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Area forecast discussion 
National Weather Service Marquette Michigan
416 am EDT Monday Jul 28 2014

Short term...(today and tonight)
issued at 408 am EDT Monday Jul 28 2014

Upper trough and cooler weather pattern has become established and
persists through the week. For today...primary surface low pressure
system that brought the showers and thunderstorms to the area on
Sunday is tracking across upstate New York and northwest Pennsylvania
early this morning while high pressure over the Canadian prairies
expands south across the Central Plains. Scattered-broken middle clouds are
quickly filling in from Minnesota across western and north Central Lake
Superior and over Ontario. At first glance...setup into tonight
appears to support mainly dry weather. However...need to consider
shortwave/enhanced cloud currently dropping south across northeast
Manitoba and far northwest Ontario. 00z radiosonde observation from cyyq in northern
Manitoba indicated only narrow moist layer around h6 with this
wave...with very dry air below h6. Yet upstream at this time...nighttime
satellite fog product does show expanding shroud of cloud with observation of
bkn070 and sct140. Seems that as shortwave drops south today...broken
middle clouds will spread over much of Upper Michigan. Forecast soundings
indicate NAM is most bullish on depth of moisture /higher relative humidity from 850 mb
through h6/ compared to GFS and ruc13 /narrower area of higher relative humidity
centered on h7/. A subtle difference for sure...but this will impact
shower potential for later today.

Forcing with the shortwave does not appear to be that strong or
widespread as positive vorticity advection and 850 mb-500 mb q-vector convergence is quite weak with
the wave. Seems that the 800 mb-700 mb lift/uvm present is mostly due to the
cold temperatures aloft along track of shortwave. This results in some
marginally steep middle-level lapse rates and pocket of 50+ total
totals.

Trended toward more clouds today with the incoming shortwave. This
adjustment resulted in a lowering of maximum temperatures. Based on mixing to
h9 with onshore northwest flow near Lake Superior and clouds...went middle
60s near Lake Superior and based on mixing to 850 mb have around 70
inland. Now onto the those shower chances. NAM/NCEP WRF-arw/WRF-nmm
and local WRF runs indicate scattered quantitative precipitation forecast maximizing in the afternoon
during peak heating. Dprog/dt of NAM and GFS indicate good run to run
consistency in the last few model runs. Signals mixed though as Gem-
regional which once showed decent quantitative precipitation forecast has backed off and the European model (ecmwf)
shows little quantitative precipitation forecast. Ruc13...which shows a lot of middle clouds... looks
similar to Gem-regional with little quantitative precipitation forecast over land areas of Upper
Michigan. Local WRF points to isolated rain showers over far scntrl...which does
make sense as it is further away from modification/stabilization off Lake
Superior. Thinking the NAM idea is overdone due to how it is handling
the depth of the moisture and since it also has temperatures into the middle
70s with dewpoints in the middle 50s resulting in too much surface based
instability. Even so...a rouge shower is not out of the question with
the moisture advection and some heating. By far the better shot at
showers should be late this afternoon into the evening over Western Lake
Superior and western Upper Michigan due to uvm from shortwave/cold pool.
Small chance of showers...quite isolated in coverage...should slide
across rest of County Warning Area through the night as the shortwave crosses the
area while shearing out. Another shortwave will be moving toward
north Central Lake Superior late tonight...but this will mainly affect
the forecast into Tuesday.

Long term...(tuesday through sunday)
issued at 336 am EDT Monday Jul 28 2014

Overall...limited changes to the going forecast as models remain
consistent in the highly amplified (for late july) flow pattern
remains over the the area through the upcoming work week. This
will place the upper Great Lakes region under north to northwest
flow aloft as the area is between the upper ridge over The Rockies
and the upper low rotating near James Bay. Disturbances rotating
around the upper low will periodically drop through the
region...which combined with diurnal heating lead to a largely
afternoon/evening shower and occasional thunderstorm potential. The
best opportunity for precipitation remains on Tuesday...as the
strongest disturbance and weak surface trough drop southeast through
the area. Will continue to show rising probability of precipitation through the morning and
peaking in the middle-late afternoon hours before diminishing through
the evening. 0-6km shear still looks unidirectional and around
20-25kts and with MLCAPE values generally 200-700 j/kg (and skinny
with ncape values below 0.08) Don/T expect any severe threat at
this point. Wouldn/T be surprised to see some locations along the
Wisconsin border or south central that see between 0.25-0.50in of
rain...although the exact location will depend on where the
heaviest showers track.

The rest of the week will be dependent on the timing of the
shortwaves. Only have slight chances of diurnally driven showers
(mainly interior towards Wisconsin border) on Wednesday due to the
area being between waves and as a result a little drier middle level
air in the area. There are indications that a stronger wave will
rotate around the upper low somewhere between Wednesday afternoon
and Thursday morning...which would likely lead to some showers
depending on when it moves through and have slight chances for
Wednesday night to account for that. After that point waves become
subtle through Thursday night and a surface ridge tries to nose back
east into the area from the Dakotas. Thus...will continue diurnal
slight chances towards the Wisconsin border during that period. Will
show better chances on Friday afternoon with help from lake breezes
over the central/east. As for temperatures during this work
week...the below normal 850mb temperatures and cooler flow off Lake
Superior will lead to high temperatures a little below normal.

For the weekend...the upper low near James Bay will broaden and
lift to the northeast while the ridge over the west remains in
place. Meanwhile...models are indicating weak troughing to remain
over the eastern Continental U.S. And will continue the northwest flow aloft
over the County Warning Area. Thus...expect the temperatures to remain slightly
below normal. In addition...even though a weak high pressure ridge
will be over the area...there will be the potential for diurnally
driven isolated to scattered showers around lake breezes on
Saturday as the upper trough axis slides through. There is the
potential Sunday will end up dry...but with the pattern we are
in have left slight chance probability of precipitation in for now.
&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 127 am EDT Monday Jul 28 2014

Expect VFR conditions to predominate this forecast period as drier
airmass shown on the 00z inl and ypl radiosonde observations slides to the S. There
may be some shallow ground fog with occasional lower visibilities through sunrise at
iwd where winds are lighter. Although there will be more clouds on Monday
afternoon and possibly even a -shra late in the day into the evening with
the aprch of a disturbance in the presence of daytime heating...the
llvls will be sufficiently dry to ensure VFR weather even if a -shra
impacts any of the sites.
&&

Marine...(for the 4 am Lake Superior forecast issuance)
issued at 408 am EDT Monday Jul 28 2014

North to northwest winds 15-20 kts linger today over mainly Eastern
Lake Superior due to tighter pressure graident remaining in wake of low
pressure crossing the Middle-Atlantic States. High pressure with winds
less than 15 kts expected the rest of the week. &&

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

$$

Short term...jla
long term...srf
aviation...kc
marine...jla

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