Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 160523
Area Forecast Discussion
National Weather Service Marquette MI
1223 AM EST Thu Feb 16 2017
.SHORT TERM...(This evening through Thursday)
Issued at 408 PM EST WED FEB 15 2017
WV imagery and RAP analysis indicated an amplified pattern with a
ridge from srn CA to central Canada and a trough from Quebec into
the northeast CONUS resulting in nrly mid/upper level flow through
the wrn Great Lakes. At the surface, a ridge from nw Ontario through
ern MN was slowly building to the east as nnw flow LES continued
across Lake Superior.
Tonight, as the ridge builds into the area and the winds diminish,
the higher res models suggest that lake induced troughing and
land breezes will focus the LES bands into the n cntrl cwa and
along the shoreline near Marquette by late tonight. With -16C
temps at the top of the 3k ft inversion, expect mainly light snow
showers but with high SLR values aoa 30/1 with the shallow
convective cloud in the DGZ.
Thursday, expect any remaining LES to diminish during the morning as
the ridge builds into the ern cwa and winds become offshore.
Otherwise, mainly cloudy conditions will prevail with low level
moisture remaining below the lowering inversion. Highs will range
from the lower 20s east to lower 30s west.
.LONG TERM...(Thursday night through Wednesday)
Issued at 249 PM EST WED FEB 15 2017
Real good agreement in the models and GEFS ensemble that upper ridge
over the western Conus builds across central Plains and Great Lakes
Fri into Fri night. Shortwave trough crossing northern Ontario on
Sat will flattern ridge slightly but it should build again Sun into
Mon with GEFS h5 heights and h85 temps both 2-3 standard deviations
above normal. Ridge will result in dry weather this weekend. Main
question will be how warm it will get Fri through Sun.
Latest NAM indicates increasing moisture 950-900mb (500ft-1500ft
agl) as early as Fri and certainly by Sat. Just not sure if this is
realistic or an artifact of models trying to generate too much low-
level moisture due to warming temps and expected melting snow.
Previous GFS runs were showing similar idea with low-level moisture
but 12z run looks more realistic with minimal moisture. With ridge
overhead, main low and cyclonic flow well to the north across
northern Ontario and sfc dwpnts Fri into Sat staying mainly below
freezing, have doubts that either day will have bkn-ovc low clouds
as NAM would indiate. Could see sct cumulus clouds though. Mixing to
925mb as soundings (even from the drier GFS) show seems too low with
upper ridge overhead and plenty of dry air in mid-upper levels. For
the warm Monday we saw earlier this week (set record high at NWS MQT
that day of 44F) the forecast soundings leading up to that day were
indicating similar scenario as NAM indicates on Fri and Sat (low
clouds and limited mixing height). Instead INL and GRB RAOBs at 00z
Tue indicated a mixing depth to 875mb to 850mb was achieved. Skies
were mostly sunny.
Though there was stronger mixing on Mon in lowest 5kft compared to
what should occur on Sat, think it could end up just as warm if not
warmer since h85 temps are much warmer (-2c on Mon and at least +8c
on Sat). Will continue to use 900mb temps as gage for high temps
which supports highs Fri mainly in the 40s and mainly in the upper
40s to middle 50s Sat and Sun. Since is it forecast to be drier in
low-levels on Sun that day may end up the warmer day. Lake breezes
are possible either day which would result in falling temps in the
aftn locally near the Great Lakes. Overall this weekend will feel
more like spring instead of winter. Record highs this weekend are
mostly in the 50s to low 60s. Here is a sampling of the record highs
for Fri 2/17 through Sun 2/19. Record highs seem possible.
Ironwood: 2/17 is 60 (2011), 2/18 is 58 (1981) and 2/19 is 60 (1930)
Irn Mtn: 2/17 is 58 (1981), 2/18 is 51 (1930) and 2/19 is 62 (1930)
NWS MQT: 2/17 is 61 (1981), 2/18 is 52 (1997) and 2/19 is 46 (1988)
Mqt city: 2/17 is 55 (2011), 2/18 is 52 (1954) and 2/19 is 62 (1930)
Newberry: 2/17 is 47 (1954), 2/18 is 46 (1997) and 2/19 is 47 (1994)
Shortwave trough moving over the Pacific Northwest later this
weekend deepens as it tracks across the northern Plains on Mon and
over the Great Lakes Mon night into Tue. Sfc trough over the plains
on Mon deepens to 995-1000mb low while lifting across northern
Ontario by Tue morning. With enough morning sunshine on Monday could
see temps again rise well into the 40s if not reach the 50s. Clouds
should thicken later in the day though as shortwave comes closer.
Upper Great Lakes will be well within warm sector of this system on
Mon night with h85 temps up to +10c and sfc dwpnts rising toward
40F. SW H85 winds over 50 kts will pump PWATs over 1 inch or roughly
4-5 standard deviations above normal. The abundant deep moisture
should help to develop rain showers over Upper Michigan late Mon
into Mon night. Timing still varies, though would expect a period of
rain sometime from late Mon aftn through daybreak on Tue. Given
strength of theta-e ridge just upstream and moisture advection
suppose there could also be thunder. Sfc dwpnts over 40F advecting
over the melting snowpack could result in areas of fog Mon night.
Sfc trough crossing the area on Tue morning will shift winds to the
W or NW pushing a drier and cooler airmass across Upper Michigan
through the day.
Tue into Wed the shortwave trough will head east across Quebec and
New England while weakening. Upper flow will become more zonal again
which casts doubt on the cold air that was showing up for mid to
late next week in model runs 24 hour ago. GFS remains cooler than
ECMWF and GEM especially for middle of the week, but consistency in
the ECMWF and GFS runs is lacking. Will leave consensus for now
given the poor run to run continuity, but overall think models are
heading toward zonal pacific flow pattern with temps at least
slightly above normal.
Beyond the end of the long term, recent runs of GFS and ECMWF
including latest runs hint at stronger storm system over ncntrl
Conus late next week (24-25 Feb). That system could bring snow to
portions of northern Plains and snow and/or mixed precipitation
across Upper Great Lakes.
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1223 AM EST THU FEB 16 2017
Lake effect snow showers are showing a diminishing trend tonight and
have generally only affected KSAW earlier this evening with light
snow. Look for MVFR conditions at all the TAF sites to improve to
VFR overnight into Thu morning as drier air continues to diminish
lingering les and erode lower cloud cover.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 408 PM EST WED FEB 15 2017
With high pressure building into the region, winds to around 25
knots over the ern lake will continue to diminish tonight. Winds
through the weekend will remain at or less than 25 knots as the
pressure gradient remains week across the area in the absence of any
major pressure systems.