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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1124 AM CDT Sun Jul 21 2024 Valid 211700Z - 221200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE NORTHWESTERN GREAT BASIN INTO CENTRAL/SOUTHEAST OREGON... Behind the mid-level shortwave trough now over northwest Oregon/western Washington, thunderstorm potential has decreased in parts of southwestern Oregon. The isolated dry thunder area has been modified to account for this decreased potential. Elsewhere, the outlook remains unchanged as isolated to scattered thunderstorms remain possible late this morning into this afternoon. ..Wendt.. 07/21/2024 .PREV DISCUSSION... /ISSUED 0203 AM CDT Sun Jul 21 2024/ ...Synopsis... A weak upper trough moving along the western periphery of the stout ridge centered west of the Rockies will bring increasing mid-level moisture onshore through today. Multiple rounds of thunderstorms are possible, along with hot, dry and unstable conditions, from the northern Great Basin through much of the Pacific Northwest. An outbreak of dry lightning is probable over receptive fuels across the interior Northwest today and tonight. ...Northern Great Basin and Northwest... Isolated high-based thunderstorms are likely to be ongoing at the start of the period underneath the northward-moving upper trough along the coastal ranges of OR and southern WA. While gradually decreasing in coverage through the morning, a few storms may persist with a risk for lightning strikes as they move north into WA along and west of the Cascade Crest. Behind the initial round of storms, weak height falls and mid-level moisture advection will continue through the day across parts of northern CA/NV and south-central OR. Weak broad-scale ascent, in combination with diurnal heating and orographic lift, will support scattered thunderstorm development from mid afternoon through the evening hours. A combination of wet (displaced farther south), but mostly dry thunderstorms appear likely with weak buoyancy atop deep mixed-layers and moderate storm motions. Given the low precipitation efficiency and faster storm motions, wetting rainfall potential appears quite low. A significant outbreak of dry lightning is probable within very dry fuel beds across parts of the northern Great Basin and interior Northwest. Thunderstorms may continue overnight expanding northward along the northern Cascades and into the Columbia Basin. Some risk for isolated lightning strikes may extend into Day2/Monday. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sun Jul 21 2024 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL AND SOUTHERN ARIZONA...AND FROM SOUTHERN COLORADO TO EASTERN NEW MEXICO... ...SUMMARY... Isolated, marginally severe thunderstorms are possible this afternoon into early evening across parts of central and southern Arizona, and from southern Colorado to eastern New Mexico. ...Synopsis... The mid/upper-level pattern will remain rather blocky over and near the CONUS through the period, with longwave ridging remaining over the West, and a persistent, positively tilted longwave trough from QC across the mid Mississippi Valley to central/south TX. A series of mostly small shortwaves will traverse the modest northerly flow aloft, in between those features, over the Plains States and central/southern Rockies. A long-lived anticyclone -- initially centered over the lower Colorado River Valley -- will continue to retrograde, drifting northwestward over parts of NV while expanding somewhat. Farther northwest, a strong shortwave trough was apparent in moisture-channel imagery over and offshore from the coastal OR/CA border. This feature should accelerate northward through the period and weaken, being absorbed into the eastern semicircle of a massive, slow-moving cyclone centered over the Gulf of AK. The trough will pass along and just off the OR/WA coastline today, and over Vancouver Island to coastal west-central BC by 00Z. At the surface, 11Z analysis showed a weak, muddled surface pattern north of an increasingly diffuse, wavy frontal zone that extended from the Hampton Roads region across the Tennessee Valley region to parts of southern OK and north TX. That front should continue to demarcate richest Gulf moisture from a lesser-modified, more continental air mass to the north, and should remain quasistationary. ...South-central Rockies and adjoining High Plains... Widely scattered to scattered thunderstorms will form from midday through the afternoon and move generally southward, with local deviance to the southeast or southwest as boundary and outflow- driven processes force. Weak low/middle-level winds will limit deep shear, with multicells the dominant storm mode. Due to the lack of greater buoyancy, and high-elevation nature of the surface limiting boundary-layer depth in many instances, much of this convection should remain relatively shallow and struggle to organize. However, the most vigorous cells, including those that move over valleys and lower Great Plains elevations with deeper subcloud layers and greater boundary-layer moisture content, will pose a threat for isolated severe gusts and marginal hail. Some cold-pool aggregation also may occur, especially over Plains areas of east-central/ northeastern NM and extreme southeastern CO. 300-800 J/kg MLCAPE should be common across this region in the preconvective air mass. The overall strong/severe thunderstorm-wind potential should diminish through the evening as the foregoing boundary layer stabilizes diabatically, and stable-outflow coverage increases. ...AZ... Scattered thunderstorms should develop today, primarily as strong insolation