Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0727 AM CDT Tue May 09 2017 Valid 091300Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT FROM EASTERN NEW MEXICO AND WEST TEXAS INTO EASTERN COLORADO... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK...FROM SOUTHWEST TEXAS TO KANSAS AND THE FOUR CORNERS... ...SUMMARY... Scattered severe thunderstorms with large hail, damaging winds, and a few tornadoes are expected from eastern New Mexico and west Texas into eastern Colorado through tonight. ...Southern and central High Plains through tonight... A closed low over the northern Gulf of CA will begin to move toward the northeast in response to the primary embedded speed maxima rotating around the southeastern periphery of the low. Weak lee troughing will be maintained close to the higher terrain in NM as the midlevel low approaches from the southwest, and as stronger southerly/south-southwesterly flow spreads slowly eastward over NM and west TX. In the low levels, northwestward transport of upper 50s to lower 60s boundary-layer dewpoints will continue into west TX and eastern NM, along and east of the lee trough. With the moisture already spreading west into the mountains and with only a weak cap, thunderstorms will gradually increase in coverage/intensity from late morning through the afternoon near the front range in NM. Moderate buoyancy (MLCAPE around 1500 J/kg) and effective bulk shear in excess of 40 kt will favor supercells capable of producing large hail and isolated damaging winds. A few tornadoes will also be possible given sufficient low-level shear/hodograph curvature and moisture, especially with any supercells that can remain discrete. The convection will spread north-northeastward across eastern CO through the afternoon/evening and grow upscale into clusters, with severe storms possible up to the remnant baroclinic zone close to I-70. Isolated storm development will be possible this afternoon across west TX. Forcing for ascent will be weak, and the 12z Midland sounding showed a stout cap. However, some weakening of the cap will likely occur from the west by afternoon per the 12 hour changes at El Paso, as well as from below with surface heating/mixing along the west edge of the richer moisture. Storms that form during the afternoon would likely become discrete supercells with large hail, and there would be some risk for tornadoes as low-level moisture surges west and shear increases in the evening. Additional bands/clusters of storms are expected to form early tonight along the retreating dryline in southeast NM, as the midlevel trough approaches. This convection will subsequently spread northeastward to the TX South Plains and Panhandle through Wednesday morning, with the potential for at least isolated large hail and/or damaging winds. ...OH Valley this afternoon/evening... A weak midlevel speed max and associated weak surface low will move southeastward today across IL/IN/KY. Operational models continue to show excessive evapotranspirative moistening of the boundary layer, which is exaggerating CAPE and reducing CIN too much. Present indications are that the majority of the convection will remain elevated on the cool side of the surface front, and that buoyancy feed from the west and any surface-based storm chances will be reduced. ..Thompson/Kerr.. 05/09/2017Read more
from SPC Forecast Products http://ift.tt/rATNzD
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