765
FXUS63 KGRR 171756
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
156 PM EDT Fri May 17 2024

.KEY MESSAGES...

- Isolated showers and storms today

- Dry tonight and milder Saturday

- Warm and dry weekend

- Showers/storms Monday-Wednesday

&&

.UPDATE...
Issued at 1051 AM EDT Fri May 17 2024

Stratus deck lingers from GRR to the north and west while diurnal
cumulus has been filling in across the former clear area south
and east of GRR. Overall trend will be for a gradually lifting
cloud deck today, scattering out near and west of Hwy 131 in
stable lake shadow, but probably staying in place east of Hwy
131. (Turning mostly sunny west; remaining partly sunny east.)

CAMs suggest a few widely scattered showers/storms developing
along the lake breeze front toward mid afternoon near Hwy 131.
Also a weak convergence zone related to last night`s weak/stalled
sfc cold front over the ern CWFA could be an impetus for
scattered storm developing during the diurnal peak. We have 1500
J/KG or so of SBCape available but little shear, so these cells
should be slow movers with local/brief heavy downpours.

Marine web cams at Holland, Muskegon, and Grand Haven are still
pretty socked in with fog. Issued a Marine Dense Fog Advisory
earlier which goes til Noon, but confidence is low regarding how
long it will linger (and over how much of the nearshore area).
This may need to be extended and if it does mix out soon it may
just return again tonight.

&&

.DISCUSSION...
Issued at 330 AM EDT Fri May 17 2024

- Isolated showers and storms today

An upper level shortwave is bringing a few showers and storms to
our nw fcst area early this morning and isolated showers also
clipping our extreme se fcst area. We expect this pcpn to taper
off toward daybreak with dry wx for the vast majority of our fcst
area today.

However with a cold front moving slowly through our area we
expect a few showers and isolated storms to redevelop mainly this
afternoon over our eastern fcst area. In fact 00Z HREF guidance
suggests sb/mu capes will reach around 1000 j/kg this aftn just
ahead of the front. However potential for stronger or organized
convection is mitigated significantly by weak shear. No severe
weather is expected today.

- Dry tonight and milder Saturday

Fair wx is fcst tonight through Saturday as weak sfc ridging
builds in. Some patchy fog is expected late tonight through mid
morning Saturday. Ample sun and southerly waa along with h8 temps
reaching around 14-15 C will result in high temps Saturday
reaching the lower to perhaps middle 80s across most of our area.
The weak sfc gradient will be conducive to lake breeze development
which will keep temps near the Lake MI shoreline considerably
cooler.

- Warm and dry weekend

Upper ridging will develop over the weekend leading to very warm
temperatures by Sunday. H8 temps climb to around 14c leading to
highs in the mid 80s. A weak cold front moving across northern Lower
will probably not have enough energy to produce precipitation over
the northern cwa, but it may lower dewpoints enough to result in
some elevated fire weather concerns Sunday afternoon along the
northern tier of counties.

- Showers/storms Monday-Wednesday

A cold front will slowly move toward the Great Lakes Monday ahead of
a high amplitude upper trough. For several days the models have been
advertising showers and thunderstorms developing along the front.
Monday, this precipitation will be generally west of the cwa, but
may see some convection drift over the western cwa during the
afternoon. The better and stronger setup arrives Tuesday as we see a
stronger surface low develop in the southern Plains and move
northeastward across Wisconsin. Strong southerly flow ahead of the
low will send moisture into the cwa and short waves rotating through
the upper trough will help in firing convection. Once again the
latest models suggest fairly robust values for SBCAPE, bulk shear,
and EHI. This points toward the potential for convective
organization Tuesday and a potential severe threat.

Another warm day is expected Monday with highs in the mid 80s, but
once clouds/showers/storms move across the cwa Tuesday, temperatures
will fall back into the 70s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 156 PM EDT Fri May 17 2024

Fog has diminished across the area this afternoon, with the last
of the fog lasting near and along the lakeshore. Expect fog to
redevelop late tonight to early Saturday morning with visibilities
down to 1/2 mile possible.

Isolated showers have begun to initiate along the lake front this
afternoon. These showers will move east through 00z this evening.
Sufficient instability with limited shear will mean short-lived
slow moving localized heavy downpours with a few rumbles of
thunder possible.

&&

.MARINE...
Issued at 330 AM EDT Fri May 17 2024

No wind or higher wave hazards are expected across our nearshore
waters in the near term. Wind speeds through the weekend will be
fairly light. Some patchy fog is possible early this morning and
then again tonight.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert from midnight tonight to midnight EDT Saturday
     night for MIZ050-056-057-064-071.
MARINE...Dense Fog Advisory until 4 PM EDT this afternoon for LMZ844>847.

&&

$$

UPDATE...Meade
DISCUSSION...Laurens/04
AVIATION...Thielke
MARINE...Laurens