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Area forecast discussion 
National Weather Service Grand Rapids Michigan
1230 PM EDT Tuesday Jul 29 2014

Latest update...

issued at 1150 am EDT Tuesday Jul 29 2014

A relatively cool and unsettled period of weather for late July is
expected to continue through most of the rest of this week. The area
will see high temperatures mainly in the 70s through the end of the
week. Weak waves of low pressure will pass through the area through
the week. This will provide some shower and storm chances mainly
during the afternoon and early evening hours. There will be many
hours during each day for any one location that it will not be


Mesoscale update...
issued at 1155 am EDT Tuesday Jul 29 2014

Latest rap forecast soundings for this afternoon around lan/jxn show only
about 500-800 joules of skinny cape to work with. Not too
impressive but just enough to pop a few cells during peak heating.
In addition to the small hail threat related to the low freezing
levels... a gusty wind threat probably exists as well as forecast soundings
have inverted-v look by middle to late afternoon with convective
cloud bases around 7k feet. The best surface convergence continues to be
prognosticated east of Highway 131 on the lake breeze shadow. Convective
temperatures are in the middle to upper 60s and the diurnal cumulus is
already popping. Moderate to towering cumulus should develop by 2pm with
little to to cin currently present.


Short term...(today through thursday)
issued at 328 am EDT Tuesday Jul 29 2014

The main focus of the forecast will be on the trends for rain chances each
day and what if any severe chances will be present. The upper low
centered near Hudson and James bays will remain in control of the
weather across the state/region. Short waves will continue to rotate
in across the area from the north-northwest as we remain under the cyclonic flow
of the low.

There are a couple of light rain showers near Manistee as of 07z
this morning heading to the southeast. These rain showers are directly
related to a short wave that is coming in from Northern Lake Michigan. We
will see a few showers remain possible through 12-14z with this as
it progresses southeast out of the County warning forecast area by that time.

We will then see the threat for showers and storms increase quite a
bit this afternoon. Some convection that is ongoing northwest of Lake
Superior early this morning with a short wave will gradually shift
south-southeast into the region this afternoon during peak heating. Hi res
models are indicating that the bulk of the convection with this wave
will be across WI and central and eastern lower Michigan. There continues to
be good agreement that wrly winds will limit instability immediately
downwind of Lake Michigan and limit convection there as a result.

We agree with the swody1 from Storm Prediction Center that the severe threat is limited
in our neck of the Woods this afternoon. Forecast soundings indicate
relatively thin cape profiles. This and pattern recognition with the
upper low would point toward hail occurring with the storms...but
staying sub-severe with cape in the -10 to -30c layer not overly
impressive. We can not rule out some wind gusts...but limited middle
level winds below 40 knots should keep wind gusts sub-severe also.

After an expected lull in the precipitation after early this evening through
Wednesday morning...additional showers and a few storms will be possible
once again Wednesday afternoon. The threat looks to be more southeast on Wednesday
afternoon as a short wave and associated surface trough are over the southeast
corner of the County warning forecast area during peak heating. The lake will also limit
instability immediately downwind of the lake with wrly flow again.
Short wave ridging will likely limit convection a little elsewhere.
Again. Forecast soundings indicate some hailers will be likely.

We will repeat the situation on Thursday...although instability looks a
little more limited as temperatures aloft look to warm slightly. Winds
aloft also drop off a little...which will also limit the wind threat
a little more.

Long term...(thursday night through monday)
issued at 328 am EDT Tuesday Jul 29 2014

Upper troughing will be well established at the beginning of the
long term (thursday night) over the eastern half of the lower 48.
The trough will be centered from ont/Quebec through the Great Lakes.
This will remain the case through Saturday. Sunday/Monday the trough
lifts out somewhat with a general northwest flow in place.

At the surface very weak features to key on with occasional troughs
associated with middle level shortwaves moving through. Timing of these
features is somewhat difficult and vary from the GFS to the European model (ecmwf).

Air mass will have modified by the long term and generally thinking
highs will be right near normals for this time of year...around 80
to the lower 80s.

Sensible weather will feature afternoon and evening showers and
storms Friday and Saturday as the upper trough enhances instability.
European model (ecmwf) brings a front through the area on Monday of next week...where
the GFS is more wrapped up with its surface low and delays this
until Tuesday. At this point have small probability of precipitation...20 percent in the
forecast for next Monday into Tuesday to play a bit of a middle
ground with the frontal passage.


Aviation...(for the 18z tafs through 18z wednesday)
issued at 1230 PM EDT Tuesday Jul 29 2014

VFR conditions are anticipated through 18z Wednesday. Ceilings with
cloud bases of 3500-5000ft are expected much of the time. A few
showers may develop mainly at our eastern terminals from middle to late
afternoon into early evening before ending.

A couple of isolated storms are possible middle to late afternoon but
there is not enough confidence in convective potential to warrant
inclusion in the terminal forecasts. Any heavier showers may cause
conditions to briefly deteriorate to MVFR conditions.


issued at 1155 am EDT Tuesday Jul 29 2014

Two north flow upwelling/overturning events in the last week has
resulted in very cold water temperatures in the 40s developing along the
coast per buoy readings. This is actually resulting in some patchy
fog as shown on the Muskegon web cam despite a cool and relatively
dry air mass. Surface dew points however are in the middle 50s which over 40
degree water with winds 10 kts or less is promoting some fog. Will
therefore add this threat to the nearshore forecast over the next few
days. Periods of stronger winds in the afternoon and early evening
may mix the fog out at times.


issued at 330 PM EDT Monday Jul 28 2014

No Hydro concerns at this time given isolated to scattered nature of
the convection over the next few days. Some brief locally heavy
downpours with small hail may occur east of Highway 131 and
especially east of U.S. 127 on Tuesday.


GRR watches/warnings/advisories...


Mesoscale update...Meade
short term...njj
long term...Duke

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