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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Tue Feb 04 2025 Valid 041630Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms will be possible across northern/central California this afternoon and evening. ...Northern/Central CA... Morning water vapor imagery shows a shortwave trough approaching the coast of northern CA. An associated surface cold front is also moving southeastward into northern CA, with an increasingly large shield of showers along/ahead of the front. Forecast soundings show the development of very weak CAPE later today, which could result in a few lightning flashes within the embedded precip shield. No severe storms are expected. ..Hart/Leitman.. 02/04/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Tue Feb 04 2025 Valid 041630Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms will be possible across northern/central California this afternoon and evening. ...Northern/Central CA... Morning water vapor imagery shows a shortwave trough approaching the coast of northern CA. An associated surface cold front is also moving southeastward into northern CA, with an increasingly large shield of showers along/ahead of the front. Forecast soundings show the development of very weak CAPE later today, which could result in a few lightning flashes within the embedded precip shield. No severe storms are expected. ..Hart/Leitman.. 02/04/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Tue Feb 04 2025 Valid 041630Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms will be possible across northern/central California this afternoon and evening. ...Northern/Central CA... Morning water vapor imagery shows a shortwave trough approaching the coast of northern CA. An associated surface cold front is also moving southeastward into northern CA, with an increasingly large shield of showers along/ahead of the front. Forecast soundings show the development of very weak CAPE later today, which could result in a few lightning flashes within the embedded precip shield. No severe storms are expected. ..Hart/Leitman.. 02/04/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Tue Feb 04 2025 Valid 041630Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms will be possible across northern/central California this afternoon and evening. ...Northern/Central CA... Morning water vapor imagery shows a shortwave trough approaching the coast of northern CA. An associated surface cold front is also moving southeastward into northern CA, with an increasingly large shield of showers along/ahead of the front. Forecast soundings show the development of very weak CAPE later today, which could result in a few lightning flashes within the embedded precip shield. No severe storms are expected. ..Hart/Leitman.. 02/04/2025 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0957 AM CST Tue Feb 04 2025 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... The previous forecast remains on track with no changes needed. Latest guidance and morning observations continue to suggest that fire weather concerns will remain confined to portions of the Desert Southwest, but the coverage/duration of elevated conditions should remain patchy with limited overlap with receptive fuels. See the previous discussion for additional details. ..Moore.. 02/04/2025 .PREV DISCUSSION... /ISSUED 0159 AM CST Tue Feb 04 2025/ ...Synopsis... Ridging aloft is forecast to intensify over the central US, while a deepening trough moves over much of the West. Several embedded perturbations will cross the southern Rockies deepening a lee low over the southern High Plains and a second low over the Great Basin. This could support gusty winds and periods of locally elevated fire-weather potential over parts of central NM and eastern AZ. ...Southwest... A backdoor cold front will move south over the Plains and into eastern NM early this morning associated with a weak lee low. The influx of cooler air and more moisture should moderate RH over the High Plains. To the west over the High country of central NM, periodic gusty winds and low humidity are still expected to overlap for several hours. Some localized fire-weather risk is possible over central NM and eastern AZ. However, more widespread fire-weather concerns are not currently expected given the relatively minor overlap of sustained winds, low humidity and sporadic receptive fuels. ...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 0957 AM CST Tue Feb 04 2025 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... The previous forecast remains on track with no changes needed. Latest guidance and morning observations continue to suggest that fire weather concerns will remain confined to portions of the Desert Southwest, but the coverage/duration of elevated conditions should remain patchy with limited overlap with receptive fuels. See the previous discussion for additional details. ..Moore.. 02/04/2025 .PREV DISCUSSION... /ISSUED 0159 AM CST Tue Feb 04 2025/ ...Synopsis... Ridging aloft is forecast to intensify over the central US, while a deepening trough moves over much of the West. Several embedded perturbations will cross the southern Rockies deepening a lee low over the southern High Plains and a second low over the Great Basin. This could support gusty winds and periods of locally elevated fire-weather potential over parts of central NM and eastern AZ. ...Southwest... A backdoor cold front will move south over the Plains and into eastern NM early this morning associated with a weak lee low. The influx of cooler air and more moisture should moderate RH over the High Plains. To the west over the High country of central NM, periodic gusty winds and low humidity are still expected to overlap for several hours. Some localized fire-weather risk is possible over central NM and eastern AZ. However, more widespread fire-weather concerns are not currently expected given the relatively minor overlap of sustained winds, low humidity and sporadic receptive fuels. ...