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Area forecast discussion 
National Weather Service Gaylord Michigan
149 PM EDT Wednesday Sep 2 2015

issued at 1026 am EDT Wednesday Sep 2 2015

Still in wait and see Mode with regards to afternoon
shower/storm potential. 12z sounding somewhat ominous...with already
over 2k j/kg of ml cape and decent middle level lapse rates. Modifying
such sounding for an expected middle 80 afternoon temperature/upper 60s dew
points yields upwards of a couple hundred joules more of ml cape
than currently advertised. However...any dynamics to work over this
rather impressive instability is significantly lacking...with well
defined vorticity/wave out west expected to not impact our area until
tonight (if at all) and weak front dropping in from our north
lacking any forced deep convergence. Gotta believe thermal induced
inland low/attendant lake breeze development will force some
enhanced convergence...with background weak west flow suggesting
best convergence targeting the south side of the sunrise side and
points inland to the I-75 corridor. Would expect this area to see
the best chance for showers/storms to develop this afternoon...with
attendant outflows driving additional storm development and
propagation. Given lack of deeper dynamics...would expect any
development to remain scattered. Not expecting much severe potential
with disorganized and weak wind fields. Said cape and rather
moisture rich profiles does support at least some wet microburst
potential and associated gusty winds. Will continue to monitor.


Near term...(today through tonight)
issued at 304 am EDT Wednesday Sep 2 2015

High impact weather: scattered thunderstorms through tonight.

Synoptic pattern and observations:

Early morning analysis...weak westerly flow aloft over northern Michigan
with one defined shortwave driving showers and storms across southern
Ontario. This wave is riding along an ill-defined/weak frontal
boundary...which stretches back across central Minnesota and ultimately to
low pressure in the Dakotas...associated with a weaker shortwave.
Showers and storms were in tune with this wave as well...lifting
through SW Minnesota and western Iowa on the nose of low level Theta-E
advection...buried underneath 6.5 c/km lapse rates. The air mass was
warm and moist along and south of this frontal zone...sporting
summertime-like readings in the upper 60s to lower 70s...with dew
points not far behind. Light winds in this atmosphere has led to the
development of fog.

Synoptic pattern evolution and associated weather:

The aforementioned frontal boundary will drop south through eastern
upper prior to optimal daytime heating...laying out across northern lower
for the peak heating this afternoon. The wind fields will get
garbled up by developing lake breezes...with the best convergence
across NE lower. This will provide the focus/location for the
development of showers and storms late in the afternoon and into the
evening. Conditions will certainly be unstable out there...with the
steep 6.5 c/km laying over the top of US. The resulting MLCAPES this
afternoon are expected to reach 3000 j/kg. Rather impressive for
here. Would feel more confident in a greater coverage of storms if
the weaker wave from the Dakotas can get here to help...which is not
really the case right it should be over eastern Wisconsin.
Thus...can see scattered activity though...mainly over NE
lower...into the evening. Locally heavy rainfall with weak flow
aloft is certainly possible. Also...the amount of instability
could result in a large hail threat...and precipitation loading a
possible strong downburst. Any severe threat would be isolated
with such weak flow aloft. Meanwhile...lake breeze- focused storms
across eastern Wisconsin (greater coverage due to the wave) will
be crossing Lake Michigan...or other storms can develop from the
wave...focusing better chances for showers/storms in the gtv Bay

Highs ranging from the lower 80s in eastern upper behind the
front...and again 85-90f for much of northern lower.


Short term...(thursday through Friday night)
issued at 304 am EDT Wednesday Sep 2 2015

..continued very warm temperatures...

Suddenly a seemingly easy forecast became a tougher one. This is a
result of a short wave evident on water vapor imagery over southwest
Minnesota. This wave will sneak under the ridge and possibly stall
out over the region leading to more chances for mainly afternoon and
evening thunderstorms Thursday and possibly beyond. This wave should
eventually dampen out...but the European model (ecmwf) is insistent that it will hold
on long enough to spark more activity Friday afternoon (though am
being optimistic and not including any probability of precipitation in the forecast at this
time which could end up being a mistake). Temperatures will remain
well above normal for early September with highs in the lower and
middle 80s (though it may be cooler if shower activity is more
extensive than forecast).


Long term...(saturday through tuesday)
issued at 304 am EDT Wednesday Sep 2 2015

..very warm temperatures then cooling off early next week...

Extended models are in general agreement that the upper level ridge
will strengthen this weekend yielding very warm but precipitation
free conditions through Sunday. An approaching cold front will then
bring chances for showers and thunderstorms later Sunday night on
into Labor Day evening. High pressure is then shown to build in
Tuesday ending the shower threat. Temperatures will remain well
above normal through Monday then fall off to near average for


Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 143 PM EDT Wednesday Sep 2 2015

A rather low confidence forecast. Still watching diurnally driven
showers/storms this afternoon and early evening...affecting
primarily tvc and apn. These will remain scattered...and specific
impacts/if any/ will have to wait until storm organization and
propagation are realized. Uncertainty increases tonight as
initial convection wanes...waiting on what impacts upstream wave
has on renewed development overnight. Still believe some potential
for showers/storms to drift across Lake Michigan with this
feature...impacting tvc and mbl during the late overnight and
early morning. Other issue will be br/fog development with
abundant low level moisture. Given little appreciable change in
the overall airmass...would expect similar development as seen
the last few night.

What happens tonight will greatly dictate Thursday morning
conditions. For now will trend a touch optimistic...letting things
evolve tonight before hitting with much detail in the forecast.


issued at 304 am EDT Wednesday Sep 2 2015

Lake Michigan is seeing some gustiness early this morning out ahead
of a frontal boundary that drapes itself across the region this
afternoon...and possibly into Thursday...bringing the chance for
showers and storms for lakes Michigan and Huron. Winds will fall off
with the front...and lake breezes will develop. Light winds Thursday
and Friday with More Lake breezes...before a SW wind picks up again
over the weekend for primarily Lake Michigan.


Apx watches/warnings/advisories...


near term...smd
short term...Sullivan
long term...Sullivan

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