Area Forecast Discussion
Issued by NWS Gaylord, MI

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743
FXUS63 KAPX 251103 CCA
AFDAPX

Area Forecast Discussion...CORRECTED
National Weather Service Gaylord MI
703 AM EDT Sat Mar 25 2017

.NEAR TERM...(Today through Tonight)
Issued at 330 AM EDT Sat Mar 25 2017

...Active weather continues with more wintry mixed precip...

High Impact Weather Potential...Ice accumulation tonight into
Sunday across eastern upper Michigan and tip of the mitt.

Pattern Synopsis/Forecast...Split flow pattern remains across the
CONUS with the slow moving stacked/occluded low pressure system
over Oklahoma, and warm front arcing up through the midwest and
across far SE lower Michigan between Detroit and Toledo. System
has become reinvigorated through the course of Friday...ingesting
Gulf moisture and producing some rather active weather up through
the Mississippi River Valley.

Meanwhile, northern stream rides across the northern high plains
then through the northern lakes region with a nice upper jet core
stretching from Lake Superior eastward through Quebec and mid
level confluent axis sitting right across northern lower Michigan.
Persistent deformation along the tight thermal gradient that sits
across lower Michigan...and aided by entrance region jet forcing...
continues to produce a narrow corridor of widespread precipitation
mainly between M-55 and M-32. OBS suggest mainly rain although
polarimetric radar data does suggest some mix along the northern
edge of the precip. Precip amounts within this axis have been
respectable over the last 24 hours...running around three quarters
of an inch. A second corridor of precip sits through southern
lower Michigan along the warm front itself.

Primary Forecast Concerns...P-type issues...of course.

Today: Elongated deformation axis and upper jet forcing finally
looking to weaken while getting suppressed down into central
lower Michigan by mid to late morning...as strong Canadian high
pressure pivots across the northern lakes region. Will keep some
high pops going early on with a little bit of wintry mix in the
high terrain...before diminishing PoPs to just chancy and mainly
for areas south of M-72. Despite the mixy precip, temperatures
remain largely in the middle 30s where precip is occurring. Thus
no headline for today.

Otherwise, high pressure and drier air nudging in from the north
should help thin out cloud cover through the day. Far northern
part of the CWA may even see a fair amount of sunshine today,
particularly in eastern upper Michigan.

Tonight: Closed/occluded low in the plains expected to finally
open up and advance up into the western Ohio Valley/lower Great
Lakes by Sunday morning. This will bring a northward bulge of
warmer air back up into northern Michigan as we go through the
night while opening up that feed of Gulf moisture into the Great
Lakes...spreading precip back up through the region. Once again,
primarily liquid anticipated as pronounced wedge of warm air aloft
surges northward (H8 temps exceeding 8C by morning). So once
again, surface temperatures will be paramount. Strong easterly dry
flow from the departing high pressure system will be a player and
will likely keep temps below freezing across eastern upper Michigan
through the night...and possibly parts of NE lower Michigan/tip
of the mitt. But a solid freezing rain event appears likely for
eastern upper Michigan while some freezing rain/light icing is
likely across the tip of the mitt.

Headline-wise: Currently have between one and two tenths of an
inch of ice for much of eastern upper Michigan and around one
tenth or less for the tip of the mitt. Thus, a high probability
that an advisory will be needed in eastern upper Michigan and
perhaps the tip of the mitt...which I may be issuing within the
next few hours. Will be collaborating with surrounding WFOs to
make that call.

Finally as a side note...will need to keep a close eye on river
gages over the next few days given the decent amount of rainfall
we have see.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 330 AM EDT Sat Mar 25 2017

...To Ice or not to Ice Part Trois(three)...

High Impact Weather Potential...Significant ice is likely into
Sunday morning in E Upper with smaller chances in NE Lower.

There is a small chance for icing Sunday night into Monday.

Pattern Synopsis/Forecast...By 12z/Sun the rain is over the region,
and model soundings are showing that the FZRA that was in NE Lower
overnight has moved to E Upper for the first few hours of the
morning. 15z/Sun, temperatures are back above freezing so that we
should begin to lose the ice. Sfc temperatures continue above
freezing through 00z/Mon, and probably later as we are still warm
advecting. Overnight, it is possible that there will be patches of
freezing rain, but overall, it looks like rain on into Monday. It
looks like there could be a period where things stop, before a
deformation zone moves into the forecast area and brings the rain
back. after 00z/Tues it looks like the rain, or maybe evening light
snow is possible before the models dry things out.

Primary Forecast Concerns...Freezing rain on Sunday morning looks
like a sure bet in E Upper, the question is whether the warmer air
pushes into NE Lower in time to stop the freezing much into the
morning period. SREF plumes seem to say yes with the most dominate
precipitation type after 12z/Sun being rain.

SREF plumes also show that there is little chance for freezing rain
in E Upper, with only two to the 27 members being below freezing. So
will adjust to keep the FZRA Monday night to a minimum.


.LONG TERM...(Monday night through Friday)
Issued at 330 AM EDT Sat Mar 25 2017

High Impact Weather Potential...None

Extended (Tuesday through Friday)...After the system moves east,
then high pressure builds into the forecast area through Wednesday
night, before the next system begins to move into the forecast which
looks like as early as Thursday on the ECMWF, and Friday morning on
the GFS. And like the timing that is different on both the p-type is
as well, with the GFS showing snow and the ECMWF showing rain.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 652 AM EDT Sat Mar 25 2017

Drier air will nose down into northern lower Michigan today and
should bring improving conditions to the terminal sites...where
conditions should slowly improve to VFR. Low pressure will track
up into the midwest today and up through lower Michigan tonight.
This will bring another slug of rainfall up through the region
tonight with conditions dropping back to MVFR/IFR. PLN may see a
period of FZRA tonight with temps around freezing.

&&

.MARINE...
Issued at 330 AM EDT Sat Mar 25 2017

Easterly flow will be increasing through the day as high pressure
slides through the northern lakes...and low pressure lifts into
the midwest. This will lead to small craft advisory waves/gusts on
Lake Michigan and Lake Huron today and most of tonight.
Winds/waves will weaken on Sunday as the low tracks up through
lower Michigan.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 AM EDT Sunday for
     LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 AM EDT Sunday for
     LMZ323-341-342- 344>346.
LS...NONE.

&&

$$

NEAR TERM...TBA
SHORT TERM...JSL
LONG TERM...JSL
AVIATION...TBA
MARINE...TBA



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