preferentially erodes MLCINH amidst at least marginal moisture, over the Mogollon Rim and adjoining higher elevations of eastern/central/northern AZ. With the retrogression of the mid/ upper ridge, the mid/upper flow will be largely northerly, and through a fairly deep layer (roughly 700-300 mb, sometimes higher). Activity therefore should move southward to southwestward across deeper mixed layers of the lower desert elevations, with at least isolated severe downdrafts possible. Peak MLCAPE may reach the 500-1000 J/kg range in some areas, and should be at least 250 J/kg over most of the outlook, with DCAPE commonly over 1000 J/kg. Boundary mergers, orographic effects and storm-scale outflow aggregations may focus the severe threat locally within this broader "marginal risk" area. Convection may go as far as the borderlands before weakening this evening -- hence the minor extension of the outlook area. ...Interior Northwest... Widely scattered to scattered, high-based thunderstorms are expected to develop this afternoon over much of inland OR, northeastern CA and northern NV, amid peripheral large-scale lift from the Pacific trough and strong surface diurnal heating. This activity may produce locally strong, often dry downbursts -- indeed, scattered dry thunderstorms are forecast in the SPC fire-weather outlook. Large dewpoint depressions (40-70 deg F) should result after a few hours of diurnal mixing, causing a drop in buoyancy, but with enough (200-600 J/kg MLCAPE) to support thunderstorms with subcloud/ boundary-layer depths reaching into the 500-600 mb layer. Lack of greater low/middle-level flow and buoyancy both preclude an unconditional severe outlook, but a downdrafts approaching severe limits cannot be ruled out. ..Edwards/Broyles.. 07/21/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sun Jul 21 2024 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL AND SOUTHERN ARIZONA...AND FROM SOUTHERN COLORADO TO EASTERN NEW MEXICO... ...SUMMARY... Isolated, marginally severe thunderstorms are possible this afternoon into early evening across parts of central and southern Arizona, and from southern Colorado to eastern New Mexico. ...Synopsis... The mid/upper-level pattern will remain rather blocky over and near the CONUS through the period, with longwave ridging remaining over the West, and a persistent, positively tilted longwave trough from QC across the mid Mississippi Valley to central/south TX. A series of mostly small shortwaves will traverse the modest northerly flow aloft, in between those features, over the Plains States and central/southern Rockies. A long-lived anticyclone -- initially centered over the lower Colorado River Valley -- will continue to retrograde, drifting northwestward over parts of NV while expanding somewhat. Farther northwest, a strong shortwave trough was apparent in moisture-channel imagery over and offshore from the coastal OR/CA border. This feature should accelerate northward through the period and weaken, being absorbed into the eastern semicircle of a massive, slow-moving cyclone centered over the Gulf of AK. The trough will pass along and just off the OR/WA coastline today, and over Vancouver Island to coastal west-central BC by 00Z. At the surface, 11Z analysis showed a weak, muddled surface pattern north of an increasingly diffuse, wavy frontal zone that extended from the Hampton Roads region across the Tennessee Valley region to parts of southern OK and north TX. That front should continue to demarcate richest Gulf moisture from a lesser-modified, more continental air mass to the north, and should remain quasistationary. ...South-central Rockies and adjoining High Plains... Widely scattered to scattered thunderstorms will form from midday through the afternoon and move generally southward, with local deviance to the southeast or southwest as boundary and outflow- driven processes force. Weak low/middle-level winds will limit deep shear, with multicells the dominant storm mode. Due to the lack of greater buoyancy, and high-elevation nature of the surface limiting boundary-layer depth in many instances, much of this convection should remain relatively shallow and struggle to organize. However, the most vigorous cells, including those that move over valleys and lower Great Plains elevations with deeper subcloud layers and greater boundary-layer moisture content, will pose a threat for isolated severe gusts and marginal hail. Some cold-pool aggregation also may occur, especially over Plains areas of east-central/ northeastern NM and extreme southeastern CO. 300-800 J/kg MLCAPE should be common across this region in the preconvective air mass. The overall strong/severe thunderstorm-wind potential should diminish through the evening as the foregoing boundary layer stabilizes diabatically, and stable-outflow coverage increases. ...AZ... Scattered thunderstorms should develop today, primarily as strong insolation preferentially erodes MLCINH amidst at least marginal moisture, over the Mogollon Rim and adjoining higher elevations of eastern/central/northern AZ. With the retrogression of the mid/ upper ridge, the mid/upper flow will be largely northerly, and through a fairly deep layer (roughly 700-300 mb, sometimes higher). Activity therefore should move southward to southwestward across deeper mixed layers of the lower desert elevations, with at least isolated severe downdrafts possible. Peak MLCAPE may reach the 500-1000 J/kg range in some areas, and should be at least 250 J/kg over most of the outlook, with DCAPE commonly over 1000 J/kg. Boundary mergers, orographic effects and storm-scale outflow aggregations may focus the severe threat locally