yoda

SPC AC 071244 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Mon Aug 07 2023 Valid 071300Z - 081200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FAR EASTERN KY/NORTHEAST TN/NORTHWEST NC...WESTERN AND NORTHERN VA...SOUTHERN AND EASTERN WV...CENTRAL MD...AND FAR SOUTH-CENTRAL PA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY OVER THE CENTRAL HIGH PLAINS... ...SUMMARY... A severe weather outbreak is possible across parts of the eastern U.S. today with widespread damaging winds, locally destructive, and isolated tornadoes as the greatest threats from the southern and central Appalachians to the Mid-Atlantic States. ...Southeast to the Upper OH Valley to the Mid-Atlantic States... A shortwave trough over the Lower OH Valley will advance across the northern Appalachians by this evening. A pair of 500-mb speed maxima from 55-65 kts are expected to be centered by late afternoon across eastern KY/TN and southern WV into western VA/NC, and separately over the Mid-South. Peak flow within an expansive 700-mb jet should be centered between the 500-mb maxima across the TN Valley. A plume of large potential buoyancy supported by high PW and steep mid-level lapse rates, and centered over the Mid-South/TN Valley will expand east-northeast towards the central/southern Appalachians with an expansive swath of MLCAPE from 2000-3500 J/kg expected by peak heating. The 12Z BNA sounding well-sampled this potentially volatile environment. To the north of the steeper mid-level lapse rate plume, minimal inhibition will result in scattered thunderstorms forming by midday centered on far southern OH across eastern KY ahead of the aforementioned trough. This activity will progress into an increasingly favorable thermodynamic and kinematic environment downstream, yielding many supercells capable of producing large hail, damaging winds, and tornadoes. Upscale growth into several linear clusters with embedded supercells is anticipated during the afternoon as convective coverage becomes widespread from PA/MD south-southwest across the southern Appalachian states. Forecast soundings suggest the greatest tornado threat will probably exist across eastern KY/TN northeast across southern/eastern WV, western VA, central MD and into southeast PA. Given the supercell wind profiles, significant severe wind gusts will also be possible on a localized basis. Across the Southeast, the separate mid-level speed max approaching the Mid-South, aiding in the low-level warm-advection regime of elevated thunderstorms over OK/AR this morning, will likely support scattered surface-based thunderstorms forming across the TN Valley by early afternoon. With large buoyancy downstream within the gradient of the strong low to mid-level flow, an extensive linear MCS will likely develop and spread east-southeast across the Carolinas and GA. Widespread damaging winds will be possible here as well, with convection likely weakening towards/after sunset as it approaches the south Atlantic coast.

Large 45 percent hatched wind

Um, that's a large 10% tor probs on the 1300z SPC OTLK... was not really expecting that

