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Area forecast discussion 
National Weather Service Grand Rapids Michigan
1112 PM EDT Monday Aug 31 2015

Latest update...

issued at 327 PM EDT Monday Aug 31 2015

High pressure will be in control of the areas weather over the next
few days. This will keep the region warm with highs in the 80s and
mainly dry. There will be the chance for scattered showers and
storms however Wednesday afternoon and Wednesday night.

Shower chances appear to remain low through the weekend. It should
stay warm with highs in the 80s...with a few temperatures near 90.


issued at 1112 PM EDT Monday Aug 31 2015

Much like last night we are watching fog formation across
southwest lower Michigan. Conditions so far tonight are highly
variable ranging from a 1/4 mile visibility in a few spots to 10
miles in Lansing. Not convinced at this point that all areas are
going to see very low visibilities to the point where a dense fog
advisory would be needed. An advisory is certainly possible
though...but confidence is not high enough right now.

Two things that may change conditions just a bit tonight are winds
in the 1000-3000ft layer that increase to 10-20 knots. This may be
just enough to temper radiational cooling to the point where
widespread dense fog does not form. The other factor is that we
had a good amount of sunshine this afternoon which may have tended
to dry out the boundary layer just a bit.

Bottom line...areas of fog tonight...some of which that may be
locally dense. Lows in the lower to middle 60s across the area.


Short term...(this evening through Wednesday night)
issued at 327 PM EDT Monday Aug 31 2015

An upper ridge will dominate the weather into Tuesday...but then it
slowly breaks down. A short wave tries to move into the ridge
Wednesday/Wednesday night that could be enough to produce isolated or widely
scattered showers and storms.

Little change to the forecast for tonight and Tuesday with the upper
ridge in place. There will be a weak upper low over central Indiana
in the meantime...but any isolated convection associated with this
feature should remain south. Areas of fog are likely again
tonight...but a bit more mixing should lead to less areas of dense
fog. Highs on Tuesday away from the lake mainly in the middle 80s...
with a few upper 80s well inland.

As the upper ridge breaks down some of the moisture from the Indiana
upper low may creep into the southern County Warning Area Tuesday night. Have 20
probability of precipitation in case a stray shower or storm moves in. Increased min temperatures
Tuesday night as southerly winds and high dew points produce a
warm/muggy night.

The increased moisture into Wednesday could produce diurnal showers
and storms...mainly east of U.S. 131. Then there is not good
agreement in the models as to how successful the next short wave
moves through the weakening upper ridge by Wednesday night. But it
would seem that this ridge weakness and short wave should lead to an
mesoscale convective system moving along the western edge of the ridge. Added chance probability of precipitation
for this mesoscale convective system to impact the northwest County Warning Area.

Long term...(thursday through monday)
issued at 327 PM EDT Monday Aug 31 2015

The main story in the long term is that very warm temperatures and
humid conditions will continue through the Holiday weekend. The
daily risk of rain is quite low with limited coverage of convection

A few showers or thunderstorms are possible on Thursday due to the
combination of a middle level shortwave passing through and a weak
backdoor cold front slipping down from the northeast and stalling.
This ill-defined surface boundary may still be situated northwest-southeast or north-S
across the area on Friday and weak convergence along it... or the
lake breeze... could focus a few isolated showers or storms.

On Saturday and Sunday the upper ridge re-amplifies in response to
the upper low/trough dropping south through the Pacific northwest.
The ridge does begin to flatten out on Labor Day as shortwave energy
ejects out of the western trough. The shower and thunderstorm potential may
increase as this happens... although confidence is low as to when
(and if) the cold front will arrive.


Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 900 PM EDT Monday Aug 31 2015

Stratus and fog were widespread last night and expecting somewhat
of a repeat performance tonight. VFR conditions are present in
most locations at 01z...with some MVFR visibility fog already showing
up. Dew point depressions are again less than 10 degrees f this
evening and fog should become prevalent by midnight.

The question tonight is will a little bit more wind aloft
(10-20kts at 1000-2000ft)...and some drying of the boundary layer
that occurred this afternoon result in less fog/stratus.

Decided to keep with the going forecast of expecting the return of
IFR conditions. Thinking we will see visibilities dip at least to
around 1 mile with stratus clouds below 1000ft. Not sure we will
drop to LIFR or below at this point...but there certainly is
potential for it.

Fog and stratus should lift fairly quick once again Tuesday
morning. VFR conditions are expected Tuesday afternoon.


issued at 327 PM EDT Monday Aug 31 2015

Rather quiet regime on the lake with ridging overhead. The pressure
gradient should tighten a bit into Tuesday night and south-southwest winds should
pick up. It cause the lake to become a bit rough with some 2-3 foot


issued at 327 PM EDT Monday Aug 31 2015

Hydro concerns are low this week. There are small chances for a
shower in any given location from middle week into the weekend.
Excessive rainfall is unlikely.


GRR watches/warnings/advisories...


short term...jk
long term...Meade

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