Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 301047 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 647 AM EDT Thu Mar 30 2017 .AVIATION...
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Prolonged intervals of moisture transport into an elevated frontal boundary draped over srn Mi will support widespread rain today. The more steady rainfall will occur generally north of PTK while things will be more showery to the south. Wet bulb cooling will keep MBS on the threshold of rain vs snow this morning. There is actually a chance for a burst of heavy wet snow at MBS prior to enough warm air spreading in to change things over to all rain. Ceilings will remain VFR to start the morning but will steadily drop during the course of the day as precipitation and moisture advection act to lower cloud bases. Very low stratus and fog are then expected tonight as the main surge of low level moisture lifts into srn Mi ahead of the actual sfc low. For DTW...In addition to lowering ceilings during the course of the day, A strong easterly gradient will support gusts over 20 knots at times through the rest of the morning and afternoon. Thunderstorms will be possible throughout the day given the presence of weak instability aloft. The most probable time period looks to be during the evening (21Z to 03Z) when the greatest push of elevated instability into NW Ohio/Far Se Mi is expected. //DTW THRESHOLD PROBABILITIES... * High in ceilings below 5000 ft after 14Z. * Low in thunderstorms this morning and afternoon. Moderate this evening. * Low in ceilings and/or visibilities below 200 ft/ one half mile tonight and Friday morning.
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&& .PREV DISCUSSION...
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Issued at 347 AM EDT Thu Mar 30 2017 DISCUSSION... The storm system that will bring us wet weather the better part of the next two days is still centered over Missouri early this morning. The longwave trough is quite deep, reaching down into the Gulf of Mexico and the strong southerly flow in advance of it is proving quite efficient with moisture transport as leading showers associated with the warm front draped across the Ohio Valley. Showers this morning are being generated by broad isentropic ascent along the warm frontal slope. There has been a few enhanced bands through the early morning hours, but a deep low level dry layer of around 7kft is eating away at most precip before it can reach the ground. All models agree, and have agreed for a few days now, that widespread showers will affect the region Thursday and Friday as the low slides east just south of the MI border. I will be hitting on a few potential issues with the system vs regurgitating high pop/high qpf forecasts once again. Initial concern remains the snow potential across our northern counties. This is not a slam dunk forecast by any means and confidence is actually decreasing with this package, but potential still exists. Model soundings start off cold (but with no moisture) and quickly trend to a deep isothermal layer hovering right around 0C. Surface dewpoints remain in the upper 20s north of I69 whereas temperatures look to be stuck in the mid 30s. So wet bulbing could swing the isothermal profile to the snow production side. Additionally, the earlier model runs were hinting at a narrow fgen band lighting up over the area, but so far the initial band lit up further south and a second band looks to be converging over northern lower. Regardless, setup still suggest snow is possible before turning to all rain and will stick with a forecast of "up to an inch" of wet snow possible before the changeover. Next issue will be potential for thunder. As the warm front draws nearer this afternoon, some elevated instability and marginally favorable mid level lapse rates will lift along the front possibly resulting in a few thunderstorms. With the low tracking along the warm front tonight just south of the area, will keep a mention of thunder going til the low gets east of the area. Deep plume of moisture and the 850mb jet will be pushed east of the area by Friday but the upper low and trailing deformation region of the surface low will remain over SE MI through much of Friday. The low remains cutoff from the main flow thus slowly drudges east. How fast the trailing showers will end will depend on how fast the surface high in its wake can build into the area. In addition, mid level ridge will begin building into the Great Lakes Saturday morning. The weekend will shape up to be fairly nice (dry) with temperatures climbing each day from 50 Saturday to mid 50s Sunday. Active pattern will continue into the new week though with a system sliding through every couple days. Next system looks to slide through Sunday night and Monday with another coming around Thursday. MARINE... There will be a steady increase in easterly winds today into tonight. This will be the result of the increase in gradient due to the approach of sfc low pressure into the Ohio Valley with persistent strong high pressure anchored over Quebec. Lingering shallow cold air will also support neutral to slightly unstable conditions across Lake Huron. This easterly wind direction will support hazardous conditions to small craft today through the day Friday. The strongest winds will occur tonight across central and northern Lake Huron. There remains high probability that wind gusts will reach 30 knots, with a chance for a brief period of gale force wind gusts (duration of which should remain less than three hours). The winds will back toward the northeast tonight into Friday morning before weakening later in the day Friday as the sfc low exits the region to the east and weakens. HYDROLOGY... Low pressure over the Mid Mississippi Valley today will transport abundant moisture into a slow moving frontal boundary across southern and central Lower Michigan. This will result in multiple intervals of showers with a few thunderstorms also possible. Portions of central Lower Mi and the thumb region will see snow during the first half of the day before temperatures warm. The low will drift across the northern Ohio Valley tonight before exiting the region to the east late in the day Friday. This will sustain intervals of showers into Fri evening. Some of the precipitation will be moderate to heavy at times. Total two day liquid rain totals are now expected to range from eight tenths of an inch up to an inch and a half. This will certainly lead to rises on area rivers. There is a potential for locally higher amounts, especially within any thunderstorms. The slow moving nature of the forcing on Friday also raises some concerns for some locally higher totals. These factors do suggest a potential for some minor flooding.
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&& .DTX WATCHES/WARNINGS/ADVISORIES...
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MI...NONE. Lake Huron...Small Craft Advisory from 5 PM this afternoon to 4 AM EDT Saturday for LHZ421-422-441>443. Lake St Clair...NONE. Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.
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&& $$ AVIATION.....SC DISCUSSION...DRK MARINE.......SC HYDROLOGY....SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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