April 30, 2016 – 12z

Low pressure is located over northeast Kansas this morning and a cold front is pushing eastward across Oklahoma and Texas.  It is quite cool from New England to the Northern Plains, and cool air has filtered south across the Plains behind the cold front.  Temperatures below 32 degrees are common across the Central Rockies and Central High Plains and heavy snow has been falling in parts of Wyoming and western Nebraska.  In the warm sector, severe thunderstorms have been occurring across Louisiana and southeast Texas, and widespread showers and thunderstorms extend from the Lower Mississippi Valley to the Ohio Valley and Midwest.

Otherwise, the most widespread precipitation is associated with a storm system over the Southwest U.S.  Scattered showers extend from northwest Arizona westward into California.

April 29, 2016 – 12z

Low pressure is deepening near the New Mexico/Texas border this morning.  A nearly stationary front extends from the low eastward along the Red River, to the southeast U.S.  The atmosphere is very moist across the Southern Plains and Lower Mississippi Valley and widespread showers and thunderstorms extend from southeast Texas and Louisiana northwestward to the Central Rockies.  Heavy snow is falling across parts of Colorado and northern New Mexico.  Some severe thunderstorms are occurring across Arkansas and western Texas.

Unseasonably cool temperatures with some areas below freezing are found from New England westward to the Northern Plains to the Central and Northern Rockies.

Severe thunderstorms possible Friday

The basics are fairly straight forward this evening.  An upper low is located just west of the Four Corners, and it will be moving to south central or southeast Colorado on Friday.  A strong and diffluent mid level jet with H5 winds in excess of 70 knots will extend from far southwest Texas to northwest Oklahoma.   Surface low pressure will be deepening, moisture will be returning and there will be thunderstorms.  The details are much more complex and the forecast is a complicated one.

At Midnight, severe thunderstorms are occurring over the western end of the Oklahoma Panhandle and far northwest corner of the Texas Panhandle.  More widespread thunderstorm activity is expected to develop during the overnight hours, advancing eastward, reaching western Oklahoma just prior to daybreak on Friday.  Also, more isolated thunderstorms are likely to form in developing warm air advection over south central and southeast Oklahoma.  Any of these storms will have the potential to be severe with marginally severe hail and wind.   How the precipitation evolves through the morning and early afternoon hours is a big question which has a significant impact on the severe potential during the afternoon and evening.  Model guidance is all over the place with respect to this.  The latest runs of the HRRR indicate that the most widespread thunderstorm activity will stay across northern Oklahoma, and that the southern half of the state will see atmosphere recovery during the afternoon.  If this occurs, the atmosphere south of I-40 would become prime for severe thunderstorms with moderately strong low and deep layer shear and high instability.  Supercell storms with all facets of severe weather would be possible.  Other model guidance suggest more widespread thunderstorm activity Friday morning – farther south – effectively reducing the severe risk and shoving it south of the Red River.  Some other outlying model groups suggest that atmosphere recovery could occur as far north as the Kansas border.  The bottom line is that we won’t know until late morning which camp of model guidance is likely to be correct.  Most areas of the state will have the potential for severe thunderstorms on Friday.  The area that has the greatest potential for seeing significant severe weather events / including tornadoes / is across southwest and south central Oklahoma.

April 28, 2016 – 12z

Filling low pressure is located over Iowa this morning.  A front meanders from the Mid-Atlantic to the Ohio Valley to central Texas and the Southern Rockies.  The air is warm and moist southeast of this boundary, while cool air has filtered southward across the Plains.  Temperatures below freezing are found across the Northern and Central Rockies and Northern Plains.  Showers and thunderstorms are occurring across the Deep South and a considerable amount of precipitation is falling from the Mid-Atlantic northwestward to the Upper Midwest.  Snow is falling across higher elevations of Montana and Colorado, and scattered rain and snow extends from the Great Basin to California.

Severe thunderstorms possible Thursday

This Wednesday evening, a strong upper wave is diving southeastward along the California coast.  The closed low will be located just west of the Four Corners by 7 pm on Thursday.  An upper ridge just west of the state will be shifting eastward during the day and have an axis from central Nebraska to eastern Oklahoma by evening.  Increasing southwest flow and subtle lifting will be spreading from west to east across the High Plains during the day.  In response, deepening low pressure will be found over the Texas Panhandle.  Low level moisture will be making a return as a southeasterly low level jet strengthens, with sufficient moisture for thunderstorms making it northwestward to the Oklahoma Panhandle and extreme northeast New Mexico.  Afternoon heating and steep mid level lapse rates of 8.5 to 9.5 C/km will result in the atmosphere becoming quite unstable during the day, especially across the eastern panhandles, southwest Oklahoma and northwest Texas where MUCAPE will range from 1500 to 2000 j/kg.  Southeast low level flow with over topping southwest mid level flow will result in a shear profile favorable for rotating storms.  Supercells with very large hail and damaging winds will be possible by late afternoon, which will continue into the evening hours.  While the tornado threat is non-zero, it is expected to be low due to somewhat limited moisture.  Other severe thunderstorms will be possible by late evening in the area of a front which will be located near the Red River.  Also, severe storms will be possible farther south along the dryline into southwest Texas.

April 27, 2016 – 12z

Deep low pressure is located over south central Nebraska this morning.  Some snow is falling over the western Dakotas, otherwise a widespread area of rain is falling across portions of the Central and Northern Plains.  Thunderstorms / some severe / are advancing across the Mississippi Valley.  Other showers and thunderstorms extend from Kentucky to the Mid-Atlantic.  Widely scattered showers and mountain snows are falling across the Great Basin and northern California.