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    • MD 1485 CONCERNING SEVERE THUNDERSTORM WATCH 510... FOR PORTIONS OF SOUTHERN SOUTH DAKOTA INTO NORTHERN NEBRASKA Mesoscale Discussion 1485 NWS Storm Prediction Center Norman OK 1014 PM CDT Mon Jul 15 2019 Areas affected...Portions of southern South Dakota into northern Nebraska Concerning...Severe Thunderstorm Watch 510... Valid 160314Z - 160445Z The severe weather threat for Severe Thunderstorm Watch 510 continues. SUMMARY...Severe threat continues for the remainder of Severe Thunderstorm Watch 0510. Severe wind gusts will be the main threat, with occasional large hail possible. Trends are currently being monitored for the potential of a downstream WW issuance. DISCUSSION...Multicellular convection has gradually congealed into a loosely organized MCS along the northwest NE/southwest SD border, with a few severe wind reports noted within the past couple of hours. While the overall kinematic fields are weak downstream of the MCS (with no anticipated appreciable ramp up in a nocturnal low-level jet), adequate buoyancy resides across all along the NE/SD border, owing to steep lapse rates in the 700-300 mb layer, and rich low-level moisture extending up to 850 mb (per latest RAP forecast soundings). As such, ample elevated instability is expected throughout the night in advance of the storms, even with a gradually stabilizing boundary layer, which may sustain the MCS, as indicated by several members of the 00Z HREF, and the last few runs of the HRRR. Still, the marginal deep-layer and low-level shear environment may also promote progressive cold pools, which may outrun the antecedent convection, potentially weakening the MCS. Given the uncertainty in MCS evolution within the ambient weakly forced but highly buoyant environment, convective trends will continue to be monitored for a potential downstream WW issuance. ..Squitieri/Grams.. 07/16/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...OAX...GID...LBF...UNR...CYS... LAT...LON 41050128 42020215 42600255 43130287 43360279 43450236 43349979 43129784 42199766 41849784 41509829 41269881 41050128 Read more View the full article
    • No Mesoscale Discussions are in effect as of Tue Jul 16 01:46:02 UTC 2019. View the full article
    • MD 1484 CONCERNING SEVERE THUNDERSTORM WATCH 509... FOR PORTIONS OF SOUTHEASTERN MN INTO WESTERN/CENTRAL WI Mesoscale Discussion 1484 NWS Storm Prediction Center Norman OK 0715 PM CDT Mon Jul 15 2019 Areas affected...Portions of southeastern MN into western/central WI Concerning...Severe Thunderstorm Watch 509... Valid 160015Z - 160145Z The severe weather threat for Severe Thunderstorm Watch 509 continues. SUMMARY...Primarily an isolated strong to damaging wind threat continues across remaining valid portions of Severe Thunderstorm Watch 509. Downstream watch issuance into more of western/central WI and southeastern MN is not expected this evening. DISCUSSION...Over the past couple of hours convection has consolidated into a line along a pre-frontal surface trough extending from northwestern WI into parts of southeastern MN. Given the linear mode, isolated strong to damaging outflow winds should be the main threat through the remainder of the evening. However, a brief tornado cannot be ruled out in the short term along the southern flank of the line, where a recent rotational velocity couplet around 40 kt was observed in Scott County MN before weakening. Instability rapidly decreases into central WI and far southeastern MN, where convective overturning from earlier thunderstorms has generally stabilized the low levels. Current expectations are for the ongoing line of storms to weaken as it progresses southeastward into WI and far southeastern MN through the evening. Therefore, an additional Severe Thunderstorm Watch into more of western/central WI and far southeastern MN is not anticipated at this time. ..Gleason.. 07/16/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GRB...DLH...ARX...MPX... LAT...LON 44159474 44869453 45159419 45099287 45939181 46459113 46559057 46469030 46309012 46238981 45878930 44318998 43549129 43549417 44159474 Read more View the full article
