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Displaying AFOS PIL: AFDDTX Received: 2018-10-18 11:05 UTC
274 FXUS63 KDTX 181105 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 705 AM EDT Thu Oct 18 2018 .AVIATION... Ideal aviation conditions will be in place across SE Michigan as a broad region of high pressure moves through the Ohio valley today and tonight. VFR clear is expected to last well into tonight as westerly flow brings in very dry low level air from the Midwest. Early morning satellite imagery indicates the air is too dry even for lake effect stratocu off Lake Michigan which suggests little if any cloud response over land with daytime heating. Expect wind to hold under 15 knots across the region with a few gusts around 20 knots possible in the MBS area during the afternoon. Moderate southwest wind continues tonight with clear sky only giving way to a few patches of high clouds by sunrise Friday. .DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 341 AM EDT Thu Oct 18 2018 DISCUSSION... Seasonably cold resident airmass now firmly entrenched throughout the region, noting early morning temperatures currently settling below freezing. Moderation of the existing thermal profile will prove modest today, owing to the limited thermal advection as surface ridging only slowly exits eastward and effectively delays the onset of greater low level southwest flow. The advent of gradually increasing upper heights as the mean trough axis releases to the northeast will leave a relatively standard response off the cold morning readings. Afternoon temperatures projected to reach the upper 40s to lower 50s. Increasing stability and depth to the dry layer contained within the background of confluent mid level northwest flow will afford plenty of insolation potential. However, a period of greater lake Michigan moisture flux within the emerging southwest gradient may support some downstream expansion of stratocumulus into the Flint and Saginaw Valley regions this afternoon. Shortwave upper ridge axis currently draped across the midwest will slip through the region tonight. Ensuing increase in low-mid level warm air advection under strengthening southwest flow will subsequently provide an additional upward trend in temperatures both tonight and Friday. Limited radiational cooling potential tonight despite a mostly clear sky, given the likelihood of a well mixed boundary layer condition maintained by the firm southwest gradient. Lows of upper 30s in the coldest locales. Some increase in mid cloud funneling downstream of the next system could muddle the overall diurnal temperature response on Friday. Otherwise, pure advective component alone should support highs of mid to upper 50s. Turning gusty by afternoon within a moderately mixed late day boundary layer. Gusts 25 to 30 mph, highest Saginaw Valley and thumb region. Closed mid level circulation fixated over the four corners region will release a piece of energy into the southern periphery of the mean northern stream flow over the next 24 hours. This pv anomaly will accelerate eastward on Friday, arriving over southeast Michigan early Friday night immediately in advance of a rapidly amplifying longer wave northern stream trough. This will provide a window for shower development within the associated uptick in mid level ascent and along the attendant cold frontal boundary, although somewhat limited in potential as greater theta-e advection remains south of the region. Strong height falls will descend over the great lakes during the first half of the weekend, leaving high amplitude troughing to define conditions throughout the duration of the weekend. This translates into another stretch of well below normal temperatures - 850 mb temperatures bottoming out at -7 to -9C Sunday morning. Initial period of modest cold air advection commences early Saturday in the wake of the lead cold front, with a secondary stronger surge likely tied to the inbound mid level trough axis late Saturday into Saturday night. Another day of gusty conditions given the underlying pattern of caa and prospects for a deep mixed layer. Precipitation potential Saturday and Saturday night less defined at this stage, owing to uncertainty in placement of stronger pva streaming through the trough and overall moisture quality/depth. Outgoing forecast will maintain a simplistic chance mention during this period. Higher confidence for dry conditions during the latter half of the weekend, the region residing within the increasingly subsident region contained along the backside of the departing trough axis. MARINE... Marine wind backs to the southwest today as high pressure builds across the Ohio valley and speed increases tonight as low pressure moves into northern Ontario. The strongest wind tonight will be across Saginaw Bay and central Lake Huron where gusts around 30 knots will be common. A gust near gale force remains possible tonight but is expected to be marginal and brief as subsidence and low level warm advection continuously lower the mixed layer through the night and into Friday morning. The low pressure system then deepens considerably Friday afternoon and night which ramps up potential for southwest gales with more substantial magnitude and duration. Small Craft Advisories are in effect tonight and lead into a Gale Watch late Friday through Friday night. Moderate northwest wind trailing the front continues Saturday but is projected to remain below gales through Saturday night. The weekend finishes with high pressure moving across the central Great Lakes Sunday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Gale Watch from Friday afternoon through late Friday night for LHZ362-363-421-462-463. Small Craft Advisory from 8 PM this evening to 4 AM EDT Saturday for LHZ441>443. Small Craft Advisory from 2 PM this afternoon to 2 PM EDT Friday for LHZ421. Small Craft Advisory from 2 PM this afternoon to 4 AM EDT Saturday for LHZ422. Gale Watch from Friday morning through Friday evening for LHZ361. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....BT DISCUSSION...MR MARINE.......BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.