dimanche 14 avril 2019

Central Great Lakes Sector

Central Great Lakes sector loop

Southeast Sector

Southeast sector loop

Apr 14, 2019 1300 UTC Day 1 Convective Outlook

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0752 AM CDT Sun Apr 14 2019

   Valid 141300Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
   WESTERN CAROLINAS TO PORTIONS OF PENNSYLVANIA AND OHIO...

   ...SUMMARY...
   Severe thunderstorms are forecast today in parts of the Ohio Valley
   southward through the southern Appalachians and northeast Gulf
   Coast. Severe thunderstorms are possible this evening/tonight east
   of the Appalachians from the Carolina Piedmont northward into parts
   of the Mid-Atlantic states.

   ...Synopsis...
   In mid/upper levels, a synoptic-scale trough is evident in moisture-
   channel imagery from MN/IA across the Ozarks and southwestward over
   south TX, with embedded vorticity max and remnant low over the
   western Ozarks region.  This trough will move east-northeastward to
   a 00Z position from Upper MI to the IL/IN border, western TN, MS,
   and southeastern LA.  By 12Z the trough should lost amplitude, but
   still remain large and well-defined, from southern ON to WV, the
   Carolinas, and southern/eastern GA.

   At the surface, 11Z analysis showed an elongated surface cyclone in
   the PAH-MEM corridor.  A more-coherent low is forecast to
   consolidate through midday then move northeastward to near the CLE/
   CAK area by 00Z, then over or very near VT by 12Z.  The associated
   leading cold front was drawn from the low across northern/
   southwestern AL and south of southeastern LA over the Gulf.  A
   secondary/reinforcing cold front extended southwestward over AR.  By
   00Z, the main front should reach eastern OH, WV, the western
   Carolinas, and central/southern GA.  By 12Z, the front is forecast
   over the southeastern NY/NJ area, then over Atlantic waters to south
   FL.  A warm front, drawn initially in wavy fashion over eastern TN
   and western/northern NC -- will shift northward erratically through
   the afternoon, catching up to a synoptic boundary initially
   extending from the low east-northeastward across northern portions
   of KY/WV/MD.  The combined warm front then should move northward
   through much of the Mid-Atlantic region.

   ...Upper Ohio Valley, Mid-Atlantic to southeastern CONUS...
   Scattered thunderstorms are expected to move from southwest to
   northeast across the outlook area through this evening, offering a
   primary threat of damaging to severe gusts, but with a few tornadoes
   also possible.

   A broken, messy band of precip and embedded thunderstorms is ongoing
   ahead of the front from portions of southeastern TN across the
   western FL Panhandle, with at least isolated severe potential
   remaining in a low-CAPE/high-shear setting.  Refer to the remaining
   portions of watches 57-59, and accompanying mesoscale discussions,
   for more on the near-term scenario.

   An extensive shield of clouds/precip is apparent in a prefrontal
   low-level warm-advection/moisture-transport zone from eastern TN
   northward over much of KY/OH/IN.  A narrow corridor of
   destabilization is expected behind this precip and ahead of the
   low/front today, related to pockets of surface-diabatic heating and
   theta-e advection in the warm sector.  This and weak MLCINH will
   offset modest midlevel lapse rates enough to support scattered
   thunderstorms along/ahead of the surface cold front, including
   prefrontal confluence/convergence lines.  Convection generally will
   assume quasi-linear configurations with embedded LEWPs, bowing
   segments, and perhaps a few supercells possible.

   The environment will be characterized by strong deep-layer/speed
   shear and modest but sufficient buoyancy, with 500-mb winds
   strengthening to more than 70 kt over much of the central
   Appalachians region, and 45-60 kt of 850-mb flow crossing the same
   area. Buoyancy fields will be rather fragmented, but with general
   500-1000 J/jg MLCAPE values spreading northeastward over eastern
   KY/OH and over areas from the Blue Ridge eastward.  A relative min
   in low-level theta-e and buoyancy is likely in higher elevations
   from southwestern VA northeastward, but with at least marginal
   instability to support convection.  Bands of convection should
   shift/form east of the mountains with time as well, also offering a
   dominant wind threat and secondary tornado potential in the
   strong-shear environment.  Overall severe potential is expected to
   diminish after dark, and as the stronger upper support and mass
   response ejects northeastward in step with the trough aloft.

