Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KGRR 171052

Area Forecast Discussion
National Weather Service Grand Rapids MI
652 AM EDT Wed May 17 2017


Issued at 310 AM EDT Wed May 17 2017

A large area of high pressure located off the mid atlantic states
will continue to funnel a very warm airmass into the Great Lakes
Region into tonight. A cold front located in the Western Plains
will only slowly track through the region on Thursday. As a result
the area will be mostly dry into tonight...then an increasing risk
for showers and thunderstorms are forecasted for Thursday.


.SHORT TERM...(Today through Friday)
Issued at 310 AM EDT Wed May 17 2017

The main change to the forecast was to reflect gustier winds
today...add a small risk for thunderstorms for parts of the area
today and tonight.

A strong low level jet is shown to form this afternoon and
tonight...especially across IL and IN. Given the better mixing
this afternoon...we may see some gusts approaching 40
mph...especially closer to the Kalamazoo to Jackson region. This
is close to wind advisory criteria. I did raise the wind gusts as
a result for this afternoon.

Elevated instability moves in today and tonight. There are some
small showers and thunderstorms in IL that may try to move into
the region north of MKG this morning. I raised POPs for the
western zones today and this evening as a result. The stronger low
level jet this evening may support the convection to move into
western zones later this evening. Models are struggling with the
current some uncertainty.

Once the front moves in...given the stronger wind fields that will
be in place...any convection could result in stronger wind
gusts...especially on Thu.

.LONG TERM...(Friday night through Tuesday)
Issued at 310 AM EDT Wed May 17 2017

The first main feature that has our attention in the long term will
be the upper low that is expected to bring rain chances in here Fri
night into Sun. This low will dig to the SE and draw plentiful Gulf
moisture northward toward the area. The favored period for rain
looks to be Sat afternoon into Sun as the best moisture transport
and eventually the front moves through. Some storms will be possible
as sfc based and elevated instability will be present.

The timing of the rain out of the area is still a bit uncertain. It
looks like the rain will move out at some point from Sun afternoon
through Sun evening depending on the timing of the front. Once it
does move through we should dry out a bit. Some of the models are
trying to bring some light QPF to the area on Mon with some
semblance of troughing aloft remaining over the area. A dry low
level E/NE flow will limit th rain potential.

The next best chance of rain will come as early as Tue and into Wed.
This occurs as we see yet another fairly amplified upper trough
bring the chcs in. This one looks to dig over the Upper Midwest as
some phasing of the two branches of the jet occurs. The strength and
development of the trough is still uncertain with regard to the
details. This will have implications on the rain chcs.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 646 AM EDT Wed May 17 2017

A small area of showers and thunderstorms will track northeast
over Lake MI early this am and may clip the KLDM region. The
remainder of the daylight hours looks to be dry...warm and breezy.
With some south to southwest wind gusts topping 25 knots. We may
see some wind shear at times into tonight.

Scattered thunderstorms may move in tonight for western TAF sites...closer
to Lake MI...and possibly further inland after midnight.


Issued at 310 AM EDT Wed May 17 2017

Southerly flow will continue over the nearshore waters into
tonight. With a tight pressure gradient...stronger winds will
occur. Given the fetch...the highest waves will occur for the
northern zones...while only marginally high waves expected in the
southernmost zones. As we go through tonight the winds my veer
southwest...which could result in locations around South Haven
seeing 4 footers as well. Will keep the current headlines going.


Issued at 328 PM EDT Mon May 15 2017

Rivers are running well within banks. Rain still looks on track for
the weekend. Basin average rainfall currently looks to be about
0.50"-1.00" but with locally higher amounts possible. Some river
rises are likely with this rain but not expecting flooding at this
time. Smaller streams and rivers may need to be watched for above
bankfull rises. Main stem rivers should be able to handle this
rainfall fine unless guidance trends upward.


Issued at 310 AM EDT Wed May 17 2017

Record High Minimum Temperatures for 5/17:
Grand Rapids - 68 degrees in 1906
Muskegon - 66 degrees in 2015
Lansing - 67 degrees in 1908

Record High Maximum Temperatures for 5/17:
Grand Rapids - 91 degrees in 1962
Muskegon - 88 degrees in 1962
Lansing - 89 degrees in 1977, 1889


LM...Small Craft Advisory until 6 AM EDT Thursday for LMZ846>849.



MARINE...MJS is the U.S. government's official web portal to all federal, state and local government web resources and services.