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Area forecast discussion 
National Weather Service Marquette Michigan
744 am EDT Monday Sep 1 2014

Short term...(today and tonight)
issued at 510 am EDT Monday Sep 1 2014

WV imagery and RUC indicated a broad middle/upper level trough from The
Rockies into the northern/Central Plains. At the surface...a cold front
extended from near inl through central Minnesota into northwest Iowa. A weak shortwave
from NE Minnesota into northwest WI supported an area of showers and isolated thunderstorms and rain
over eastern Minnesota into northwest WI and Lake Superior. A stronger shortwave was
located over SW Minnesota into northwest Iowa. With only modest 500-1000 j/kg
MUCAPE...only a few thunderstorms and rain were noted over the region. The more active
convection over Eastern Lake Superior was associated with an area of
stronger 850 Theta-E advection at the nose of the low level jet.

Today...as the northwest Iowa shortwave lifts toward the area with moderate
700-300 mb qvector conv and the cold front approaches the
area...expect rain showers/thunderstorms and rain coverage to increase this morning. Even with
0-1km/0-6km shear around 40 knots...since instability will remain
limited...mainly just brief heavy rain is expected. Overall rainfall
amounts should be limited given the quick movement of the convective
cells and lack of large scale organization. The precipitation will diminish
from west to east this afternoon as the cold front moves through and
qvector divergence spreads into Upper Michigan in the wake of the shortwave. Cloud
cover will keep high temperatures near or slightly below seasonal averages
in the upper 60s to around 70.

Tonight...any lingering precipitation over the eastern County Warning Area in the evening will
end early. Otherwise...a drier airmass moving into the area with
dewpoints dropping toward the lower 50s will allow temperatures to also
drop into the lower to middle 50s as skies partially clear. An increase
in cloud cover is expected late over the SW County Warning Area ahead of the next
weak shortwave.

Long term...(tuesday through sunday)
issued at 321 am EDT Monday Sep 1 2014

In the wake of stronger shortwave and surface front moving through
today...another shortwave clips across the area on Tuesday in
increasingly zonal flow aloft. Moisture is limited with the wave as
soundings only show moisture h8-h7. Pretty high based rain showers and will
also mention isolated thunderstorms and rain with MLCAPE 500-1000 j/kg per European model (ecmwf) and GFS.
Will include slight chance probability of precipitation. A lull for Tuesday night as surface ridge
moves from middle Mississippi River valley to the Ohio Valley. Light
SW winds on perifery of the ridge will limit cooling. Lowest precipitable water
far east County Warning Area where min temperatures may fall to around 50 degrees. On
Wednesday...GFS and Gem-New Hampshire indicate some showers could occur in the
afternoon over mainly the west half County Warning Area. Weak shortwave is there but only
appears that best moisture inflow is over far West County warning area. Warm air
advection boosts 850 mb temperatures to around +15c so as long as skies stay
at least partly cloudy...maximum temperatures will top out in the middle 70s to
lower 80s.

Later Wednesday night into Thursday morning larger scale lift
ahead of upper trough increases over northern plains and western
Great Lakes. Likely will be some shortwaves sliding out of northern
plains as well...though right now signal of any stronger shortwave
is minimal. There is a middle level jet maximum sliding over the area and
850 mb-500 mb q-vector convergence will be on the increase. Primary surface
trough will be over Minnesota and based on surface winds and
dewpoints...there will be a warm front vicinity of southern/central
Minnesota into western Wisconsin. Bulge of warmth aloft results in
an elevated mixed layer with 700 mb-500 mb lapse rates over 8c/km making it
over upper lakes ahead of the surface trough. Reservoir of ml MUCAPE over
2000j/kg will be just southwest of Upper Michigan with middle level flow
SW-NE. Edge of surface based cape and orientation of 850 mb-300 mb thicknesses
indicate that stronger storms may be more to southwest of Upper
Michigan later Wednesday night into Thursday morning. Tough to say
at this point though. Consensus chance probability of precipitation work for now since there
will be large scale warm air advection and 850 mb-700 mb moisture transport
aimed into the area. More rain showers/thunderstorms and rain possible as surface front works
across Upper Michigan later on Thursday. Plenty of instability as
temperatures in the south-southwest flow ahead of front should reach toward
80 degrees with even a few hours of partial clearing since 850 mb temperatures
are 18-20c. Moisture availability/middle level capping along the front
remains a concern for coverage of surface based storms in the afternoon. Models
may be picking up on this as GFS/European model (ecmwf) show a min in quantitative precipitation forecast 18z-24z but
then increase it by 06z on Friday as front will mainly be south and
east of County Warning Area by that time. No need to get too fancy with the grids
at this time given all the uncertainty. Kept with the consensus chance probability of precipitation
on Thursday with this dropping off to lower chances Thursday night
closer to the departing front.

Rest of the forecast looks dry and cooler as high pressure builds in
on Friday and will hold on through next weekend. Maximum temperatures in the
middle 60s to lower 70s. Chilly lows possible inland both Friday night
and Saturday night due to the dry airmass and light winds beneath the
high pressure. Bias corrected guidances showed mins in the lower 40s
but would not be surprised to see readings dipping into the 30s
either of those nights.
&&

Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 743 am EDT Monday Sep 1 2014

Iwd...although there may be some breaks in the rain showers...MVFR
conditions will predominate early. The ceilings are likely to fall into the IFR
range briefly during middle morning as the front passes and the wind shifts
to an upslope west-northwest direction. The west wind behind the frontal passage will tap
drier air and allow for conditions to improve to VFR during the afternoon.

Cmx...MVFR conditions will predominate early with periods of showers.
A wind shift to an upslope west direction behind a frontal passage and with some
continued -shra should result in a period of IFR conditions during the
late morning/early afternoon before the west wind taps drier air and results in
improvement to VFR by late in the day.

Saw...expect IFR ceilings to persist this morning with abundant low
level moisture and upslope srly flow. Expect some rain showers with MVFR
conditions to developp by late morning with the approach of a surface
cold front. Expect improvement late in the afternoon with a wind shift to
a downslope west direction and the arrival of drier air following the
frontal passage.
&&

Marine...(for the 4 am Lake Superior forecast issuance)
issued at 510 am EDT Monday Sep 1 2014

Winds will be 20 knots or less through this forecast period with
areas of fog persisting until drier air moves into the region
tonight.
&&

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

$$

Short term...jlb
long term...jla
aviation...jlb
marine...jlb

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