Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 132351
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
751 PM EDT Wed Mar 13 2024

.KEY MESSAGES...

- Dry weather and above normal temps expected through Friday night
- A weekend storm system brings light rain/snow mix and blustery
  conditions on Saturday.
- Below-normal temperatures and several days of accumulating
  lake effect snow potential Saturday night thru Tuesday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 402 PM EDT Wed Mar 13 2024

A broad mid level ridge overhead and a sfc ridge building in from
the northwest are providing another unseasonably warm and dry day
for the U.P. GOES WV imagery shows some mid and high level clouds
currently passing eastward over the U.P. as well as some cumulus
developing along the lake breeze off Lake Superior in Marquette
County and the Lake Michigan lake breeze in Menominee/southern Delta
County; the Lake Superior lake breeze is also noted on radar data.
Mixing today is not quite as strong as yesterday with model
soundings only indicating mixing up to 2-3kft, but this still
brought down some lower dew point temps and lowered RHs into 20%
range over the interior west half of the U.P. with a few spots
dipping into the upper teens. Luckily, winds are staying lighter
than yesterday with gusts mainly staying below 15 mph so fire
weather concerns remain low. While some interior areas may see temps
climb an additional degree or two yet this afternoon, especially
near the WI/MI state line, we begin to cool off the rest of today.

The dry weather pattern with above normal temps continues tonight.
With high pressure to the north and east and a low pressure
approaching the region, light north to northeast winds set up
tonight and cloud cover continues to increase ahead of the low.
Temps are expected to settle into the upper 20s to low 30s.

&&

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
Issued at 524 PM EDT Wed Mar 13 2024

A rex block building over British Columbia results in 500mb positive
height anomalies approaching 340m (+3 st devs) this weekend. This
blocking ridge forces a deepening trough downstream across eastern
North America Friday night through Wednesday. This deepening trough
provides most of the noteworthy weather during this forecast period.
The most prevalent hazards appear to be gusty west winds Saturday
into Sunday followed by a period of accumulating lake effect snow
Saturday night into Monday night. Meanwhile, daily temperatures
anomalies of +6 to +10 trend to -1 to -3 below normal behind a cold
front currently progged for Sunday morning through early next week.

A low pressure tracks to our south on Thursday and model guidance
continues to trend further south. As a result, Upper Michigan is
increasingly likely to stay dry, except for maybe the far southern
tip of Menominee County. Otherwise, steady northeast winds off Lake
Superior keep temperatures cooler (upper 30s) near the lakeshores on
Thursday with locations farther from the lake warming into the upper
40s. A high pressure ridge settles across the area Thursday night
into Friday allowing for light winds and a large diurnal temperature
swing exceeding 20F (lows in the 20s, highs in the 40s).

The primary weather maker approaches the region Friday night. The
event begins with a ~50 kt westerly low level jet resulting in WAA,
isentropic ascent, and perhaps some weak frontogenesis too.
Operational models have ~9 hour period of deep moisture aloft, but
the antecedent air mass is quite dry so I`m skeptical of the high
end PoPs advertised by NBM and decided to limit PoPs at 50% on
Saturday. Northern and eastern portions of our CWA are most likely
to get precipitation with this feature. NAM guidance advertises all
snow via evaporative cooling whereas the GFS guidance advertises
more of an elevation-dependent rain/snow mix. Either way, the going
forecast is likely too aggressive with the duration and magnitude of
Saturday`s precipitation chances. The other thing to watch on
Saturday is the potential for gusty west to northwest winds within
the cold air advection regime. Models are advertising fairly deep
mixing into a layer of moderate winds aloft and EFI guidance
highlights the potential for strong winds mainly across the west
half of Upper Michigan. As is usually the case, the Keweenaw looks
breeziest and EPS means already advertise peak gusts in the 40-45
mph range suggesting potential for a wind advisory.

Continued cold air advection increases lake effect snow potential
Saturday night and a secondary shortwaves digs into the base of the
trough. This disturbance should enhance any ongoing LES in
addition to sending a reinforcing cold front that should cool
temperatures below normal for the first time since Feb 29th.
With lake average temperatures around 2-3C, the critical 850 mb
temp threshold for pure lake effect is around -11C. Ensemble
means cool 850 mb temps below that threshold Saturday night and
don`t warm temps back above that threshold until Tuesday. Model
soundings advertises deeper moisture in addition to the lake-
induced inversion moving into the DGZ later on Sunday suggesting
fairly high coverage and higher SLRs. In addition to LES, we`re
also well into the time of year where cold upper level
troughing can support diurnal snow showers developing due to
daytime heating. Grand ensemble means advertise around 0.25
inches of QPF within the lake effect snow belts during the
period of LES and there should be locally higher amounts. In an
average year, this would not be particularly noteworthy but this
year is different.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 750 PM EDT Wed Mar 13 2024

With dry air continuing to dominate thru the low and mid-levels, VFR
will be the rule tonight at IWD/CMX/SAW. However, will be monitoring
the southward progress of some low cloudiness currently well n of
Lake Superior. It appears that during early Thu morning, some of
these clouds will reach Upper MI. For now, only included a low MVFR
cig at SAW where sharpest upsloping will occur under NNE winds. At
CMX/IWD, kept mention of lower clouds to just few to sct at around
2000ft.

&&

.MARINE...
Issued at 653 PM EDT Wed Mar 13 2024

A sfc ridge building in from the northwest will keep winds below 20
kts as they become northeast this evening into tonight. Northeast
winds continue on Thursday to around 15-25 kts, backing north to
north-northeast Thursday night. Strongest winds are expected over
the east half on Thursday and west half Thursday night with internal
probabilistic guidance showing 60-90% probabilities of winds
exceeding 22 kts. Winds back southwest on Friday, but generally
remain below 20 kts.

Southwesterly winds continue increasing Friday night ahead of a low
pressure system with gusts of 20-30 kts possible. As this system
passes just north of the lake on Saturday, winds veer west then
northwest. Cold advection will result in unstable conditions over
the waters Saturday into early next week. Guidance suggests a 30-60%
chance for low-end west gales to 35 kts becoming northwesterly on
Saturday. Saturday night probabilities for northwest becoming north
gales to 35 kts are around 20-40%, mainly over the east half of the
lake.

Unstable conditions remain into the early part of next week, but
winds gradually diminish to around 20 kts for Tuesday and Wednesday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...Jablonski
LONG TERM...EK
AVIATION...Rolfson
MARINE...Jablonski


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