Area forecast discussion National Weather Service Detroit/Pontiac Michigan 709 am EDT Thursday may 23 2013 Aviation... //discussion... Conditions will rapidly deteriorate to MVFR this morning as winds turn northerly behind a cold front making its way through Southeast Michigan. The front is currently between fnt and ptk and should pass through ptk around 12z...and the metropolitan airports around 13z. Rain showers could reduce ceilings to IFR at times as north winds gust to 20 knots. The front will continue moving south tonight...as approaching high pressure brings dry air and VFR conditions to the taf sites during the evening hours. //Dtw threshold threats... * high confidence in ceilings below 5000 feet by 13z...continuing through the early evening hours. && Previous discussion...issued 352 am EDT Thursday may 23 2013 Short term...today and tonight A slowly sinking cold front will bring an abrupt change in temperatures across Southeast Michigan today. In contrast to several days approaching or exceeding 80 degrees...todays highs will only get into the 50s across the north...with 60s expected across the south. The highs realized today will occur in the morning hours...before the push of cold air pushes afternoon temperatures down into the 40s across the north and into the 50s across the south. In addition to cooling temperatures...the front will bring rain showers and a brisk north wind behind it during the afternoon. Overall Southeast Michigan is in for a wet...windy and cool day with the best weather occurring during the early morning hours. The piece of good news today is the threat for thunderstorms appears to have diminished to the Point of leaving thunder out of the morning forecast as MUCAPE values struggle to get to 100 j/kg ahead of the approaching cold front. Dynamics will be easy to come by today as the low that has been out to our west for the past several days tracks through the central Great Lakes as a positively tilted trough with several embedded shortwaves as shown on the water vapor imagery. A cross section through Michigan shows abundant moisture and fgen from 925 mb to 850 mb as the cold front sinks south...warranting categorical probability of precipitation as the front tracks through Southeast Michigan today. The front will push east early this evening as the middle level trough becomes neutrally tilted and moves east with the front. High pressure will bring dry air and quiet weather to the central Great Lakes later tonight as 850 mb temperatures sink to around zero degrees. With clearing skies and the push south of these cold temperatures...some frost is possible away from the Great Lakes and the Detroit metropolitan area as low temperatures fall into the middle to upper 30s. Closer to the lakes and across the metropolitan area lows are expected to get down to around 40. The main factor inhibiting widespread freezing temperatures will be surface winds around 10 miles per hour as a tight pressure gradient remains between the departing low and the high building in from the north. Long term...Friday through Wednesday Fairly quiet weather through most of the extended forecast. A blocking pattern...upper lows over both coasts...will set up across the Continental U.S. For the Holiday weekend locking US under the eastern edge of upper level ridge and directly under broad area of surface high pressure. Pattern breaks down by middle week as East Coast trough gets absorbed in northern stream flow and lifted into the Atlantic. Meanwhile strong midlevel shortwave will shoot around the West Coast trough and will begin to break down the amplified ridge. Only real chance of precipitation will come Wednesday/Thursday as the short wave will attempt to lift a warm front through the area. Friday through Sunday will feature a cool dome of surface high pressure building south from Canada with midlevel confluent flow. Friday will start off on the breezy side as we fall on the eastern side of the high under a decent NE/SW pressure gradient. The persistent feed of cool air...850 mb temperatures in the single digits through the day...will keep daytime highs in the low 60s which is about 10 degrees below normal. The exception will be The Thumb region where the onshore flow will keeps temperatures in the low/middle 50s. Heights will gradually rise through the weekend. This combined with clear skies and decreasing northerly flow will produce a warming trend through the weekend by Monday. For the middle part of the week...the aforementioned shortwave will eject out of the West Coast trough and track up across the northern plains into Ontario. This will lift a warm front up through the Great Lakes bringing mild westerly/southwesterly flow back to Southeast Michigan and allowing temperatures to jump back near 80. Models disagree with timing of the frontal passage and amount of moisture associated with it so went with low chance/slight chance probability of precipitation starting Tuesday night for the time being. Marine... A cold front sinking south will cause winds to shift to the north across all waters this morning...as the main surface low and trailing cold front push off to the east. Winds and waves will increase greatly with the advection of cold and dry air...leading to Small Craft Advisory conditions for all of the Lake Huron nearshore waters and Lake St. Clair. Further south offshore flow will cause winds to stay below criteria for Western Lake Erie. Therefore will continue and issue small craft advisories for these zones today and tonight. Although winds may briefly reach gale force across Southern Lake Huron this afternoon...the window appears brief enough and wind speeds marginal enough to avoid hoisting gale warnings for this afternoon. A continued north wind and long fetch along Lake Huron will continue small craft conditions for the Lake Huron nearshore zones and outer Saginaw Bay as waves remain elevated on Friday. High pressure will bring lower winds and waves across the central Great Lakes this weekend...with conditions expected to be well below any headlines. && DTX watches/warnings/advisories... Michigan...none. Lake Huron... Small Craft Advisory...inner Saginaw Bay...until 8 PM Thursday. Small Craft Advisory...nearshore waters from Port Austin to Port Huron...until 6 PM Friday. Small Craft Advisory...outer Saginaw Bay...until noon Friday. Lake St Clair... Small Craft Advisory...from noon Thursday to midnight Friday. Michigan waters of Lake Erie...none. && $$ Aviation.....Kurimski short term...kurimski long term....drk marine.......kurimski You can obtain your latest National Weather Service forecasts online at www.Weather.Gov/Detroit (all lower case).