Quincy

I've been casually watching Sunday across the north-central states. A lot can change and there has been some model adjusting, but keeping an eye on a vigorous shortwave forecast to eject across the northern Plains Sunday into early Monday. There may be somewhat of a disconnect between the best forcing, strongest wind fields and the warm sector, but details can be ironed out in the coming days. Based on model indications now, I'd peg the focus on the eastern Dakotas into the Upper Midwest as an area to keep an eye on. Nothing significant and not outbreak-material, but the way this year has gone, at least it's something on the radar. I wonder how this fall will shape up, if it may try to pull a 2013 or keep the trend of generally lackluster severe threats. I'd tend to lean toward the latter.

One of the biggest flops of the year, I'd say. I don't think the models handled it all that badly. The HRRR was pretty much onboard with storms merging into a massive line fairly quickly. The parameters weren't off the charts either, so I'm not sure a 10% tornado threat over such a large area was warranted. Only two severe reports, period, north of Omaha. One in Minnesota and one in North Dakota. A prime example of #2015ing.

Mid-level lapse rates are just awful tomorrow. One of several mitigating factors. I do think that eastern Kansas to perhaps far southeastern Nebraska has a conditional risk for something interesting, severe-wise. The NAM is trying to keep the low-levels a bit backed, which would be more favorable than the typical cold frontal passage. Even with that said, storm mode and convection evolution looks rather messy across the board.

Nice looking supercell (tornado warned) in far northwestern Minnesota. There were several reports earlier of baseball sized hail, including a 3" hail report out of Roseau, MN.

SPC going with higher confidence today is a potential tornado threat across South Dakota and adjacent Nebraska. Although instability and moisture return will not be nearly as favorable as yesterday, the overall timing with respect to peak heating and coverage of convective initiation should result in several strong to severe thunderstorms. Forcing will be more focused with water vapor imagery showing a shortwave through moving east through Montana. Mid level temperatures are cooler, so capping is not a concern. Convection allowing model solutions include thunderstorms developing by midday to early afternoon. Combine the aforementioned setup with a weak surface low lingering across southern South Dakota/far northern Nebraska and the locally backed flow could support a few tornadoes. HRRR has fluctuated a bit with respect to exact placement, however it has consistently showed convective initiation across South Dakota with at least a few more robust looking semi-discrete storms on the southern flank of the activity. ...SD INTO NORTH CENTRAL/NERN NEB AND NWRN IA... A MOIST ENVIRONMENT WITH SURFACE DEW POINTS IN THE MID 60S F EXTENDS NWD INTO CENTRAL/ERN PARTS OF SD AND NEB. OVERNIGHT CONVECTION HAS BEEN GRADUALLY WEAKENING DURING THE PRE-DAWN HOURS AND THIS SHOULD LEAD TO A DECREASE IN CLOUD COVER THIS MORNING WITH SUBSEQUENT POCKETS OF STRONGER ADIABATIC HEATING AND DIURNAL DESTABILIZATION OCCURRING. MODEL CONSENSUS INDICATES STORMS WILL DEVELOP BY EARLY AFTERNOON OVER PARTS OF CENTRAL SD WHERE LOW LEVEL CONVERGENCE WILL BE ENHANCED NEAR THE FRONT AND ASSOCIATED SURFACE LOW. STRONGER WESTERLY MID LEVEL WINDS /35-45 KT AT 500 MB/ COUPLED WITH AN EASTERLY COMPONENT TO THE LOW-LEVEL WINDS ALONG/NORTH OF THE FRONT WILL PROVIDE SUFFICIENT DEEP LAYER SHEAR TO SUPPORT SUPERCELL STRUCTURES CAPABLE OF PRODUCING LARGE HAIL...DAMAGING WIND GUSTS...AND POSSIBLY SEVERAL TORNADOES. THIS ACTIVITY IS LIKELY TO SPREAD SEWD WITH TIME AS THE WINDS ALOFT VEER TO A MORE NWLY COMPONENT...WITH THE SEVERE THREAT SPREADING ACROSS NORTH CENTRAL/NERN NEB AND POSSIBLY NWRN IA BY THIS EVENING. THE THREAT IS EXPECTED TO DIMINISH AFTER SUNSET WITH THE ONSET OF LOW-LEVEL COOLING AND AIR MASS STABILIZATION.

Tornado touched down right around 9:00 just east of Elk Creek. I had a visual on it by 9:01 (wooded area). Began roping out and lifted at 9:11 p.m. 8 SE Elk Creek.

