Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kgrr 200215 
afdgrr

Area forecast discussion
National Weather Service Grand Rapids Michigan
1015 PM EDT Tue Sep 19 2017

Latest update...
update

Synopsis...
issued at 330 PM EDT Tue Sep 19 2017

A few showers and isolated thunderstorms will continue into this
evening over south central lower Michigan. These are expected to
diminish sometime after midnight. Expect all areas to see fog
develop late tonight into early Wednesday.

A weak cold front will bring the chance of more scattered showers
and storms Wednesday night and again Thursday afternoon. Much of
the rest of the week and into early next week looks to be dry.

Daily high temperatures are expected to be in the 80s each day, with
some locations possibly hitting 90 Friday and Saturday.

&&

Update...
issued at 1015 PM EDT Tue Sep 19 2017

On the fence about issuing a dense fog advisory for late tonight
and Wednesday morning. Believe that some will develop but
confidence remains low on how widespread it will become. The area
along/near I-94 that had the rain today is currently mostly
covered in clouds and should continue to be much of the night
(limiting radiation fog potential), but guidance still suggests
some lower vsbys developing. Meanwhile it is mostly clear north
and west of GRR but this area has slightly lower dew points and
was warmer/drier today. This could end up being more of a stratus
event vs a widespread dense fog event. Will continue to monitor,
but for now no fog headline.

&&

Short term...(this evening through Thursday night)
issued at 330 PM EDT Tue Sep 19 2017

Passing short wave will continue to produce some showers over the southeast
County Warning Area into tonight. Then isolated convection will be possible with a
front Wednesday night, but could linger into Thursday night.

A mid level short wave was slowly moving across the County Warning Area this
afternoon. I extended the pops into tonight on the morning update,
and this still looks good for areas southeast of a Alma to Kalamazoo line.
These should diminish toward midnight as the wave exits.

Enough boundary moisture and light winds to expect fog development
late tonight. Vsbys below a mile seem plausible across the County Warning Area. The
fog will probably hold into the Wednesday morning, but conditions
should improve toward 10 am.

After a quiet Wednesday a weakening cold front pushes toward the
area Wednesday night. Also in this time frame we will see upper
ridging attempting to build into the Great Lakes. This will be the
battle zone as to while one wins out, the front or the ridge. Expect
the best chance of seeing storms from this front will be northwest of GRR
Wednesday night. The front washes out into Thursday, but some
diurnal convection will be possible over the interior County Warning Area Thursday
afternoon.

Quite a Summer-like setup by Thursday night with a large upper high
sitting over the southern Great Lakes. Expect steamy conditions
with dewpoints reaching 65 to 70. We may become capped by Thursday
night, but its possible an isolated storm could occur if the capped
is broken. So largely expect dry conditions by Thursday night, but
we can not rule out an isolated storm.

Long term...(friday through tuesday)
issued at 330 PM EDT Tue Sep 19 2017

Hot and dry are the main themes of the long term period which
stretches from Friday through early next week. The pattern is
somewhat blocked with tropical systems off the East Coast and a
trough out across the western U.S. The Great Lakes will be situated
in between with a building ridge overhead. Given this pattern we see
little to no chances for rainfall.

As for temperatures it is going to feel like deep Summer as compared
to late September. Record highs in Grand Rapids from Friday through
Monday are 90, 90, 91 and 90 respectively. We will be at least near
record highs with readings in the upper 80s to around 90 given very
high 500mb heights (around 590dm) and 850mb temps between +16c and
+20c the entire time. Friday and Saturday may be our warmest days.

&&

Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 745 PM EDT Tue Sep 19 2017

Confidence is fairly high that widespread IFR/LIFR conditions due
to stratus and fog will develop after midnight tonight and linger
through mid morning Wednesday. VFR should become commonplace by
Wednesday afternoon.



&&

Marine...
issued at 330 PM EDT Tue Sep 19 2017

Offshore flow will continue tonight into Wed, when the winds
gradually turn more southerly. Speeds are expected to be 15 knots
or less keeping waves on the low side. A thunderstorm risk Wed night



&&

Hydrology...
issued at 330 PM EDT Tue Sep 19 2017

Rainfall this morning was fairly light and occurred south of a line
from Holland to Lansing. Most rainfall totals were under 0.10
inches, but a few locations did pick up more than 0.25 inches.
Weakening low pressure tracking south of the area will continue to
provide a chance for showers south of I-96 today. Rainfall this
afternoon and evening will be even more hit and miss than this
morning. A few locations in Ingham, Jackson, and Calhoun counties
could pick up more than a tenth of an inch of new rainfall, however.
A weak frontal boundary will provide the next chance for showers or
a thunderstorm Wednesday night into Thursday. High confidence then
exists with very warm and dry conditions late Friday through the
weekend.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...none.
&&

$$

Update...Meade
synopsis...jk
short term...jk

National Weather Service Glossary of Abbreviations