   ..Edwards/Wendt.. 04/14/2019

https://www.spc.noaa.gov/products/md/md0337.html

Valid MD ImageMD 337 graphic

https://www.spc.noaa.gov/products/watch/

Valid WW ImageWW0059 RadarWW0058 RadarWW0057 Radar

SPC Apr 14, 2019 1300Z Thunderstorm Outlook

samedi 13 avril 2019

NWS Forecast Office Little Rock, AR

A strong storm system will bring showers and thunderstorms to the region this weekend. Some of these storms could be strong to severe Saturday afternoon through the evening hours generally south of a Texarkana to Little Rock to West Memphis line. The primary concern at this time is strong winds but tornadoes, some strong, will be possible across far southeastern Arkansas.

NWS Forecast Office Jackson, MS

A significant severe weather outbreak is likely this afternoon into early Sunday morning. Tornadoes are likely throughout the entire region with some strong and long track tornadoes possible. Large hail and damaging wind gusts will be a significant threat as well. We advise everyone to stay weather aware this afternoon and overnight!

NWS Lake Charles

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHEAST TEXAS AND WESTERN/CENTRAL LOUISIANA... 

Severe thunderstorms will be possible Saturday afternoon/evening from southeast Texas northeastward through Louisiana and into parts of the Tennessee Valley. All modes of severe weather will be possible. This includes damaging winds, hail, tornadoes, and flash flooding. 

NWS Forecast Office Shreveport, LA

There is a risk for severe storms across much of Four State Region today and into this evening. The main threat this morning will be large hail and damaging winds. However, the threat will increase this afternoon during peak daytime heating. Tornadoes, large hail, damaging winds, and locally heavy rainfall will be possible. The severe weather threat should diminish by late this evening.

Southern Mississippi Valley Sector

Southern Mississippi Valley sector loop

South Plains Sector

South Plains sector loop

Public Severe Weather Outlook (PWO) https://www.spc.noaa.gov/products/outlook/pwo.html

201904130743 PWO graphicshttps://www.spc.noaa.gov/products/outlook/archive/2019/pwo.mp4

ZCZNote: Multimedia briefing MP4. Please note the briefing may be out of date 5 hours after its issuance and there will be no subsequent updates during the day. Please send comments or questions to spc.feedback@noaa.gov or via the feedback page. 
View What is a Watch? clip.

C SPCPWOSPC ALL
   WOUS40 KWNS 130742
   ALZ000-ARZ000-LAZ000-MSZ000-TXZ000-131800-

   PUBLIC SEVERE WEATHER OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0242 AM CDT SAT APR 13 2019

   ...Severe thunderstorms expected over parts of the East Texas to
   lower Mississippi Valley region later today and tonight...

   * LOCATIONS...
     Central and northern Louisiana
     Mississippi
     East Texas
     Southern Arkansas
     Western Alabama

   * HAZARDS...
     Several tornadoes, a few intense
     Widespread damaging winds
     Scattered large hail, some baseball size

   * SUMMARY...
     Numerous severe thunderstorms capable of producing tornadoes,
     wind damage and large hail, are expected across parts of east
     Texas, Louisiana, southern Arkansas, Mississippi, western
     Alabama and surrounding areas today and tonight. The greatest
     risk is from east Texas to central Mississippi.

   Preparedness actions...

   Review your severe weather safety procedures for the possibility
   of dangerous weather today. Stay tuned to NOAA Weather Radio, 
   weather.gov, or other media for watches and warnings. A tornado
   watch means that conditions are favorable for tornadoes to form
   during the next several hours. If a tornado warning is issued for
   your area, move to a place of safety, ideally in a basement or
   interior room on the lowest floor of a sturdy building.

   &&

   ..Edwards.. 04/13/2019

SPC Apr 13, 2019 0600Z Thunderstorm Outlook

Current Mesoscale Discussions

Valid MD ImageMD 315 graphicMesoscale Discussion 0315
   NWS Storm Prediction Center Norman OK
   0450 AM CDT Sat Apr 13 2019

   Areas affected...portions of west-central Texas southward toward the
   Rio Grande

   Concerning...Tornado Watch 49...

   Valid 130950Z - 131045Z

   The severe weather threat for Tornado Watch 49 continues.

