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Area forecast discussion 
National Weather Service Marquette Michigan
742 PM EDT Sat Oct 25 2014

Short term...(this evening through sunday)
issued at 343 PM EDT Sat Oct 25 2014

12z radiosonde observations/latest WV imagery and RUC analysis show west-northwest flow aloft
over the upper Great Lakes between upper ridge extending from Texas through The
Rockies and deepening upper trough near Hudson Bay enhanced by strong
shortwave digging through northwest Ontario that is accompanied by 12hr 500 mb height
falls up to 130m. Tight pressure gradient between associated low pressure near
James Bay and hi pressure in the northern plains is allowing for gusty west-northwest
winds over Upper Michigan early this afternoon. The 12z inl radiosonde observation showed winds
near 40 kts at 3-4k feet above ground level...and surface wind gusts have reached at or above 40
miles per hour over much of the County Warning Area with daytime heating allowing the mixing of
those higher winds to the surface. The airmass streaming into Upper Michigan is a
dry one... so there have only been some scattered diurnal cu/SC. But more
SC is noted over Ontario closer to core of colder air at 850 mb. Looking
well upstream...there is a potent shortwave aprchg the Pacific northwest.

Main forecast concerns in the short term are focused on winds into this
evening and then on temperatures for sun.

Late tday/tngt...with loss of daytime heating/mixing and slow but
steady aprch of surface hi pressure ridge from the west/diminishing h925 winds...
the gusty west-northwest winds that linger through the afternoon will diminish. Higher
waves whipped up by the strong winds this afternoon and impacting areas
from Ontonagon through Copper Harbor and east of Marquette may cause some
minor beach erosion along the lake supply shore. Skies should be mostly clear...
but as the flow veers a bit more to the northwest over the east and advects
somewhat colder 850 mb air into that area...some of the broken SC in
Ontario may move into the eastern County Warning Area. This cad will also maintain gusty
winds over the east for a bit longer. A steady northwest wind through the night will
limit the diurnal temperature drop even where skies are clear. Expect the
lowest min temperatures over the interior west...where winds will become lighter
toward daybreak with the closer aprch of surface hi pressure ridge.

Sun...hi pressure Ridge Crossing Upper Michigan will bring a mainly sunny day...
except for some scattered daytime cumulus over the east closer to slowly departing
850 mb thermal trough. Steady northwest winds over the east in the morning will diminish
with the arrival of the ridge. With 850 mb temperatures rebounding to 10c over
the west by 00z Monday...maximum temperatures should rise into the 50s and perhaps
touch 60 over the west where developing southeast flow will downslope. More
persistent northwest flow off the chilly waters of lake supply will keep the east
coolest...and temperatures there near lake supply may be hard pressed to reach
50.

Long term...(sunday night through saturday)
issued at 332 PM EDT Sat Oct 25 2014

A 500mb ridge will be over the County Warning Area at 00z Monday...but will move east by
12z Monday as an upper trough moves into the northern plains accompanied by
a broad surface low across Minnesota. Expect showers /and possibly some
thunderstorms/ associated with warm air advection/isentropic ascent ahead of the
low to move across the western County Warning Area Sun night in Monday morning...then
across the rest of the area Monday morning and afternoon. The upper
trough will then shift across the County Warning Area Tuesday into Tuesday night...with
intensification of the broad surface low occurring. Exactly when/where
the best cyclogenesis occurs is uncertain due to model disagreement
on multiple shortwaves moving through the upper trough. Despite
lacking exact details...the precipitation forecast remains somewhat more
certain. Rain showers /again with a chance of thunderstorms/ should
move across the area late Monday evening through Monday night...but the
dry slot will lead to a drier forecast for Tuesday morning. Wrap around
moisture and cooler northwesterly flow will lead to lake enhanced rain and
snow showers late Tuesday into Thursday as 850mb temperatures fall as low as
-5c...although a diminishing trend in shower coverage is expected
through this time. Monday and Tuesday will see high temperatures in the upper 40s
to middle 50s...but Wednesday will only see highs reach the low to middle 40s.

Wednesday night and Thursday morning look dry for the most part as a surface ridge
shifts across the area...but clouds will cover the area due to ample
low level moisture as well as flow off Lake Superior.

Poor run to run continuity from the models does not lend much
confidence for Thursday through next Sat as they point to a deeper trough
moving through the region...bringing much colder temperatures at or below
-10c. As mentioned models vary from run to run and disagree with
each other on all but the very general pattern...and even at that
the timing of when and for how long the cold air moves overhead is
not agreed on. Will have chances of lake effect/enhanced snow Thursday
night into Friday night. For Sat...models want to bring a surface high into
the area but with continued uncertainty. Will keep probability of precipitation going into
Sat for lake effect...but just slight chance for now. High temperatures on
Friday may not make it out of the 30s in many locations.
&&

Aviation...(for the 00z tafs through 00z Sunday evening)
issued at 740 PM EDT Sat Oct 25 2014

Under a dry air mass...VFR conditions will prevail at kiwd/kcmx/ksaw
through this forecast period. Gusty west-northwest winds into the 20-30kt range will
diminish during the night as air mass becomes more stable and as
pressure gradient begins to relax with approach of surface high pressure ridge
from the West. Ridge will move across the area during the middle and late
afternoon hours on Sunday...providing a period of light winds.
&&

Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 332 PM EDT Sat Oct 25 2014

As strong low pressure system moves slowly west to east over
northern Ontario...SW to west gales over 35 kts are expected into
this evening...mainly central and East Lake Superior. Northwest winds of 20
to 30 kts will linger into Sunday morning in wake of the low and
before surface ridge crosses the upper Great Lakes region. After a brief
period with winds less than 20 kts with the high pressure...southeast winds
increase to 30 kts over mainly East Lake Superior on Monday ahead of
an approaching low pressure system. Once this low moves to the east
of Lake Superior on Tuesday...west winds to 30 kts and possibly up
to gale force of 35 kts will develop late Tuesday into Tuesday
night. Winds will then shift northwest and stay up to 30 kts into
Wednesday...before gradually diminishing to less than 25 kts by
Thursday.
&&

MQT watches/warnings/advisories...
Upper Michigan...
none.
Lake Superior...
Gale Warning until 5 am EDT Sunday for lsz251-267.

Gale Warning until 2 am EDT Sunday for lsz250-265-266.

Lake Michigan...
none.
&&

$$

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

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