45% hatched I would guess

Very detailed and well written AFD this morning about all threats even into tonight re tornado potential re-emergeing after the QLCS threat NEAR TERM /THROUGH TONIGHT/... This morning, low stratus is becoming more widespread east of the Blue Ridge, and should cover most of that area by sunrise. To the west, a combination of low stratus and patchy fog is expected. The upper level clouds have mostly cleared, so once daytime heating begins the stratus should burn off by late morning. Daytime heating brings temperatures into the upper 80s to low 90s. Combined with dew points in the low to mid 70s, expect peak heat indices between 100- 105 east of the Blue Ridge, and 95-99 west. One feature that bears watching is a decaying MCS, with an apparent MCV, that is moving into southern OH as of 3AM. This complex has a high chance of bringing some light rain and cloud cover to our area at some point this morning. That could disrupt some of the severe potential for this afternoon, though the remnant MCV could also act to enhance severe potential - IF it tracks through at the right time. This something to closely follow this morning. Looking ahead at this afternoon and evening, given that we destabilize, all signs point to a likely widespread severe wind event across our area, though all modes of severe weather are possible. A large mid-level trough over the western OH Valley this morning will move eastward toward the Central Appalachians, with two surface lows noted early this morning - one over southern ON and the other along the IN/IL border. These surface lows deepen through the afternoon, with models indicating pressure in the low 1000mb range, which is quite impressive for early August (for a non-tropical low). Storms are expected to develop in a favorable environment today where surface dew points in the low 70s and impressive mid-level lapse rates of 6-7 C/km yield around 1500-2000 J/kg of MLCAPE (SBCAPE up to 2500+ J/kg possible). Storms should easily become organized with deep-layer shear of 35-50KT. Multiple rounds of storms are likely to impact the area today. The moist airmass, approaching PVA max, and remnant MCV could initiate late morning to early afternoon activity west of I-81 into north- central MD. There is some potential for a storm or two to become severe, with damaging winds and hail as the main threats. The main surge is expected to develop by mid afternoon as the strong synoptic forcing arrives, and is enhanced by the existing terrain circulation and lee-side pressure trough. Models are rather good agreement on timing, indicating numerous storms developing west of the Blue Ridge between 2PM-3PM. These initial semi-discrete/cluster storms could pose a large hail threat, in addition to damaging wind gusts and a tornado or two. These storms move east of the Blue Ridge between 4PM-5PM, and likely congeal into a solid/quasi-solid line that reaches the I-95 corridor between 6PM-7PM. This QLCS will be capable of producing widespread damaging wind gusts, in addition to the possibility of embedded QLCS tornadoes. Tornadoes that develop within these squall lines typically have little lead time due to their rapid genesis. It is important to take immediate action if a Tornado Warning is issued for your area. The hail threat should diminish as the line of storms pushes eastward. Finally, as the main mid-level trough moves over our area it could initiate an additional broken line of showers and thunderstorms later this evening. A low-level jet will have developed by that time, and model soundings respond to the increasing low-level shear with very wide hodographs, especially east of the Blue Ridge. There will be a conditional tornado threat that lasts past sunset, and given the strong shear, it won`t take much instability for these storms to intensify. Be sure you have multiple ways of receiving severe weather alerts today, and take immediate action if a severe thunderstorm or tornado warning is issued for your location.

Is it clear out west along the i81 corridor right now?

If @Ellinwood is posting about chasing, does that mean we are at Level 4?

45 percent wind and 5 percent tornado both increased in size on new Day 1

Should be raining right now for you per Radarscope

True, but I believe LWX mentioned in their AFD from this morning that we don't necessarily need a lot of sunshine to destabilize tomorrow due to the extreme shear ETA - yup, it was this morning Let me preface the further detailed environmental analysis that uncertainty remains regarding how morning cldcvr or convective debris may impact the SVR potential in the afternoon. Latest guidance moves clouds out by mid-late morning and quickly destabilizes the region. Given the dynamics and kinematics at play, a long period of heating may not be necessary for the potential of this event to be realized

Not saying it's the same at all, but didn't one of our June derechos have this type of potential scenario happen?

Should move into the DC metro within the hour Starting to thunder here There's more down SW of EZF moving NE... wonder if that makes it up here later this evening

Kinda of odd to say, but the best team in the AL right now is the Orioles with 70 wins

Some real impressive soundings coming out from both the 18z NAM and 18z NAM NEST tomorrow evening across the region, particularly approaching the i95 corridor as get closer to 00z

Afternoon AFD from LWX about tomorrow .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... Given the persistent low-level warm advection overnight, low clouds and patchy fog will likely blanket portions of the area. How quickly the mid-summer solar angle can erode these stratus clouds will dictate the timing and intensity of Monday`s convective weather event. All severe parameters are coming into alignment, accompanied by rather extreme shear profiles for early August. A robust shortwave tracking from the Upper Great Lakes will arrive during the peak in the diurnal heating cycle. Further, between 18Z Monday and 06Z Tuesday, 12-hour height falls are likely to run between 5-7 dm which is impressive for the time of year. The Storm Prediction Center has highlighted the entire area in an Enhanced Risk for severe thunderstorms. While the main threat is damaging to locally destructive winds, a few tornadoes and large hail reports are also possible. If convection is able to thrive into the mid/late evening, an increasing low-level jet will lead to enlarged 0-1 km hodographs. This would support some degree of tornado risk if the event persists. An additional issue will be the risk for flash flooding given the threat for 1-2 inches of rainfall, locally up to 3-5 inches. The HREF signal really jumps off the charts with some of the Day 2 totals noted in a few of its ensemble members. Depending on how this evening`s convection pans out, this will dictate areas which would be vulnerable to additional heavy rainfall.

