Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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393 FXUS63 KDTX 192005 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 305 PM EST Sun Feb 19 2017 .DISCUSSION...
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Warm air in place and sunshine has brough another day of record high temperatures across the region as temperatures have surged into the upper 50s to mid 60s. At 3PM the temperature in Detroit (DTW) was 65, breaking the old record of 64 (1884). Saginaw (MBS) was 58, breaking its old record of 57 (1930), and Flint was 57, just a few degrees shy of its record of 59 (1994). Will handle with Record Event Reports (RERs) and social media this evening after the diurnal cycle has completed. Axis of surface high pressure will slide overhead this evening, providing dry weather and light winds. A backdoor cold front will meanwhile slip across Lake Huron and into the Thumb this evening. Cooler air combined with cold northerly, and then easterly, flow off Lake Huron will allow temperatures to drop more rapidly this evening across the Thumb, with temps expected to fall into the 30s after about 8PM. The remainder of the area will exhibit more of a diurnal cooling cycle. Some mid clouds will settle into the area with the front this evening and early tonight, while high clouds also stream in ahead of low pressure lifting through the Northern Plains. Cloud cover will limit radiational cooling, mitigating the fog threat (there was quite a bit under the ridge axis upstream and into the Ohio Valley last night). Will keep mention out of forecast given virtually no support from forecast soundings. Clouds should keep mins in the upper 20s over the Thumb, with low to mid 30s expected elsewhere. Cooler airmass at the start of the day will be offset some by renewed warm air advection late tomorrow and Monday night as surface low pressure lifts from the Northern Plains into Manitoba/Ontario. This will provide another day with well-above normal temperatures, despite highs 5-10 degrees cooler than today. Increasing easterly flow off the cold waters of the Great Lakes will have some impact on temperatures however, as will increasing clouds, holding max temps near the lakeshores and much of the Thumb in the 40s, while allowing areas further inland to warm into the low and even upper 50s. Upper trough over the Western U.S. will dampen as it lifts northeast and across the Great Lakes Monday night into Tuesday. Nice plume of theta-e will advect up into the area ahead of a weak cold front, with PW values forecast to rise to over 1 inch. Combination of moisture and (mostly) mid-level forcing will provide a good coverage of showers. Frontal boundary looks to clear the far southeast corner of Michigan before the onset of the diurnal cycle, keeping thunderstorms to our southeast later in the day. Lack of strong cold air advection on Tuesday will not drop temps, but rather expect to see an increase (warming to mid 50s-near 60) as the inversion we will hold onto over the next few days is weakened by cooler air aloft and steeper lapse rates in the low-levels fueled by sunshine. Next area of low pressure tracking across the Northern Great Lakes Wednesday will increase southerly flow and feed more warm air into the area. There is some uncertainty as to how high we will be able to mix as an inversion again strengthens, but it appears much of the area will have a solid shot at 60 degree temperatures once again, possibly even mid 60s. Upper level ridge will hold across the area through Wednesday, which will allow for dry weather to continue. A low pressure system then skirts across the northern Great Lakes region late Wednesday into early Thursday bringing a slight chance for rain showers. A more significant storm system with then sets up over the Rockies and moves northeast across the Central Plains on Friday before moving across the region early Saturday. This system has the potential to bring rain, thunderstorms and gusty winds as it moves through the area. Temperatures will remain well above normal to end out the upcoming week before temps drop back to more near normal for the upcoming weekend.
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&& .MARINE...
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Light northerly winds tonight to become easterly on Monday as high pressure drifts across the area. Winds then strengthen out of the southeast late Monday and Monday night in advance of a cold front. Gusts of 25 to 30 knots during the overnight period, before diminishing on Tuesday as the gradient weakens with the frontal passage. A modest post-frontal southwest wind to persist through the mid week period.
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&& .PREV DISCUSSION...
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Issued at 1147 AM EST Sun Feb 19 2017 AVIATION... Dry and stable low level environment sustained under prevailing high pressure ensures continued clear skies across the lowest 10 kft through the period. The degree of drying will keep any potential shallow fog development very limited despite the weak gradient flow. Northwest flow into the evening to become light/variable overnight, then light easterly on Monday. //DTW THRESHOLD PROBABILITIES... * None
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&& .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ DISCUSSION...HLO/SS MARINE.......MR AVIATION.....MR You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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