Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 190828

Area Forecast Discussion
National Weather Service Marquette MI
428 AM EDT Sat May 19 2018

.SHORT TERM...(This evening through Saturday)
Issued at 354 PM EDT FRI MAY 18 2018

WV imagery and RAP analysis indicated a ridge from NY/PA into the
northern Great Lakes and a troughs from Manitoba into the nrn Plains
and from ern Missouri into Alabama. At the surface, moderate south
to southeast winds of 10-15 mph gusting to 20-25 mph prevailed
across Upper Michigan between high pressure over Quebec and an
inverted trough into nw MN. Dewpoints in the 25-30F range with temps
from the 60s east to 70s west have dropped RH values into the 20-25
percent range over much of the area. The breezy, warm dry conditions
have resulted in an elevated wildfire risk. Since winds are expected
to remain below Red Flag criteria, an SPS was reissued to highlight
the risk into this evening.

Tonight into early Saturday, models have trended significantly
farther west with a shortwave trough lifting to the nne from IL. As
a result, rain chances have increased over the southeast half of
Upper Michigan from late tonight into Saturday morning. However,
rainfall amounts should remain light, at or below a tenth of an
inch. Temps dropping into the 40s along with some additional low
level moisture, will aid RH recovery into the 70-80 pct range.

The Manitoba/nrn plains shrtwv will slide to the east dragging a
cold front through Upper Michigan. Although the 700-300 qvector conv
and fgen with this feature is relatively modest, it should still be
able to generate sct -shra advancing through the west half of Upper
Michigan by late afternoon into the evening. Again, any rainfall
amounts will be light. Temperatures will drop substantially by mid
to late afternoon into the 40s over the north as onshore nrly winds
develop off of Lake Superior.

.LONG TERM...(Sunday through Friday)
Issued at 427 AM EDT SAT MAY 19 2018

Latest round of medium range ensemble guidance shows no changes to
the overall pattern from guidance viewed 24hrs ago. Over the next
7-10 days, pattern will feature mean ridging over western Canada
and mean troffing over eastern Canada. To the s, shortwaves will
occasionally progress across the CONUS in a weak southern stream.
Since the big late season snowstorm in mid Apr, it`s been dry for
the last 30 days, especially so over the w half of Upper MI. W of
a Grand Marais to Manistique line, pcpn over the last 30 days has
been less than 50pct of normal with the majority of that area now
less than 25 pct of normal. The upcoming pattern will favor
continuation of overall dry weather as the ridge/trof pattern over
Canada will work to force the more important pcpn producing
southern stream shortwaves mostly s of Upper MI while the more
dynamic northern stream shortwaves pass well to the ne. There will
be 2 opportunities for rainfall over the next week or so.
Fortunately, some areas will see rain today. However, after today,
the next chc of meaningful rainfall won`t arrive until the end of
the upcoming week. Temps over the next 7 days will fluctuate
around normal as shortwaves dropping into and reinforcing the mean
eastern Canada trof will send cold fronts occasionally s thru the
Upper Lakes, bringing periods of cooler weather, especially so
close to Lake Superior where cooling will be significantly
amplified by the chilly lake waters. Overall though, for most
locations, more days will be above normal than blo normal.

Beginning Sun...In the wake of the cold front passing today, another
very dry air mass will settle over the area for Sun. Based on mixing
heights and dry air aloft that can be mixed down, favored the low
side of bias corrected guidance for dwpts. Under abundant sunshine,
expect highs in the interior up around 70F with RH falling to 15-
20pct. Fortunately, winds will be on the lighter side on Sun to
prevent enhancement of fire wx concerns. Will be cooler along the
Great Lakes, especially Lake Superior. With sfc high pres over the
area Sun night, winds will fall off to calm for much of the area,
leading to a good radiational cooling night with only some high
clouds passing at times. Precipitable water increases from during
the day Sun, so it won`t be a perfect setup for unusually cold
conditions. Favored the low side of guidance, led by the global CMC
bias corrected which is normally a superior performer on radiational
cooling nights. Traditional interior cold spots should fall into the
upper 20s/around 30F.

Mon into Tue...Medium range guidance has moved into much better
agreement for this time period. In recent days, most of the guidance
with each run was suggesting a shortwave over the Plains would
either be strong enough or track far enough n to bring pcpn into the
fcst area at some point Mon into Tue. With the 00z guidance today,
models have moved toward better agreement on dry weather prevailing,
which had been viewed as the more likely scenario over the last
couple of days. Daytime RH should mostly fall into the 20-30pct
range Mon and Tue with Mon the drier day of the two. Fortunately for
fire wx concerns, winds will be on the lighter side both days.

As was the case 24hrs ago, models continue to show a northern stream
shortwave dropping into/reinforcing eastern Canada trof midweek.
Cold front associated with wave will pass across the fcst area Tue
night or Wed morning. Other than a wind shift, front will pass
uneventfully given lack of moisture and forcing. With sfc high pres
building across northern Ontario, Wed will be cooler near Lake
Superior under gradient n to ne wind enhanced by lake breeze
component. Depending how aggressively the high builds southward,
high temps Wed could be only in the 40s lakeside while in the
interior toward the MI/WI state line temps rise well into the 70s.
High pres will linger into Thu, providing continued dry weather.
Daytime minimum RH will still be low Wed/Thu, mostly 25-35pct.

Fri into the Memorial Day Holiday weekend...Despite being so far out
in the model runs, there has been a fairly consistent signal in
recent days for a potentially wet period late in the upcoming week.
The pcpn would be the result of the remnants of an early week closed
mid-level low over the sw states. This energy is fcst to lift ne
into the northern Rockies, then progress ese ahead of the next
northern stream shortwave dropping se and reinforcing the eastern
Canada trof. So, at the moment, while it would be unfortunate for
outdoor activities during the early part of the holiday weekend,
there appears to be a fairly decent potential of much needed
rainfall in the Fri/Sat time period.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 155 AM EDT SAT MAY 19 2018

Ahead of an cold front currently advancing eastward across the
Arrowhead of Minnesota, VAD wind profile data from KDLH/KMQT show at
35-45 knot low-level jet spread across the region and bringing low-
level wind shear to all terminals early this morning. Cloud cover
will thicken across all terminals through the early-mid morning
hours, with ceilings dropping down into at least the MVFR category
as rain showers approach KSAW. Further west at KIWD/KCMX, the onset
of these lower ceilings and rain showers are expected to be a bit
later in the afternoon as the above mentioned cold front begins to
push into the area. Models do show the potential for ceilings to
drop lower than MVFR, but given the magnitude of dry air in place
and moisture profiles being rather shallow, opted to maintain MVFR
ceilings for now. Visibilities aren`t expected to drop below MVFR at
this time. Also, as this front moves through winds will become
northwest to northerly with gusty winds first at KIWD/KCMX this
afternoon, and a bit later at KSAW. Showers along the cold front
will continue to diminish from west to east tonight along with
the strength of the gusty winds.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 354 PM EDT FRI MAY 18 2018

Southeast winds of 15 to 25 knots will persist over eastern Lk
Superior tonight, before diminishing late. Winds will be less than
20 kts to start day on Sat but will shift north 20 to 30 kts in the
aftn and evening behind a front dropping across Lk Superior. Winds
will diminish to less than 20 kts late Sat night through the rest of
the forecast period as high pressure parks itself over the Upper
Great Lakes.

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


LONG TERM...Rolfson
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