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Area forecast discussion 
National Weather Service Gaylord Michigan
400 am EDT Wednesday Sep 17 2014

issued at 400 am EDT Wednesday Sep 17 2014

A weak surface boundary over Lake Superior...may generate a few
light rain showers or sprinkles across eastern Upper Michigan today.
Otherwise...a large area of high pressure will build in tonight into
Thursday leading to cooler temperatures once again. A storm
system is then expected to push into the Great Lakes Friday night
and linger into the weekend...generating warmer temperatures and
rain showers across northern Michigan.


Short term...(today through tonight)
issued at 400 am EDT Wednesday Sep 17 2014

..rain north and sun south today/frost possible tonight...

High impact weather potential: frost/freeze possibilities early
Thursday morning.

Pattern synopsis/forecast: midnight surface/composite analysis shows
a 1019mb high over Illinois/Indiana...with a cold front running
east-west across the Upper Peninsula and stretching northwest to a
frontal wave (1012mb) over far southeast Manitoba. Chilly
temperatures behind the front across northern Ontario with Tuesday
afternoon highs in the 40s. Short wave trough digging southeast
across Manitoba with an impressive baroclinic Leaf signature over
northwest Ontario which coincides with much of the precipitation
associated with this feature. Frontogenesis and warm advection
along/ahead of the front (nice low level veering signature in kapx
VAD wind profile) has resulted in a band of warmer topped
altocumulus/altostratus spilling into the Upper Peninsula with
spottier showers over the boundary waters. South of The Straits
skies were mostly clear along northern edge of a pocket of drier air
with the area of high pressure to the south. Narrow axis of higher
precipitable water values (20-25mm) along the front from western
Upper Michigan to Lake Winnipeg.

Cold front expected to sink into the tip of the mitt counties this
morning...and linger across northern lower Michigan through the day
before cool high pressure builds into the upper Great Lakes
overnight and pushes the boundary into Southern Lower Michigan.
Accompanying short wave trough will mostly impact northern
Ontario/Lake Superior/Upper Michigan today...with rising heights and
resultant synoptic subsidence/drying across the region tonight.

Primary forecast concerns: extent of precipitation chances with the
system passing through northern portions of the forecast area
today. Cloud cover and resultant frost potential tonight given
Post-frontal reinforcing chilly air mass pushing across the forecast

Today...rain has been working its way southeast into Western Lake
Superior over the past couple of hours...and is taking a bead on
eastern Upper Michigan. Looks like there will be a pop gradient
setting up from south to north across Chippewa/Mackinac counties...
with higher probabilities across northern Chippewa County and
adjacent areas of Lake Superior/northern Ontario. Anticipate rain
threat to wind down by late afternoon. Meanwhile...rain should have
a harder time getting south of The Straits and expect more sun the
farther south you go today...though looks like there will probably
be a band of low clouds spreading across eastern upper and into far
northern lower by late in the day. Highs today will be cooler
across eastern upper where it should be cloudy most if not all of
the day (50s)...with temperatures warming into the 60s across
northern lower.

Tonight...low cloud band mentioned above expected to sink into
northern lower Michigan this evening...likely aided by some lake
component within north/Northeast Boundary layer flow (especially off
lake huron). Clouds are expected to clear across eastern upper
given strong cold advection and more of a northeast/downslope
trajectory to boundary layer winds. Not certain if there will be
any nuisance lake induced precipitation with this cloud band as it
sinks southward...not inclined to add any to the forecast just yet.
Most of the cloud cover expected to push into southern lower during
the pre-dawn hours...though northeast lower south of Thunder Bay
will probably continue to see clouds drift in off Lake Huron.
Surface winds will veer around to a more northeast direction
overnight and will likely persist across northern lower. Best
chances for decoupling winds will be across interior eastern upper
and the tip of the mitt counties. Low temperatures will be
dependent on winds decoupling...but does look like lows near
freezing are quite possible across eastern upper...and probably over
some of the typical cold spots of interior northwest/north central
lower Michigan. Will mention areas of frost across eastern
upper...and patchy frost across interior northwest/north central
lower. If these trends hold will need frost/freeze headlines on the
day shift (typically prefer to issue these for the first period of
the forecast only).


