Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
320 am EDT Wednesday Jul 23 2014

Latest update...
synopsis/short term/long term/Hydro/marine

issued at 320 am EDT Wednesday Jul 23 2014

A cold front moving through Southern Lower Michigan will usher in
cooler and drier air for the next few days. Dry weather is expected
through Friday before low pressure moves toward the region and
brings a chance of showers/storms over the weekend.


Short term...(today through friday)
issued at 320 am EDT Wednesday Jul 23 2014

Forecast concerns are minimal today now that the cold front is
passing through the southern County Warning Area.

The next few days will be much less humid as dewpoints fall from the
upper 60s back to the upper 40s later today. Temperatures will also be much
cooler with highs in the middle 70s through Friday.

Latest infrared loop shows convective debris clouds moving south across
lower Michigan. These clouds will exit the County Warning Area later this morning
leading to mostly sunny skies. As high pressure drifts over the
state fair skies are expected through Thursday night.

An increase in clouds will occur late Friday as low pressure moves
east from the plains toward the Great Lakes. Short range models show
this precipitation holding off until Friday night/Saturday.

Long term...(friday night through tuesday)
issued at 320 am EDT Wednesday Jul 23 2014

Little question a cooler than normal temperature pattern will
persist through the long term forecast period. It would also seem
there is a good chance of showers Saturday into Monday...a few
thunderstorms would not be out of the question.

The models are in overall good agreement with an amplification of
the upper air pattern over the weekend into early next week. As it
turns out the recurving of typhoon matmo may well be a large part of
the reason for this. Recent published research now shows recurving
Pacific typhoons... through rossby wave propagation... cause a
trough to develop over eastern North America about 5 days after the
storm recuvers. This happened recently after typhoon neoguri
recurved during the first week of July. Given how the models
underplayed the development of that trough at longer ranges I have
to believe the slower and deeper European model (ecmwf) has the best Handel how this
will all play out over the next 5 to 7 days.

As for the details day to day... there is a system coming onshore
near the Washington coast as I write this. That system rides over
the longwave ridge into Friday then helps to amplify the eastern
trough as it merges with the much larger circulation going on over
eastern Canada. As this system comes into the Great Lakes we get the
warm advection precipitation later Friday night or more likely
Saturday. Then as the northern and southern stream systems wrap up
together we get wrap around showers starting Sunday and likely
continuing into Monday. Given that this upper low does not get
dislodged through middle week I could see scattered showers lasting
through a good part of next week but temperatures will be at least
10 degrees below normal from Monday on.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1200 am EDT Wednesday Jul 23 2014

For the 06z forecasts...the showers and storms should have exited the
area to the south by 06z. A VFR ceiling from 3500-7000 feet is hanging
around behind the precipitation. We are then watching an area of MVFR ceilings
across northern lower that looks to drop down into the area except kmkg
late tonight and just after daybreak. This will bring the
potential for some ceilings around 1500 feet with some light hz/br. This
will then lift out into a cumulus/stratocumulus ceiling around 4k feet
or so for the day on Wednesday. This will dissipate toward 00z Thursday.


issued at 320 am EDT Wednesday Jul 23 2014

Small Craft Advisory and beach hazards statement remains in effect today. Winds will
increase from the north today behind the cold front and waves will
increase to 3 to 5 feet. Longshore currents will likely develop
later today. North facing piers will be a target area for structural
currents and swimmers would be wise to avoid those areas.


issued at 320 am EDT Wednesday Jul 23 2014

Hydro concerns are minimal. Overnight rainfall was around 1.25
inches along the Lake Shore which shouldn/T cause Hydro problems.


GRR watches/warnings/advisories...
Michigan...Beach hazards statement through Thursday morning for miz056-064-

Beach hazards statement through late tonight for miz037-043-050.

Lm...Small Craft Advisory until 2 am EDT Thursday for lmz847>849.

Small Craft Advisory until 8 am EDT Thursday for lmz844>846.



short term...93
long term...wdm

National Weather Service Glossary of Abbreviations