I think some of it will depend on how much sun we get tomorrow morning with regards to cloud debris, as you and others have mentioned. If we can get sun going by like 10am... we might be off to the races. I expect some decent tornado potential tomorrow with the curved hodo's and low LCLs as well.

Flood Watch up for I95 corridor from near EZF to DC metro into Baltimore metro this evening into the overnight Flood Watch National Weather Service Baltimore MD/Washington DC 239 PM EDT Sun Aug 6 2023 ...Heavy rainfall will move through the area this evening into the overnight hours leading to scattered instances of flash flooding... DCZ001-MDZ011-013-014-504-506-508-VAZ053>055-527-070245- /O.NEW.KLWX.FA.A.0005.230807T0000Z-230807T0600Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ District of Columbia-Southern Baltimore-Prince Georges-Anne Arundel- Central and Southeast Montgomery-Central and Southeast Howard- Southeast Harford-Fairfax-Arlington/Falls Church/Alexandria-Stafford- Central and Southeast Prince William/Manassas/Manassas Park- Including the cities of Montclair, Rockville, Annapolis, Bowie, Falls Church, Annandale, Lake Ridge, Manassas, Aberdeen, Columbia, Bethesda, Dale City, Laurel, Odenton, Severn, South Gate, College Park, Herndon, Gaithersburg, Reston, Camp Springs, Severna Park, Arnold, Suitland-Silver Hill, Chantilly, Clinton, Alexandria, Silver Spring, Baltimore, Franconia, Falmouth, Greenbelt, Glen Burnie, Woodbridge, Centreville, Ellicott City, Washington, Arlington, and McLean 239 PM EDT Sun Aug 6 2023 ...FLOOD WATCH IN EFFECT FROM 8 PM THIS EVENING TO 2 AM EDT MONDAY... * WHAT...Flash flooding caused by excessive rainfall is possible. * WHERE...Portions of DC, Maryland and northern Virginia, including the following areas: in DC, District of Columbia. In Maryland, Anne Arundel, Central and Southeast Howard, Central and Southeast Montgomery, Prince Georges, Southeast Harford and Southern Baltimore. In northern Virginia, Arlington/Falls Church/Alexandria, Central and Southeast Prince William/Manassas/Manassas Park, Fairfax and Stafford. * WHEN...From 8 PM this evening to 2 AM EDT Monday. * IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. * ADDITIONAL DETAILS... - Heavy rainfall moving through with the potential for 1 to 2 inches of rainfall, locally higher, in a short period of time. - Please visit www.weather.gov/safety/flood for flood safety and preparedness information

