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Area forecast discussion 
National Weather Service Grand Rapids Michigan
740 am EDT Wednesday may 6 2015

Latest update...

issued at 328 am EDT Wednesday may 6 2015

A stationary front over central Indiana will move north today across
lower Michigan. Temperatures will climb into the 70s this afternoon
and be even warmer Thursday when highs reach the lower 80s. The best
chance of thunderstorms comes Friday when a cold front will approach
from the west. Showers and thunderstorms will remain in the forecast
through the weekend as that frontal boundary will get hung up over
lower Michigan.


issued at 739 am EDT Wednesday may 6 2015

An area of fog...locally dense continues to spread slowly
northward this morning from the intestate 94 area toward the
intestate 96 area. I believe the fog will mix out by middle morning
so I will not issue a fog advisory but this will need to be
watched if it does not mix out as quick as I am thinking it will.
I did update the grids and zones to put areas of dense fog till
middle morning.


Short term...(today through friday)
issued at 328 am EDT Wednesday may 6 2015

Forecast concerns deal with precipitation trends through the period. The
upper ridge axis will remain overhead today as it moves from the
plains to the eastern US. The ridge coupled with little in the way
of moisture transport means that precipitation chances won't be very high.
Kgrr-88d currently shows some weak showers over Lake Michigan but
the trend has been a diminishing on during the past several hours. A
stationary front will move north through the County Warning Area today. We/ll keep a
slight chance of a shower for this feature but not much more.
There/S a little cape but not much instability today. Tonight and
Thursday look dry and mild with temperatures topping 80 Thursday. The
better chance of rain comes Friday as a stronger SW flow develops on
the back side of the ridge. A cold front will move to Wisconsin
Friday. This should be close enough to see higher chances of showers
and thunderstorms. Moisture transport vectors are much larger Friday
afternoon and so is the instability. Li/S fall to -6c as MLCAPE
climbs to around 1k j/kg. Shear values are very low so severe storms
not expected Friday.

Long term...(friday night through tuesday)
issued at 328 am EDT Wednesday may 6 2015

It would seem a change to cooler temperatures is likely by the end
of this forecast period. Till then through temperature will continue
to run above normal through the weekend...including Monday of next

This could be a stormy period as the primary frontal system stalls
near US on Saturday and remains in place into Monday before the main
system comes through. This would mean thunderstorms are possible
each day but the greatest chance of strong to severe storms would
seem to be Monday as the main system comes through the area.

Currently we have an upper ridge over the eastern United States with
a closed cold core upper low over Hudson Bay creating confluent flow
over Michigan. By Friday evening... the upper low over the southwest
United States starts to get sheared out by the next upstream Pacific
system. Just how far north the surface system with that gets
relative to Michigan Monday determines if we get strong storms and
warm air Monday (ecmwf) or if it turns out more like yesterday with
Michigan in the cold air (gfs solution). Given the strength of the
system now...I am favoring the European model (ecmwf). So I am thinking strong storms
are possible Monday. After that the cold air comes back in for


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 717 am EDT Wednesday may 6 2015

Little question the fog has moved in and I would expect it try to
spread north to lan and GRR but day time heating should help mix it
out before it gets that far north. Still considering how far south
this fog GOES (i-94 to I-80) it may take awhile for this fog to
mix out. This afternoon the warm front will push north into the
area. That should clear out all of the low clouds and fog by 20z
or so. I expect mostly clear skies with light winds tonight.


issued at 328 am EDT Wednesday may 6 2015

Some fog is possible over the lake today...otherwise no hazards are


issued at 1149 am EDT Tuesday may 5 2015

Todays precipitation is in the immediate scope of attention while
the next big challenge is keying in on next weekends rain
potential. Any river concerns would be in the late week and
weekend timeframe.

Precipitation materialized fairly well this morning which is
some needed relief to areas recently considered abnormally dry.
Additional rainfall is possible through the afternoon with localized
moderate to heavy rainfall. Locations along and south of I-94 have
the greatest chance for seeing convective type rainfall...but lower
instability would limit the threat.

The forecast gets a bit tricky going into late week and next weekend.
A system will develop out over the plains and is expected to
travel north and east. The Gulf of Mexico opens up to allow for
abundant moisture to feed northward as well. Meanwhile...the
system over the southeast off the Carolina coast could play a part
in how the pattern responds. Inland motion of the southeast system
could aid in draping a stationary boundary through the Ohio Valley
or somewhere through the Midwest. The result could very well end
up being periods of rainfall...possibly heavy...spanning from
late Friday on through Monday. This is something that bares
watching as we head into Thursday and Friday. If the scenario were
to play out the biggest concern would then become multiple rounds
of heavier rain. Though rivers and streams are well within
banks...forecasts will be monitored for this potential.


GRR watches/warnings/advisories...


short term...04
long term...wdm

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