Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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167 FXUS63 KGRR 021615 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1215 PM EDT Thu May 2 2024 .KEY MESSAGES... - Chance for thunderstorms later today into Friday - Warm and Mostly Dry Weekend - Showers and Storms Tuesday/Tuesday Night && .UPDATE... Issued at 1114 AM EDT Thu May 2 2024 Isolated thunderstorm moving into Berrien County has not really shown any signs of weakening. Its occurring on a wing of weak elevated instability moving into the southwest parts of the CWA. We will update the forecast to reflect a risk for an isolated thunderstorm this afternoon for southwest zones. Instability builds this evening and into tonight as low level wind fields strengthen. Overall the instability still remains weak and deep layer shear is relatively low. However models are showing increasing convection overnight so high POPs remain warranted. Isolated stronger wind gusts could accompany the storms. && .DISCUSSION... Issued at 347 AM EDT Thu May 2 2024 - Chance for thunderstorms later today into Friday The first half of the day today should continue where Wednesday left off with mild temperatures and some cloud cover in place. We will see some smaller rain chances start to develop after noon for areas further North and West. The reason this is the case is that the low level jet that will be driving this round of showers and storms will be focused much more to our NW. In addition, the lower level moisture is lacking here, with a good deal of mid clouds moving through. This is likely to result in a few sprinkles/light showers falling from a mid cloud deck. The best chance for rain will come later this evening and last through Friday morning before starting to push east of the forecast area. This is when the last part of the low level jet is exiting the area, and moisture pooling ahead of the sfc front will be sufficient for rain to be likely. Thunder chances start to move over the area this afternoon, once again further NW, closer to the low level jet and the better moisture and warmth aloft. Some of the convection allowing models are trying to bring MU CAPEs up into the 1500 J/kg toward midnight tonight, supporting a thunder mention. The amount of instability is likely what the Marginal Risk from the SPC is focused on. It is a pretty healthy amount of instability present. The limiting factors that will keep the storms likely on the more tame side is due to the upper wave staying well west of the area. This track will also take the core of the low level jet further west. The entire system will take its time to move through the entire area with the front almost nearly parallel to the upper flow. - Warm and Mostly Dry Weekend A secondary weak sfc cold front is shown to slowly drift in from the west over the weekend as the nrn Plains upper low/trough moves to Hudson Bay. Only 20-30 pct pops are in the forecast ahead of this feature however due to lack of stronger forcing, and the bulk of the weekend should be dry with warm temperatures in the 70s. A weak sfc high and drier air mass builds in behind that front for Sunday night into Monday and the baroclinic zone temporarily settles just south of MI. Also an upper ridge builds overhead during this time as next upper low/trough moves into the nrn Plains, suggesting a dry day. However the warm front returns north again on Monday night which brings a renewed chance of showers and storms. - Showers and Storms Tuesday/Tuesday Night A potentially active period is Tuesday afternoon and evening as a shortwave heads northeast from KS and sends a front in our direction. Moisture return from the Gulf via 40 kt low level jet should result in numerous showers and storms developing and will carry 60-70 pct pops. Fcst confidence in convective potential decreases by the middle of next week with large ensemble QPF/timing spread noted, but temps look to remain above normal. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1216 PM EDT Thu May 2 2024 Low pressure moving toward the Great Lakes will push clouds over the terminals tonight. We`ll see high clouds this afternoon and perhaps a weak shower passing close to AZO around 18z. Otherwise, more showers/storms are expected tonight. Models show a fairly strong signal of MVFR/IFR moving across the termimals from northwest to southeast beginning around 07z at MKG and lasting roughly 5 hrs before returning to VFR. This also coincides with the showers/storms arriving and departing. && .MARINE... Issued at 347 AM EDT Thu May 2 2024 We are cautiously optimistic that we will not need any marine headlines for the next couple of days. There is an increasing pressure gradient coming in later today and tonight. This looks to be offshore in nature, and will be warmer air riding up over the cooler waters of Lake Michigan. Winds could be up around 20 knots, just below criteria. High pressure building over the area for this coming weekend will give boaters a chance to get out on the waters with good boating conditions expected. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...MJS DISCUSSION...Meade/NJJ AVIATION...04 MARINE...NJJ