within this broader "marginal risk" area. Convection may go as far as the borderlands before weakening this evening -- hence the minor extension of the outlook area. ...Interior Northwest... Widely scattered to scattered, high-based thunderstorms are expected to develop this afternoon over much of inland OR, northeastern CA and northern NV, amid peripheral large-scale lift from the Pacific trough and strong surface diurnal heating. This activity may produce locally strong, often dry downbursts -- indeed, scattered dry thunderstorms are forecast in the SPC fire-weather outlook. Large dewpoint depressions (40-70 deg F) should result after a few hours of diurnal mixing, causing a drop in buoyancy, but with enough (200-600 J/kg MLCAPE) to support thunderstorms with subcloud/ boundary-layer depths reaching into the 500-600 mb layer. Lack of greater low/middle-level flow and buoyancy both preclude an unconditional severe outlook, but a downdrafts approaching severe limits cannot be ruled out. ..Edwards/Broyles.. 07/21/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sun Jul 21 2024 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL AND SOUTHERN ARIZONA...AND FROM SOUTHERN COLORADO TO EASTERN NEW MEXICO... ...SUMMARY... Isolated, marginally severe thunderstorms are possible this afternoon into early evening across parts of central and southern Arizona, and from southern Colorado to eastern New Mexico. ...Synopsis... The mid/upper-level pattern will remain rather blocky over and near the CONUS through the period, with longwave ridging remaining over the West, and a persistent, positively tilted longwave trough from QC across the mid Mississippi Valley to central/south TX. A series of mostly small shortwaves will traverse the modest northerly flow aloft, in between those features, over the Plains States and central/southern Rockies. A long-lived anticyclone -- initially centered over the lower Colorado River Valley -- will continue to retrograde, drifting northwestward over parts of NV while expanding somewhat. Farther northwest, a strong shortwave trough was apparent in moisture-channel imagery over and offshore from the coastal OR/CA border. This feature should accelerate northward through the period and weaken, being absorbed into the eastern semicircle of a massive, slow-moving cyclone centered over the Gulf of AK. The trough will pass along and just off the OR/WA coastline today, and over Vancouver Island to coastal west-central BC by 00Z. At the surface, 11Z analysis showed a weak, muddled surface pattern north of an increasingly diffuse, wavy frontal zone that extended from the Hampton Roads region across the Tennessee Valley region to parts of southern OK and north TX. That front should continue to demarcate richest Gulf moisture from a lesser-modified, more continental air mass to the north, and should remain quasistationary. ...South-central Rockies and adjoining High Plains... Widely scattered to scattered thunderstorms will form from midday through the afternoon and move generally southward, with local deviance to the southeast or southwest as boundary and outflow- driven processes force. Weak low/middle-level winds will limit deep shear, with multicells the dominant storm mode. Due to the lack of greater buoyancy, and high-elevation nature of the surface limiting boundary-layer depth in many instances, much of this convection should remain relatively shallow and struggle to organize. However, the most vigorous cells, including those that move over valleys and lower Great Plains elevations with deeper subcloud layers and greater boundary-layer moisture content, will pose a threat for isolated severe gusts and marginal hail. Some cold-pool aggregation also may occur, especially over Plains areas of east-central/ northeastern NM and extreme southeastern CO. 300-800 J/kg MLCAPE should be common across this region in the preconvective air mass. The overall strong/severe thunderstorm-wind potential should diminish through the evening as the foregoing boundary layer stabilizes diabatically, and stable-outflow coverage increases. ...AZ... Scattered thunderstorms should develop today, primarily as strong insolation preferentially erodes MLCINH amidst at least marginal moisture, over the Mogollon Rim and adjoining higher elevations of eastern/central/northern AZ. With the retrogression of the mid/ upper ridge, the mid/upper flow will be largely northerly, and through a fairly deep layer (roughly 700-300 mb, sometimes higher). Activity therefore should move southward to southwestward across deeper mixed layers of the lower desert elevations, with at least isolated severe downdrafts possible. Peak MLCAPE may reach the 500-1000 J/kg range in some areas, and should be at least 250 J/kg over most of the outlook, with DCAPE commonly over 1000 J/kg. Boundary mergers, orographic effects and storm-scale outflow aggregations may focus the severe threat locally within this broader "marginal risk" area. Convection may go as far as the borderlands before weakening this evening -- hence the minor extension of the outlook area. ...Interior Northwest... Widely scattered to scattered, high-based thunderstorms are expected to develop this afternoon over much of inland OR, northeastern CA and northern NV, amid peripheral large-scale lift from the Pacific trough and strong surface diurnal heating. This activity may produce locally strong, often dry downbursts -- indeed, scattered dry thunderstorms are forecast in the SPC fire-weather outlook. Large dewpoint depressions (40-70 deg F) should result after a few hours of diurnal mixing, causing a drop in buoyancy, but with enough (200-600 J/kg MLCAPE) to support thunderstorms with subcloud/ boundary-layer depths reaching into the 500-600 mb layer. Lack of greater low/middle-level flow and buoyancy both preclude an unconditional severe outlook, but a downdrafts approaching severe limits cannot be ruled out. ..Edwards/Broyles.. 