SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Thu Jun 03 2021 Valid 031200Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE MID ATLANTIC AND NORTHEAST... ...SUMMARY... Strong to severe storms are possible across parts of the Mid Atlantic and Northeast, mainly this afternoon and evening. Damaging wind gusts are expected to be the primary threat, though isolated hail and a tornado or two will also be possible. ...Synopsis... A positively tilted upper trough extending from the Great Lakes into the lower MS Valley this morning is forecast to move slowly eastward through the period, as an upper ridge amplifies over the Great Basin vicinity. A warm front will move northward through portions of New England during the day, while a weak surface trough will move eastward from the Ohio Valley into the Appalachians. ...Mid Atlantic into Western New England... Scattered clusters of convection are expected through the day along and east of the weak surface trough moving out of the Ohio Valley, within a plume of moist southwesterly flow ahead of the upper trough. The area most likely to see some diurnal heating and at least modest destabilization prior to the onset of convection is the Mid Atlantic into portions of western New England. In this area, MLCAPE potentially exceeding 1000 J/kg in conjunction with effective shear of 35-45 kt will favor organized convection by mid afternoon. Locally damaging wind is expected to be the primary hazard, given the anticipated cluster mode, but some hail cannot be ruled out despite generally weak midlevel lapse rates. If any supercells (either discrete or cluster-embedded) can be sustained, low-level flow/shear will also be sufficient to support a tornado or two. ...Carolinas... Compared to areas further north, convection is expected to blossom early in the day across portions of the Carolinas, in conjunction with the sea breeze and a moisture surge from the Atlantic. Generally weak low/midlevel lapse rates and modest effective shear should tend to limit the overall severe threat, though localized damaging wind and perhaps a brief tornado will be possible with the strongest convective elements, with some low-end threat potentially persisting into the evening. ...TN Valley into the OH Valley... Widespread clouds and precipitation will likely be ongoing at the start of the period across portions of the TN and OH Valleys. Uncertainty remains regarding the magnitude of heating/destabilization that will occur later today across the region, but a few clusters of organized convection will be possible as the upper trough approaches the region. The primary threat will likely be locally damaging wind gusts, though some hail will also be possible, given somewhat cooler midlevel temperatures closer to the upper trough axis. ...Oregon northeastward into western Montana... A midlevel shortwave trough is forecast to move into the Pacific Northwest later today into tonight, which will tend to flatten the northern portion of the upper ridge with time. In conjunction with the shortwave trough, a cold front will move into portions of eastern OR, northern ID, and western MT by this evening. Isolated to widely scattered high-based thunderstorms are expected in association with the front. Steep low/midlevel lapse rates will support a threat of localized severe wind gusts and perhaps some hail with initial development across OR/ID. A small cluster may move northeastward into western MT later tonight, with a continued threat of isolated strong gusts. ..Dean/Squitieri.. 06/03/2021 Read more LIVE: spc.noaa.gov
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