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Displaying AFOS PIL: AFDGRR Received: 2017-12-07 05:01 UTC
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888 FXUS63 KGRR 070501 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1201 AM EST Thu Dec 7 2017 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 329 PM EST Wed Dec 6 2017 A period of lake effect snow will continue through tonight and Thursday. Areas along and west of U.S. 131 will see 2 to 4 inches with locally higher amounts. Meanwhile areas east of U.S. 131 will see two inches or less. We will see a brief lull in the snow Thursday night. Then more lake effect snow kicks back up on Friday, mainly from Holland north and west of U.S. 131. All areas will see snow by late Friday night as a clipper system moves in. Once again the heaviest snows can be expected from U.S. 131 westward, while a more widespread snow can be expected to the east too. The snow will wind down on Saturday, then more solid snow chances return Monday night through Tuesday night. Temperatures will remain chilly with daytime highs mainly in the upper 20s to mid 30s. Lows will mainly be in the 20s into the middle of next week. && .SHORT TERM...(This evening through Friday night) Issued at 329 PM EST Wed Dec 6 2017 A WNW flow lake effect will impact the CWA tonight and Thursday. Then more lake effect, with a WSW flow, is expected Friday into Friday night. This will occur ahead of a strong clipper system that will increase the snow across all of the CWA late Friday night. Will not change any of the winter headlines at this time. We will need watch how the bands set up over the SW CWA as it is possible we will need to add Barry and Calhoun Counties to the advisory. With a 285-310 flow through the event the more intense bands crossing the widest part of the lake could also spill into these two counties. Inversion heights continue to lift tonight and the lake effect will continue to increase. The peak snowfall intensity will probably be occurring during the morning rush on Thursday. The first significant snow during a rush hour certainly raises concerns. After a morning peak in the moisture, it begins to lessen through Thursday, likely resulting in diminishing snows through the afternoon. All in all, expect 2 to 4 inches across much of the lakeshore counties and localized more. A bulge inland is expected across Lake and Kalamazoo Counties, and as mentioned above, perhaps Barry and Calhoun Counties. Away from these counties accums are expected to be 2 inches or less. Breezy winds will cause some drifting snow. The short wave crosses the region mid day Thursday which will lead to a lull in the snow Thu night. But then the moisture depth increases again on Friday when inversion heights of 6-7k feet move in. The flow in this time frame is more WSW ahead of an approaching clipper. 1 to 2 inches seems the likely snow accums range, with locally higher amounts. This mainly falls north of Holland and west of U.S. 131. Once again it will be breezy, so some drifting is expected. The clipper system continues to look impressive and will likely need winter headlines. It moves in late Friday night. Lake enhanced snow will continue and could become quite heavy. Given a synoptic system, inland areas will also see a more widespread snow too. At this point an additional 2 to 5 inch snowfall appears likely, heaviest toward the lakeshore. However these types of systems will over perform at times. Winds lighten up overnight so drifting is not expected. .LONG TERM...(Saturday through Wednesday) Issued at 329 PM EST Wed Dec 6 2017 Bouts of lake effect snow are expected through the long term period as the deep upper trough remains across the eastern half of the country. Lake effect will be boosted on Saturday via a low pressure system diving southeast through the Great Lakes region. Most areas on Saturday will see an inch or two of snow via the low. Lakeshore counties will see even more given a lake enhanced snow regime. Southwest flow will turn northwest through the course of Saturday making accumulations likely in all areas towards the lake. Lake effect snow events that are enhanced via synoptic systems can be some of the more impactful snow we see, so traveling on Saturday will need to be monitored. A lull in the snow activity will occur on Sunday as ridging moves through the area. A nose of warm air on Sunday and Sunday night may actually take lake effect snow out of the equation for a time as delta t's dwindle near or below critical values. A cold front will drop through the area on Monday ushering in cold air and another round of northwest flow lake effect. The lake effect will last into Tuesday and Wednesday. After a delayed start to this wintry pattern at least in the Southern Great Lakes, we should see most areas covered in snow by early next week. Temperatures much of the long term will be below normal, the exception being Sunday into Monday. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1157 PM EST Wed Dec 6 2017 A cold front moving through the state will create in increase in snow showers as colder air moves south over the lake. That in turn will result in some MVFR conditions through mid afternoon. Snow showers will diminsh by late in the day and VFR conditions will return. && .MARINE... Issued at 329 PM EST Wed Dec 6 2017 Small craft advisory will be in affect at least through Friday given the brisk westerly winds. && .HYDROLOGY... Issued at 329 PM EST Wed Dec 6 2017 Several rounds of snow are expected over the next week due to a combination of lake effect processes and passing low pressure systems. The first round of more widespread snow will occur late today through Thursday afternoon, bringing several inches of snow to counties near the lakeshore. Total liquid equivalent (melted snow) through Thursday evening will be below one-quarter of an inch for most locations, but locations in Allegan, Van Buren, and Kalamazoo counties could see locally higher totals up to one-half inch. No issues with flooding or rivers are expected. Another round of more widespread snow is expected to start mid-day Friday and last through Saturday afternoon. This looks to bring another tenth to one-quarter of an inch of liquid equivalent, and again not cause any issues aside from accumulating snowfall. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 4 PM EST Thursday for MIZ037-038- 043-050-056-064-071-072. LM...Small Craft Advisory until 7 PM EST Friday for LMZ844>849. && $$ SYNOPSIS...JK SHORT TERM...JK LONG TERM...Duke AVIATION...04 HYDROLOGY...HLO MARINE...JK