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Area forecast discussion 
National Weather Service Marquette Michigan
136 am EDT Sat Aug 1 2015

Short term...(this evening through saturday)
issued at 336 PM EDT Friday Jul 31 2015

Another gusty day with isolated to scattered showers and some
thunder. A couple shortwaves moving through the region are producing
isolated to scattered showers and thunderstorms. The greatest
coverage over the County Warning Area is along a lake induced convergence line from
near Skandia to near Manistique. These showers and thunderstorms
will diminish this evening as instability decreases. Another area of
greater coverage is over Western Lake Superior under the shortwave. This
area of precipitation will continue to move southeast then diminish after loss of
surface heating this evening. Model trends for tonight have been toward
no precipitation...so went along with that in removing probability of precipitation tonight. A surface
ridge moves into the west Sat...so slight chance of precipitation are confined
to the eastern County Warning Area as additional shortwave energy passes.

Northwest-west-northwest wind gusts to 21-23kts are pretty Standard over land this
afternoon with relative humidity percentages from the middle 30s to the middle 40s. Have
been closely monitoring fire weather conditions as a result. Sat
looks to see similar relative humidity levels to today...but winds gusts will
generally be 3-5kts lower than today. With little or no precipitation for
most of the area...fire weather will be a concern Sat as well.

Long term...(saturday night through friday)
issued at 314 PM EDT Friday Jul 31 2015

Series of shortwaves embedded in northwest flow aloft on the southern flank of
closed low over Hudson Bay will pass through the upper lakes and bring the
threat of showers/some ts to Upper Michigan Sat night and sun. The last shortwave
is forecast to amplify the upper trough into the Great Lakes next week. So
after near normal temperatures this weekend...next week will feature much
cooler weather.

Sat night through sun...DPVA/deep layer qvector cnvgc in advance of initial
shortwave aprchg from the northwest are forecast to move into the upper lakes on Sat
evening. As the low level flow backs more to the west-southwest...the guidance...
especially the 12z NAM...hints at a return of higher 850 mb dewpoints under
the incoming dynamics. So despite loss of daytime heating...plan to
add chance probability of precipitation for Sat night. Based on expectation of more moisture return/
cloud cover...raised forecast min temperatures a couple of degrees. Concerns then
shift to impact of drying in the wake of the initial shortwave on the
stronger trailing disturbance that will arrive during the day on sun.
The 12z NAM remains the most aggressive showing some low level drying/
negative 850 mb Theta-E advection following the initial disturbance and
forecasts only light precipitation over mainly the southeast half of the County Warning Area where
arrival of attendant cold fnt will be in better sync with daytime
heating/destabilization. But even the drier NAM shows MUCAPE incrsg
to 500-1000 j/kg...so will retain chance probability of precipitation in the forecast for sun. Forecast
will show the higher probability of precipitation focused over the southeast County Warning Area due to greater
destabilization and potential for some enhanced low level cnvgc between cold
fnt/lake breezes off Lake Michigan. Expect probability of precipitation to diminish northwest-southeast later in the
day with arrival of deep layer qvector dvgc and drying following the
cold frontal passage.

Sun night...arrival of dnva/larger scale qvector dvgc and subsidence
behind the shortwave in the presence of nocturnal cooling will result in
a dry forecast. As the upper trough deepens into the upper lakes and 850 mb temperatures
fall toward 6-8c by 12z Monday...models show some incrsg surface-850 mb moisture
in more cyclonic low level northwest flow. Expect incrsg SC over mainly the higher
terrain of the northwest County Warning Area with upslope wind component as the cooler
pushes into the County Warning Area.

Monday...with weakly cyclonic northwest 850 mb flow...fairly substantial low level moisture
forecast under larger scale subsidence/middle level inversion and incoming 850 mb
thermal trough...expect an expansion of cumulus/SC with daytime heating. A
number of the models generate some light quantitative precipitation forecast...so will retain some low
chance probability of precipitation mainly away from lake supply to account for the potential of some
relatively shallow convection/showers. With 850 mb temperatures in the 6-8c
range and a good deal of cloud cover...expect a much cooler day/below
normal temperatures.

Monday night...arrival of more anti-cyclonic flow/nocturnal cooling under
continued larger scale subsidence should result in at least some
dissipation of the low clouds. Depending on the degree of clearing...the
cooler interior locations over the west half could see temperatures fall well
into the 40s.

Tuesday through Friday...another shortwave is forecast to swing through the upper lakes on
Tuesday under northwest flow aloft...so will maintain some low chance probability of precipitation. During
the middle/late week time...larger scale northwest flow aloft is prognosticated to
persist around fairly deep upper trough in southeast Canada. There is poor
agreement among the larger scale guidance on timing/track of these
features...so will hold on to model consensus probability of precipitation. Looks like the
best chance for dry weather is on Wednesday. Temperatures will run below normal during the
longer term period.
&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at 132 am EDT Sat Aug 1 2015

VFR conditions will continue through the forecast period at kiwd/kcmx/ksaw
as low-level air mass remains dry. Within a few hours after sunrise...
west-northwest winds will become gusty to around 20kt again. Winds will then
diminish toward sunset.
&&

Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 336 PM EDT Friday Jul 31 2015

A low spinning over southern Hudson Bay will sweep a series of
trough across Lake Superior through this weekend. Winds will
generally remain in the 10-20kt range through the start of the
weekend. A broad surface trough will move across the upper Great
Lakes region on Sunday before high pressure from the Canadian
prairies gradually moves into the region for the start of next week.
&&

MQT watches/warnings/advisories...
Upper Michigan...
none.
Lake Superior...
none.
Lake Michigan...
none.
&&

$$

Short term...Titus
long term...kc
aviation...rolfson
marine...Titus

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