Correct on both counts

45 WIND ADDED ON 1730Z OTLK @high risk @Kmlwx @Eskimo Joe

Well written AFD this morning from LWX about Monday SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... Monday has the potential to be an impactful SVR wx day across the region as anomalously strong flow for this time of year moves into a favorable airmass. Synoptically, a shortwave trough will be moving through the Ohio Valley during the day on Monday. At the sfc, an area of low pressure will trek from northern Ohio into northwestern PA and western NY Monday afternoon/evening. This area of low pressure is anomalous for this time of year (~1000-1004 mb depending on model of choice) as indicated by NAEFS/EPS CFSR climatology. The associated cold front is forecast to move through the area during peak heating in the afternoon/early evening. Let me preface the further detailed environmental analysis that uncertainty remains regarding how morning cldcvr or convective debris may impact the SVR potential in the afternoon. Latest guidance moves clouds out by mid-late morning and quickly destabilizes the region. Given the dynamics and kinematics at play, a long period of heating may not be necessary for the potential of this event to be realized. From an environmental standpoint, not much has changed. Wind shear will be anomalous/impressive for early August standards (40-60 kts) with lesser, but still notable values of low-level shear. There remains dry air forecast in the mid-levels, which should at least locally enhance the downburst potential given inverted V sounding profiles. Low level lapse rates will be favorable given heating of sfc temps to near 90F. Mid-level lapse rates will be okay for Mid-Atlantic standards (6-6.5C/km). The one observation in hodographs over the past ~24 hours is how the vertical wind profile is not a linear increase in winds with height. Different jet streaks are forecast at different levels between 18-00Z, which is showing up on several models now and causing the hodographs to be wavy in the mid-upper levels. Should this come to fruition, this is not conducive for long- lasting mesocyclones. This may result in a linear storm mode with an embedded TOR threat. Now should the storm initiation be delayed into the 21-03Z window, the potential for mesocyclones becomes more favorable ad the LLJ makes the hodographs wider in the low levels. Will continue to monitor these trends. LCLs are forecast to be rather low which adds confidence to the TOR threat given the wind profiles. In terms of impacts: 1) All modes of SVR wx are possible. While damaging winds are the greatest threat at this time, there is also a tornado and large hail threat. The large majority of the FA is under an Enhanced Risk from SPC west of the Chesapeake Bay. See spc.noaa.gov for the latest SVR wx outlook and probabilities for different phenomena. 2) The seasonably moist airmass will result in torrential rainfall as the storms move through. Rain rates could be high enough to support flash flooding given the forecast 2" PWATs, especially across the DC/Baltimore metro into northeast MD where WPC has a Slight Risk for Excessive Rainfall.

Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sun Aug 06 2023 Valid 071200Z - 081200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL/SOUTHERN APPALACHIANS AND THE MID-ATLANTIC STATES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY ACROSS THE CENTRAL HIGH PLAINS... ...SUMMARY... Severe thunderstorms are possible Monday across portions of the southern Appalachians, mid-Atlantic and northeast U.S. Scattered swaths of damaging gusts are expected with this activity. Additional widely scattered thunderstorms are possible across the central High Plains, posing a risk for large hail and damaging gusts. ...Synopsis... A potent mid/upper shortwave trough this time of year will shift east from the Mid-MS Valley to the Appalachians on Monday. This will bring a band of anomalously strong west/southwesterly flow to the region, with the strongest flow focused from southern PA southward to northern GA and the Carolinas vicinity. At the surface, low pressure will shift east from northern IL into northern OH through evening, before lifting northeast across the lower Great Lakes overnight. A cold front attendant to the surface low will sweep east/southeast across the Midwest, and become positioned from western NY/PA into northern AL/MS by Tuesday morning. Mid 60s to mid 70s F surface dewpoints are forecast across the large warm sector ahead of the cold front and ejecting mid/upper trough. ...OH Valley to Mid-Atlantic... Some areas of showers and cloudiness are possible early in the day across parts of the Mid-Atlantic vicinity in association with an ejecting lead shortwave impulse, continued warm advection and backed low-level flow to the east of a lee surface trough should keep the atmosphere primed for severe thunderstorm potential during the afternoon/evening. Convection is expected to develop by midday closer to the surface front over parts of OH/KY. Multiple bands of convection are then expected into the afternoon with eastward extent into WV/southern PA and the Delmarva. A mix of semi-discrete cells and clusters are possible initially. A risk for all severe hazards is expected given effective shear greater than 40 kt, effective SRH greater than 200 m2/s2 and MLCAPE 1500-3000 J/kg. With time, upscale growth into a bowing MCS is possible across parts of southern PA/WV and into the Delmarva vicinity, posing an Enhanced risk (level 3 of 5) for severe/damaging gusts during the afternoon/evening. Instability will weaken with northward extent into NY and southern New England. However, isolated strong/severe storms posing a risk mainly for strong gusts and perhaps small hail are expected.