07/21/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sun Jul 21 2024 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL AND SOUTHERN ARIZONA...AND FROM SOUTHERN COLORADO TO EASTERN NEW MEXICO... ...SUMMARY... Isolated, marginally severe thunderstorms are possible this afternoon into early evening across parts of central and southern Arizona, and from southern Colorado to eastern New Mexico. ...Synopsis... The mid/upper-level pattern will remain rather blocky over and near the CONUS through the period, with longwave ridging remaining over the West, and a persistent, positively tilted longwave trough from QC across the mid Mississippi Valley to central/south TX. A series of mostly small shortwaves will traverse the modest northerly flow aloft, in between those features, over the Plains States and central/southern Rockies. A long-lived anticyclone -- initially centered over the lower Colorado River Valley -- will continue to retrograde, drifting northwestward over parts of NV while expanding somewhat. Farther northwest, a strong shortwave trough was apparent in moisture-channel imagery over and offshore from the coastal OR/CA border. This feature should accelerate northward through the period and weaken, being absorbed into the eastern semicircle of a massive, slow-moving cyclone centered over the Gulf of AK. The trough will pass along and just off the OR/WA coastline today, and over Vancouver Island to coastal west-central BC by 00Z. At the surface, 11Z analysis showed a weak, muddled surface pattern north of an increasingly diffuse, wavy frontal zone that extended from the Hampton Roads region across the Tennessee Valley region to parts of southern OK and north TX. That front should continue to demarcate richest Gulf moisture from a lesser-modified, more continental air mass to the north, and should remain quasistationary. ...South-central Rockies and adjoining High Plains... Widely scattered to scattered thunderstorms will form from midday through the afternoon and move generally southward, with local deviance to the southeast or southwest as boundary and outflow- driven processes force. Weak low/middle-level winds will limit deep shear, with multicells the dominant storm mode. Due to the lack of greater buoyancy, and high-elevation nature of the surface limiting boundary-layer depth in many instances, much of this convection should remain relatively shallow and struggle to organize. However, the most vigorous cells, including those that move over valleys and lower Great Plains elevations with deeper subcloud layers and greater boundary-layer moisture content, will pose a threat for isolated severe gusts and marginal hail. Some cold-pool aggregation also may occur, especially over Plains areas of east-central/ northeastern NM and extreme southeastern CO. 300-800 J/kg MLCAPE should be common across this region in the preconvective air mass. The overall strong/severe thunderstorm-wind potential should diminish through the evening as the foregoing boundary layer stabilizes diabatically, and stable-outflow coverage increases. ...AZ... Scattered thunderstorms should develop today, primarily as strong insolation preferentially erodes MLCINH amidst at least marginal moisture, over the Mogollon Rim and adjoining higher elevations of eastern/central/northern AZ. With the retrogression of the mid/ upper ridge, the mid/upper flow will be largely northerly, and through a fairly deep layer (roughly 700-300 mb, sometimes higher). Activity therefore should move southward to southwestward across deeper mixed layers of the lower desert elevations, with at least isolated severe downdrafts possible. Peak MLCAPE may reach the 500-1000 J/kg range in some areas, and should be at least 250 J/kg over most of the outlook, with DCAPE commonly over 1000 J/kg. Boundary mergers, orographic effects and storm-scale outflow aggregations may focus the severe threat locally within this broader "marginal risk" area. Convection may go as far as the borderlands before weakening this evening -- hence the minor extension of the outlook area. ...Interior Northwest... Widely scattered to scattered, high-based thunderstorms are expected to develop this afternoon over much of inland OR, northeastern CA and northern NV, amid peripheral large-scale lift from the Pacific trough and strong surface diurnal heating. This activity may produce locally strong, often dry downbursts -- indeed, scattered dry thunderstorms are forecast in the SPC fire-weather outlook. Large dewpoint depressions (40-70 deg F) should result after a few hours of diurnal mixing, causing a drop in buoyancy, but with enough (200-600 J/kg MLCAPE) to support thunderstorms with subcloud/ boundary-layer depths reaching into the 500-600 mb layer. Lack of greater low/middle-level flow and buoyancy both preclude an unconditional severe outlook, but a downdrafts approaching severe limits cannot be ruled out. ..Edwards/Broyles.. 