    • MD 1482 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF WESTERN UPPER MI INTO FAR NORTH-CENTRAL WI Mesoscale Discussion 1482 NWS Storm Prediction Center Norman OK 0610 PM CDT Mon Jul 15 2019 Areas affected...Portions of western Upper MI into far north-central WI Concerning...Severe potential...Watch unlikely Valid 152310Z - 160045Z Probability of Watch Issuance...20 percent SUMMARY...An isolated strong/gusty wind threat may exist across parts of western Upper MI into far north-central WI this evening. Watch issuance appears unlikely. DISCUSSION...A line of convection that has developed ahead of a surface cold front in association with a low-amplitude shortwave trough over MN and southern Ontario will continue eastward across western Lake Superior. With generally 1000-1500 J/kg of MLCAPE (locally stronger) and 25-40 kt of mid-level westerly flow present over this region, there is some concern that the line will be able to maintain its intensity as it crosses Lake Superior and subsequently moves over parts of western Upper MI and far north-central WI over the next couple of hours. The best threat area does appear to be spatially confined to a small part of western Upper MI in the wake of earlier convection now over northeastern WI and northward-moving outflow. Still, mainly an isolated strong/gusty wind threat could exist through the evening where diurnal heating has been able to steepen low-level lapse rates. Although watch issuance appears unlikely at this time, observational trends will continue to be monitored. ..Gleason/Grams.. 07/15/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MQT...GRB... LAT...LON 46518725 46088758 45888815 45888928 46318991 46649029 46838993 47418847 47568786 47488755 47088743 46518725 Read more View the full article
    • MD 1483 CONCERNING SEVERE THUNDERSTORM WATCH 510... FOR EASTERN WYOMING INTO SOUTHWESTERN SOUTH DAKOTA AND WESTERN INTO CENTRAL NEBRASKA Mesoscale Discussion 1483 NWS Storm Prediction Center Norman OK 0642 PM CDT Mon Jul 15 2019 Areas affected...Eastern Wyoming into southwestern South Dakota and western into central Nebraska Concerning...Severe Thunderstorm Watch 510... Valid 152342Z - 160115Z The severe weather threat for Severe Thunderstorm Watch 510 continues. SUMMARY...The severe threat continues across Severe Thunderstorm Watch 0510. Large hail and severe wind gusts remain the primary threat. Upscale growth of convection remains possible across northwestern portions of the watch, where severe winds may become the predominant threat. Outflow from earlier storms have stabilized the airmass across southeast parts of the watch, where the short term severe threat has been tempered. DISCUSSION...Semi-discrete to discrete storms, including transient supercell structures, have developed and matured across the lower-terrain areas in eastern Wyoming over the past few hours. Ample buoyancy (1500-2500 J/kg MLCAPE) and adequate deep-layer shear (35-45 knots of bulk effective shear) are in place to foster the maintenance of this convection. Poor speed and directional shear in the lowest 3 km, however, suggests that some outflow dominant tendencies should exist with some of the more intense cells with more robust, water/hail loaded downdrafts. As such, cold-pool merging is expected to commence over the next few hours, promoting upscale growth for potential MCS development, as suggested by both the 12Z HREF and the last few runs of the HRRR. Should this occur, severe wind gusts should become the main threat, particularly in far east WY into southwest SD. The intensity of the potential MCS is somewhat uncertain, as a meager to negligible low-level jet is expected to develop during the evening. As such, robustness of the MCS will depend entirely on cold pool propagation processes, and the amount of buoyancy available ahead of the convective leading line. Meanwhile, multicellular convection in northern Nebraska, supported by 3000+ J/kg MLCAPE, have exhibited copious outflow given the very weak low-level and deep-layer shear environment in place. A substantial cold pool has been left behind across southeast parts of Severe Thunderstorm Watch 0510, suggesting that the severe threat has been dampened to a degree via boundary layer stratification and mid-level convective overturning/diminishing of lapse rates. Still, at least a few hours of diurnal heating remain, and the chances for additional severe weather will hinge on the trajectory and intensity of the potential aforementioned MCS. ..Squitieri/Grams.. 07/15/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...LBF...UNR...CYS...BYZ...RIW... LAT...LON 41280519 44830716 44820124 41289960 41280519 Read more View the full article
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