Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Gaylord Michigan
146 am EDT Tuesday Sep 16 2014

issued at 354 PM EDT Monday Sep 15 2014

A weak area of low pressure will continue to bring showers to
portions of the area this afternoon before high pressure builds in
tonight and holds through Tuesday night...resulting in precipitation
free and cool conditions. On Wednesday...a weak disturbance will
bring another chance for showers before conditions improve again for
the end of the work week.


issued at 958 PM EDT Monday Sep 15 2014

Precipitation associated with shortwave has pretty much
exited/dissipated across northern Michigan...with low level moisture
/over-lake instability now helping to re-develop clouds over
Northern Lake Michigan. Also seeing fog develop in several
locations under clearing skies...light winds and decreasing
temperature/dewpoint spreads. Developing area of lower clouds over Northern
Lake Michigan will gradually slide inland overnight...mainly
impacting areas west of I-75. Will expand patchy fog eastward more
into the Au Sable valley and southeast portions of the area. Low
temperatures generally in the upper 30s to lower 40s.

Update issued at 654 PM EDT Monday Sep 15 2014

Shortwave moving through southern Michigan with backside of main precipitation/
cloud deck making steady progress to the south/east. Current
forecast in good shape with just a few cosmetic timing changes needed.
Still looking for some additional cloud cover to develop closer to
the Lake Michigan coast later this evening thanks to lingering low
level moisture/over-lake instability.


Short term...(this evening through tonight)
issued at 354 PM EDT Monday Sep 15 2014

..rain ending this evening with mixed skies overnight...

High impact weather potential: minimal.

Pattern synopsis/forecast: afternoon surface/composite analysis
shows a cold front cutting across lower Michigan...extending
southwest to a frontal wave over northwest Missouri. Compact short
wave trough spinning its way eastward across southern Wisconsin and
pushing showers into the forecast area south of the M-32 corridor.
More breaks for sun north of M-32 with diurnal cloud development
over Mackinac County. Scattered showers have also popped across
western/central Upper Michigan and far northeast Wisconsin.

Short wave trough will move quickly across Southern Lower Michigan
this evening...with synoptic scale subsidence/drying expected in its
wake. High pressure across the northern plains will build east into
the upper lakes overnight.

Primary forecast concerns: timing of ending of ongoing rainfall
across and near the forecast area. Overnight cloud cover and fog

Tonight...current radar trends suggest precipitation associated with
the approaching short wave trough should end by middle evening across
the far southeast corner of the forecast area. Also expect synoptic
middle clouds to push east as well. Loss of heating will put paid to
scattered shower activity across central Upper Michigan...residual
moisture and instability over Lake Michigan may result in clouds
"flaring up" over the lake later this went a little
more pessimistic on cloud cover later tonight across northwest
lower. Otherwise another cool afternoon expected to lead to a
chilly night with lows dropping into the upper 30s-lower 40s most
areas. Some patchy fog not out of the question especially across
interior northern lower if skies can stay clear much of the night
where dew points are elevated from lack of mixing.

Long term...(tuesday through monday)
issued at 354 PM EDT Monday Sep 15 2014

..a mainly quiet work week but active weekend...

High impact weather potential: frost possible Wednesday
night...though confidence continues to decrease as there may be
clouds around. Thunderstorms possible (along with perhaps some heavy
rain) this weekend as the remnants of Odile push toward the Great

Pattern summary: broad upper troughing is set to remain across the
region through Thursday (surprise...surprise)...but with a nice
change toward rising heights expected for a brief time into late
week and the early weekend. That will come as western Continental U.S. Ridging
currently is punted east ahead of a stronger northern stream
shortwave trough crossing The Rockies on Friday. That feature
appears increasingly likely to pick up the remnants of Hurricane
Odile and perhaps lift it north toward the Great Lakes...though the
exact timing of that is still a bit in question.

A look at the forecast details:

Tuesday-Tuesday night: fairly quiet as high pressure builds through
the lower lakes/Ohio Valley but with low level ridging working up
into northern Michigan. Could see a little bit of remnant stratus
across eastern areas through the morning...with a little cumulus likely
to fire up beneath the relative coolness aloft. However...the
air mass isn't cold enough to support any lake clouds...especially
with a weak push of warm advection into the afternoon ahead of a
backdoor cold front works across Lake Superior. That boundary may
prove pesky heading into late Tuesday night as shallow cold air
(925mb temperatures down around 4c) works into eastern upper...with said
low level cooling likely to drive an expanding axis of low stratus
and perhaps a little drizzle...mainly after 06z.

