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Displaying AFOS PIL: AFDDTX Received: 2019-03-20 03:46 UTC
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824 FXUS63 KDTX 200346 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1146 PM EDT Tue Mar 19 2019 .AVIATION... The onset of nighttime cooling will lead to a clearing of the remnant diurnal cu field over the next couple hours and will lower the south-southwest winds speeds around/shortly after sunset. Se Mi will remain under the influence of departing sfc high pressure through the night. So other than a few high clouds, this system will sustain clear skies into early Wed morning. A deepening low pressure system will advance into Lower Mi Wed afternoon/evening. This system and its associated moisture transport will allow widespread rain, with steadily lowering ceilings, to advance across Se Mi during the course of the afternoon Wednesday. .DTW THRESHOLD PROBABILITIES... * High in ceilings below 5000 ft late Wed afternoon and evening. * High in precip type being all rain Wed afternoon and evening. && .PREV DISCUSSION... Issued at Detroit/Pontiac MI 342 PM EDT Tue Mar 19 2019 DISCUSSION... Confluent flow aloft and departing left entrance jet streak region leading to weak subsidence and continued quiet weather across Southeast Michigan this afternoon and evening. Surface heating and boundary layer growth paired with enough moisture in the low levels today has allowed for the development of stratocumulus across the region, while surface high pressure moving into the Appalachians has resulted in light southwest return flow. Low clouds will clear out again this evening as daytime mixing wanes. Lack of abundant cloud cover tonight will allow for decent radiational cooling potential, but the increasing gradient due to the departing high pressure will keep winds slightly elevated and prevent full cooling potential from being realized. Low temperatures in the lower 30s still look good for tonight. Rain returns to the forecast tomorrow as an amplifying upper shortwave swings through the Great Lakes from the north and a weak surface low develops over the Lower Peninsula. Another shortwave visible in water vapor imagery over western Nebraska this afternoon will swing into the mid-Mississippi Valley Wednesday afternoon and lead to a southwesterly 40 kt low level jet that will transport ample moisture to the southern Great Lakes ahead of the northern shortwave. Widespread light rain will develop during the early afternoon into the evening as height falls move in, becoming more scattered overnight as the trough axis moves overhead. Rain will be the primary precip type, but some wet snowflakes have the potential to mix in north of I-69 late Wednesday night as the low pressure and main area of precip move out. QPF has trended upward with latest model guidance, so have increased rainfall totals - more details are described in the Hydrology section below. Modest southwest flow will persist through the day Wednesday with gusts in the afternoon up to 20 to 30 mph. Modest warm advection and good mixing in this flow will help temperatures reach the mid to upper 40s before clouds thicken and rain sets in. A weak cold front will pass through early Thursday and usher in dry air aloft from the northwest which will shut off any lingering showers during the morning hours. Thursday will be dry and seasonable with temperatures in the mid 40s. However, there will be another chance for light rain and snow for the eastern Thumb overnight into early Friday as another shortwave dives southward into the region. The bulk of the precipitation looks to remain to the east. High amplitude ridge sliding across the central US on Friday. The result will be a mostly dry end to the work week with Michigan placed on the east side of this ridge. The exception being a slight chance for some lingering light precipitation on Friday across the Thumb region under NNW flow behind the passing cold front. High temperatures will dip into the mid/upper 30s and low 40s for Friday before temperatures trend upward through the weekend. Expecting mostly sunny skies through the majority of the weekend as surface high pressure moves through the Great Lakes region. Temperatures warming into the 50s by Sunday as 850 mb temperatures increase to around 2C. Precipitation chances return to the forecast late Sunday as the ridge breaks down and weak waves track over Michigan with a cold front also advancing southward. Passing cold front will maintain precipitation chances into Monday morning with high temperatures Monday afternoon cooling back into the 30s and 40s. MARINE... A rather complicated near surface pressure pattern will evolve the next day or so, as two systems attempt a merger over the Great Lakes region on Wednesday. Winds will respond by initially ramping up from the southwest tonight into Wednesday areawide, with highest gusts exceeding 25 knots on Lake Huron. Winds and waves will relax somewhat, as the combined low pressure system weakens over the region, Wednesday night. A modest west-northwest flow will become established on Thursday before increasing in strength Thursday night on the way to possible northerly gale conditions on Friday over Lake Huron. Expect ice breakup to continue with the changing wind conditions and relatively mild weather. HYDROLOGY... Light rain is expected to overspread southeast Michigan Wednesday afternoon with rather uniform rainfall totals of three to four tenths of an inch. Most mainstem rivers have subsided significantly over the last several days. The additional precipitation will only serve to slow the steady decrease with no additional river flooding expected. Susceptible collection areas, that likely already contain run-off water, will swell with the additional precipitation. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC DISCUSSION...TF/AA MARINE.......Mann HYDROLOGY....Mann You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.