RSS Mesoscale Discussions from Storm Prediction Center
WW 98 SEVERE TSTM TX 241650Z - 250000Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 98
NWS Storm Prediction Center Norman OK
1150 AM CDT Wed Apr 24 2019
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Parts of south central Texas and the Hill Country
* Effective this Wednesday morning and evening from 1150 AM until
700 PM CDT.
* Primary threats include...
Scattered large hail events to 1.5 inches in diameter likely
Isolated damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Mainly elevated thunderstorms are expected to continue
developing through the afternoon, with large hail the main threat.
Isolated damaging gusts, and perhaps a tornado, will be possible
with storms closer to the outflow boundary that will sag southward
near the southern edge of the watch area.
The severe thunderstorm watch area is approximately along and 60
statute miles north and south of a line from 80 miles west northwest
of Cotulla TX to 50 miles east southeast of Austin TX. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU8).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
23030.
...Thompson
Read more
WW 0098 Status Updates
STATUS REPORT ON WW 46
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 NNW RWI
TO 20 SE RZZ TO 30 SSE RIC TO 30 NNE RIC.
..SQUITIERI..04/08/19
ATTN...WFO...MHX...AKQ...RAH...
STATUS REPORT FOR WS 46
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
NCC013-015-029-041-053-065-073-079-091-101-107-117-127-139-143-
147-187-191-195-090040-
NC
. NORTH CAROLINA COUNTIES INCLUDED ARE
BEAUFORT BERTIE CAMDEN
CHOWAN CURRITUCK EDGECOMBE
GATES GREENE HERTFORD
JOHNSTON LENOIR MARTIN
NASH PASQUOTANK PERQUIMANS
PITT WASHINGTON WAYNE
WILSON
VAC001-057-073-093-095-097-103-115-119-131-175-199-550-620-650-
700-710-735-740-800-810-830-090040-
VA
. VIRGINIA COUNTIES INCLUDED ARE
ACCOMACK ESSEX GLOUCESTER
ISLE OF WIGHT JAMES CITY KING AND QUEEN
LANCASTER MATHEWS MIDDLESEX
NORTHAMPTON SOUTHAMPTON YORK
Read more
No Mesoscale Discussions are in effect as of Wed Apr 24 17:32:03 UTC 2019.
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 AM CDT Wed Apr 24 2019
Valid 241300Z - 251200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A LARGE PART
OF SOUTHERN INTO EASTERN TEXAS AND WESTERN LOUISIANA...
...SUMMARY...
Thunderstorms associated with large hail, wind damage and a tornado
threat are expected to develop across parts of south-central and
southeast Texas today into western Louisiana tonight.
...Texas to Louisiana...
A low-latitude upper trough centered over Chihuahua Mexico early
this morning will reach central Texas by evening while generally
maintaining a slight positive tilt. As this occurs, a ribbon of
steadily strengthening mid/high-level southwesterly winds (50+ kt at
500mb) will overspread much of south/southeast Texas especially late
today and tonight.
Regenerative showers and thunderstorms are ongoing this morning from
the Rio Grande Valley to east-central/northeast Texas, with this
convection and related outflow continuing to reinforce a composite
southwest/northeast-oriented front. Although a couple of strong
storms could occur early today, the primary severe risk is expected
later today, likely increasing across south-central Texas/Rio Grande
Valley this afternoon.
One key uncertainty related to the magnitude of the overall severe
risk remains the exact disposition of early-day convection across
the region and subsequent air mass impacts. The RAP in particular
suggests heating and related low-level lapse rates may remain
somewhat muted owing to lingering cloud/scattered precipitation,
aside from outflow influences in some areas. Even so, a diurnal
destabilization trend with pockets of moderate-caliber buoyancy will
occur in conjunction with an increase in moist southerly flow
near/above the surface. The 12Z observed sounding from Corpus
Christi sampled a very moisture-rich air mass with a 15 g/kg
mean-mixing ratio and a Precipitable Water value of 1.78, which are
near daily climatological record values.
Some supercells with an associated risk for large hail, severe
gusts, and a tornado risk are feasible, especially with initial
development this afternoon. However, over time and with eastward
extent, a mixed convective mode seems likely toward across
south-central Texas Hill County and Edwards Plateau vicinities. The
late-day acceleration of the cold front, some flow weakness around
3km AGL, and shear orientation to the boundary all suggest that a
more linear evolution should become prevalent, with the possibility
of embedded bows/mesovortices given the magnitude of the low-level
shear/SRH. These storms will spread toward/east of I-35 corridor
toward southeast Texas this evening. It is still possible that
severe wind gusts may become a bit more widespread as stronger
700-500mb flow becomes coincident with a 40-kt southerly low-level
jet in vicinity of a weak surface wave, although the potential for a
couple of squall-line embedded tornadoes will also linger this
evening.
Will maintain current risk category given some lingering forecast
uncertainties, but subsequent outlook updates will continue to
reevaluate observational/short-guidance trends for a possible
Enhanced Risk upgrade for portions of south-central/southeast Texas.