   SUMMARY...The severe threat continues across WW 49.

   DISCUSSION...Convection has generally struggled to deepen across the
   WW area this morning, although one cell recently crossed the Rio
   Grande near DFX.  This storm is surviving despite weak inhibition,
   and has a threat of all modes of severe as long as it can persist.

   Uncertainty persists with regard to the extent of convection across
   the region. However, it appears that severe convection will remain
   possible through the entirety of the valid WW period as the region
   remains under the grazing influence of ascent from a mid-level wave
   over New Mexico/northern Mexico.  It is also possible that
   convection moving eastward from Terrell County may interact
   favorably with the warm frontal zone near that region and pose a
   severe threat as well.  PFCs/profiles remain supportive of organized
   convection favoring all modes of severe - thus the severe threat
   across WW 49 continues.

   ..Cook.. 04/13/201MD 314 graphicMesoscale Discussion 0314
   NWS Storm Prediction Center Norman OK
   0435 AM CDT Sat Apr 13 2019

   Areas affected...west-central into north-central Texas

   Concerning...Severe Thunderstorm Watch 48...

   Valid 130935Z - 131030Z

   The severe weather threat for Severe Thunderstorm Watch 48
   continues.

   SUMMARY...The severe threat continues across WW 48 downstream of a
   complex of storms between San Angelo and Midland, TX.  Additional
   elevated convection may also pose a hail threat this morning.

   DISCUSSION...The severe threat continues across WW 48.  Convection
   has congealed into a mix of linear and cellular modes in west Texas,
   with one lone supercell continuing to exhibit occasionally strong
   velocity signatures and indications of 1-2" diameter hail potential
   in Irion County.  There storms are slightly elevated and just north
   of the warm frontal zone, which is probably mitigating any tornado
   threat.  Downstream of this activity, convection continues to deepen
   within a steep-lapse-rate environment, with effective shear
   supporting organization and updraft rotation.  These storms could
   also produce occasional 1" hailstones at times as they mature.

   Over time, high-resolution guidance suggests that the current linear
   complex and cells out ahead will continue to migrate east-northeast,
   with hail being the primary severe risk.  A new WW may be needed
   downstream of the current one pending 1) severity of the ongoing MCS
   and cells out ahead and 2) northward progress of the warm front on
   the southern periphery of the watch, which may increase the
   tornado/damaging-wind threat with storms that can become surface
   based.  A new MD will probably be issued to update on downstream
   watch potential later this morning.

   ..Cook.. 04/13/2019

Current Convective Watches

Valid WW ImageWW0049 RadarURGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 49
   NWS Storm Prediction Center Norman OK
   150 AM CDT Sat Apr 13 2019

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Southwest and south-central Texas

   * Effective this Saturday morning from 150 AM until 900 AM CDT.

   * Primary threats include...
     A couple tornadoes possible
     Scattered large hail and isolated very large hail events to 3
       inches in diameter possible
     Scattered damaging wind gusts to 70 mph possible

   SUMMARY...A gradual increase in convection has been noted across the
   area in an environment conditionally favorable for supercells and
   tornado potential, along and south of a warm front.  The threat
   should increase through early/mid morning as lift and moisture each
   strengthen.

   The tornado watch area is approximately along and 80 statute miles
   either side of a line from 60 miles northwest of Del Rio TX to 45
   miles north northeast of Hondo TX. For a complete depiction of the
   watch see the associated watch outline update (WOUS64 KWNS WOU9).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and 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.

   &&

   OTHER WATCH INFORMATION.WW0048 Radar

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 48
   NWS Storm Prediction Center Norman OK
   130 AM CDT Sat Apr 13 2019

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     West-central and southwest Texas

   * Effective this Saturday morning from 130 AM until 900 AM CDT.

   * Primary threats include...
     Scattered large hail and isolated very large hail events to 2
       inches in diameter possible
     Isolated damaging wind gusts to 70 mph possible

   SUMMARY...Thunderstorms should increase in coverage and intensity
   across the area through the remainder of the pre-dawn hours, as both
   moisture and lift strengthen near a surface low and north of a warm
   front.  Hail is the main threat, though sporadic damaging gusts may
   penetrate to the surface.

