Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 011730
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
130 PM EDT Fri Jul 1 2022

LATEST UPDATE...
Aviation

.DISCUSSION...(Today through next Thursday)
Issued at 342 AM EDT Fri Jul 1 2022

-- Chance of showers/storms today --

Above a surface cold front which will slide through the area today
will be some support for scattered shower and thunderstorm
development this morning into mid afternoon:
- Modest upper level divergence over southern Michigan midday
  associated with a jet streak entrance region.
- Mid-level lapse rates a fair 6.5 to 7 degrees C/km within a high
  plains sourced EML plume.
- A ribbon of moisture streaming in at 800-700 mb.
- MUCAPE around 1000 J/kg and effective updraft-layer shear
  around 30 knots.

There may be some mitigation of convection this morning in the
I-96 portion of the area as lift will be minimal at that time from
upper level dynamics and 850 mb wind speed divergence. The latest
CAMs/HREF members tend to increase convection around I-94 (and/or
farther south) during the early/mid afternoon, and this
convection may trend toward being surface-based east of Kalamazoo.
CAPE in the hail growth layer looks fairly thin, but upper level
shear may support some at least small hail growth despite the
thin CAPE, and any hail melt could contribute to downdraft
enhancement into a well mixed atmosphere below 5,000 feet. If
updrafts do become more vigorous or organized in southern
Michigan, it could result in locally gusty winds with downpours at
the surface. The threat of severe weather is marginal.

-- Holiday weekend outlook --

Ensembles of the GFS/Euro/Canadian are in moderate agreement for
the Independence Day weekend featuring Sat/Sun near-normal
temperatures, comfortably low dew points, and minimal chance of
rain under high pressure. Temperatures will likely be warmer and
dew point higher on Mon the 4th, with shower/storm chances
increasing late in the day as upstream convective complexes on the
northern periphery of the "ring of fire" pattern move through the
Midwest.

-- Next week --

Though far from settled, the pattern could support occasional
thunderstorm chances Tue/Wed/Thu as a strengthening subtropical
upper-level high over the southern CONUS develops with a quasi-
zonal jet over the northern CONUS. Later in the week, this heat
dome high may migrate toward west-central or western CONUS while
troughing would be favored over the Northeast. Michigan may end up
in the temperature goldilocks zone (near-normal July warmth)
while the brutal heat (above-normal even for July) is kept
west/southwest.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 131 PM EDT Fri Jul 1 2022


VFR conditions are expected at all TAF sites during the next 24
hours. However between now and 5 pm, a line of showers and a few
thunderstorms developed as we expected them to from near
Kalamazoo to Lansing. These storms will impact BTL prior to 18z
and should pass south of Lansing by 1830z or so. Expect brief
heavy rain and gusty winds in an near thunderstorms.

Tonight into Saturday expect mostly clear skies with a prevailing
northwest wind.

.MARINE... Issued at 342 AM EDT Fri Jul 1 2022

Winds and wave heights at the buoys have dropped below advisory
thresholds early this morning so the Small Craft / Beach Hazards
headlines have been canceled. The stronger winds at 1000 feet
above the water are not mixing down very effectively due to the
stability between the marine layer and the warmer air above.
Showers and thunderstorms associated with this warm and moist
layer of air above the cooler marine layer will not be affected by
Lake Michigan. Scattered development is expected to migrate from
its present location near Ludington toward the southern part of
the lake by afternoon. Lightning would be the primary and possibly
only hazard for marine interests today. Winds and waves during the
holiday weekend are not expected to be a concern.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

DISCUSSION...CAS
AVIATION...WDM
MARINE...CAS


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