07/21/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sun Jul 21 2024 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL AND SOUTHERN ARIZONA...AND FROM SOUTHERN COLORADO TO EASTERN NEW MEXICO... ...SUMMARY... Isolated, marginally severe thunderstorms are possible this afternoon into early evening across parts of central and southern Arizona, and from southern Colorado to eastern New Mexico. ...Synopsis... The mid/upper-level pattern will remain rather blocky over and near the CONUS through the period, with longwave ridging remaining over the West, and a persistent, positively tilted longwave trough from QC across the mid Mississippi Valley to central/south TX. A series of mostly small shortwaves will traverse the modest northerly flow aloft, in between those features, over the Plains States and central/southern Rockies. A long-lived anticyclone -- initially centered over the lower Colorado River Valley -- will continue to retrograde, drifting northwestward over parts of NV while expanding somewhat. Farther northwest, a strong shortwave trough was apparent in moisture-channel imagery over and offshore from the coastal OR/CA border. This feature should accelerate northward through the period and weaken, being absorbed into the eastern semicircle of a massive, slow-moving cyclone centered over the Gulf of AK. The trough will pass along and just off the OR/WA coastline today, and over Vancouver Island to coastal west-central BC by 00Z. At the surface, 11Z analysis showed a weak, muddled surface pattern north of an increasingly diffuse, wavy frontal zone that extended from the Hampton Roads region across the Tennessee Valley region to parts of southern OK and north TX. That front should continue to demarcate richest Gulf moisture from a lesser-modified, more continental air mass to the north, and should remain quasistationary. ...South-central Rockies and adjoining High Plains... Widely scattered to scattered thunderstorms will form from midday through the afternoon and move generally southward, with local deviance to the southeast or southwest as boundary and outflow- driven processes force. Weak low/middle-level winds will limit deep shear, with multicells the dominant storm mode. Due to the lack of greater buoyancy, and high-elevation nature of the surface limiting boundary-layer depth in many instances, much of this convection should remain relatively shallow and struggle to organize. However, the most vigorous cells, including those that move over valleys and lower Great Plains elevations with deeper subcloud layers and greater boundary-layer moisture content, will pose a threat for isolated severe gusts and marginal hail. Some cold-pool aggregation also may occur, especially over Plains areas of east-central/ northeastern NM and extreme southeastern CO. 300-800 J/kg MLCAPE should be common across this region in the preconvective air mass. The overall strong/severe thunderstorm-wind potential should diminish through the evening as the foregoing boundary layer stabilizes diabatically, and stable-outflow coverage increases. ...AZ... Scattered thunderstorms should develop today, primarily as strong insolation preferentially erodes MLCINH amidst at least marginal moisture, over the Mogollon Rim and adjoining higher elevations of eastern/central/northern AZ. With the retrogression of the mid/ upper ridge, the mid/upper flow will be largely northerly, and through a fairly deep layer (roughly 700-300 mb, sometimes higher). Activity therefore should move southward to southwestward across deeper mixed layers of the lower desert elevations, with at least isolated severe downdrafts possible. Peak MLCAPE may reach the 500-1000 J/kg range in some areas, and should be at least 250 J/kg over most of the outlook, with DCAPE commonly over 1000 J/kg. Boundary mergers, orographic effects and storm-scale outflow aggregations may focus the severe threat locally within this broader "marginal risk" area. Convection may go as far as the borderlands before weakening this evening -- hence the minor extension of the outlook area. ...Interior Northwest... Widely scattered to scattered, high-based thunderstorms are expected to develop this afternoon over much of inland OR, northeastern CA and northern NV, amid peripheral large-scale lift from the Pacific trough and strong surface diurnal heating. This activity may produce locally strong, often dry downbursts -- indeed, scattered dry thunderstorms are forecast in the SPC fire-weather outlook. Large dewpoint depressions (40-70 deg F) should result after a few hours of diurnal mixing, causing a drop in buoyancy, but with enough (200-600 J/kg MLCAPE) to support thunderstorms with subcloud/ boundary-layer depths reaching into the 500-600 mb layer. Lack of greater low/middle-level flow and buoyancy both preclude an unconditional severe outlook, but a downdrafts approaching severe limits cannot be ruled out. ..Edwards/Broyles.. 07/21/2024 Read more

000
ABPZ20 KNHC 211133
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sun Jul 21 2024

For the eastern North Pacific...east of 140 degrees west longitude:

Western East Pacific:
A large area of disorganized showers and thunderstorms located over
the far western portion of the eastern Pacific is associated with a
broad area of low pressure. Environmental conditions are forecast
to be marginally conducive for some gradual development during the
next couple of days while the system moves westward at 10 to
15 mph toward the central Pacific basin. By midweek, stronger
upper-level winds are expected to inhibit further development.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...low...20 percent.

Central and Western East Pacific:
A tropical wave located well to the south-southwest of the southern
tip of the Baja California Peninsula is producing disorganized
showers and thunderstorms. Environmental conditions appear
conducive for some gradual development of this system over the next
several days while it moves westward to west-northwestward at 10 to
15 mph across the central and western portions of the basin.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...30 percent.

