Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 191535
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1035 AM EST Mon Feb 19 2018

.UPDATE...
Issued at 1035 AM EST Mon Feb 19 2018

Inverted trough axis now extends from the Ontario/Quebec border
thru Central Upper Michigan and Central Wisconsin to a complex
area of low pressure centered along the Kansas/Missouri border.
Long train of convection continues to develop along the associated
warm front...impacting areas from the Mid Mississippi Valley thru
Illinois...Indiana and Ohio. Northern edge of this convection is
slowly creeping northward into Wisconsin and Lower Michigan...
marking the first wave of several areas of energy and resulting
precip that will impact our CWA over the next 48 hours. Still
expect this convection will continue to creep northward thru our
CWA this afternoon. Latest model soundings still show a good
possibility of freezing precip north of M-32 where Winter Wx
Advisories are already in effect. locations along and south of
M-32 still appear to be all liquid. No changes are needed to the
forecast or to headlines at this time...but will certainly keep a
close eye on the evolution of precip type as this prolonged event
begins to unfold. Will also keep a close eye on rainfall amounts
in our far southern CWA.

&&

.NEAR TERM...(Today through Tonight)
Issued at 352 AM EST Mon Feb 19 2018

...Freezing rain and a wintry mix for some areas...

High Impact Weather Potential...icing potential across the
northern part of the CWA. Heavy rain south.

Pattern Synopsis/Forecast...Pattern shift continues across NOAM as
strong short wave energy digs into the western CONUS forcing
downstream highly anomalous ridging through the eastern CONUS...
anchored by strong upper level high pressure developing off the
coast of Florida. In between...deepening/strengthening SW flow
aloft now targeting the Midwest and Great Lakes region with a
strong upper jet riding up through the northern lakes region...and
a tightening thermal gradient/quasi-stationary front/inverted sfc
trough that stretches from the central plains up through the
northern lakes. Tap of rich gulf moisture also underway with high
dewpoint air/PW values in excess of 1 inch surging through the
Gulf states and pushing up into the Midwest/Ohio Valley this
morning. Warm/moisture rich air will be advancing into the lower
lakes region later today through Tuesday (dewpoints possibly
pushing 60F across southern lower MI Tuesday).

Primary Forecast Concerns...A prolonged active weather period
lies ahead with mixed precip types/potential for ice
accumulations across the northern part of the CWA the main
forecast concern. Also...heavy rainfall potential across the
southern part of the CWA with snowmelt...frozen ground and runoff
bringing hydro concerns.

Aforementioned quasi-stationary boundary and tight baroclinic zone
leans into lower Michigan this afternoon and becomes the main
focus for periodic strong isentropic ascent and f-gen forcing...all
aided by upper jet entrance region forcing. Combined with robust
moisture transport from the Gulf and PW values forecast to edge up
to over 1 inch across the southern part of this CWA tonight...
still anticipate precip to develop and expand into the state
starting later this afternoon and continuing right on through
Tuesday with several waves of heavier precip along and south of
the boundary. Heaviest storm total precipitation still expected
primarily south of M-72 into central and southern lower Michigan
with the potential for over 1.5 inches of rain along and south of
the M-55 corridor.

That said...flooding potential remains a bit uncertain given the
steadier drawn-out nature of the rainfall and forecast amounts
that are basically under flood guidance. However...given the
snowpack/frozen ground and that we do have a few river forecast
points (SHRM4/STRM4) forecast to go above action and even flood
stage by Wednesday...I plan on hoisting a flood watch for my far
SE counties where the highest forecast QPF resides...which matches
up fairly well with the flood watches issued by GRR and DTX.

Further north...much lower total precip is anticipated through
this event. But of course heading into the cold side of the
boundary precip type issues come into play...specifically
freezing rain/icing potential with such a pronounced warm nose
aloft poking into the region. Ice accumulations are always tricky
and modulated by a host of things including surface temps/dewpoints
(can still get accumulating ice with temps a little above 32F if
sfc dewpoints are below 32F)...wind and time of day. Considering
all these factors the best icing potential still appears to be
across eastern upper Michigan this afternoon through Tuesday
morning...with a little bit of accumulating snow to start things
off. Some light icing also anticipated tonight down into the tip
of the mitt where surface temps will hover either side of freezing
through the night.

