Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 221938
Area Forecast Discussion
National Weather Service Marquette MI
338 PM EDT MON AUG 22 2016
.SHORT TERM...(This evening through Tuesday)
Issued at 338 PM EDT MON AUG 22 2016
Mid-level clouds and a couple of showers across the Keweenaw late
this morning associated with a narrow region of mid-level WAA has
shifted to the NE this afternoon. Subsequent capping advecting in
at around 6kft has suppressed any widespread cumulus formation.
A second pocket of WAA within a layer of higher moisture between 800
and 700hPa has been evident by patch of alto-cumulus drifting NE
across western WI this afternoon. As this area spreads across the
west half of the CWA this evening, convergence on the nose of a
developing LLJ around 800hPa should initiate at least some
convection. Given the shallow layer of moisture, confidence is low
on the coverage of any precip. So, have maintained slight chance
PoPs across the central mid evening into the early overnight hours,
and chance PoPs across most of the east half late evening through
most of the overnight. MuCAPE for parcels forced from the
aforementioned layer will be around 750j/kg, so elevated thunder
will be possible with any precip formation.
For Tuesday, capping will result in mostly sunny skies across the
area. 900hPa temps around 20C and winds up to 30 knots will support
sfc temps well into the 80s and gusty SW winds to 25mph,
respectively. Would not be surprised to see a few downslope
locations along Lake Superior approach 90 late in the afternoon.
Lastly, with the recent rain of at least an inch across all of
Upper Michigan, fire wx concerns are minimal.
.LONG TERM...(Tuesday through Sunday)
Issued at 458 AM EDT MON AUG 22 2016
Models suggest that a progressive pattern will prevail with a
mid/upper level low/trough over srn Alberta/Sask Tuesday will move to
nrn Ontario by Thursday. This will bring unseasonably warm air into
the wrn Great Lakes with waa ahead of the sfc low Tuesday and
increasing shra/tsra chances Wednesday as the sfc trough/front moves
into the region. Cooler and drier weather will then move in from
Thursday into Friday as high pressure builds from the nrn plains into
the Great Lakes. Unsettled weather returns by the weekend as the low
amplitude pattern will allow another mid level trough to move into
Tuesday, continued waa and increasing mid level capping will will
preclude any pcpn chances and allow temps to climb well above
normal. Forecast mixing heights into the 900-850 mb range support
highs into the mid to upper 80s with dewpoints into the lower 60s.
Wednesday and Wednesday night, as the sfc trough moves into the area
expect shra/tsra chances to increase by late wed into wed night as
moisture advection bring PWAT values above 1.5 inches. However, only
chance pops were included with uncertainty remaining with the
timing/position/strength of any convectively modified shortwaves
emerging from the plains that will help support the pcpn.
Instability (MLCAPE values into the 500-1000 J/Kg range) and shear(0-
6km to 30 knots) will be marginal for any stronger storms. The pcpn
chances will shift to mainly the ern cwa by Thursday morning.
Thursday, a trailing secondary cold front and shrtwv could bring
some isold -shra into the nw cwa. Otherwise, cooler air and drier
air will prevail with highs from the upper 60s west to mid 70s
south and east and dewpoints falling into the mid 50s.
Friday-Sunday, surface high pressure and upper ridging will then
bring dry and mostly clear conditions Friday into early Saturday.
With a continued progressive pattern, pcpn chances will increase as
models suggest potential for a shrtwv to bring another round of
shra/tsra toward the area from later Saturday into Sunday. However,
confidence in any details is low given models differences and lack
.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 142 PM EDT MON AUG 22 2016
VFR conditions are expected for all sites through the period. Main
concern will be LLWS developing at KIWD and KSAW as a strong low-
level jet forms this evening and persists through daybreak Tuesday.
There are some indications that SW winds up to 50kts will be possible
as low as 1kft AGL. Otherwise, some -SHRA and possibly thunder will
be possible for KSAW tonight.
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 505 AM EDT MON AUG 22 2016
A high pressure ridge will continue to slide east of the U.P.
today causing winds to become or remain south to southwesterly
through the day. The pressure gradient is expected to tighten today
through Tuesday between this departing high pressure center and an
approaching cold front, so expect the SSW winds to pick up to 20-25
kts again as early as tonight and then continue at times through
Wednesday. Winds will then shift to the west and west-northwest up
to 25 kts following the cold frontal passage Wednesday evening.
These gusty winds will linger through Thursday morning before slowly
diminishing below 20 knots in the afternoon. After the trailing high
pressure center shifts to the east on Friday, winds will shift back
to the southwest at less than 15 knots.