Wednesday-Wednesday night: an interesting and admittedly annoying
forecast with regard to the backdoor front on Wednesday. Said
feature is expected to push down toward the M-72 corridor by midday
before stalling/washing out. Upper support for overall precipitation isn't
anything terribly impressive...though we do have the southern tail
of a broad trough over Hudson Bay to deliver a brief window of
better qg-upward forcing. Couple that with a quite strong low level
frontogenetic response as very shallow cold air plunges into the
northern half of the County Warning Area...and the chances are definitely there for
a "streaky" band of light rain to roll across the area. The
placement of that rain is very much a challenge...but the best
probabilities seem to lie from the tip of the mitt counties on
north...but with some wiggle room for low confidence. This all makes
for a very tricky temperature forecast as stratus/precipitation could well
hold readings only in the lower 50s north of the front while sun
boosts readings well into the 60s south.

Of course the whole cloud/precipitation mess could become an issue into
Wednesday night as well with the washing out boundary nearby...all
while stronger low level ridging tries its best to nose in from
Ontario. Shallow cool air down low in easterly flow continues to
raise some red flags regarding possible Lake Huron stratus...but
have to admit the arriving air mass looks awfully dry. However...
there may be plenty of lower junk still leftover from the afternoon
that gets stuck/spread out beneath a lowering inversion. Suffice it
to say forecast confidence is very low when it comes to low temperatures
overnight. A more cloudy scenario would easily hold readings up in
the 40s...while a clear scenario would support lows down well into
the lower 30s...colder for the usual chilly locales. Based on the
setup...really getting the feeling clouds will win out for more
areas than not. Still Worth an severe weather potential statement mention and of course something
to watch closely the next 24 hours.

Thursday-friday: a great stretch of weather as Summer comes to a
close...with high pressure working into New England and favoring
strengthening return flow as we wrap up the work week. Based on
guidance trends the past few days and the more amplified low level
pattern at the onset...continue to believe much of Friday will be
dry as the best thermal/moisture advection is focused into the
western lakes. As such will remove any precipitation mention through Friday
afternoon. Could be a sneaky chilly morning Friday...especially
eastern areas...with highs warming back through the 60s by Friday

Friday night-monday: upstream sharp upper trough and its associated
cold front will be on the move through the weekend...currently
slated to arrive here Saturday night or early Sunday. In advance of
that feature...and elevated warm front may bring a round of
showers/thunder to parts of the area sometime Friday night...but it
appears the best chances will be west of our area...focused more in
a zone of much more impressive moisture transport and low level jet
forcing. Our best shot should come with the actual cold front
Saturday night...with thunder a distinct possibility. Coupled with
some impressive wind fields...may have to be on the lookout for some
stronger storms...but plenty of time to let that unfold the next few
days. Also of interest is the possibility for the remnants of Odile
to become absorbed int this system...indicating a heavy rain
threat...though the northward extent of deeper tropical moisture
remains to be seen. Could be looking at a quite warm day on
Saturday...provided the rain holds off...with strong thermal ridging
supporting highs well into the 70s...before taking a dive by Sunday
and especially Monday with the arrival of another shot of strong
cold advection.


Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 140 am EDT Tuesday Sep 16 2014

Colder low level air over the warmer lakes was resulting in some
broken VFR isolated MVFR ceilings across northwest lower. Flow is rather weak out
a westerly direction...and clouds will hang closer to the shore
with time. Higher pressure and drier air does continue to slide
into mainly the mbl area...and just some few-scattered cumulus
expected for the afternoon...with a period of broken VFR ceilings
possible at times in the afternoon for apn. A reinforcing cold
front will continue on a southward track from Canada...and try and
dip into eastern upper tonight. After a fairly clear start to the
evening...scattered middle/broken high level clouds will be punching
into pln/apn through the night.

Maybe some west gusts to 15-16 kts at apn this
afternoon...otherwise general light winds backing more SW tonight.


issued at 354 PM EDT Monday Sep 15 2014

Relatively weak gradient expected to keep winds and waves below
advisory criteria through Tuesday morning...winds may pick up from
the southwest Tuesday afternoon.


Apx watches/warnings/advisories...



short term...jpb
long term...Lawrence

National Weather Service Glossary of Abbreviations