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Displaying AFOS PIL: AFDGRR Received: 2020-01-28 23:38 UTC
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923 FXUS63 KGRR 282338 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 638 PM EST Tue Jan 28 2020 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 242 PM EST Tue Jan 28 2020 - Light precipitation mostly diminishing tonight - Light snow Friday/Saturday - Swing in temperatures, chance for more precip early next week && .DISCUSSION...(This evening through next Tuesday) Issued at 242 PM EST Tue Jan 28 2020 -- Light precipitation mostly diminishing tonight -- A mixture of drizzle and snow showers will diminish overnight but may not dissipate entirely going into Wed as winds shift northerly and weak surface ridging/subsidence occurs. Several models are advertising trace amounts of drizzle or flurries Wed afternoon into the night from subtle low level convergence zones and surface troughing, but the signal is less than what it was for today. An upper level wave approaching during that time with moisture in the DGZ may not have much effect on our weather at the surface either. Seeder-feeder precip is unlikely with very little lift the DGZ and a substantial dry layer between the DGZ and the moist boundary layer. A persistence forecast of temperatures will work well these next couple of days, though lows tonight may be a few degrees cooler. -- Light snow for Friday/Saturday -- An energetic northeast Pacific jet and its associated baroclinicity should move into North America on Friday, rounding down the anticyclone off the California coast. An amplifying trough over the Great Lakes in the exit region will provide us with another opportunity for light precipitation Friday through Saturday, which should mostly fall as snow. Not all ensemble members of the ECMWF are sold on precip, but between 0.05 and 0.20 inches is the expected range if precip does occur, which translates to about a half inch to two inches of snow. -- Swing in temperatures, chance for more precip early next week -- On the poleward side of the jet, mild Pacific air will flood the central US Sunday into Monday. The GFS and ECMWF show 850 mb air reaching +9 to +12 C over Lower Michigan Sunday night from west- northwest flow. Not far north of it will be -20 C air advecting southeastward over the northern Plains. While there is a decent chance of a warmup into the 40s (with an outside chance of 50) on Monday, this should be short-lived as the next progressive Rossby wave trough deepens over the continent. This would set us up for falling temperatures Tuesday into Wednesday, and depending on how things play out, a mixed precipitation or snow event. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 632 PM EST Tue Jan 28 2020 Overall the pattern of cloudy skies with mainly MVFR impacts is forecasted to continue through the period. There are some holes in the cloud cover...so conditions could briefly improve. A low risk for light precipitation still exists this evening...with snow showers being the most likely type. && .MARINE... Issued at 242 PM EST Tue Jan 28 2020 Generally light winds and low waves are expected over the next few days. An uptick in wind Friday and through the weekend may push waves up to the 2 to 4 and perhaps 5 foot range. && .HYDROLOGY... Issued at 242 PM EST Tue Jan 28 2020 Area rivers remain elevated due to saturated soils (e.g. abundant groundwater) and the onset of a gradual snowmelt. No meaningful precipitation is expected over the next 5 days, and temperatures at or above freezing are expected. The snowpack is about as "wet" as it can get and will continue gradually melting in the coming days, especially next week as temperatures build into the 40s. Roughly an inch of water from snowmelt and in ditches is available to move into the river systems over the coming week, which will lead to a continuation of elevated levels. No flooding is forecast, though several rivers will remain at bankfull. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...CAS DISCUSSION...CAS AVIATION...MJS HYDROLOGY...Borchardt MARINE...CAS