All told...I still like our current placement/timing of winter
weather advisory headlines. That is...across the tip of the mitt
and eastern upper Michigan for a combination of some accumulating
snow and some accumulating ice (under ice storm warning criteria
for any 12 hour period). Thought about adding the M-32 corridor
counties (Otsego to Alpena) to the advisory as the higher terrain
areas over toward APN always seem to get in on the winter weather
fun. Again all will depend on the above mentioned factors but for
now will leave them out and we can see just how things unfold.

&&

.SHORT TERM...(Tuesday through Wednesday)
Issued at 352 AM EST Mon Feb 19 2018

...End of the Ice, and Beginning of Dry Weather...

High Impact Weather Potential...Freezing rain in Upper Michigan and
in N Lower during the morning, and then in the early evening.
Another tenth of an inch of ice is possible. Rain will continue in
the southern counties, especially near Saginaw Bay, which could
produce flooding along area streams and rivers.

Pattern Synopsis/Forecast...Models have a strong baroclinic zone
that stretches roughly from MBL to APN at 12z/Tue. This baroclinic
zone slowly pivot north and west as the sfc low moves into N Lower.
Models are in better agreement with the low center as the GFS has
moved toward the ECMWF look, which is what the ECMWF was advertising
2 runs ago. This pushes +5c or so air at 850 mb to around Whitefish
point While the sfc temperatures barely make freezing in E Upper
around 21Z. N Lower by that time will be into the 50s from M-32
south, with mid 40s north to the Straits. This should alleviate ice
issues during the afternoon. By 00z/Wed, sfc temperatures begin to
cool again, ahead of the cold front so that there could be short
period of FZRA in E Upper, but by 06z/Wed, the cool air at 850 mb
begins to move south and east so that the rain on the warm side is
more likely to chance to snow briefly before ending around 12z/Wed.
Then high pressure builds in the region allowing the area to dry
out. There will still be some flooding concerns as the runoff from
the rain on Monday and Tuesday will not be complete until about
Thursday.

Primary Forecast concerns...Concerns will be the amount of warm air
that drives north on Tuesday morning and changes the FZRA into RA.
As stated before, the models are in better agreement, so will go with
the consensus. The lingering problem will be the amount of QPF
translating into ice accumulation. If the sfc temperatures verify,
then it looks like E Upper and areas near the Straits get 0.10" or
less through the day and again into the evening, before changing to
snow and tapering off. Pwats are an inch or better from PLN south to
HTL so will expect that the best amounts will be in the SE counties
of the forecast area.

.LONG TERM...(Wednesday night through Sunday)
Issued at 352 AM EST Mon Feb 19 2018

...A Brief Cool off, then Gradually Warming for the Weekend...

Extended (Thursday through Sunday)...Wednesday`s dryness extends
into Thursday, until the next system moves into the region Thursday
night and produces light snow into Friday. Models are not in
agreement with the precipitation ending, with the ECMWF end by
00z/Sat, but the GFS leaving some low level chances into Saturday
morning, before drying out. The models then bring another system
through Sunday morning. The Sunday morning storm is 7 days out, but
both the ECMWF and GFS have similar positions and strength with the
sfc low. This could have some significant accumulations if it holds
together. However, the sfc temperatures rise into the lower 40s
Sunday (temperatures trend up through the week), so rain and snow
are possibilities.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 629 AM EST Mon Feb 19 2018

...Deteriorating conditions later today and tonight...

VFR conditions across northern lower Michigan for the moment with
sct-bkn mid and high cloud cover rolling through the region. Quasi
stationary front draped up across western upper Michigan will lean
into the region as we go through the day. Strong southerly flow
will transport a warm/moist airmass up into lower Michigan as we
go through the day and is expected to bring quickly lowering cigs
along with precipitation that expands into the region later this
afternoon and tonight. Mainly rain for areas south of M-32
(TVC/MBL). But a wintry mix of precip is expected at PLN and
possibly APN later tonight. CIGS and VSBYS continue to lower to
MVFR and eventually IFR as we go through tonight.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY from 4 PM this afternoon to 1 AM EST
Wednesday for MIZ008-015.

WINTER WEATHER ADVISORY from 7 PM this evening to 1 PM EST
Tuesday for MIZ016>019.

FLOOD WATCH through late Tuesday night for MIZ035-036-041-042.

&&

$$

UPDATE...MR
NEAR TERM...BA
SHORT TERM...JL
LONG TERM...JL
AVIATION...BA


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