Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 AM CDT Mon May 01 2017 Valid 011300Z - 021200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN/CENTRAL APPALACHIANS AND PARTS OF THE NORTHEAST/MID-ATLANTIC STATES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF GA/CAROLINAS TO THE NORTHEAST STATES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE EASTERN STATES... ...SUMMARY... Severe thunderstorms are expected especially this afternoon into evening across parts of the Appalachians and Northeast/mid-Atlantic States southward to the Carolinas. Damaging winds and some severe hail is expected along with a risk for a few tornadoes. ...Synopsis... A closed trough centered over parts of IA/MO/IL early this morning will continue to spread northeastward and decelerate as it reaches the upper Great Lakes by this evening. On the eastern periphery of this trough, a steadily strengthening belt of mid/high-level south-southwesterly winds will overspread an eastward-moving cold front into the pre-frontal warm sector, particularly over the northern/central Appalachians and mid-Atlantic/Northeast. This eastward-moving cold front will generally reach the spine of the Appalachians by early evening and exit much of the eastern seaboard early Tuesday morning. ...Appalachians to Northeast/mid-Atlantic/Carolinas... Along and ahead of the eastward-moving cold front, an extensive north-south corridor of showers and embedded thunderstorms are ongoing early this morning from the Lake Huron and Lake Erie vicinities and middle/upper OH River Valley south-southwestward into GA/AL. This cloud cover and precipitation may hinder the degree of destabilization in some areas west of the spine of the Appalachians, with the relatively strongest destabilization (albeit only 500-1000 J/kg MLCAPE) expected this afternoon from the western/central Carolinas and western/northern VA into PA and upstate NY, as a warm front effectively shifts northward toward northern NY and southern New England by early evening. An upper-low-peripheral vorticity maxima over the TN Valley this morning will steadily continue northeastward toward the upper OH River Valley, with diminishing mid/high-level cloud cover via the northeastward-spreading upper-level dry slot. Current thinking is that even with front-preceding cloud cover and precipitation this morning, storms should initially intensify by early afternoon from eastern OH and WV/western VA into western PA, and a bit later into southern NY and around mid/late-afternoon across the western/piedmont portions of the Carolinas. While some severe hail will be possible, wind damage should become the most prevalent risk as largely unidirectional wind profiles support the evolution of northeastward-accelerating linear bands of convection with embedded bows, especially across the northern Appalachians vicinity (northern half of the Enhanced Risk) where forcing for ascent will be greatest. Aside from a more prevalent wind-damage risk along with some hail, current thinking is that the relatively greatest risk for some tornadoes will be this afternoon across parts of WV and MD panhandle into western and central portions of PA/NY. This would be related to the possibility of a few semi-discrete supercells and evolving QLCS-related mesovortices with the strongest corridor of 2-3 km AGL southerly winds, where 0-1 km SRH will be in excess of 250 m2/s2. At least some severe risk is likely to continue east/northeastward through early/mid-evening, reaching areas spanning eastern NY/possibly western New England southward to the Delmarva and coastal Carolinas. ...Southeast AL/north FL into GA... A somewhat separate regime of severe risk will exist early today from southeast AL and the FL Panhandle into GA/north FL. This is near/ahead of a weak frontal wave and eastward-moving cold front where moistening and destabilization continues to occur early today in the wake of last evening's storms/outflow. At least some potential for a tornado and/or wind damage may exist this morning, although low-level winds/SRH will begin to weaken this afternoon. See Mesoscale Discussion 620 for additional short-term details. ..Guyer/Peters.. 05/01/2017Read more
from SPC Forecast Products http://ift.tt/rATNzD
No comments:
Post a Comment