Below normal temperatures expected.

General Overview: AN ACTIVE WEATHER PATTERN WILL UNFOLD ACROSS MUCH OF THE CONTIGUOUS UNITED STATES THROUGH THE COMING DAYS, WITH THE MOST SIGNIFICANT HAZARDS CENTERED ON A POTENT SEVERE WEATHER AND HEAVY RAIN THREAT STRETCHING FROM THE SOUTH CENTRAL STATES INTO THE OHIO VALLEY AND MID-ATLANTIC. A BROAD SWATH OF SEVERE THUNDERSTORMS IS EXPECTED TUESDAY INTO WEDNESDAY, WITH HEAVY RAIN AND FLASH FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTH CENTRAL REGION AND LOWER MISSISSIPPI VALLEY. A COLD FRONT WILL SWEEP EASTWARD THROUGH MID-WEEK, PUSHING THE ACTIVE WEATHER FOCUS TOWARD THE EAST COAST BY THURSDAY AND FRIDAY. MEANWHILE, SNOW AND MIXED PRECIPITATION WILL AFFECT PORTIONS OF THE NORTHERN ROCKIES AND NORTHERN PLAINS, WHILE THE WEST REMAINS RELATIVELY QUIET. A NOTABLE TEMPERATURE CONTRAST WILL PERSIST, WITH WELL-ABOVE-NORMAL READINGS ACROSS THE EAST EARLY IN THE PERIOD GIVING WAY TO NEAR-NORMAL OR BELOW-NORMAL TEMPERATURES AS THE FRONTAL PASSAGE OCCURS, WHILE BELOW-NORMAL TEMPERATURES GRIP THE INTERIOR WEST EARLY BEFORE MODERATING LATER IN THE PERIOD.

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EAST: The eastern United States will be at the center of the most impactful weather during the first half of the forecast period. On Wednesday evening, a cold front extending from the Great Lakes southwestward into the Gulf Coast region will serve as the primary focus for widespread thunderstorm activity. A broad corridor of thunderstorms is expected from the Tennessee Valley and Ohio Valley northeastward through the Mid-Atlantic, with the threat for severe thunderstorms particularly pronounced from the lower Mississippi Valley and Arkansas northeastward through the Ohio Valley and into the Mid-Atlantic states. Heavy rain and flash flooding will be a significant concern across this corridor, and residents from the South Central states through the Appalachians and into the coastal Northeast should remain alert for rapidly developing dangerous conditions. Rain will extend into portions of the Northeast and New England as well, with the cold front pushing precipitation northeastward and offshore by Thursday evening. Behind the front, rain will linger across the Southeast and Gulf Coast through Thursday, with thunderstorms continuing across the Deep South and Florida Peninsula. By Friday evening, a low pressure system tracking across the South Central region will draw a warm front northeastward into the Mid-Atlantic and Ohio Valley, keeping thunderstorm activity ongoing across the Southeast and Gulf Coast while rain spreads across the Mid-Atlantic and Northeast. By Saturday, the precipitation focus shifts, with rain covering much of the Northeast, Mid-Atlantic, and Great Lakes, while thunderstorms continue across the Southeast and Gulf Coast states. The overall pattern will be one of persistent, multi-day precipitation across the East, with the severe weather and heavy rain threats being the primary concerns early in the period.

Temperature Anomalies:

-Days 1-3: Temperatures will run well above normal across much of the East, with anomalies of 6 to more than 12 degrees above average particularly pronounced across the Ohio Valley, Mid-Atlantic, and Northeast. The Southeast and Gulf Coast will also be above normal, though by a lesser margin. By Day 3, above-normal readings begin to retreat as the frontal boundary pushes through, though the Mid-Atlantic and parts of New England remain notably warm.

-Days 4-6: The above-normal temperature signal weakens considerably across the East as the frontal passage takes hold. Temperatures trend closer to seasonal normals across most of the region, with only isolated pockets of slight above-normal readings remaining, particularly near the Mid-Atlantic coast and parts of New England. A brief below-normal signal is possible across portions of the Great Lakes and Ohio Valley by Day 4-5.

-Days 7-10: A broad return to above-normal temperatures is expected across the Great Lakes, Ohio Valley, and portions of the Mid-Atlantic and Northeast as a warming trend takes hold heading into the Memorial Day holiday weekend and beyond. Anomalies of 3 to 6 degrees above normal are expected across much of this region, with the warmest departures centered on the Great Lakes and Ohio Valley.