   The severe thunderstorm watch area is approximately along and 60
   statute miles north and south of a line from 55 miles southwest of
   Midland TX to 15 miles north of Brownwood 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.

Apr 13, 2019 0600 UTC Day 1 Convective Outlook

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1248 AM CDT Sat Apr 13 2019

   Valid 131200Z - 141200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   FAR EAST TEXAS...LOUISIANA...FAR SOUTHEAST ARKANSAS AND WEST-CENTRAL
   MISSISSIPPI...

   ...SUMMARY...
   Numerous severe thunderstorms capable of producing tornadoes, wind
   damage and large hail, are expected across parts of east Texas,
   Louisiana, southern Arkansas, Mississippi, western Alabama and
   surrounding areas today and tonight.

   ...East Texas/Louisiana/Southern Arkansas/Mississippi/Western
   Alabama...
   A vigorous upper-level trough will move across the southern Plains
   today as a mid-level jet rounds the base of the system. At the
   surface, a low will move into the Arklatex with a moist airmass in
   place to the southeast of the low across east Texas, Louisiana and
   western Mississippi. Surface dewpoints in the moist sector should be
   in the upper 60s and lower 70s F by late morning. Thunderstorms
   should be ongoing across north-central into northeast Texas at the
   start of the period. This convection with a hail threat, is likely
   to move into the Arklatex by midday. Further south across southeast
   Texas into Louisiana, the airmass should become moderately unstable
   and remain primarily undisturbed. In response to the approach of the
   upper-level trough, a low-level jet is forecast to move into far
   eastern Texas and western Louisiana during the early afternoon.
   Thunderstorms should initiate to the northwest of the low-level jet
   on the northern edge of the stronger instability. Strong deep-layer
   shear profiles will favor supercell development. Supercells will
   have a potential for large hail in the early afternoon. The more
   dominant storms could produce 2-inch diameter hailstones. As the
   upper-level trough approaches and the exit region of a progressive
   mid-level jet moves into southeast Texas during the early afternoon,
   surface-based thunderstorms should rapidly initiate and move
   eastward into western Louisiana.

   RAP forecast soundings across the moist sector at 21Z from Monroe,
   LA southward to Alexandria, LA show MLCAPE values in the 2000 to
   2500 J/kg range. Deep-layer shear is forecast to steadily increase
   due the approach of the mid-level jet with forecast soundings
   showing 0-6 km shear of 50 to 60 kt by late afternoon. This combined
   with strong low-level shear will be favorable for supercells and
   tornadoes across the moderate risk area. 0-3 km storm-relative
   helicities are forecast to be in the 350 to 450 m2/s2 range
   supporting strong tornadoes with the more dominant supercells near
   the axis of the low-level jet. A potential for long-track tornadoes
   will be possible and a regional outbreak of tornadoes could occur
   across parts of the moderate risk area. By early evening, the
   cluster of severe storms is forecast to move into southwestern and
   central Mississippi where a potential for strong tornadoes will
   continue. However, the wind-damage threat may become the more
   dominant hazard as the convection moves further to the east where
   instability is forecast to be weaker.

   ...Northern South Carolina/Central and Eastern North Carolina/Far
   Southeast Virginia...
   Southwest mid-level flow will be in place across the East Coast
   today. At the surface, a moist airmass will exist across the
   Atlantic Coastal plains where dewpoints should be in the upper 60s
   and lower 70s F.  As surface temperatures warm across the moist
   airmass, pockets of moderate instability may develop from northern
   South Carolina northeastward into eastern North Carolina.
   Thunderstorms are forecast to initiate in the foothills of the
   Appalachians and move eastward into the stronger instability during
   the afternoon. SBCAPE values around 1000 J/kg evident on RAP
   forecast soundings, along with 30 to 40 kt of 0-6 km shear should be
   enough for a marginal severe threat. Strong wind gusts and hail will
   the primary threats.

   ..Broyles/Bentley.. 04/13/2019

dimanche 7 avril 2019

Southern Mississippi Valley sector loop

Apr 7, 2019 1630 UTC Day 1 Convective Outlook

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1113 AM CDT Sun Apr 07 2019

   Valid 071630Z - 081200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   SOUTHEAST TEXAS AND WESTERN/CENTRAL LOUISIANA...