$$
Forecaster Brown

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0327 AM CDT Sun Jul 21 2024 Valid 241200Z - 291200Z ...DISCUSSION... A somewhat more progressive upper-level pattern will emerge during the Day 4-8/Wed-Sun period. The upper trough over the Great Lakes/Midwest early in the period will shift east across the Northeast and Mid-Atlantic through Day 6/Fri. As this occurs, the western upper ridge will overspread the central portion of the CONUS while a series of upper shortwave troughs move across the northern Rockies and Pacific Northwest. The Great Lakes upper trough will deepen on Day 4/Wed, and a cold front will sag south/southeast across Lower MI and northern IL/IN/OH. This could focus a corridor of strong thunderstorm potential, but vertical shear will remain modest and training thunderstorm activity may favor heavy rain rather than organized severe. As the upper trough migrates east toward the Northeast Days 5-6/Thu-Fri, a surface cold front will spread across the Midwest into the Mid-Atlantic and New England. Deep-layer flow is not forecast to be very strong, but a very moist airmass will be in place, and some potential for strong thunderstorms is possible near the end of the work week from VA northward into southern New England. Overall, organized severe potential appears low during the Day 4-8 period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0327 AM CDT Sun Jul 21 2024 Valid 241200Z - 291200Z ...DISCUSSION... A somewhat more progressive upper-level pattern will emerge during the Day 4-8/Wed-Sun period. The upper trough over the Great Lakes/Midwest early in the period will shift east across the Northeast and Mid-Atlantic through Day 6/Fri. As this occurs, the western upper ridge will overspread the central portion of the CONUS while a series of upper shortwave troughs move across the northern Rockies and Pacific Northwest. The Great Lakes upper trough will deepen on Day 4/Wed, and a cold front will sag south/southeast across Lower MI and northern IL/IN/OH. This could focus a corridor of strong thunderstorm potential, but vertical shear will remain modest and training thunderstorm activity may favor heavy rain rather than organized severe. As the upper trough migrates east toward the Northeast Days 5-6/Thu-Fri, a surface cold front will spread across the Midwest into the Mid-Atlantic and New England. Deep-layer flow is not forecast to be very strong, but a very moist airmass will be in place, and some potential for strong thunderstorms is possible near the end of the work week from VA northward into southern New England. Overall, organized severe potential appears low during the Day 4-8 period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0327 AM CDT Sun Jul 21 2024 Valid 241200Z - 291200Z ...DISCUSSION... A somewhat more progressive upper-level pattern will emerge during the Day 4-8/Wed-Sun period. The upper trough over the Great Lakes/Midwest early in the period will shift east across the Northeast and Mid-Atlantic through Day 6/Fri. As this occurs, the western upper ridge will overspread the central portion of the CONUS while a series of upper shortwave troughs move across the northern Rockies and Pacific Northwest. The Great Lakes upper trough will deepen on Day 4/Wed, and a cold front will sag south/southeast across Lower MI and northern IL/IN/OH. This could focus a corridor of strong thunderstorm potential, but vertical shear will remain modest and training thunderstorm activity may favor heavy rain rather than organized severe. As the upper trough migrates east toward the Northeast Days 5-6/Thu-Fri, a surface cold front will spread across the Midwest into the Mid-Atlantic and New England. Deep-layer flow is not forecast to be very strong, but a very moist airmass will be in place, and some potential for strong thunderstorms is possible near the end of the work week from VA northward into southern New England. Overall, organized severe potential appears low during the Day 4-8 period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0327 AM CDT Sun Jul 21 2024 Valid 241200Z - 291200Z ...DISCUSSION... A somewhat more progressive upper-level pattern will emerge during the Day 4-8/Wed-Sun period. The upper trough over the Great Lakes/Midwest early in the period will shift east across the Northeast and Mid-Atlantic through Day 6/Fri. As this occurs, the western upper ridge will overspread the central portion of the CONUS while a series of upper shortwave troughs move across the northern Rockies and Pacific Northwest. The Great Lakes upper trough will deepen on Day 4/Wed, and a cold front will sag south/southeast across Lower MI and northern IL/IN/OH. This could focus a corridor of strong thunderstorm potential, but vertical shear will remain modest and training thunderstorm activity may favor heavy rain rather than organized severe. As the upper trough migrates east toward the Northeast Days 5-6/Thu-Fri, a surface cold front will spread across the Midwest into the Mid-Atlantic and New England. Deep-layer flow is not forecast to be very strong, but a very moist airmass will be in place, and some potential for strong thunderstorms is possible near the end of the work week from VA northward into southern New England. Overall, organized severe potential appears low during the Day 4-8 period. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0207 AM CDT Sun Jul 21 2024 Valid 221200Z - 231200Z ...Synopsis... A broad upper trough over the Pacific Northwest is forecast to intensify as it merges with a second trough moving onshore from the eastern Pacific. Stronger flow aloft ahead of the trough will move inland, increasing mid-level moisture to the west of a weakening mid-level ridge. Thunderstorms are likely ahead of the trough over parts of the northern Rockies and Northwest, with dry fuels and little rainfall supporting a risk for dry lightning ignitions. ...Northwest, and Northern Rockies... Isolated dry thunderstorms are expected to be ongoing early in the period as convection from the previous day continues to advect north with the advancing upper trough. Additional storm development is possible later in the afternoon, as peak diurnal heating and lingering mid-level moisture allow for weak buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorm are also possible farther south across parts of the Great Basin, but a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, IsoDryT probabilities are warranted. ..Lyons.. 