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Displaying AFOS PIL: AFDGRR Received: 2018-01-12 17:42 UTC
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172 FXUS63 KGRR 121742 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1242 PM EST Fri Jan 12 2018 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 330 AM EST Fri Jan 12 2018 Arctic air returns to the region today behind a cold front and will be with us into next week. Some roads will be slick for the morning commute as temperatures fall into the 20s and residual moisture freezes up. Also a 1 to 4 inch snowfall is expected this morning for areas south and east of a line from South Haven to Alma. Lake effect snow will occur near Lake Michigan over the weekend but no significant accumulations are expected. A more widespread snow is expected beginning Sunday night and continuing through Tuesday, with some light accumulations likely over most of the area. && .UPDATE... Issued at 1105 AM EST Fri Jan 12 2018 We trimmed most of the western counties from the advisory leaving Gratiot and Ionia from the group that is scheduled to expire at 1 pm. The eastern group remains unchanged. Latest radar trends show the back edge of the pcpn slowly moving east but will take several more hours until it clears the cwa. Meanwhile, light snow showers in north flow can be seen on radar over the west/northwest cwa, but accums will be limited to less than an inch this afternoon. UPDATE Issued at 926 AM EST Fri Jan 12 2018 Increased snow amounts for east and southeast counties as the banding continues. I did add inch per hour rates to the WSW. High res models show the snow diminishing later this morning into the afternoon. No other changes at this time. && .SHORT TERM...(Today through Sunday) Issued at 330 AM EST Fri Jan 12 2018 No changes to the existing Winter Weather Advisory. Good lift and FGEN forcing will be present this morning as upstream mid level trough deepens and moves east. Also there is plenty of moisture to work with as precip transitions quickly to snow, with 4-5 g/kg mixing ratios still noted on the 300K sfc from GRR to the south and east. Snow could become briefly heavy at times during the morning commute, and some localized 4-5 inch total accums cannot be ruled out within any of the more intense FGEN bands which set up south and east of GRR. The period of freezing rain and sleet in the transition zone is expected to be relatively brief this morning given the fast arrival of the cold air behind the front, and have raised total snow amounts a bit for the LAN/JXN/BTL areas. This is supported by latest trends in the HRRR which are farther north and west with the snow this morning and show the banded nature of the snow. Most of the snow should be done by noon, but increasing northerly winds could lead to some blowing snow lingering into the afternoon where accums occur. Things turn relatively quiet but cold after today. The lake effect snow over the weekend does not look too impressive since moisture is fairly shallow and inversion heights generally below 5K feet. However there still may be some localized light accumulations west of Highway 131. .LONG TERM...(Sunday night through Thursday) Issued at 330 AM EST Fri Jan 12 2018 A stacked low is progged to be moving into the Western Great Lakes by early next week. This will keep the region in the cold air, along with a prolong period of snow that should start late Sunday night and last until Monday night or Tuesday. This system will also see some lake enhancement with H8 temps around -15C. This will be mainly true once the low is to our east, by Monday night. Snow amounts could be rather impressive, with 2-4 inches expected inland, and perhaps 6-9 inches for areas west of U.S. 131 by Tuesday morning. Once this system is to our east another reinforcing surge of arctic air moves in for Tuesday and Wednesday. Lake effect snow, mainly hugging the coast should persist these two days. By Wednesday night and Thursday temperatures should not be as cold as an upper ridge builds over the upper Midwest. Surface high will also accompany the ridge, so it appears dry for this period. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1238 PM EST Fri Jan 12 2018 The band of snow is forecasted to keep pushing east of the TAF sites this afternoon...slowly. Impacts will be seen mainly around KJXN. Along the lakeshore...there will be some lake effect snow showers...which could move into the KMKG region this afternoon. Otherwise...a trend toward VFR is forecasted into Saturday. Local gusts over 25 knots from the north are possible this afternoon. && .MARINE... Issued at 330 AM EST Fri Jan 12 2018 Gales and freezing spray expected on Lake Michigan as arctic air pours in. && .HYDROLOGY... Issued at 957 AM EST Fri Jan 12 2018 The water from the snow melt of late has made it into the rivers across the area and some minor river flooding is ongoing. The colder temperatures that have moved back into the region will cause ice to reform and solidify into next week. Therefore, additional flooding is not expected and river ice will likely be locked down by the end of the weekend. Will need to monitor rivers for potential ice jam flooding. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 7 PM EST this evening for MIZ059- 066-067-073-074. Winter Weather Advisory until 1 PM EST this afternoon for MIZ052- 058. LM...Gale Warning until 4 AM EST Saturday for LMZ844>849. && $$ UPDATE...04 SYNOPSIS...Meade SHORT TERM...Meade LONG TERM...JK AVIATION...MJS HYDROLOGY...63 MARINE...Meade