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Area forecast discussion 
National Weather Service Grand Rapids Michigan
746 PM EDT Tuesday Sep 2 2014

Latest update...

issued at 308 PM EDT Tuesday Sep 2 2014

Fair weather will continue through Wednesday with weak high
pressure in control. Thundershowers and a return to muggy weather
will follow on Thursday into Friday as low pressure moves west to
east across southern Canada. Seasonably cool and dry weather then
follows as a Canadian high pressure system moves overhead for the


Short term...(this evening through Thursday night)
issued at 308 PM EDT Tuesday Sep 2 2014

500 mb-3 shortwave axis now moving east of the region with drier air
continuing to filter in at the surface...but still expecting a
few isolated showers well north of I-96 through 800 PM EDT with
cape around 250-500 j/kg.

Warm front supported by healthy low-level-jet approach region
early Thursday with thunderstorm threat. So far the
European model (ecmwf)...fim...and GFS have been pretty consistent with mesoscale convective system
formation over northern Wisconsin Wednesday night that then moves east
affecting northern half of lower Michigan by midday Thursday. This
looks reasonable given supporting middle-level frontogenesis
associated with warm front.

Strong storms and locally heavy rain will be good possibilities
beginning Thursday night as the cold front pushes into the
region. Storms will be supported by frontal convergence...deep
cape of 2000 j/kg...bulk shear of 30 kts...and upper divergence
with middle-level frontogenesis. Further...locally heavy rainfall
with fairly high percipitable water.

Long term...(friday through tuesday)
issued at 308 PM EDT Tuesday Sep 2 2014

A cold front moving across Michigan should bring a round of showers
and thunderstorms to the County Warning Area Friday. We/ll have to watch out for the
potential for severe storms Friday late morning and afternoon. High
instability with Li/S near -7 and MUCAPE 3k+ j/kg coupled with
30-35kt shear values should lead to some cell organization. It/S not
a slam dunk though. The low level jet is moving away from the County Warning Area by middle
morning Friday which may limit the severe potential. Favorable upper
jet dynamics though may mitigate the departing low level jet however. If model
timing is accurate...and so far both the GFS and European model (ecmwf) are in pretty
good agreement...the precipitation should end by Friday evening. After
that...cooler and drier air will move into the Great Lakes and the
weekend looks very pleasant with highs in the lower 70s and lower
humidity. As the high moves east Tuesday a warm front will move
toward the County Warning Area and the chances for showers and storms will increase.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 745 PM EDT Tuesday Sep 2 2014

VFR conditions are expected tonight and Wednesday. Some patchy
shallow ground fog cannot be ruled out 09z-13z... but feel it is not
likely enough to include any visibility reductions in the tafs at this


issued at 308 PM EDT Tuesday Sep 2 2014

No significant weather through Wednesday. Expect small craft /
beach hazard will be needed on Thursday as 15-25 knots south flow
developing as warm front pushes northeast across the lake early
Thursday. Waves should reach 3 to 6 feet with a rather choppy
period Friday as winds shift to west and then northwest behind
cold front.


issued at 1240 PM EDT Tuesday Sep 2 2014

Rivers are running a little above normal... but are still far below
bank full. Expecting precipitation totals mostly under a half inch
through the remainder of the work week. This should lead to small
rises on area rivers with peak levels well below bank full.


GRR watches/warnings/advisories...


short term...Cobb
long term...93

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