-- Discussion containing changed information from previous version are highlighted. --
577
FXUS63 KGRR 071457
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1057 AM EDT Fri Jun 7 2024

.KEY MESSAGES...

- Breezy Today, Showers This Morning and Saturday

- Diminishing Showers Saturday Evening

- Monday looks like the coolest day next week

- Still looks like a warmup for the end of the week but it
  trending more toward a gradual temperature increase

&&

.UPDATE...
-- Changed Discussion --
Issued at 1037 AM EDT Fri Jun 7 2024

Local radar shows showers moving southeast across the central cwa
due to mid level instability associated with the upper low. As the
low moves east today, lapse rates will decrease a bit and we`ll
see showers diminish. Partly sunny/mostly cloudy skies are
expected north of a Whitehall to Lansing line with mostly sunny
skies south of there. The breezy conditions will begin to diminish
by mid to late afternoon as weak ridging builds in. Highs today
will be in the mid to upper 60s.
-- End Changed Discussion --

&&

.DISCUSSION...
Issued at 312 AM EDT Fri Jun 7 2024

- Breezy Today, Showers This Morning and Saturday

The main driver of our weather through this evening is a deep upper-
low across the region visible on mid-level water vapor imagery. This
low is driving isolated instability driven showers north of I96
which will diminish through the morning as the upper-low pulls away.
The northwest flow will support deeper mixing today, and when
combined with the isallobaric addition to the wind behind the
departing low will make it breezy today. The best winds/gusts will
be near and south of I94 where winds around 20 mph gusting to 30-35
mph (isolated gusts near 40 mph) are expected. Across the northern
CWA winds will be lower around 10-15 gusting to 25 mph. Highs today
will be in the upper 60s to near 70.

Skies clear out tonight as dry air makes its way in along with
surface and upper-level ridging with lows around 50. Near
daybreak Saturday, showers will arrive north of M46 as a
shortwave tracks into the area. They then expand during the
afternoon across the rest of the area. Highest QPF of 0.25-0.5"
will be north of I96 due to deformation on the north side of the
surface reflection, with up to 0.25" south. As 850mb temps climb
above 10C Sunday, highs climb back into the low 70s.

- Diminishing Showers Saturday Evening

A 700 mb trough is advertised by most models to shift through the
CWA Saturday evening.  Forecast soundings show fairly saturated
conditions through 500 mb with some lift noted in Bufkit overviews.
As a result, we will bump up the POPs for Saturday evening across
the CWA to account for the passage of this feature. The atmosphere
is shown to dry out on the backside of this system so after 06z
Sunday we will feature mainly dry conditions.

- Monday looks like the coolest day next week

Models are advertising fairly significant 850 mb temperature
anomalies on Monday.  Ensemble surface max temperatures have trended
downward.  Deterministic values and ensemble values suggest we will
struggle to reach 70 degrees as the 850 mb thermal trough tracks
through. We will nudge the max temperatures slightly downward for
Monday and feature most locations topping out in the 60`s.

- Still looks like a warmup for the end of the week but it trending
more toward a gradual temperature increase

Previous runs of the Canadian model have featured hot weather
arriving by Thursday, but the 00z run has trended a degree or two
lower.  The ECMWF has trended up with the temperatures slightly
Thursday and now has values topping 80 degrees, while the GFS is
showing 70`s then. Blending the values suggest we may struggle to
top 85 degrees on Thursday.  Thus I will lower values slightly and
feature most of the CWA in the 80 to 85 degree range, which is still
above normal.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 723 AM EDT Fri Jun 7 2024

The vad wind profile from the KGRR 88d shows west northwest winds
of 25 knots 2000 ft above radar level. Thus with some mixing we
will see the surface winds shifting and increasing. Those gusty
winds will persist through much of the day. Towards sunset the
mixing will decrease and that will support diminishing winds. Some
clouds will be around today, but VFR levels are expected.

&&

.MARINE...
Issued at 312 AM EDT Fri Jun 7 2024

Gusty winds of 20-25 knots gusting to 25-30 knots will continue
through the morning with associated 3-5 foot waves (highest between
South Haven and Muskegon) before subsiding this afternoon. The Beach
Hazards Statement and Small Craft advisory currently in effect cover
this well so no changes will be done. Lower winds and waves continue
into the weekend as gradient winds are weaker so no headlines are
expected.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 4 PM EDT this afternoon for MIZ037-
     043-050-056-064-071.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for
     LMZ844>849.

&&

$$

UPDATE...04
DISCUSSION...MJS/Thomas
AVIATION...MJS
MARINE...Thomas