Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 212338

Area Forecast Discussion
National Weather Service Marquette MI
738 PM EDT Fri Apr 21 2017

.SHORT TERM...(This evening through Saturday)
Issued at 353 PM EDT FRI APR 21 2017

WV imagery and RAP analysis indicated a split flow pattern with a
ridge over the nrn plains and a trough into Quebec resulting in
confluent nrly mid/upper level flow through the nrn Great Lakes. At
the surface, brisk nrly winds were diminishing into Upper Michigan
as high pressure over the eastern Dakotas builds toward the area.

Tonight, the high will move overhead tonight with clear
skies/light winds. With PWAT values aob 0.25 inch very favorable
radiational cooling conditions will allow temps to drop toward the
lower end of guidance, into the lower 20s over interior west.
Expect higher readings tonight in the mid 30s near the relatively
warmer Great Lakes.

Saturday, sunshine and mixing through 850 mb temps in the 3C to 5C
range will push inland max temps into the lower to mid 60s. Winds
will be light enough to allow lake breeze development over the
central and east.

.LONG TERM...(Saturday night through Friday)
Issued at 325 PM EDT FRI APR 21 2017

Although there may not to be any hi impact wx events during the
upcoming week, the fcst pattern is fcst to be changeable/active,
with a sw flow alf bwtn an upr trof over the Plains/upr rdg over the
se CONUS in the srn branch dominating next week. A cold fnt wl pass
the Upr Lks on Sat ngt accompanied by some patchy lgt pcpn on the
srn flank of a disturbance passing thru Ontario within the nrn
branch flow. There wl be some drying in the wake of this fnt on Sun
that wl persist for the most part thru Mon, but a shrtwv/sfc lo pres
aprchg fm the sw wl then bring a return of more showers on Mon
ngt/Tue, especially over the w. Depending on whether the cold fnt
attendant to this lo pres stalls nearby on Tue ngt into Wed, there
could be another round of showers mainly over the se cwa later on
Tue into Wed. After a period of drying associated with hi pres bldg
over Hudson Bay, another shrtwv aprchg fm the sw wl likely bring
more ra back to the area by next Fri. Most of the medium range time
wl feature aob normal temps, except perhaps on Tue and next Fri.

Sat ngt...Lingering dry air associated with sfc hi pres retreating
slowly to the se wl bring dry wx early in the evng, but then a cold
fnt associated with a disturbance in the nrn branch tracking thru
Ontario wl pass during the early mrng hrs on Sun. The bulk of the
models show a narrow band of lgt pcpn under axis of fgen on the cold
side of the fnt arriving over the far nw cwa toward midngt and
influencing mainly the nrn tier with an upslope nly flow in the wake
of the fropa. Any pcpn, which wl start as ra but could mix with sn
as colder air follows, wl be on the light side with an absence of
sgnft mstr inflow and passage of sharper dynamic forcing to the n
closer to the shrtwv track.

Sun...Hi pres bldg into nw Ontario under larger scale subsidence
following the exiting shrtwv is fcst to extend a sfc rdg axis into
the Upr Lks. Although the arrival of this rdg axis/some drier llvl
air and acyc flow wl tend to diminish any pcpn lingering in the mrng
over mainly the nrn tier, a good deal of mid lvl mstr/cld cover wl
linger near an h85-7 fntl bndry that remains near the area to the n
of the relatively shallow cooling left in the wake of the sfc fnt
that wl stall in WI. The best chc for more aftn clrg wl be over the
ne cwa, which wl be more influenced by deeper drying/subsidence. H85
temps falling as lo as -5 to -6C over the Keweenaw and llvl nly flow
off Lk Sup wl cause much cooler wx for the cwa, with hi temps
holding in the 30s near Lk Sup.

Sun ngt into Wed...A shrtwv in the srn stream flow that wl be moving
thru the central Rockies on Sun ngt wl dvlp a sfc lo pres in the
central Plains. This shrtwv/sfc lo pres are then fcst to lift enewd
toward the far nw Great Lks and across wrn Lk Sup on Tue mrng toward
James Bay by Wed mrng. Some mixed pcpn may return to the nw cwa as
early as Sun ngt as the flow alf veering to the sw results in incrsg
isentropic ascent within the mid lvl fntl bdnry best shown on the
290K sfc. Most of the medium range guidance shows some rather
vigorous mid lvl dry slotting following the shift of the mid lvl
fntl bdnry to the n of the cwa on Mon before the sharper dpva/upr
dvgc ahead of the shrtwv aprchg fm the wsw arrives with some deeper
mstr/hier pops for showers on Mon ngt over the w. The sfc lo pres is
fcst to lift to the ne acrs wrn Lk Sup on Tue, with only sct showers
along its attendant cold fnt then spreading to the e during the day
into the evng. Many of the medium range models indicate the fnt may
stall just to the e on Tue ngt under a more sw flow alf on the nw
flank of an upr rdg over the se CONUS. Another shrtwv/sfc lo pres
riding ne along this bndry could bring more showers for at least the
se cwa on Tue ngt into Wed. The best chc for above normal temps
during this stretch wl be on Tue when the sfc lo pres wl be passing
to the nw of Upr MI.

Wed thru Fri...There wl be a period of drying on Wed into at least
Thu under the subsidence in the wake of the shrtwv riding to the ne
along the fnt to the e. Although a sfc rdg axis on the srn flank of
hi pres bldg over Hudson Bay is fcst to prevail over the Upr Lks,
there could be quite a bit of lo cld lingering in the rather shallow
nly flow of cool air. Another shrtwv riding to the ne in the sw flow
alf btwn an upr trof in the Plains/upr rdg over the se CONUS wl
bring a return of some hier pops and perhaps a TS/heavy rain Thu
ngt/Fri. Temps should run blo normal on Wed into Thu, but then may
rebound aoa normal on Fri depending on the track of the sfc lo pres
that could pass over or just to the w of Upr MI.

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 737 PM EDT FRI APR 21 2017

Dry high pres will dominate thru Sat aftn, ensuring VFR conditions
prevail at KIWD/KCMX/KSAW thru this fcst period.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 325 PM EDT FRI APR 21 2017

Lingering stronger nnw winds up to 20-25 kts over the e portion of
the Lake will diminish this evening with the arrival of a surface hi
pres. Expect a wind shift to the wsw on Sat as the hi center sinks
to the se. As the pres gradient tightens ahead of an approaching
cold front, wind speeds up to 20-25 kts will be possible in the
afternoon/evening in the area between the Keweenaw and Isle Royale,
where the topography funnels this flow. In the wake of the frontal
passage, n winds up to 20-25 kts will occur late Sat night into Sun
before the gradient slackens on Sun as hi pres building into Ontario
extends a ridge into the Upper Lakes. E veering s winds will then
increase up to 25 to 30 kts on Mon into Tue as a lo pres moves from
the ncentral Plains across the Upper Lakes. Where the winds are
stronger over portions of the ncentral and e parts of the Lake, not
out of the question there could be a gale at least a part of this
time depending on the strength of the lo pres. Expect a wind shift
to the n up to 25-30 kts on Wed following the exiting lo pres/
attendant cold frontal passage.

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


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