Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 141738
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
138 PM EDT Thu Mar 14 2024

.KEY MESSAGES...

- Showers and Scattered Thunderstorms Today

- Chance of rain Saturday, then colder with snow showers

&&

.UPDATE...
Issued at 1134 AM EDT Thu Mar 14 2024

Showers and a few thunderstorms continue to track eastward through
the region as of late morning. Highest rainfall amounts so far are
around Kalamazoo where about three quarters of an inch has
fallen. The rain will migrate northeastward through the remainder
of the CWA through early afternoon. Clearing upstream in IL will
need to be monitored closely.It may try to slip into southern
parts of MI.  With the warm front near I-94 and 850 mb VWPs
around Chicago and northern IL showing a southwest flow of 25 to
30 knots, we may keep the warm front in southern parts of the CWA
and build some surface based CAPE starting around mid afternoon.
Given the very strong deep layer shear(0 to 6 KM) of around 70
knots overriding that clearing in IL, close monitoring for
possible increase in severe weather for southern parts of our CWA
will be needed. The main window for severe weather still looks to
be in the 3 pm to 8 pm window.

&&

.DISCUSSION...
Issued at 300 AM EDT Thu Mar 14 2024

- Showers and Scattered Thunderstorms Today

A warm front extending from west to east near the MI/IN border
will focus development of showers and scattered thunderstorms
today. The overall svr wx risk which was low has decreased further
as an overall short range guidance consensus and 00Z HREF all
suggest the warm front will not make it much further north than
the MI/IN border. This keeps instability of any significance
focused south of our area across IN/OH. The 00Z HREF shows only
100-250 j/kg of SB/MU CAPE near to south of I-94.

So the svr wx risk looks very low today and mainly confined to
near/south of I-94. Weak elevated instability north of the warm
front will result in scattered non severe convection. Rainfall
amounts with this system should generally fall into the one
quarter to three quarters inch range with locally higher amounts
in excess of an inch as suggested by the 00Z HREF LPMM product.
These type of rainfall amounts are not sufficient enough to cause
any significant hydro issues.

Lingering evening showers and isolated convection early will come
to an end rather quickly by mid to late evening on the back side
of this system. Skies will become partly sunny Friday and it will
be cooler with weak northerly flow cool air advection.

- Chance of rain Saturday, then colder with snow showers

No significant changes planned for this forecast. As noted
previously, late Saturday is trending slightly drier south of M-46.
We will get a shot of light lake effect snow Sunday morning in the
wake of the cold front associated with Saturday`s precipitation.
Accumulations should be nearly non-existent given relatively warm
surface temperatures.

No changes in expectations for Sunday night into Monday with the
secondary surge of colder air. Light accumulations by the lakeshore
seem like a reasonably good bet, with an emphasis on "light". A
slight chance for light snow remains possible early Tuesday due to
the possibility of a clipper type of feature dropping down the back
side of the broader scale exiting upper trough.

After reasonable confidence for a dry Wednesday, predictability
breaks down again from Thursday onward. This is due to possible
development of a southern stream trough over the southern plains. At
this time thunderstorms are not expected, however.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 138 PM EDT Thu Mar 14 2024

Scattered showers moved through the area this morning with some
rumbles of thunder across far southern MI impacting AZO, BTL, and
JXN. As a dry slot noses into the southwest portion of the state
visibility improves as rain exits to the northeast, but
widespread IFR persists into this afternoon. Another round of
showers and storms are expected across northern IN/IL and far
southern MI that may impact AZO, BTL, and JXN between about 20z to
00z.

Ceilings will begin to improve from the northwest to southeast
after 00z tonight and into Friday morning. Would expect MKG and
GRR to return to VFR after 06z Friday morning, and the rest of the
TAF sites to gradually lift into MVFR/VFR after 12z Friday.

&&

.MARINE...
Issued at 300 AM EDT Thu Mar 14 2024

Northeast winds will be light this morning before increasing a bit
this afternoon. Winds will back to the north tonight but will be
rather light. Winds will back to the southwest and increase
considerably Friday night and Saturday. Small craft advisories will
likely be needed Saturday as southwest winds increase to over 20
knots.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

UPDATE...MJS
DISCUSSION...Laurens/TJT
AVIATION...Thielke
MARINE...Laurens


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