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CENTRAL: The central United States will be home to some of the most significant weather hazards during the forecast period. On Tuesday into Wednesday, a vigorous severe weather outbreak is anticipated from eastern Texas and Arkansas northeastward through the lower and middle Mississippi Valley, the Ohio Valley, and into the Great Lakes region. **Severe thunderstorms capable of producing damaging winds, large hail, and tornadoes will be possible across this corridor, and the threat for heavy rain and flash flooding is particularly elevated across portions of Texas, Arkansas, and the lower Mississippi Valley.** A low pressure system over the South Central Plains will be the primary driver of this activity, with a cold front sweeping eastward and a warm front extending northeastward. By Thursday evening, the low pressure system shifts into the central Plains, with thunderstorm activity continuing across the South Central states and heavy rain remaining a flash flooding concern over portions of Texas and Oklahoma. Snow and mixed precipitation will affect the northern Rockies and portions of the northern High Plains during this period as colder air filters southward behind the frontal system. By Friday, a reorganizing low pressure system over the central Plains will maintain a threat for thunderstorms across the South Central region, with rain and snow continuing across the northern Rockies and portions of the northern Plains. By Saturday, precipitation coverage across the central United States diminishes somewhat, though scattered rain and thunderstorms will persist across the South Central states and portions of the central Plains.

Temperature Anomalies:

-Days 1-3: A sharp temperature contrast will be evident across the central United States. The North Central states and northern Plains will experience temperatures running 6 to 12 or more degrees below normal, with the core of the cold anomaly centered over the central and northern Rockies and High Plains. Meanwhile, the South Central states will be running above normal by 3 to 6 degrees. By Day 3, the below-normal temperature signal begins to expand southward and eastward across the central Plains and Midwest as the cold front advances.

-Days 4-6: Below-normal temperatures will persist across the central Plains, Rockies, and portions of the Midwest through Day 4 and into Day 5, with anomalies of 3 to 9 degrees below normal focused over the central Rockies and central Plains. The below-normal signal gradually weakens by Day 6, with temperatures trending back toward seasonal normals across most of the central United States.

-Days 7-10: A broad warming trend takes hold across the central United States heading into the Days 7-10 period. Above-normal temperatures, generally 3 to 6 degrees above average, will spread across the northern Plains, Midwest, and portions of the central Plains. A notable exception will be a lingering below-normal signal across portions of southern Texas, where temperatures remain slightly below average.

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WEST: The western United States will be relatively less active compared to the rest of the country, though the region will not be entirely without weather concerns. On Wednesday evening, snow and mixed precipitation will be ongoing across portions of the northern Rockies and Intermountain West, associated with a frontal system and low pressure tracking through the region. The Pacific Northwest and northern Rockies will see the most persistent precipitation, with snow at higher elevations and mixed precipitation at lower elevations. Low pressure systems will be present across the Desert Southwest and southern California early in the period, though significant precipitation is not expected with these features. By Thursday evening, snow and mixed precipitation continue across the northern Rockies and portions of the Pacific Northwest, with the overall precipitation pattern gradually shifting northward and eastward. By Friday, a cold front pushing through the northern Rockies will bring additional snow to higher terrain, while the remainder of the West stays largely dry. The Desert Southwest and California will see little to no precipitation throughout the forecast period.

Temperature Anomalies:

-Days 1-3: Temperatures across the West will be running significantly below normal during the early part of the forecast period, with anomalies of 6 to more than 12 degrees below average across the northern and central Rockies, Great Basin, and northern Plains. The Pacific Coast will be near to slightly above normal. By Day 3, the below-normal signal contracts but remains focused over the central Rockies and portions of the central Plains, while California trends slightly above normal.

-Days 4-6: The below-normal temperature signal across the West weakens considerably by Days 4-6. The central Rockies and portions of the Great Basin will still see temperatures running 3 to 6 degrees below normal through Day 5, but the anomalies moderate. The Pacific Coast, including California and the Pacific Northwest, will trend above normal by 3 to 6 degrees during this period.

-Days 7-10: A broad warming trend takes hold across the West by Days 7-10, with above-normal temperatures spreading across much of the Pacific Northwest, northern Rockies, and Intermountain West. Anomalies of 3 to 6 degrees above normal are expected across much of this region. The Desert Southwest will be near normal to slightly above normal.

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TROPICAL: The tropics are quiet at this time. No tropical cyclone activity is expected across either the Atlantic basin or the eastern Pacific basin during the next seven days, and no areas of disturbed weather are currently being monitored for development potential.