Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 132030

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EST Mon Nov 13 2017

Synopsis/Short Term/Long Term/Marine

Issued at 330 PM EST Mon Nov 13 2017

We will stay in a somewhat milder pattern this week with highs
mostly in the 40s. Our next rain will come late Tuesday night and
Wednesday morning with a cold front, then rain is likely again
Friday into Saturday as a stronger storm impacts the region. It
will turn windy and colder behind that system.


.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM EST Mon Nov 13 2017

The main challenge tonight and Tuesday is cloud trends and fog
potential. We are under the sfc ridge tonight with light winds so
if enough clearing and radiational cooling takes place we could
be looking at a dense fog event. However we already have a
persistent deck of stratocu clouds overhead and considerable mid
and high level cloudiness is around and upstream so will go
mostly cloudy tonight.

Will continue the areas of fog theme tonight, although not
confident enough to issue a dense fog advisory at this time. If
temps fall below freezing tonight with any lengthy period of
clearing, there is also a low probability of some freezing fog and
patchy black ice for the morning commute - but again this is a
low confidence scenario.

If we do get socked in tonight with fog and low stratus, highs on
Tuesday will be held to near 40. For now will go the idea of
mainly mid and high clouds leftover by afternoon and highs
reaching 45 to 50 in the southerly flow/waa ahead of the
approaching front.

No change in thinking with the next rain event as models have been
very consistent with timing and QPF amounts. Will continue
categorical pops late Tuesday and Wednesday morning but thunder
prospects look too low to mention.

.LONG TERM...(Thursday through Monday)
Issued at 330 PM EST Mon Nov 13 2017

Shortwave ridging will work through the western and central Great
Lakes Thursday and Thursday night as the shearing wave currently
over the Pacific Northwest exits Michigan and the next system works
into the western U.S. and Canada. Upper ridge/surface high will
provide dry weather, and may allow for partly cloudy skies by
afternoon before higher-level moisture ahead of the next system
arrives. Post-frontal cold air advection will hold highs into the
upper 30s to low 40s on Thursday.

Medium-range models are still showing some large timing differences
with the system expected to impact the area for the end of the week,
but depict a similar idea on synoptic evolution. Upper energy now
dropping down the western Canadian coast will amplify as it drops
into the central CONUS, with good surface cyclogenesis occuring lee
of the rockies and into the Great Lakes as the system takes on a
negative tilt and encounters good diffluence at the nose of a 160kt
jet streak. The passage of this system through the area will bring
unsettled weather to the area Friday-Sunday, first in the form of
precipitation, then wind and cold/snow showers.

Rain showers, possibly mixing with wet snow early, will spread into
the area as the warm front begins to lift through early on Friday.
Precipitation will then change to all rain by Friday afternoon and
become steadier as ascent/moisture advection increases (PW rises to
an impressive 1"+). Differences in model timing then become more
apparent as timing of cold frontal passage and changeover of
precipitation to snow showers ranges from Saturday morning to
Saturday night. Will favor non-GFS solutions at this time, and keep
precipitation on Saturday mostly rain until evening. Lake-effect
showers should persist into Sunday in a cold northwest flow regime.
Max temperatures may make a run at 50 degrees south of I-96 on
Friday, before barely reaching the freezing make on Sunday.

Models have trended less deep with the low lifting up through the
Great Lakes Friday night into Saturday. Windy conditions are still
favored Saturday/Saturday night however given tight pressure
gradient and degree of cold air advection.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 110 PM EST Mon Nov 13 2017

Partial clearing of the MVFR cloud layer is possible this
afternoon before ceilings re-form and lower overnight. Expecting
at least IFR visibility or ceilings over most of the area in the
early morning hours... possibly LIFR depending on the amount of
clearing earlier the night. There will be gradual recovery to
MVFR by late in the morning.


Issued at 330 PM EST Mon Nov 13 2017

No marine headlines needed at this time, but small craft
advisories will likely be needed starting Tuesday afternoon and
continuing into Thursday morning.


Issued at 110 PM EST Mon Nov 13 2017

River levels are running near to above normal for mid-November.
Another quarter to half inch on Wednesday will keep the ground
soggy. A Fall storm system may produce rainfall totals around a
half to 1 inch Friday into Saturday, which would cause river
levels to rise again.




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