Cap winning out via TOP 00z sounding. Limited instability/poor low-level thermal profile at OAX:

Not surprised that the SPC toned up the wording a bit for day 2. Still some mixed signals, but a few signs are there for a potentially enhanced severe weather threat. Both the NAM and GFS show enlarged hodographs and considerable shear, including in the low levels, from far eastern Nebraska into west-central/southwestern Iowa, coinciding with strong instability. Some red flags/uncertainties arise from the high PW values forecast, some warming in the mid-levels, attributing to initially modest mid-level lapse rates and storm mode. While the 4km NAM is actually late with renewed storm development, the GFS shows more of a mass of convection developing over Iowa. I would suspect that the storm model will be fairly messy and if any semi-discrete or discrete storms do fire, they would be HP and merge relatively quickly. Nonetheless, a tornado threat may exist, especially if any storms can fire in the vicinity of strong low-level shear, perhaps near any lingering outflow boundaries from early-day convection.

A series of supercell thunderstorms moved through central and eastern Massachusetts this afternoon. Some of the storms prompted tornado warnings and there were multiple significant severe weather reports as a result. Some of the thunderstorms originated as far west as eastern New York and later reached peak intensity as they moved into portions of central and southern New England. Even the coastal community of Boston was hit with some regionally impressive severe weather. The prelude to these afternoon storms actually came in the form of early-day severe storms this morning. A line of severe wind-producing thunderstorms affected portions of southeastern Connecticut, Rhode Island and Cape Cod. An area that does not often see severe weather, especially during the morning hours. Once those storms moved out, there was some clearing, which led to plenty of daytime heating to fuel another round of thunderstorms. By early afternoon, there was an area of moderate to strong instability developing across the eastern half of Massachusetts, coinciding with seasonably strong wind shear. The mesoanalysis showed a corridor of moderate buoyancy coinciding with more than adequate wind shear for supercell thunderstorms. Bulk wind shear was in excess of 50 knots across the region. With clusters of thunderstorms ongoing across portions of the area, the storm mode was going to be critical in the evolution of the event. If storms merged, lines would form, suggesting more of a damaging wind threat. If the storm mode was messy, the inflow region and overall environment could be disrupted, resulting in mainly sub-severe storms. However, if any storm could remain discrete and from on the southeastern fringe of the activity, in order to take better advantage of stronger instability, then things would become a bit more interesting. Two thunderstorms began to split in northern Worcester County shortly before 2 p.m. The northern most storm tracked east-northeast into far southern New Hampshire. This storm merged with surrounding storms and did not strengthen much. The southern storm took a bit of a right turn and continued in a generally eastward direction. This cell moved through northern Worcester County, organizing quickly into a robust supercell. Velocity and hail signatures increased, indicating the likelihood of 1-2″ diameter hail. This storm further organized with rotation becoming more focused. A hook was noted on radar and a Tornado Warning was issued. The storm continued into northern Middlesex County, dropping more large to significant hail, but the velocity signature was marginal at best for tornadic development. The main story was hail. Speaking of hail, a second supercell developed on in west-central Worcester County a short time later. This storm was semi-discrete, but remained that way for quite some time. It also dropped large hail and continued for two more hours, moving right through downtown Boston. Large hail was reported throughout portions of the city and surrounding areas. Overall, there were numerous reports of golf ball or larger hail across Massachusetts, with at least three confirmed reports of hail at least two inches in diameter. A few additional discrete storms developed later in the afternoon, but earlier storms had overturned the atmosphere a bit. These storms were generally strong to only marginally severe in nature. No tornadoes have been confirmed as of 10:00 p.m. Although there was some localized backing of low-level wind fields, the lack of favorable low level helicity was a limiting factor in the tornado potential. Nonetheless, a fairly uncommon significant hail event affected the eastern half Massachusetts, an area that based on a 1980-2006 average, only reports significant hail once every 6.75 years. This is based on four reports across all of eastern Massachusetts, during the time. While there were four significant hail reports in that 27 year span, there were three such reports this afternoon alone. Keep in mind that the time of record is relatively short, as reports from 2007 to this year were also not included. A look at the 2 p.m. mesoanalysis showing 1000-1500+ J/kg MLCAPE and locally backed near-surface winds in the vicinity of the most robust supercells:

Tomorrow's setup isn't all that much different from today. If anything, somewhat stronger instability, but forcing may be slightly weaker. I'd expect a similar outcome, although the storm mode and motion may be more on the messy side. Same area too, with storms firing over northeastern New Mexico and moving toward/into the Texas panhandle.

Currently have a trio of intense supercells ongoing across the Texas panhandle. All are producing large to very large hail. The storm that passed over Channing dropped baseball sized-hail.

I find it a bit odd that the panhandle watch has <5% probs for 2+ tornadoes. I can't say I expect a bunch, but the environment looks increasingly favorable between AMA and LBB by 00-02z, IF storms can remain discrete. Dew-points are well into the 60s with backing low-level flow and moderate instability. Further north, the storms have already formed a line segment and may only pose a marginally severe hail risk with a higher likelihood of damaging winds.