Area forecast discussion National Weather Service Detroit/Pontiac Michigan 643 am EDT Wednesday Jun 19 2013 Aviation... //discussion... An extended stretch of favorable aviation conditions will exist across Southeast Michigan as high pressure slowly settles through the region. VFR conditions will plenty of clear sky during this time. Light easterly winds will exist today. //Dtw threshold threats... * none && Previous discussion...issued 339 am EDT Wednesday Jun 19 2013 Short term...today and tonight Sprawling high pressure system extending from the upper MS valley to western Quebec will maintain control across the region over the next 24 hours. This will retain a seasonably cooler and more stable environment as weak low level easterly flow tucked beneath broad middle level northwesterlies limit the diurnal recovery to simple diabatic heating provided by strong middle June sunshine. This will translate into highs of lower to middle 70s...again slightly cooler along The Thumb with the onshore wind off the cooler waters cutting slightly into the thermal response. A clear sky...weakening gradient and dry profile will again promote good radiational cooling. Coldest locales again dipping into the 40s. Long term...Thursday through Tuesday The upper pattern across the northern United States will deamplify over the next couple of days as the large Pacific northwest low shifts inland and embedded middle-level impulses trigger episodic convection across the northern plains. The simultaneous eastward migration and dampening of the downstream ridge over the central Continental U.S. Will force Canadian high pressure to exit to the east and force southerly return flow to spread into the lower peninsula beginning on Thursday. A noteworthy moderation of temperatures will be the result as daytime highs rise to 80 for Thursday and solidly into the middle-80s on Friday, particularly for western portions of the County Warning Area away from potential Lake Shadow impacts. A significant transition in the local weather will then commence from Saturday Onward as middle-level westerlies emerge across the northern tier in response to the collapse of the middle-level ridge. This will allow a moist and humid airmass to spill into the region which should have no problem yielding high temperatures near 90 degrees along with upper 60s/low 70s dewpoints. Given southeast Michigan's prognosticated favorable location along the instability gradient and nose of the veering low-level jet on Saturday, have no argument with the ecmwf's suggestion of a convective complex impacting the area on Sat, particularly given the excellent continuity observed in recent cycles. With this in mind, leaned heavily toward a conservative high temperature forecast, around 80 degrees, for Saturday. The Reservoir of instability and associated severe potential will continue to build Sunday into Tuesday as a robust zonally-oriented eml ribbon becomes increasingly well-established across the Great Lakes. Per the usual, this will also introduce Stout middle-level capping as evidenced by 00z European model (ecmwf) 850mb temperatures exceeding 20c by 00z Monday evening. As a result, both hot temperatures and severe convective potential will be in play for Southeast Michigan from Sunday Onward. Also Worth noting is that moist boundary layer conditions will limit overnight lows to the 70s. Marine... Canadian high pressure will maintain control across the region through Thursday. This will provide a stretch of favorable marine conditions through the end of the week. && DTX watches/warnings/advisories... Michigan...none. Lake Huron...none. Lake St Clair...none. Michigan waters of Lake Erie...none. && $$ Aviation.....Mr short term...mr long term....jvc marine.......mr You can obtain your latest National Weather Service forecasts online at www.Weather.Gov/Detroit (all lower case).