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 0957 AM CST Tue Feb 04 2025 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... The previous forecast remains on track with no changes needed. Latest guidance and morning observations continue to suggest that fire weather concerns will remain confined to portions of the Desert Southwest, but the coverage/duration of elevated conditions should remain patchy with limited overlap with receptive fuels. See the previous discussion for additional details. ..Moore.. 02/04/2025 .PREV DISCUSSION... /ISSUED 0159 AM CST Tue Feb 04 2025/ ...Synopsis... Ridging aloft is forecast to intensify over the central US, while a deepening trough moves over much of the West. Several embedded perturbations will cross the southern Rockies deepening a lee low over the southern High Plains and a second low over the Great Basin. This could support gusty winds and periods of locally elevated fire-weather potential over parts of central NM and eastern AZ. ...Southwest... A backdoor cold front will move south over the Plains and into eastern NM early this morning associated with a weak lee low. The influx of cooler air and more moisture should moderate RH over the High Plains. To the west over the High country of central NM, periodic gusty winds and low humidity are still expected to overlap for several hours. Some localized fire-weather risk is possible over central NM and eastern AZ. However, more widespread fire-weather concerns are not currently expected given the relatively minor overlap of sustained winds, low humidity and sporadic receptive fuels. ...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 0957 AM CST Tue Feb 04 2025 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... The previous forecast remains on track with no changes needed. Latest guidance and morning observations continue to suggest that fire weather concerns will remain confined to portions of the Desert Southwest, but the coverage/duration of elevated conditions should remain patchy with limited overlap with receptive fuels. See the previous discussion for additional details. ..Moore.. 02/04/2025 .PREV DISCUSSION... /ISSUED 0159 AM CST Tue Feb 04 2025/ ...Synopsis... Ridging aloft is forecast to intensify over the central US, while a deepening trough moves over much of the West. Several embedded perturbations will cross the southern Rockies deepening a lee low over the southern High Plains and a second low over the Great Basin. This could support gusty winds and periods of locally elevated fire-weather potential over parts of central NM and eastern AZ. ...Southwest... A backdoor cold front will move south over the Plains and into eastern NM early this morning associated with a weak lee low. The influx of cooler air and more moisture should moderate RH over the High Plains. To the west over the High country of central NM, periodic gusty winds and low humidity are still expected to overlap for several hours. Some localized fire-weather risk is possible over central NM and eastern AZ. However, more widespread fire-weather concerns are not currently expected given the relatively minor overlap of sustained winds, low humidity and sporadic receptive fuels. ...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 0957 AM CST Tue Feb 04 2025 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... The previous forecast remains on track with no changes needed. Latest guidance and morning observations continue to suggest that fire weather concerns will remain confined to portions of the Desert Southwest, but the coverage/duration of elevated conditions should remain patchy with limited overlap with receptive fuels. See the previous discussion for additional details. ..Moore.. 02/04/2025 .PREV DISCUSSION... /ISSUED 0159 AM CST Tue Feb 04 2025/ ...Synopsis... Ridging aloft is forecast to intensify over the central US, while a deepening trough moves over much of the West. Several embedded perturbations will cross the southern Rockies deepening a lee low over the southern High Plains and a second low over the Great Basin. This could support gusty winds and periods of locally elevated fire-weather potential over parts of central NM and eastern AZ. ...Southwest... A backdoor cold front will move south over the Plains and into eastern NM early this morning associated with a weak lee low. The influx of cooler air and more moisture should moderate RH over the High Plains. To the west over the High country of central NM, periodic gusty winds and low humidity are still expected to overlap for several hours. Some localized fire-weather risk is possible over central NM and eastern AZ. However, more widespread fire-weather concerns are not currently expected given the relatively minor overlap of sustained winds, low humidity and sporadic receptive fuels. ...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 0957 AM CST Tue Feb 04 2025 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... The previous forecast remains on track with no changes needed. Latest guidance and morning observations continue to suggest that fire weather concerns will remain confined to portions of the Desert Southwest, but the coverage/duration of elevated conditions should remain patchy with limited overlap with receptive fuels. See the previous discussion for additional details. ..Moore.. 