   ...SUMMARY...
   Damaging winds and hail will be possible through this evening from
   southeast Texas northeastward to parts of the Tennessee Valley.

   ...TX/LA...
   A large and increasingly organized linear MCS is tracking along the
   middle TX Gulf coast.  This system is expected to move across
   southeast TX and into much of LA through early evening.  So far,
   forward speed of the system has been modest (30-35kt).  However,
   rather strong mid-level flow into the back of the MCS and favorable
   low-level moisture/instability ahead of the system may aid in
   acceleration later today.  Damaging winds along the leading edge of
   the convection are the main concern, so have upgraded to an ENH risk
   across this area.  Isolated QLCS tornadoes are also possible if the
   system continues to organize/intensify.

   ...Southern AR into MS/TN/KY...
   Scattered strong thunderstorms have been occurring along the surface
   boundary extending from southern AR into parts of TN and KY.  The
   air mass south of the boundary will slowly destabilize this
   afternoon, with various 12z CAM solutions suggesting a few intense
   convective clusters capable of hail and damaging wind.

   Later this evening and tonight, the large MCS over TX may persist
   and move into northern MS and west TN, posing a risk of damaging
   winds.  Confidence that system will remain severe for that long is
   not high, but given the generally favorable thermodynamic
   environment, it is not out of the question.  This risk will be
   re-evaluated in later outlooks.

   ..Hart/Gleason.. 04/07/2019

Current Convective Watches

Valid WW ImageWW0041 Radar URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 41
   NWS Storm Prediction Center Norman OK
   710 AM CDT Sun Apr 7 2019

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Southeast Texas
     Coastal Waters

   * Effective this Sunday morning and afternoon from 710 AM until
     300 PM CDT.

   * Primary threats include...
     Scattered damaging wind gusts to 70 mph possible
     Scattered large hail events to 1.5 inches in diameter possible
     A tornado or two possible

   SUMMARY...A maturing squall line across south central Texas will
   develop east-northeastward through the day, with additional storm
   development possible in advance of the line.  The storm environment
   will favor damaging winds and large hail as the primary threats with
   the strongest embedded cells and bowing segments.  A tornado or two
   will also be possible with circulations embedded in the line, or
   with cell interactions immediately in advance of the line.

   The severe thunderstorm watch area is approximately along and 90
   statute miles north and south of a line from 40 miles west northwest
   of Palacios TX to 50 miles east southeast of Huntsville TX. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU1).

   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.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 40...

   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 550. Mean storm motion vector
   26030.

   ...Thompson

SPC Apr 7, 2019 1630Z Thunderstorm Outlook

Mesoscale Discussion 277

Valid MD ImageMD 277 graphicMesoscale Discussion 0277
   NWS Storm Prediction Center Norman OK
   1113 AM CDT Sun Apr 07 2019

   Areas affected...Southeast TX...Middle/Upper TX Coast

   Concerning...Severe Thunderstorm Watch 41...

   Valid 071613Z - 071745Z

   The severe weather threat for Severe Thunderstorm Watch 41
   continues.

   SUMMARY...Threat for damaging wind gusts, hail, and a tornado or two
   remains across southeast TX and the middle/upper TX Coast.

   DISCUSSION...Air mass ahead of the ongoing convective line continue
   to destabilize amidst continue moisture advection. Dewpoints are now
   between 70 and 72 deg F areawide and mesoanalysis estimates 2000+
   J/kg. Additionally, the overall system is well organized, evidenced
   by strong (i.e. 3-5 mb) height rises behind the line and sharpening
   reflectivity gradient along its leading edge. Another factor
   suggesting intensification is the southeasterly surface winds and
   resulting increased convergence.

   Two factors potentially impeding further
   intensification/organization are the line-parallel orientation of
   the shear vectors and the slowing of the shortwave trough currently
   moving through south TX.

   Overall expectation is for gradual intensification/organization over
   the next few hours with the forward speed of the overall system to
   increase. Strong wind gusts are the primary severe threat. Some hail
   also remains possible. A brief tornado or two is also possible,
   particularly as the system intensifies and forward motion increases.

   ..Mosier.. 04/07/2019

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

   ATTN...WFO...LCH...SHV...HGX...CRP...EWX...

   LAT...LON   28029674 30239688 31749469 29159468 28029674