Long term...(thursday through tuesday)
issued at 400 am EDT Wednesday Sep 17 2014

..moderating temperatures into the weekend then cooling off again...

High impact weather potential: frost possible Thursday night and a
small chance for severe storms Saturday/Saturday night.

The seemingly semi-permanent ridge out west and the trough out this
way is expected to take a vacation Friday into the weekend before
this pattern likely reestablishes itself early next week (sigh).
This is expected to lead to moderating temperatures for Friday into
the weekend before falling back to below average early next week. In
addition...showers and possibly thunderstorm chances increase late
Friday and especially Friday night into Saturday night. The main
long term forecast concerns revolve around the frost potential
Thursday night...then probability of precipitation for Friday all the way into next Monday.

The large area of Canadian high pressure continues to build in
Thursday before exiting off to our east on Friday. This system will
lead to more cool temperatures for Thursday into Thursday night
(what else is new). Many locals will have a decent shot of frost
formation early Friday. The high then slips off to the east Friday
into the weekend leading to a "warmer" and progressively more moist
southerly flow. This system will bring showers and chances for
thunderstorms late Friday into Saturday night. Middle level wind fields
are rather robust (0-6km bulk shear 40 to 50 knots) but there are
questions about the amount of stability...still leaving a low end
damaging wind threat (plenty of time to work out the details). Heavy
downpours are definitely possible as precipitable waters maximum out
around 1.75 inches on Saturday...this could be a result of tapping
remnant tropical moisture from the southwest. Another northern
stream trough then drops in for Sunday night into Monday...perhaps
even bringing a Few Lake effect showers. However...extended models
vary on just how deep/cold this system will be with 00z European model (ecmwf) not
nearly as robust as the GFS so stay tuned on that one. Either
way...chilly air looks to be slow to lift out so cool conditions are
likely to linger into midweek.

Forecast high temperatures Thursday will only range from the lower
50s north to the upper 50s south. Highs then finally rebounding to
more typical levels in the middle to upper 60s Friday (expect only
the lower 60s eastern upper). Warmer Saturday with highs in the
middle 60s to middle 70s (it is very warm aloft but expected
extensive cloud cover will likely keep temperatures in check). Highs
Sunday ranging from the slightly cooler lower 60s to lower 70s then
falling back into the middle 50s to lower 60s for both Monday and
Tuesday. Lows ranging from the around 30 in the colder low lying
spots of northern lower to near 40 near the Lake Michigan shoreline
Thursday night then the much milder middle 50s to near 60 for both
Friday and Saturday nights before settling back into the 40s Sunday
night and the chilly middle 30s to the lower 40s Monday night
(perhaps even some more frost).


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1149 PM EDT Tuesday Sep 16 2014

Moisture along a cold front that is sagging into Upper Michigan
will continue to produce high clouds overnight with the ceilings
expected to be no lower than VFR. The better moisture is upstream
near the Minnesota arrowhead, but is expected to skirt the taf
sites and remain in east Upper Michigan through the day on Wednesday.
High pressure will build into the upper Great Lakes and push the
moisture out. There could be some lake clouds as the temperatures
fall by Wednesday night, but at this time it looks like it should
still remain VFR for both ceilings and visibility through the 24 hour


issued at 400 am EDT Wednesday Sep 17 2014

A cold front will make slow progress through upper/northern lower
Michigan today and tonight...but will have an impact on winds with a
shift to the northwest expected with frontal passage. Gusty winds
from the west/southwest ahead of the front can be expected across
far Northern Lake Michigan/Huron and The Straits of Mackinac
nearshore zones today which may require small craft advisories.
Winds will gradually veer around to the northeast later tonight...
and will approach Small Craft Advisory conditions especially along
northern lower nearshore zones.


Apx watches/warnings/advisories...



short term...jpb
long term...ajs

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