02/04/2025 .PREV DISCUSSION... /ISSUED 0159 AM CST Tue Feb 04 2025/ ...Synopsis... Ridging aloft is forecast to intensify over the central US, while a deepening trough moves over much of the West. Several embedded perturbations will cross the southern Rockies deepening a lee low over the southern High Plains and a second low over the Great Basin. This could support gusty winds and periods of locally elevated fire-weather potential over parts of central NM and eastern AZ. ...Southwest... A backdoor cold front will move south over the Plains and into eastern NM early this morning associated with a weak lee low. The influx of cooler air and more moisture should moderate RH over the High Plains. To the west over the High country of central NM, periodic gusty winds and low humidity are still expected to overlap for several hours. Some localized fire-weather risk is possible over central NM and eastern AZ. However, more widespread fire-weather concerns are not currently expected given the relatively minor overlap of sustained winds, low humidity and sporadic receptive fuels. ...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 0639 AM CST Tue Feb 04 2025 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated to scattered thunderstorm development will be possible across central California and along the Oregon Coast, but no severe thunderstorms are expected. ...Synopsis and Discussion... A mid/upper cyclone is currently centered off the Pacific Northwest/British Columbia coast, with moderate southwesterly flow aloft extending from the base of this low across much of the West Coast. A low-amplitude shortwave trough is currently moving through this southwesterly flow into central CA, with continued northeastward progression across the Great Basin expected today. Another shortwave trough is expected to follow quickly behind the first, moving into central CA tonight. Cooler mid-level temperatures will accompany this second shortwave, supporting the potential for a few lightning flashes as the frontal band moves ashore. Cooler temperatures aloft and increased forcing for ascent ahead of a third shortwave trough could also support isolated lightning flashes early tomorrow morning along the OR Coast. Farther east, upper ridging is expected to amplify as it shifts eastward across the Plains. At the same time, a fast-moving, low-amplitude shortwave trough will progress through southern Ontario and the Northeast. Additional southward progress of the cold front that currently extends from the Mid-Atlantic, TN Valley, Mid-South, and TX will be limited, with the portion of this front over TX potentially returning northward as a warm front Wednesday morning. Warm mid-level temperatures and associated poor lapse rates will limit buoyancy along this boundary, precluding any thunderstorm potential. ..Mosier/Bentley.. 02/04/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0639 AM CST Tue Feb 04 2025 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated to scattered thunderstorm development will be possible across central California and along the Oregon Coast, but no severe thunderstorms are expected. ...Synopsis and Discussion... A mid/upper cyclone is currently centered off the Pacific Northwest/British Columbia coast, with moderate southwesterly flow aloft extending from the base of this low across much of the West Coast. A low-amplitude shortwave trough is currently moving through this southwesterly flow into central CA, with continued northeastward progression across the Great Basin expected today. Another shortwave trough is expected to follow quickly behind the first, moving into central CA tonight. Cooler mid-level temperatures will accompany this second shortwave, supporting the potential for a few lightning flashes as the frontal band moves ashore. Cooler temperatures aloft and increased forcing for ascent ahead of a third shortwave trough could also support isolated lightning flashes early tomorrow morning along the OR Coast. Farther east, upper ridging is expected to amplify as it shifts eastward across the Plains. At the same time, a fast-moving, low-amplitude shortwave trough will progress through southern Ontario and the Northeast. Additional southward progress of the cold front that currently extends from the Mid-Atlantic, TN Valley, Mid-South, and TX will be limited, with the portion of this front over TX potentially returning northward as a warm front Wednesday morning. Warm mid-level temperatures and associated poor lapse rates will limit buoyancy along this boundary, precluding any thunderstorm potential. ..Mosier/Bentley.. 02/04/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0639 AM CST Tue Feb 04 2025 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated to scattered thunderstorm development will be possible across central California and along the Oregon Coast, but no severe thunderstorms are expected. ...Synopsis and Discussion... A mid/upper cyclone is currently centered off the Pacific Northwest/British Columbia coast, with moderate southwesterly flow aloft extending from the base of this low across much of the West Coast. A low-amplitude shortwave trough is currently moving through this southwesterly flow into central CA, with continued northeastward progression across the Great Basin expected today. Another shortwave trough is expected to follow quickly behind the first, moving into central CA tonight. Cooler mid-level temperatures will accompany this second shortwave, supporting the potential for a few lightning flashes as the frontal band moves ashore. Cooler temperatures aloft and increased forcing for ascent ahead of a third shortwave trough could also support isolated lightning flashes early tomorrow morning along the OR Coast. Farther east, upper ridging is expected to amplify as it shifts eastward across the Plains. At the same time, a fast-moving, low-amplitude shortwave trough will progress through southern Ontario and the Northeast. Additional southward progress of the cold front that currently extends from the Mid-Atlantic, TN Valley, Mid-South, and TX will be limited, with the portion of this front over TX potentially returning northward as a warm front Wednesday morning. Warm mid-level temperatures and associated poor lapse rates will limit buoyancy along this boundary, precluding any thunderstorm potential. ..Mosier/Bentley.. 