Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 062224

Area Forecast Discussion
National Weather Service Marquette MI
624 PM EDT Mon Apr 6 2020

.SHORT TERM...(This evening through Tuesday)
Issued at 358 PM EDT MON APR 6 2020

WV imagery and RAP analysis indicated a northern stream mid/upper
level trough off from Alberta into Montana, a southern stream closed
low near the northern CA coast and a broad ridge over the
southeastern CONUS resulting in anticyclonic westerly flow through
the northern Plains and northern Great lakes. At the surface, sse
flow was increasing through the Upper Mississippi Valley between
high pressure over the central Great Lakes and a trough the western
Plains. A continued WAA pattern supported mainly mid clouds and a
few sprinkles over mainly eastern Upper Michigan.

Tonight into Tuesday, expect dry weather this evening as isentropic
lift temporarily weakens. Although the stronger forcing with a
shortwave trough lifting from southern Saskatchewan to northwest
Ontario will remain to the north of Upper Michigan the approaching
sfc-850 trough with strengthening WAA/290k-300k isentropic lift and
moisture advection will bring showers into the west late tonight and
across Upper Michigan Tue morning into the early afternoon.

Models suggest that heavier band of rain with QPF to around 0.25-
0.50 inch is expected across the north, especially the Keweenaw.
However, confidence in the location of the heavier rain band is
still low. Even with the better elevated instability remaining south
of Upper Michigan, mid level lapse rates to 7.5C/km along with the
stronger band of lift could still support some isold tsra, mainly
over southern Upper Michigan. Under cloudy skies, temps will still
climb into the mid to upper 40s north and the low to mid 50s south.

.LONG TERM...(Tuesday night through Monday)
Issued at 337 PM EDT MON APR 6 2020

The past few longterm AFDs cover the largescale features fairly
well, and latest ensemble forecasts suggest these features haven`t
changed much. A ridge over the Pacific shifts E and drives troughing
across the West Coast before this trough shifts E into the central
CONUS by mid-week. Soon after the start of the longterm period, a
strengthening system will approach Upper Michigan that brings a cold
front across the Upper Midwest as the above normal temps that start
the week transition back to near normal. As ridging over the Pacific
continues, ridging over the Atlantic develops...leaving large-scale
troughing inbetween across the central CONUS. This pattern is
expected to continue into next week, with the chance of trending
towards below normal temperatures begins to look likely.

Tuesday night into Wednesday, remaining showers from Tuesday`s
shortwave will be exiting from W to E early through the night. There
may be lingering -TSRA right along Lake Michigan, but have only
maintained the slight chc in the forecast for the first few hours
after 00Z Wed. Attention then turns to the anticipated shortwave and
associated cold front progged to pass through the region starting
Wednesday evening. 500mb heights in the low to mid 5400m`s before
the fropa quickly fall to near 5200m behind the front. Behind this
front, a rapidly developing low pressure system deepens as it passes
just to the E of Lk Superior overnight Wednesday. Pres falls right
near the sfc low pressure are fairly significant, but remain to the
E of the region. Over the UP and Lk Superior pressure falls of 0.5
mb/hr are suggested. As sfc high pressure approaches from the W,
this leaves a tightening pressure gradient over the region as winds
increase through the night Wed into Thurs. By Thursday afternoon, it
looks like for frequent gusts across the UP to reach 30 mph, with
locations across the Keweenaw, higher terrain, and along Lake
Superior (especially east) have the potential reach upwards of
40mph. In terms of precipitation, models suggest most of the
precipitation is tied to the cold front and sfc trough. As the wave
and assoc. sfc low begin to shift out of the region, models do
suggest some wrap around precipitation in pockets of vorticity and
embedded shortwaves. With 850mb temps near -10C, there is some
potential for lake enhancement of any of this wrap around showers
should synoptic forcing do most of the work.

Heights and 850mb temps will be on the rise Friday afternoon with
residual -SHRASN diminished overnight Thursday, Friday looks to be
mostly dry and cloudy in the morning, with some clearing in the
afternoon with rising heights. Then, models suggest another
shortwave to drop south from Canada on Saturday into Sunday.
Guidance today shows this wave to be more organized as widespread
troughing begins to take hold across much of the central CONUS. At
this time it doesn`t look like anything major, but another round of
nuisance -SHRASN looks possible over the weekend as temperatures
drop closer to normal.

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 624 PM EDT MON APR 6 2020

VFR conditions will continue through tonight as mid-level clouds
remain. Clouds will lower Tuesday morning with rain moving in ahead
of low pressure approaching the region. Expect cigs to drop to IFR
at all sites as the rain moves in.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 358 PM EDT MON APR 6 2020

East-northeast winds will increase to 20 knots over the west half of
Lake Superior into tonight as trough approaches from the west. East
to southeast wind gusts could increase up to 25kt over the east and
north central parts of the lake on Tue as the gradient tightens
ahead of the trough. The next big increase in winds will occur late
Wed into Thu as low pressure system deepens north and east of the
lake and an associated cold front moves through the area. West winds
increase to 20-30 knots late Wed into Wed evening and then become
northwest gales of 35-40 knots late Wed night into Thu, strongest
over the east half of the lake. Northwest winds will quickly
diminish blo gales Thu night and to less than 20 knots on Fri as
high pressure builds in from the west.

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


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