Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0730 AM CDT Sat Apr 01 2017 Valid 011300Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS NORTHWEST TEXAS...AND LATE TONIGHT ACROSS THE EDWARDS PLATEAU... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK AREA FROM SOUTHWEST OKLAHOMA INTO CENTRAL TEXAS... ...SUMMARY... Large hail and damaging winds, and an isolated tornado, will be possible this afternoon/evening across northwest Texas. Additional severe storms will likely form overnight across the Edwards Plateau. ...Northwest Texas this afternoon/evening... A closed low over the AZ/NM border will drift generally eastward as embedded speed maxima rotate northeastward around the southeast periphery of the low. At the surface, an initial surface cyclone near Midland will weaken slowly, while a surface front takes on a more northeast-southwest orientation and stalls across northwest TX today. Meanwhile, low-level moisture will spread northwestward from south TX, where boundary layer dewpoints are now in the 65-70 F range. Dewpoints in the low 60s should reach the frontal zone this afternoon, when the northeastward extension of the stronger surface heating (temperatures in the 70s), beneath midlevel lapse rates in excess of 7 C/km, will support MLCAPE values near 2000 J/kg and diminishing convective inhibition. Thunderstorm development is expected along the stalled front across northwest TX after 21z, as a weakening mid-upper speed max rotates north-northeastward in conjunction with diurnal surface heating. Buoyancy and deep-layer vertical shear will be supportive of supercells capable of producing large hail and damaging winds. Low-level flow/shear will not be particularly strong given the lack of cyclogenesis, and any marginal tornado risk should be confined to storms along the boundary this evening. Storms along the front will tend to evolve into a linear band and spread north-northeastward over western and central OK through tonight, as a result of boundary-parallel flow/shear vectors. The severe storm risk will diminish with northeastward extent in OK as a result of weak buoyancy. ...Edwards Plateau overnight into Sunday morning... A separate cluster of strong/severe storms is expected to develop late tonight and early Sunday morning across the Edwards Plateau. Storm development will occur along the front as it begins to move slowly southeastward in conjunction with another speed max rotating northeastward from northern Mexico. Low-level moisture will surge westward into this area tonight beneath steep midlevel lapse rates, and vertical shear will become favorable for supercells embedded within the larger developing cluster. Isolated very large hail, and perhaps an isolated tornado, could occur with the more discrete storms, while damaging winds will become more of a threat as the storms congeal into a larger cluster and spread northeastward toward central TX by the end of the period. ..Thompson/Peters.. 04/01/2017Read more
from SPC Forecast Products http://ift.tt/rATNzD
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