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

Latest update...
aviation

Synopsis...
issued at 306 PM EDT Thursday Sep 18 2014

Quiet and pleasant weather will continue through Friday. It will be
a 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.

&&

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 dieing 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 tonight.

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 front...as 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 00z tafs through 00z Friday evening)
issued at 810 PM EDT Thursday Sep 18 2014

The potential for stratus/fog is a challenge tonight as we are
under the influence of a surface ridge axis. Feel the highest risk of
IFR ceilings and visibilities is at lan and jxn where winds will be a bit
lighter closer to the center of the surface high... although cannot
rule out a period of IFR fog from roughly 10z-14z at any of the
terminals.

Decided to go with IFR in the tafs at lan/jxn where the winds are
prognosticated to be only 10-15 kts at 1000 feet later tonight. Went MVFR
at GRR/mkg/azo/btl where stronger winds of 20-25kts are shown at
1000 feet after 10z. This ought to limit the IFR stratus/fog
potential at the farther west terminals.

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



&&

Marine...
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.



&&

Hydrology...
issued at 306 PM EDT Thursday Sep 18 2014

Precipitation late Friday night into early Saturday night will be convective
in nature...so 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
evening...so there is potential for localized heavy rain which could
lead to some urban and poor drainage issues.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...none.
&&

$$

Synopsis...jk
short term...jk
long term...ostuno
aviation...Meade
hydrology...jk
marine...jk

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