Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210723

Area Forecast Discussion
National Weather Service Marquette MI
323 AM EDT Sun May 21 2017

.SHORT TERM...(This evening through Sunday)
Issued at 413 PM EDT SAT MAY 20 2017

WV imagery and RAP analysis indicated a mid/upper level trough
through the plains with a well-defined shortwave over ern Nebraska.
At the surface, low pressure was located over wrn IA with a warm
front through cntrl IL. 300k-305k(800-650mb) isentropic lift ahead
of the shrtwv and low supported a large area of rain from srn MN
through cntrl WI that was lifting slowly northward. Very dry low
level air ahead of the rain area has delayed the progress of the
pcpn into Upper Michigan.

Tonight into Sunday, expect the pcpn to gradually spread through
Upper Michigan btwn 21z-00z with the main area lifting north of the
area after 03z. As aggressive mid level dry slotting moves in
overnight, the rain should diminish to drizzle as lower level 285k-
295k (900-800mb) isentropic continues. As the shortwave approaches
Upper Michigan btwn 09z-15z with stronger qvector conv and steeper
mid level lapse rates, expect another period of showers with some
isold tsra possible. The pcpn should then diminish during the later
morning into the afternoon with even a few peeks of sun possible as
drier air movesino from the west. However, some additional wrap-
around shra may move into the west late. Temps will recover into the
mid and upper 50s .

.LONG TERM...(Monday through Saturday)
Issued at 322 AM EDT SUN MAY 21 2017

Upper low over the Upper Mississippi River Valley slowly lifts
across northern Ontario and the Upper Great Lakes through Monday.
Main sfc low near Minneapolis this morning should lift north of Lk
Superior on Monday. Though majority of precipitation should be in
warm conveyor belt wrapping around the sfc low, low-level moisture
and cyclonic flow should allow for some lighter showers across most
of forecast area on Monday, especially if there are any shortwaves
working through around the base of the upper level trough.

Even as this upper low center moves to Quebec by Tue more troughing
fills back in over the Upper Great Lakes through at least Wednesday.
Indication that shortwave moving from SD on Monday aftn moves to WI
on Tue. Wave of sfc low pressure should track close enough to bring
some showers over at least south central Upper Michigan on Tuesday
with some models indicating precip over much of the central and
eastern forecast area. As the stronger portion of the upper trough
that is overhead for midweek affects the Upper Great Lakes late Tue
into Tue night, could see another episode of rain with best chances
over east half of forecast area. Later Wednesday, appears sfc ridge
and dry air finally begins to win out over the western forecast
area. Lingering moisture blo h7 should keep potential for light
showers or drizzle going much of the day over north central forecast
area where northeast winds between the sfc ridge and departing low
pressure system provide additional upslope lifting. Even with
occasional chances for rain, total rain amounts through Wed look on
the light side with most areas staying under 1.00 inch. With the
upper low in the vcnty and winds off of Lk Superior expect a few
days of cool conditions, especially near Lk Superior where highs
will only top out in the upper 40s to lower 50s. Highs farther
inland and near Lk Michigan away from flow off Lk Superior should
reach lower 60s. Plenty of clouds even when it is not raining will
keep min temps from falling too much.

As the upper low drifts toward New England Thursday into Friday,
upper ridging briefly moves across the Great Lakes downstream of
another upper low expanding from the Pacific Northwest to south
central Canada. The ridging and less cloud cover will allow temps to
rebound well into the 60s, though with the high building in from the
north, shoreline of Lk Superior will see temps stay in the 50s.

Once the upper ridge moves out of the area to the east, approaching
upper low shouls bring unsettled weather pattern back to the region
for next weekend. Main sfc front should be hung up well to south of
Upper Great Lakes, but approaching sfc trough may help to to produce
some showers. Recent model runs keep lowest showalter indices (SI/s)
to the south of here so will keep tsra out of forecast attm. Only
other primary issue in the long term is potential for frost. Western
forecast area would see greater chances of frost on Wed night with
all of the interior forecast area seeing more of risk Thu night.
Since the sfc ridge is just beginning to exit on Sat morning suppose
there could also be risk of frost over at least the interior eastern
area Fri night as well.

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 152 AM EDT SUN MAY 21 2017

Scattered rain showers will continue across the area with
lingering low pressure. Conditions will stay IFR through much of
the forecast period and perhaps fall to LIFR at a few sites this
morning. KSAW will be the exception by Sun evening as sw
downslope flow allows low MVFR conditions to set up.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 413 PM EDT SAT MAY 20 2017

An increasing pres gradient ahead of low pressure lifting toward
Lake Superior will result in strong winds up to 30 kts and a few
gale force gusts to 35 knots. As the low pres passes into Ontario on
Sun and drags a trough across Lake Superior, expect the winds to
diminish and shift to the w-sw by Sun night. Winds under 20 kts
should then be the rule on Mon into Wed as a relatively flat pres
gradient dominates the Upper Lakes.

Upper Michigan...
Lake Superior...
Lake Michigan...


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