Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
1145 PM EDT Thursday Sep 18 2014

Latest update...

issued at 306 PM EDT Thursday Sep 18 2014

Quiet and pleasant weather will continue through Friday. It will be
slightly warmer with highs on Friday in the middle 60s to lower 70s
with a mix of clouds and sunshine. The risk of showers and
thunderstorms return late Friday night and are expected to linger
into Saturday and Saturday night. A few of these storms could be
strong to severe Saturday afternoon and evening. Temperatures on
Saturday will range from the upper 60s over central lower to
around 80 over far southern lower.

Much of next week appears to be dry. Temperatures are expected to
be near normal with highs in the middle 60s to lower 70s and lows in
the upper 40s to around 50.


issued at 1040 PM EDT Thursday Sep 18 2014

Updated for less cloud cover tonight than earlier expected. Also
added some patchy fog to the forecast late tonight... mainly from
GRR to the north and east. Already seeing some 1-3 mile
visibilities at Big Rapids and Montana pleasant.


Short term...(this evening through Saturday night)
issued at 306 PM EDT Thursday Sep 18 2014

A couple concerns persist in the short term...the potential for
frost tonight...and the potential for severe storms Saturday.

The frost potential seems reduced tonight as the low and middle levels
behind a dying cold front remain moist. Cloud cover should help
keep the area a bit warmer overnight so raise mins slightly and
will only mention patchy frost over the interior north late

Attention then turns to the cold front that is prognosticated to reach the
County Warning Area Saturday evening. However still quite a bit of differences
showing up in the models with the timing of the front and just how
unstable we become. With a quicker the GFS shows...we
would cloud over with showers spreading in through Saturday morning.
This would not allow for much instability. The European model (ecmwf) and NAM both
show a slower front...allowing for more instability and the better
potential for severe storms. As long as we are able to become
unstable the 0-6km bulk shear values of 35-40 kts support organized
convection. Wind fields should be in the 40-50 kts range from the
middle levels down to about 2k feet suggesting a wind threat with any
stronger storm. At this point I am leaning toward a better chance
of severe with the most likely window occurring between 20z Sat and
02z sun. Damaging line segments should be the Mode...but some
severe hail could be possible too. Showers and storms will
gradually diminish in intensity and coverage after Saturday evening.

Until then Friday appears to be a very nice day. Some clouds may
linger through the morning...but then expecting a mostly sunny
afternoon...before clouds return again toward midnight Friday
night. Southerly return flow will push temperatures toward normal values
for the first time in over a week. Tough Saturday maximum temperature forecast
due to timing issues stated above. Have upper 60s over the northwest where
the showers arrive first...while some areas in the southern County Warning Area may
hit 80 if there is a delay in the precipitation there.

Long term...(sunday through thursday)
issued at 306 PM EDT Thursday Sep 18 2014

Quiet weather expected in the extended period. There could be a few
showers on Sunday as sharp upper trough axis moves through although
moisture is limited. The rest of the week should be dry but we will
have to watch Monday night as another northern stream shortwave
trough moving through could bring some showers to northern zones. At
this point it appears any showers will remain north of the forecast
area. After a cool start to the week...temperatures will moderate as
heights rise with upper ridging by the end of the period.


Aviation...(for the 06z tafs through 06z saturday)
issued at 1145 PM EDT Thursday Sep 18 2014

VFR conditions will continue for most of the night but there is
potential for some stratus/fog to develop during the early morning
hours Friday. There is potential for a period of MVFR/IFR ceilings and
visbys from around 10z through 14z Friday at all the terminals. The
best chance for IFR ceilings/visibilities is at lan and jxn where winds will be
lighter closer to the center of the surface high.

Morning stratus and fog will mix out by middle morning Friday leaving
VFR conditions for the rest of the day through Friday evening. South
surface winds will increase to 10-20 kts in the afternoon with some
gusts over 20 kts possible along the Lakeshore at mkg.


issued at 306 PM EDT Thursday Sep 18 2014

Southerly winds will be increasing on Friday. We may need a Small
Craft Advisory north of Grand Haven by afternoon due to the long
fetch. These winds persist into Friday night and higher waves
should build over the entire nearshore waters. It will likely stay
rough until Saturday evening when a cold front pushes through. The
winds lighten up Saturday night along with shifting to the northwest.


issued at 306 PM EDT Thursday Sep 18 2014

Precipitation late Friday night into early Saturday night will be convective
in rainfall amounts will vary greatly. Overall
expecting most areas will see a quarter to half inch of rain.
However precipitable water values peak near two inches Saturday there is potential for localized heavy rain which could
lead to some urban and poor drainage issues.


GRR watches/warnings/advisories...


short term...jk
long term...ostuno

National Weather Service Glossary of Abbreviations