07/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0207 AM CDT Sun Jul 21 2024 Valid 221200Z - 231200Z ...Synopsis... A broad upper trough over the Pacific Northwest is forecast to intensify as it merges with a second trough moving onshore from the eastern Pacific. Stronger flow aloft ahead of the trough will move inland, increasing mid-level moisture to the west of a weakening mid-level ridge. Thunderstorms are likely ahead of the trough over parts of the northern Rockies and Northwest, with dry fuels and little rainfall supporting a risk for dry lightning ignitions. ...Northwest, and Northern Rockies... Isolated dry thunderstorms are expected to be ongoing early in the period as convection from the previous day continues to advect north with the advancing upper trough. Additional storm development is possible later in the afternoon, as peak diurnal heating and lingering mid-level moisture allow for weak buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorm are also possible farther south across parts of the Great Basin, but a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, IsoDryT probabilities are warranted. ..Lyons.. 07/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0207 AM CDT Sun Jul 21 2024 Valid 221200Z - 231200Z ...Synopsis... A broad upper trough over the Pacific Northwest is forecast to intensify as it merges with a second trough moving onshore from the eastern Pacific. Stronger flow aloft ahead of the trough will move inland, increasing mid-level moisture to the west of a weakening mid-level ridge. Thunderstorms are likely ahead of the trough over parts of the northern Rockies and Northwest, with dry fuels and little rainfall supporting a risk for dry lightning ignitions. ...Northwest, and Northern Rockies... Isolated dry thunderstorms are expected to be ongoing early in the period as convection from the previous day continues to advect north with the advancing upper trough. Additional storm development is possible later in the afternoon, as peak diurnal heating and lingering mid-level moisture allow for weak buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorm are also possible farther south across parts of the Great Basin, but a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, IsoDryT probabilities are warranted. ..Lyons.. 07/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0203 AM CDT Sun Jul 21 2024 Valid 211200Z - 221200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE NORTHERN GREAT BASIN AND INTERIOR NORTHWEST... ...Synopsis... A weak upper trough moving along the western periphery of the stout ridge centered west of the Rockies will bring increasing mid-level moisture onshore through today. Multiple rounds of thunderstorms are possible, along with hot, dry and unstable conditions, from the northern Great Basin through much of the Pacific Northwest. An outbreak of dry lightning is probable over receptive fuels across the interior Northwest today and tonight. ...Northern Great Basin and Northwest... Isolated high-based thunderstorms are likely to be ongoing at the start of the period underneath the northward-moving upper trough along the coastal ranges of OR and southern WA. While gradually decreasing in coverage through the morning, a few storms may persist with a risk for lightning strikes as they move north into WA along and west of the Cascade Crest. Behind the initial round of storms, weak height falls and mid-level moisture advection will continue through the day across parts of northern CA/NV and south-central OR. Weak broad-scale ascent, in combination with diurnal heating and orographic lift, will support scattered thunderstorm development from mid afternoon through the evening hours. A combination of wet (displaced farther south), but mostly dry thunderstorms appear likely with weak buoyancy atop deep mixed-layers and moderate storm motions. Given the low precipitation efficiency and faster storm motions, wetting rainfall potential appears quite low. A significant outbreak of dry lightning is probable within very dry fuel beds across parts of the northern Great Basin and interior Northwest. Thunderstorms may continue overnight expanding northward along the northern Cascades and into the Columbia Basin. Some risk for isolated lightning strikes may extend into Day2/Monday. ..Lyons.. 07/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0203 AM CDT Sun Jul 21 2024 Valid 211200Z - 221200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE NORTHERN GREAT BASIN AND INTERIOR NORTHWEST... ...Synopsis... A weak upper trough moving along the western periphery of the stout ridge centered west of the Rockies will bring increasing mid-level moisture onshore through today. Multiple rounds of thunderstorms are possible, along with hot, dry and unstable conditions, from the northern Great Basin through much of the Pacific Northwest. An outbreak of dry lightning is probable over receptive fuels across the interior Northwest today and tonight. ...Northern Great Basin and Northwest... Isolated high-based thunderstorms are likely to be ongoing at the start of the period underneath the northward-moving upper trough along the coastal ranges of OR and southern WA. While gradually decreasing in coverage through the morning, a few storms may persist with a risk for lightning strikes as they move north into WA along and west of the Cascade Crest. Behind the initial round of storms, weak height falls and mid-level moisture advection will continue through the day across parts of northern CA/NV and south-central OR. Weak broad-scale ascent, in combination with diurnal heating and orographic lift, will support scattered thunderstorm development from mid afternoon through the evening hours. A combination of wet (displaced farther south), but mostly dry thunderstorms appear likely with weak buoyancy atop deep mixed-layers and moderate storm motions. Given the low precipitation efficiency and faster storm motions, wetting rainfall potential appears quite low. A significant outbreak of dry lightning is probable within very dry fuel beds across parts of the northern Great Basin and interior Northwest. Thunderstorms may continue overnight expanding northward along the northern Cascades and into the Columbia Basin. Some risk for isolated lightning strikes may extend into Day2/Monday. ..Lyons.. 