What’s causing all this? Well yesterday’s upper level trough has swung through the US. According to the 12Z maps, it is neutrally tilted, and the models suggest that it will become negatively tilted and lift out over the New England area over the next 48 hours. This trough is associated with an MLC on the surface, which is advecting moisture from the Gulf of Mexico into the SE. The cold front with the MLC has a 20 degree F difference, a good pressure trough, and slight turning of the winds.
That is of course synoptically speaking, on the mesoscale aspects, the CAPE values are ok. The shear and helicity look good, which is why they are once again expecting tornadoes. But as said earlier it shouldn’t be as bad as yesterday. When this trough does hit our area tomorrow, snow is expected. Maybe more canceled classes?
Very big weather day today. As weather is affecting schools, elections, and even liv
es from Maine to Texas. Starting with the northeast, a low pressure system, associated with an upper level low over the Great Lakes (on the 850mb map), progressed through the northeast this morning. The Plymouth area received about 3 inches overnight, then it turned over into rain (due to very strong WAA) and it turned into a heavy wet snow. A delay was first issued, then classes were canceled for the whole day at 9am, which gave me time to do some homework, programming, and of course this post.
Our event is pretty much over, but nowhere near over for the Midwest. A very strong upper level trough has advected cold dry air over the Midwest. This along with strong southerly winds at the surface is helping to spark very strong thunderstorms. The Storm Prediction Center has issued a high convective outlook: Something that is somewhat rare within the SPC:
...AN OUTBREAK OF SEVERE THUNDERSTORMS...INCLUDING THE POSSIBILITYFOR LONG-TRACK DAMAGING TORNADOES...IS EXPECTED THIS AFTERNOON INTOTHE OVERNIGHT HOURS...LATEST VISIBLE SATELLITE IMAGERYSUGGESTS LEADING EDGE OF IMPRESSIVELARGE SCALE ASCENT IS BEGINNING TOINTERACT WITH DRYLINE OVER TX.CU FIELD IS EXPANDING/DEEPENINGALONG THE I-35 CORRIDOR AND SEVERALHEALTHY THUNDERSTORMS ARE LOCATEDOVER THE HILL/ELLIS/DALLAS COUNTYAREA. JUST EAST OF THE DRYLINE...SUBSTANTIAL SUNSHINE IS NOTEDALONG AN AXIS ROUGHLY 100 MI WIDEINTO SERN OK. AIRMASS IS WARMINGNICELY ACROSS THIS REGION WHERETEMPERATURES ARE NOW WELL INTO THE70S. 18Z SOUNDINGS JUST DOWNSTREAMACROSS THE MS VALLEY INTO THECENTRAL GULF COAST SUGGEST STRONGCAP HAS WEAKENED AND LIFTED...PERSHV/LZK/JAN. AS THE LARGE SCALEASCENT CONTINUES IT APPEARS THISCAP WILL LIFT AND BECOME NEGLIGENT. NUMEROUS SHOWERS THAT EXISTWITHIN THE BROAD WARM SECTOR ACROSSAR INTO NRN LA WILL DEEPENBECOMING DISCRETE SUPERCELL STRUCTURESWELL AHEAD OF THE DRYLINE/COLD FRONT. THIS PROCESS MAY TAKE SOME TIME...BUT ITAPPEARS BY EARLY EVENING THE SEVERE THREATWILL PROVE EXTENSIVE...STRETCHING FROMTHE ARKLATEX...NEWD INTO WRN TN/KY...SWDINTO NRN LA/MS. GIVEN THE 110KT H5 JETTHAT WILL EJECT ACROSS THIS REGION THISEVENING...EXTREME VERTICAL SHEAR PROFILESWILL ENHANCE THE SEVERE POTENTIAL. ALTHOUGH DISCRETE TORNADIC SUPERCELLS AREEXPECTED...STORM MERGERS AND CONVECTIVEOUTFLOW SHOULD ENHANCE THE POTENTIAL FORVERY STRONG/DAMAGING WINDS...ESPECIALLY IFBOW-TYPE STRUCTURES DEVELOP. THIS PROCESSMAY BECOME THE DOMINANT STORM MODELATE TONIGHT EAST OF THE MS RIVER. IN ADDITION TO TORNADOES ANDDAMAGING WINDS...LARGE HAIL MAY ACCOMPANYSUPERCELLS MAINLY ACROSSTHE WRN HALF OF THE OUTLOOK.
So far there has only been 7 hail and 0 tornado reports. With three tornado watches issued within the states of Oklahoma, Texas, Arkansas, and Missouri, tornadoes are expected through the afternoon and tonight