..Guyer/Mosier.. 04/24/2019
Read more
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1117 AM CDT Wed Apr 24 2019
Valid 241630Z - 251200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH EARLY
TONIGHT FROM SOUTH CENTRAL INTO SOUTHEAST TX AND WESTERN LA...
...SUMMARY...
Thunderstorms associated with large hail, wind damage and a tornado
threat are expected to develop across parts of south-central and
southeast Texas today into western Louisiana tonight.
...South central/southeast TX into western LA through tonight...
A midlevel shortwave trough over northern Mexico will translate
eastward to central/east TX by the end of the period. Weak surface
cyclogenesis is expected along stalled baroclinic zone across
central TX in advance of the midlevel trough. However, the surface
pattern is complicated by convective outflow that is still moving
southeastward past San Antonio as of late morning. The primary
corridor of severe-storm threat this afternoon into tonight should
be along this outflow boundary from south central into southeast TX.
Boundary-layer dewpoints of 67-70 F and surface heating in cloud
breaks (beneath midlevel lapse rates greater than 8 C/km) will drive
MLCAPE of 1500-2000 J/kg. Deep-layer vertical shear will be
favorable for supercells, with an increase in low-level shear
expected immediately east of the ejecting midlevel trough and weak
surface wave. Storm mode will likely be a mix of
clusters/supercells this afternoon, growing into a QLCS by this
evening. Low-level shear/hodograph curvature will favor some
tornado threat with supercells/clusters along the residual outflow
boundary and adjacent northern part of the warm sector. Damaging
winds and large hail will also be possible with this convection into
tonight as it reaches the TX/LA border region.
...Northeast WY and vicinity this afternoon...
A mid-upper speed max is cresting the larger-scale ridge and will
move east-southeastward over the northern High Plains this
afternoon/evening. Despite marginal low-level moisture,
sufficiently steep low-midlevel lapse rates will support some
low-topped convection this afternoon in advance of the midlevel
trough. Gusty winds will be possible given the steep low-level
lapse rates/evaporational cooling potential, though severe winds
appear unlikely.
..Thompson/Squitieri.. 04/24/2019
Read more
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Wed Apr 24 2019
Valid 251200Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
THE LOWER MS VALLEY INTO THE CENTRAL GULF COAST REGION...
...SUMMARY...
Thunderstorms associated with a wind damage and isolated tornado
threat are expected over parts of the lower Mississippi Valley
through the central Gulf Coast region Thursday.
...Lower Mississippi Valley through central Gulf Coast region...
Model consensus is that a progressive southern-stream upper trough
now over northern Mexico will reach the lower MS Valley Thursday
morning and continue through the Gulf Coast states during the day,
before reaching the Carolinas early Friday. Attendant surface low
should be near the ArkLaTex by 12Z with trailing cold front
extending south through east TX, and warm front stretching eastward
through central MS into southwest AL. By the end of the period the
cold front should extend from the OH Valley through the eastern TN
Valley into the central Gulf Coast region. Thunderstorms will likely
be ongoing ahead of the cold front within corridor of ascent along
the warm conveyor belt across a portion of the lower MS Valley. Some
of this activity might be organized with line and bowing segments,
and may pose an ongoing threat for mainly isolated damaging wind.
Farther downstream, the primary destabilization process will result
from the advection of upper 60s F dewpoints inland, but instability
will be tempered by weak lapse rates and widespread clouds with
MLCAPE from 1000-1500 J/kg. A 60+ kt mid-upper jet accompanying the
shortwave trough coupled with the low-level jet will contribute to
45-55 kt effective bulk shear along with 200-300 m2/s2 sfc-1 km
storm relative helicity. This environment should promote a few
organized storms embedded within lines and clusters with bowing
segments and a few supercells possible supporting a threat for
mainly isolated damaging wind and possibly a few tornadoes as
activity develops east during the day.
...MAXIMUM RISK BY HAZARD...
Tornado: 5% - Slight
Wind: 15% - Slight
Hail: 5% - Marginal
..Dial.. 04/24/2019
Read more
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1035 AM CDT Wed Apr 24 2019
Valid 241700Z - 251200Z
...NO CRITICAL AREAS...
The forecast remains on track with locally elevated conditions
expected to develop across portions of northeast Montana and
western/northern North Dakota this afternoon. Please see the
discussion below for more details.
..Nauslar.. 04/24/2019
.PREV DISCUSSION... /ISSUED 0113 AM CDT Wed Apr 24 2019/
...Synopsis...
An upper-level low located over portions of West Texas into northern
Mexico will lift northeast throughout the day into the lower
Mississippi Valley. Farther north, a zonal flow pattern along the
northern tier of the CONUS will begin to break down, with an
upper-level ridge building into the Pacific Northwest and a
short-wave trough developing over the Northern Plains. Mid-level
flow associated with the aforementioned trough will be marginally
enhanced, near 40-50 kt. Afternoon mixing will result in sustained
surface winds of 15-20 mph, while RH values fall into the 20-25%
range. These processes should result in locally elevated
fire-weather conditions across portions of eastern Montana and the
Dakotas. Fuels across the region remain marginally receptive, and
with chances for afternoon thunderstorms/wetting rains across some
portions of the region, no highlights have been introduced at this
time.
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
|
