- Day Three
acus03 kwns 160812
Storm Prediction Center ac 160811
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0211 am CST Sat Feb 16 2019
Valid 181200z - 191200z
..no severe thunderstorm areas forecast...
the risk of severe thunderstorms appears negligible across the U.S.
Monday through Monday night.
Although embedded short wave developments remain somewhat unclear,
models indicate that larger-scale western U.S. Mid-level troughing
may undergo some amplification during this period. It appears that
this will occur as another in a series of short wave perturbations
digs inland of the Pacific coast: this one to the south/southwest of
the preceding impulses, across the southwestern international border
Downstream, while mid-level subtropical ridging centered near/east
of the Bahamas remains prominent, short wave ridging within the
mid-latitude westerlies is forecast to build, in phase with the
subtropical stream, across lower portions of the Southern Plains
into the lower Ohio and Tennessee valleys. As a vigorous short wave
impulse digs within a branch of westerlies to the north, to the
southwest of Hudson Bay, it appears that increasingly confluent
mid-level flow will support the southeastward development of the
center of an expansive cold surface ridge, across the northern
plains through southern portions of the Great Lakes region.
The shallow southern/leading edge of the cold surface-based air
appears likely to advance off the South Atlantic coast, while
remaining quasi-stationary, beneath the mid-level ridging, across
northern portions of the Florida Peninsula through much of the
remainder of the northern Gulf Coast vicinity. Above it, a
southerly return flow will be maintained, including further
moistening off a modifying boundary layer over the western Gulf of
Mexico, into the western and central Gulf Coast states.
In the presence of weak (but increasing) elevated instability,
modest strengthening of the return flow (including 30-40 kt at 850
mb) may be accompanied by steepening isentropic ascent supportive of
increasing potential for scattered thunderstorm development by late
Monday night. Depending on the magnitude of cape and depth of the
convective layer, the environment could become conducive to severe
hail in the presence of strong vertical shear, mainly in a narrow
corridor roughly across central Louisiana and adjacent portions of
Texas and Mississippi. However, due to a number of lingering
uncertainties, including timing near the end of the period, severe
probabilities still appear less than 5 percent at the present time.