FXUS63 KGRR 280417 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1217 AM EDT Wed Jun 28 2017 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 324 PM EDT Tue Jun 27 2017 Quiet and comfortable weather will continue tonight into the first half of Wednesday. Shower and thunderstorm chances will increase Wednesday afternoon, and will be likely Wednesday night as a low pressure system approaches the area. Some of the storms could be a bit strong with hail, winds, and heavy rain all being threats. Storms will continue into Thursday morning before diminishing some as a front pushes south of the area. Showers and storms will return late Thursday night and more so Friday as another wave of low pressure moves up over the area. Cooler weather will move in over the weekend with small chances of rain possible. && .UPDATE... Issued at 951 PM EDT Tue Jun 27 2017 The on going forecast looks good to me so I not planning any updates at this time. && .SHORT TERM...(This evening through Thursday night) Issued at 324 PM EDT Tue Jun 27 2017 Our main concern in the short term portion of the fcst is on pcpn trends as rain moves in late Wed, and severe weather chances with storms Wednesday night. Quiet weather is expected through Wednesday morning across the area. Ridging has taken over control over the area for the most part, except for a few sprinkles across the far eastern portion of the area this afternoon. This is a result of the upper jet and an embedded short wave still nearby on the far wrn portion of the upper low now east of the area. All areas will clear out once the diurnal cumulus dissipate toward sunset. Wednesday will start out clear, but will see an increase in cloud cover by afternoon, and rain likely across the NW by evening. Ridging will give way to a fairly decent short wave that is currently located over the MT/WY area. This short wave will ride in fairly quick due to the upper flow becoming more zonal as the upper low departs. Strong moisture transport via a 60 knot low level jet will begin to arrive Wed afternoon, and will be overhead Wed night. The nose of the low level jet will be aimed more at Central and Northern Michigan, where we expect the best concentration of storms. Thunder chances look to come after 00z Thu when the more unstable conditions arrive. Some of the storms could become stronger, and heavy rain will be a threat. Forecast soundings indicate some decent CAPE profiles in the -10 to -30C layer based on elevated instability. The low level jet will supply quite a bit of wind energy, and there is not a significant inversion to entirely protect us with some better updrafts. Heavy downpours will be a threat as Pwats will be climbing to almost 2.0 inches. The good thing is the low level jet will be progressive, so we do not expect much larger scale training. The showers and storms will tend to diminish in coverage and intensity a bit on Thu as the low level jet departs. The cold front will be sinking south through the area, not likely moving out of the area until the evening hours. This could produce some additional convection if enough instability can build ahead of the front. This will be focused more on the southern areas for Thu. There will be a brief break Thu evening, before more convection tries to move in toward daybreak Friday morning. .LONG TERM...(Friday through Tuesday) Issued at 324 PM EDT Tue Jun 27 2017 The main weather challenges deal with the timing and strength of any thunderstorms in the long term. Overall confidence is increasing on strong/severe storms for Friday. Models are coming into better agreement in supporting a round or two of strong/severe storms on Friday. The combination of stronger deep layer shear of over 40 knots...plenty of instability and a strengthening upper level jet support this potential. Will increase the POPs and QPF for this period. For Friday evening...we are shown to hold onto some instability. Will keep the risk for thunderstorms going. Later at night the atmosphere is shown to become stable. As a result...will go with only some rain showers then. A warm front is forecasted by the High Res Euro to lift northward back into the region on Tuesday. Elevated instability is shown. Will feature some thunderstorms then. The low level wind fields are shown to be faster/about the same as the upper level winds. Commonly this leads to slower moving storms. This could lead to a heavy rain risk. The GFS though...is further south with the front and keeps it out of the area. Will keep a low chance for storms going in the southern parts of the CWA. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1205 AM EDT Wed Jun 28 2017 Vfr conditions will continue at all the terminals overnight through most of Wednesday afternoon. The only exception to this is at KMKG where showers and perhaps a thunderstorm could move in by mid to late Wednesday afternoon into the evening and cause brief reductions to ifr/mvfr. Breezy conditions will develop Wednesday as south winds increase to around 15 kts with frequent gusts to around 25 kts from midday through the afternoon and evening. Some showers may affect KGRR by mid to late evening but most of the thunderstorms should stay north to northwest of most of our area through 06Z Thursday. && .MARINE... Issued at 324 PM EDT Tue Jun 27 2017 We will be issuing a Beach Hazards Statement and Small Craft Advisory with this forecast package for Wednesday into Thursday. Winds will begin to increase overnight tonight ahead of the next incoming system that will arrive late Wed. Winds and waves will come up enough to become a hazard on Wed from North to South. These winds will remain up through Thu when the cold front will move through and a weaker gradient will move in. && .HYDROLOGY... Issued at 324 PM EDT Tue Jun 27 2017 The Chippewa and Pine River warnings have been downgraded to advisories with continued improvement. The Pine River levels are dropping at a rate such that the advisory could potentially be dropped by this time tomorrow. The Chippewa River will experience a more gradual fall. The majority of river in a stretch from Ludington eastward remain elevated, as well. Additional rainfall is slated for late Wednesday into Thursday. This midweek precipitation has the potential to delay improvement, keeping rivers elevated. Additional rainfall could affect the area again by Friday. Details in the exact placement of the heaviest rain is still not certain, but the potential exists for more than 3 inches of rain to fall in some places over the next 5-7 days. Further south, rivers are slightly above to near normal. Given recent rainfall totals, river levels are almost certain to rise if forecast precipitation amounts are achieved through the next week. Those living near rivers should pay close attention to forecast updates and monitor river trends closely. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement from 8 AM EDT Wednesday through Thursday afternoon for MIZ037-043-050-056-064-071. LM...Small Craft Advisory from 8 AM Wednesday to 2 PM EDT Thursday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...NJJ SHORT TERM...NJJ LONG TERM...MJS AVIATION...Laurens HYDROLOGY...JAM MARINE...NJJ