07/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0203 AM CDT Sun Jul 21 2024 Valid 211200Z - 221200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE NORTHERN GREAT BASIN AND INTERIOR NORTHWEST... ...Synopsis... A weak upper trough moving along the western periphery of the stout ridge centered west of the Rockies will bring increasing mid-level moisture onshore through today. Multiple rounds of thunderstorms are possible, along with hot, dry and unstable conditions, from the northern Great Basin through much of the Pacific Northwest. An outbreak of dry lightning is probable over receptive fuels across the interior Northwest today and tonight. ...Northern Great Basin and Northwest... Isolated high-based thunderstorms are likely to be ongoing at the start of the period underneath the northward-moving upper trough along the coastal ranges of OR and southern WA. While gradually decreasing in coverage through the morning, a few storms may persist with a risk for lightning strikes as they move north into WA along and west of the Cascade Crest. Behind the initial round of storms, weak height falls and mid-level moisture advection will continue through the day across parts of northern CA/NV and south-central OR. Weak broad-scale ascent, in combination with diurnal heating and orographic lift, will support scattered thunderstorm development from mid afternoon through the evening hours. A combination of wet (displaced farther south), but mostly dry thunderstorms appear likely with weak buoyancy atop deep mixed-layers and moderate storm motions. Given the low precipitation efficiency and faster storm motions, wetting rainfall potential appears quite low. A significant outbreak of dry lightning is probable within very dry fuel beds across parts of the northern Great Basin and interior Northwest. Thunderstorms may continue overnight expanding northward along the northern Cascades and into the Columbia Basin. Some risk for isolated lightning strikes may extend into Day2/Monday. ..Lyons.. 07/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Sun Jul 21 2024 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-thunderstorm potential appears low on Tuesday. ...Mid-Atlantic vicinity... Some modest deepening of the upper trough over the Great Lakes is expected on Tuesday. This may allow for some enhancement of southwesterly mid/upper flow from the central Appalachians into the Northeast. Meanwhile, forecast guidance indicates several shortwave vorticity maxima migrating through broader southwesterly flow from the Mid-South to the Mid-Atlantic/southern New England. At the surface, a weak low is forecast to migrate across the Chesapeake Bay or southern New England vicinity. The accompanying surface trough may extend generally along the I-95 corridor from southern NY into eastern VA, and could become a focus for thunderstorm development during the afternoon and evening. Some forecast soundings suggest 30-40 kt effective shear magnitudes and at least weak instability could support sporadic damaging gusts in a very moist environment. However, forecast guidance varies on the placement of surface features, as well as degree of instability across the region (influenced by cloud cover and any ongoing morning convection), as well as convective coverage. Low-end severe probabilities may be needed in subsequent outlooks, but uncertainty is too high to include a categorical severe risk at this time. ...Upper Midwest vicinity... A surface cold front will sag southward across southern MN/WI on Tuesday. Modest moisture and instability will be place ahead of the front across portions of the Mid-MO/MS Valleys. This should support scattered thunderstorms during the afternoon/evening, though vertical shear is forecast to remain very weak. This should limit organized severe potential, though isolated gusty winds may accompany any stronger cells. ..Leitman.. 07/21/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Sun Jul 21 2024 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-thunderstorm potential appears low on Tuesday. ...Mid-Atlantic vicinity... Some modest deepening of the upper trough over the Great Lakes is expected on Tuesday. This may allow for some enhancement of southwesterly mid/upper flow from the central Appalachians into the Northeast. Meanwhile, forecast guidance indicates several shortwave vorticity maxima migrating through broader southwesterly flow from the Mid-South to the Mid-Atlantic/southern New England. At the surface, a weak low is forecast to migrate across the Chesapeake Bay or southern New England vicinity. The accompanying surface trough may extend generally along the I-95 corridor from southern NY into eastern VA, and could become a focus for thunderstorm development during the afternoon and evening. Some forecast soundings suggest 30-40 kt effective shear magnitudes and at least weak instability could support sporadic damaging gusts in a very moist environment. However, forecast guidance varies on the placement of surface features, as well as degree of instability across the region (influenced by cloud cover and any ongoing morning convection), as well as convective coverage. Low-end severe probabilities may be needed in subsequent outlooks, but uncertainty is too high to include a categorical severe risk at this time. ...Upper Midwest vicinity... A surface cold front will sag southward across southern MN/WI on Tuesday. Modest moisture and instability will be place ahead of the front across portions of the Mid-MO/MS Valleys. This should support scattered thunderstorms during the afternoon/evening, though vertical shear is forecast to remain very weak. This should limit organized severe potential, though isolated gusty winds may accompany any stronger cells. ..Leitman.. 07/21/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Sun Jul 21 2024 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-thunderstorm potential appears low on Tuesday. ...Mid-Atlantic vicinity... Some modest deepening of the upper trough over the Great Lakes is expected on Tuesday. This may allow for some enhancement of southwesterly mid/upper flow from the central Appalachians into the Northeast. Meanwhile, forecast guidance indicates several shortwave vorticity maxima migrating through broader southwesterly flow from the Mid-South to the Mid-Atlantic/southern New England. At the surface, a weak low is forecast to migrate across the Chesapeake Bay or southern New England vicinity. The accompanying surface trough may extend generally along the I-95 corridor from southern NY into eastern VA, and could become a focus for thunderstorm development during the afternoon and evening. Some forecast soundings suggest 30-40 kt effective shear magnitudes and at least weak instability could support sporadic damaging gusts in a very moist environment. However, forecast guidance varies on the placement of surface features, as well as degree of instability across the region (influenced by cloud cover and any ongoing morning convection), as well as convective coverage. Low-end severe probabilities may be needed in subsequent outlooks, but uncertainty is too high to include a categorical severe risk at this time. ...Upper Midwest vicinity... A surface cold front will sag southward across southern MN/WI on Tuesday. Modest moisture and instability will be place ahead of the front across portions of the Mid-MO/MS Valleys. This should support scattered thunderstorms during the afternoon/evening, though vertical shear is forecast to remain very weak. This should limit organized severe potential, though isolated gusty winds may accompany any stronger cells. ..Leitman.. 07/21/2024 Read more