
certainly surface-based instability, may be retarded at higher
latitudes. Forecast shear profiles are impressive and supportive of
organized severe convection. At this time it appears severe
convection should evolve along the advancing cold front with
supercells possible prior to possible squall line development.
Discrete pre-frontal storms may develop which could have a
proclivity to produce tornadoes if surface-based instability
materializes as expected across the ENH risk, and surrounding areas.
Severe threat will migrate into the TN Valley and central Gulf
States during the latter half of the period. In addition to the
tornado threat, damaging winds are likely with the frontal
convection.
...MAXIMUM RISK BY HAZARD...
Tornado: 10% SIG - Enhanced
Wind: 30% - Enhanced
Hail: 15% - Slight
..Darrow.. 02/22/2019
Read more
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0113 AM CST Fri Feb 22 2019
Valid 241200Z - 251200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ALONG THE
CENTRAL GULF COAST...
...SUMMARY...
A few strong storms may occur Sunday morning along the central Gulf
Coast.
...Central Gulf Coast...
Strong upper trough that ejects across the Mid MS Valley/OH Valley
region late in the day2 period will flatten heights across the
northeastern US Sunday. Associated deep surface low will lift into
QC during the day and occlude. While primary large-scale forcing for
ascent will spread well north of appreciable buoyancy, trailing
surface front is expected to provide the focus for deep convection,
especially near the Gulf Coast. The greatest risk for a few strong
storms will occur before 18z from southeast LA into the FL Panhandle
ahead of the wind shift. Model guidance suggests a narrow corridor
of pre-frontal moisture will advance inland such that near-surface
based instability could support a few strong storms along southern
fringe of stronger cyclonic flow aloft. At this time it appears
gusty winds would be the primary threat with a loosely organized
frontal squall line. Frontal convection should weaken during the
afternoon as it encounters increasingly hostile air mass downstream.
..Darrow.. 02/22/2019
Read more
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0118 AM CST Fri Feb 22 2019
Valid 221200Z - 231200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHWEST TEXAS...
...Synopsis...
A vigorous mid-level shortwave trough will eject into the Southern
Plains, inducing strong surface low development and lee-troughing
across the southern High Plains during the day. As such, strong
south-southwesterly winds, transporting drier air to the High
Plains, will promote conditions favorable for fire spread given the
lack of recent rainfall and drying, fine fuels in place.
...Southeast New Mexico into west-central and southwest Texas...
During the afternoon hours, temperatures will rise well into the 60s
across much of west-southwest Texas, spanning northwestward into
southeast New Mexico, as a dryline associated with the
aforementioned surface cyclone advances eastward. West of the
dryline, 10-20% RH and 15-20 mph south-southwesterly winds will be
common, hence an elevated delineation from east-central New Mexico
down the southwest Texas/Mexico border. Within proximity of the
Davis Mountains and immediately surrounding mountain ranges,
downslope flow will promote surface sustained southwesterly winds
around 20-25 mph, with enhanced mixing, supporting more widespread
RH values closer to 10%, warranting a critical delineation for the
area. By evening, nocturnal cooling will encourage RH recovery and
temper the potential for wildfire spread.
..Squitieri.. 02/22/2019
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
|