02/04/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0639 AM CST Tue Feb 04 2025 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated to scattered thunderstorm development will be possible across central California and along the Oregon Coast, but no severe thunderstorms are expected. ...Synopsis and Discussion... A mid/upper cyclone is currently centered off the Pacific Northwest/British Columbia coast, with moderate southwesterly flow aloft extending from the base of this low across much of the West Coast. A low-amplitude shortwave trough is currently moving through this southwesterly flow into central CA, with continued northeastward progression across the Great Basin expected today. Another shortwave trough is expected to follow quickly behind the first, moving into central CA tonight. Cooler mid-level temperatures will accompany this second shortwave, supporting the potential for a few lightning flashes as the frontal band moves ashore. Cooler temperatures aloft and increased forcing for ascent ahead of a third shortwave trough could also support isolated lightning flashes early tomorrow morning along the OR Coast. Farther east, upper ridging is expected to amplify as it shifts eastward across the Plains. At the same time, a fast-moving, low-amplitude shortwave trough will progress through southern Ontario and the Northeast. Additional southward progress of the cold front that currently extends from the Mid-Atlantic, TN Valley, Mid-South, and TX will be limited, with the portion of this front over TX potentially returning northward as a warm front Wednesday morning. Warm mid-level temperatures and associated poor lapse rates will limit buoyancy along this boundary, precluding any thunderstorm potential. ..Mosier/Bentley.. 02/04/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0639 AM CST Tue Feb 04 2025 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated to scattered thunderstorm development will be possible across central California and along the Oregon Coast, but no severe thunderstorms are expected. ...Synopsis and Discussion... A mid/upper cyclone is currently centered off the Pacific Northwest/British Columbia coast, with moderate southwesterly flow aloft extending from the base of this low across much of the West Coast. A low-amplitude shortwave trough is currently moving through this southwesterly flow into central CA, with continued northeastward progression across the Great Basin expected today. Another shortwave trough is expected to follow quickly behind the first, moving into central CA tonight. Cooler mid-level temperatures will accompany this second shortwave, supporting the potential for a few lightning flashes as the frontal band moves ashore. Cooler temperatures aloft and increased forcing for ascent ahead of a third shortwave trough could also support isolated lightning flashes early tomorrow morning along the OR Coast. Farther east, upper ridging is expected to amplify as it shifts eastward across the Plains. At the same time, a fast-moving, low-amplitude shortwave trough will progress through southern Ontario and the Northeast. Additional southward progress of the cold front that currently extends from the Mid-Atlantic, TN Valley, Mid-South, and TX will be limited, with the portion of this front over TX potentially returning northward as a warm front Wednesday morning. Warm mid-level temperatures and associated poor lapse rates will limit buoyancy along this boundary, precluding any thunderstorm potential. ..Mosier/Bentley.. 02/04/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0639 AM CST Tue Feb 04 2025 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated to scattered thunderstorm development will be possible across central California and along the Oregon Coast, but no severe thunderstorms are expected. ...Synopsis and Discussion... A mid/upper cyclone is currently centered off the Pacific Northwest/British Columbia coast, with moderate southwesterly flow aloft extending from the base of this low across much of the West Coast. A low-amplitude shortwave trough is currently moving through this southwesterly flow into central CA, with continued northeastward progression across the Great Basin expected today. Another shortwave trough is expected to follow quickly behind the first, moving into central CA tonight. Cooler mid-level temperatures will accompany this second shortwave, supporting the potential for a few lightning flashes as the frontal band moves ashore. Cooler temperatures aloft and increased forcing for ascent ahead of a third shortwave trough could also support isolated lightning flashes early tomorrow morning along the OR Coast. Farther east, upper ridging is expected to amplify as it shifts eastward across the Plains. At the same time, a fast-moving, low-amplitude shortwave trough will progress through southern Ontario and the Northeast. Additional southward progress of the cold front that currently extends from the Mid-Atlantic, TN Valley, Mid-South, and TX will be limited, with the portion of this front over TX potentially returning northward as a warm front Wednesday morning. Warm mid-level temperatures and associated poor lapse rates will limit buoyancy along this boundary, precluding any thunderstorm potential. ..Mosier/Bentley.. 