Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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329 FXUS63 KGRR 050545 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 145 AM EDT Wed Jun 5 2024 .KEY MESSAGES... - Dry tonight, showers/storms Wednesday - Cooler and unsettled through the weekend && .UPDATE... Issued at 955 PM EDT Tue Jun 4 2024 Latest RAP shows a surge of higher PWATs over 1.5" arriving overnight from southwest to northeast, with a 30-35 kt low level jet setting up over Lk MI and the lakeshore counties. Also the H5 shortwave over wrn IL will be arriving after 06Z and will help break down the upper ridge which is currently in place. Rain chances will be ramping up accordingly, although the higher/likely probabilities through sunrise should be limited to areas near and west of Highway 131. Not much sfc based instability to work with but incoming H8 LI/s near -2C will support a late-night thunder risk. Temps holding up in the 70s for much of the night thanks to clouds and southerly flow, with early morning lows generally in the upper 60s. && .DISCUSSION... Issued at 322 PM EDT Tue Jun 4 2024 - Dry tonight, showers/storms Wednesday The 18z surface analysis showed a cold front near the Red River of the North and extending southward through western MN into northeast NE. This cold front will be a key to our weather Wednesday. Radar shows developing storms over northeast Wisconsin, but they are moving north and won`t affect southwest Lower tonight. However, CAMs suggest that more scattered convection will develop over portions of IL and southern WI later this evening and slowly move in our direction as the aforementioned cold front makes steady progress east. As instability wanes after midnight, these storms to the west should diminish somewhat, but probably not totally. Thus, we may be looking at some morning convection across the western cwa Wednesday morning. Instability is somewhat lacking during the morning and so we may see more showers than storms, and the storms that do develop will likely be non-severe. That could change by afternoon. SPC has placed the southeast cwa in a Marginal risk for severe storms Wednesday. This is mainly southeast of a Lansing to Battle Creek line with the focus on the afternoon. There is still uncertainty with this system and really hinges on how much the atmosphere can recover after morning showers/storms. If lingering clouds can thin a bit, then we`ll see more heating which will push SBCAPE higher. Bulk shear around 35 knots will support cell organization. The Nam3km, FV3, HRRR all show variations of afternoon redevelopment with the Nam3km the most aggressive. Wind would be the main threat with hail secondary. The cold front will push through by 00z Thursday, ending the severe threat, but it may not end the thunderstorm threat. Earlier runs of the HRRR hinted at a secondary line moving in conjunction with a strong upper low moving over the Great Lakes, so we`ll keep chc PoPs in the grids for this. - Cooler and unsettled through the weekend A nice shot of cooler air will flow into the cwa behind the cold front. H8 temps fall from 16c to 4c by Thursday afternoon. Friday through Sunday will see highs in the 60s...a nice refresher from today`s highs in the mid to upper 80s. The upper low will be camped out over the Great Lakes through Sunday before moving east Monday, only to be followed by another upper trough Tuesday. We`ll keep low chance PoPs in the forecast for this but by no means will it be raining all the time. A slow warming trend will develop by next Monday with highs in the mid to upper 70s by next Tuesday. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 133 AM EDT Wed Jun 5 2024 It`s looking like a stormy pattern for the TAFs through the period. Convection upstream around Nrn IL into NW IN it headed northeast towards the TAF sites. While some decrease in the convection may occur, it`s looking more likely that TS will be observed prior to 12z. This initial batch of convection should push east of TAF sites by mid morning, however the atmosphere remains unstable and high res models are regenerating new convection by midday. There is some uncertainty on the timing and overall coverage of this next round of storms but trends are supporting greater coverage. So the TAF sites will feature another period of storm with VCTS in that window. While another break in the convection is likely by mid afternoon, the cold front will still be off to the west, and will be headed east. The atmosphere will remain unstable until this feature pushes through, not until toward the end of the period, 06z Thu. It`s possible that another batch of convection could roll in ahead of the front. Any stronger storm through the period could contain gusts over 30 knots. Considerable moisture will be lifting northward into the TAF sites today. As a result, ceilings will be lowering, and MVFR levels look likely by daybreak with a potential for IFR. Visibilities could lower briefly down into the IFR range if a heavier cell tracks over a TAF site. && .MARINE... Issued at 322 PM EDT Tue Jun 4 2024 A cold front will move across the lake Wednesday. Gusty west winds behind the front will likely create waves that will necessitate a Small Craft Advisory and Beach Hazards Statement Wednesday night and Thursday. Additional headlines may be needed later in the week too as cooler air flows over the lake creating hazardous waves. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...Meade DISCUSSION...04/CAS AVIATION...MJS MARINE...04