Area forecast discussion National Weather Service Detroit/Pontiac Michigan 701 am EDT Sat may 25 2013 Aviation... //discussion... Ambient dry air through an impressive depth will keep the door shut on precipitation chances as midlevel energy passes the state to the south. The only impact on aviation conditions will be some broken-overcast ceilings at upwards of 25 kft this morning. Surface winds today are expected to emerge light northerly commencing on boundary layer growth. Models are hinting at some cumulus development this afternoon but that seems suspect at this time. //Dtw threshold threats... * none. && Previous discussion...issued 325 am EDT Sat may 25 2013 Short term...today and tonight Early morning msas analysis is showing a surface ridge extending southward through the Lake Superior/Michigan/Huron basins. The best surface ridging component inside of the County Warning Area is across the northern thumb down into Port Huron. Perusing through the surface observations...feeling is the best potential for any frost formation will be in The Thumb and low lying areas of the glacial terrain with the local office temperature at 33 degrees as of 230 am ldt. Will maintain the frost advisory as is for simplicity. There has been a decent radar presentation overnight across portions of Minnesota/WI/IA tied to the ageostrophic response of merging and shearing of shortwave energy. One hour precipitation amounts have been lessening as the precipitation/virga pushes farther to the southeast. This is likely in response to increasing confluence aloft as the entrance region lies directly over lower Michigan. The best upper level forcing in the form of 700-500mb frontogenesis will brush far southwestern sections of the state between 12-15z...before passing harmlessly to the south. The amount of ambient dry air in the lowest 12 kft above ground level supports virtually no precipitation potential today. The preference regarding high cloud forecast lies with the 25.05z RUC which brings high clouds into the southwestern 2/3rds of the County Warning Area between 9-16z this morning. Increased insolation with some moderation of the airmass will support a solid 3-8f degree uptick in high temperatures. Expect readings to range from the middle 50s in the far northern Thumb/Lake Huron shoreline to the middle 60s Detroit southward. Surface high pressure will expand across the central Great Lakes tonight...bringing the prospects of another cool to cold night. Differential airmass recovery should be good for a few degrees off this mornings mins. Worked with a blend of undercut guidance with some persistence. Expected lows tonight should range from the lower to middle 30s in The Thumb to lower 40s southeast of the terrain. Long term...Sunday through Friday Lower Michigan will reside between a high amplitude ridge across the upper Midwest and a deep upper low lifting from New England into the Canadian Maritimes during the later half of the weekend...sustaining a confluent flow aloft. At the surface...this will translate to high pressure building from the upper Great Lakes on Sunday to the eastern Great Lakes on Monday. Other than the potential for some high clouds...skies should remain mainly clear with very dry air overhead. Temperatures will slowly moderate...leading to an overall warming trend heading into Memorial Day. Expect mixing depths may overachieve with plenty of sunshine and substantial low level dry air. This supports leaning toward the higher end of guidance maximum temperatures /mid to upper 60s Sunday and around 70 Monday/. The dry airmass and weak surface gradient will support optimal radiational cooling potential...so mins Sun night will continue to be quite cold for late may /upper 30s to middle 40s/. The middle level ridge is forecast to break down early next weak as numerous short wave impulses are ejected out of the long wave trough over the western US and across the central/northern plains. The bulk of the 00z model suite suggest mesoscale convective system development across the upper Midwest or western Great Lakes Monday afternoon/night as low level inflow strengthens. The potential for remnant mesoscale convective system activity to advance into Southeast Michigan remains highly uncertain at this time. While several model solutions are quite bullish with quantitative precipitation forecast over Southeast Michigan Monday night and Tuesday...there is likely some semblance of convective feedback in the models. There is also concern that the models have a poor handling of mesoscale convective system propagation...which could lead to remnant convection being much farther south. Thus plan to carry very low chance probability of precipitation Tuesday. Persistent low level S-southwesterly flow should however lift a warmer and more humid airmass into Southern Lower Michigan by middle week...marked by the passage of a surface warm front. This will justify a chance of showers/thunderstorms late Tuesday through Wednesday. The European model (ecmwf) remains steadfast in developing a more amplified upper trough over the western US by midweek as energy ejects out of the Gulf of Alaska and into the West Coast. A seasonally strong upper jet within the base of the deep Gulf of Alaska upper low and current amplified nature of the flow lends support to the European model (ecmwf). This solution builds the subtropical ridge farther north into the eastern US late in the week and suggests Southeast Michigan may be capped. Even the less amplified GFS builds middle level heights substantially across Southeast Michigan. Thus the forecast for the later half of next week will have very low probability of precipitation with maximum temperatures well into the 80s. Marine... A stable anticyclone will expand across the Great Lakes through the Holiday weekend. This weather feature will be responsible for more typical marine conditions for late may. Wave heights are only expected to range in the 1 to 2 foot range in many areas throughout the weekend. && DTX watches/warnings/advisories... Michigan...frost advisory...miz047-miz048-miz049-miz053-miz054-miz055-miz060- miz061-miz062-miz063-miz068-miz069-miz070-miz075-miz076-miz082- miz083...until 8 am Saturday. Lake Huron...none. Lake St Clair...none. Michigan waters of Lake Erie...none. && $$ Aviation.....Cb short term...cumulonimbus long term....SC marine.......cb You can obtain your latest National Weather Service forecasts online at www.Weather.Gov/Detroit (all lower case).