02/04/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CST Tue Feb 04 2025 Valid 071200Z - 121200Z ...DISCUSSION... Medium-range models are in reasonably good agreement through day 6 (Sunday), in terms of large-scale features. Substantial divergence begins thereafter, casting substantial uncertainty into the forecast beyond the upcoming weekend. Day 4, as an upper short-wave trough crossing the Northeast moves into/across the Canadian Maritimes, the quasi-zonal flow pattern over the U.S. will continue. Weak amplification of the flow will occur over the West with time, however, as a short-wave trough moves across the Rockies. As this occurs, frontal low development is expected along the persistent west-to-east front lying from the southern Plains to the Mid-Atlantic region. However, with only weak instability expected near the developing low, and eastward along the front, convection is forecast to remain disorganized. Day 5, the upper wave is forecast to continue eastward across the central and northern Plains through the day, and into and across the Great Lakes region overnight. The associated frontal low -- initially progged to lie over the Oklahoma vicinity, will deepen as it shifts east-northeastward with time, reaching the northeast through the end of the period. The trailing surface front will sharpen and advance southeastward, extending from the Mid-Atlantic region southwestward to coastal Texas late. While showers and a few thunderstorms will be associated with the frontal advance, weak instability anticipated at this time should again hinder convective intensity. Day 6, as the low moves offshore and the front continues advancing steadily southeastward, it should clear the Atlantic and Gulf Coasts during the evening, lingering only across Florida through the end of the period. The continued trend of weak instability, as well as weakening flow with southward extent, should hinder prospects for more robust convection. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CST Tue Feb 04 2025 Valid 071200Z - 121200Z ...DISCUSSION... Medium-range models are in reasonably good agreement through day 6 (Sunday), in terms of large-scale features. Substantial divergence begins thereafter, casting substantial uncertainty into the forecast beyond the upcoming weekend. Day 4, as an upper short-wave trough crossing the Northeast moves into/across the Canadian Maritimes, the quasi-zonal flow pattern over the U.S. will continue. Weak amplification of the flow will occur over the West with time, however, as a short-wave trough moves across the Rockies. As this occurs, frontal low development is expected along the persistent west-to-east front lying from the southern Plains to the Mid-Atlantic region. However, with only weak instability expected near the developing low, and eastward along the front, convection is forecast to remain disorganized. Day 5, the upper wave is forecast to continue eastward across the central and northern Plains through the day, and into and across the Great Lakes region overnight. The associated frontal low -- initially progged to lie over the Oklahoma vicinity, will deepen as it shifts east-northeastward with time, reaching the northeast through the end of the period. The trailing surface front will sharpen and advance southeastward, extending from the Mid-Atlantic region southwestward to coastal Texas late. While showers and a few thunderstorms will be associated with the frontal advance, weak instability anticipated at this time should again hinder convective intensity. Day 6, as the low moves offshore and the front continues advancing steadily southeastward, it should clear the Atlantic and Gulf Coasts during the evening, lingering only across Florida through the end of the period. The continued trend of weak instability, as well as weakening flow with southward extent, should hinder prospects for more robust convection. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CST Tue Feb 04 2025 Valid 071200Z - 121200Z ...DISCUSSION... Medium-range models are in reasonably good agreement through day 6 (Sunday), in terms of large-scale features. Substantial divergence begins thereafter, casting substantial uncertainty into the forecast beyond the upcoming weekend. Day 4, as an upper short-wave trough crossing the Northeast moves into/across the Canadian Maritimes, the quasi-zonal flow pattern over the U.S. will continue. Weak amplification of the flow will occur over the West with time, however, as a short-wave trough moves across the Rockies. As this occurs, frontal low development is expected along the persistent west-to-east front lying from the southern Plains to the Mid-Atlantic region. However, with only weak instability expected near the developing low, and eastward along the front, convection is forecast to remain disorganized. Day 5, the upper wave is forecast to continue eastward across the central and northern Plains through the day, and into and across the Great Lakes region overnight. The associated frontal low -- initially progged to lie over the Oklahoma vicinity, will deepen as it shifts east-northeastward with time, reaching the northeast through the end of the period. The trailing surface front will sharpen and advance southeastward, extending from the Mid-Atlantic region southwestward to coastal Texas late. While showers and a few thunderstorms will be associated with the frontal advance, weak instability anticipated at this time should again hinder convective intensity. Day 6, as the low moves offshore and the front continues advancing steadily southeastward, it should clear the Atlantic and Gulf Coasts during the evening, lingering only across Florida through the end of the period. The continued trend of weak instability, as well as weakening flow with southward extent, should hinder prospects for more robust convection. Read more