National Weather Service - Area Forecast Discussion

000
FXUS63 KAPX 290715
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
315 AM EDT Sat Apr 29 2017

.NEAR TERM...(Today through Tonight)
Issued at 315 AM EDT Sat Apr 29 2017

...Dry and cool today...widespread precip developing tonight...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...Elongated inverted trough/warm front
extends from low pressure centered over Texas thru the Bootheel of
Missouri and along the Ohio Valley early this morning. Meanwhile...
high pressure is centered over the Northern Plains...with weak
ridging extending thru the Northern Great Lakes region. Weak wave
riding thru the fast SW upper level flow that produced an area of
light rain mixed with some spotty light snow last night has pushed
east out of Michigan...leaving mostly cloudy skies just a few
patches of lingering light rain/drizzle early this morning. Temps
remain quite cool in the mid 30s to lower 40s at this hour.

As we head into today...upstream high pressure will slide into
Northern Michigan in the wake of the departing short wave...
establishing a better foothold on our area. Clouds will decrease
this morning...but will begin to increase again from south to north
later this afternoon as the Ohio Valley trough/warm front begins to
lift northward toward the Great Lakes region in response to further
deepening/organization of the Southern Plains low. Widespread precip
will begin to develop from south to north across most of Northern
Lower Michigan this evening...making continued slow northward
progress thru the Tip of the Mitt and the Straits area during the
overnight hours. Gradual northward progress of WAA along with deep
moisture advection will limit any chances of snow mixing in with the
rain to the northern edge of the precip shield. Instability will be
virtually nonexistent tonight...so thunder is not expected. While
some of our southern CWA will likely see a quarter to a half an inch
of rainfall tonight...the potentially heavier rainfall should hold
off until Sunday and Sunday night.

High temps this afternoon will range from the mid 40s in Eastern
Upper Michigan to the lower 50s along and south of M-72. Low temps
tonight will be mainly in the mid 30s to near 40 degrees.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 315 AM EDT Sat Apr 29 2017

...Heavy soaking rains Sunday through Monday morning...

High impact weather potential...Moderate to heavy rainfall Sunday
through Monday morning (particularly over northern Lower MI) will
lead to rises on area streams and rivers and possibly some minor
flooding. Embedded thunderstorms possible Sunday night into Monday
morning.

Pattern Synopsis/Forecast...A very moist airmass will lift into
northern Michigan Sunday into Monday with anomalously high PWATs
climbing to 1 to 1.5" (2 to 4 standard deviations above the mean).
Pronounced baroclinic zone and warm front laid out downstate Sunday
morning will slowly lift northward through the day. Meanwhile
ongoing strong WAA just above the surface and northward creeping
band of frontogenetic lift will generate additional rounds of
moderate to heavy rainfall over northern Michigan through the day,
heaviest south of the Bridge. This will all take place out ahead of
an intense occluding low over the Central Plains that will slowly
lift into the Upper Midwest Sunday night into Monday. As the core of
this system reaches Iowa Sunday evening, a robust LLJ will develop
and nose into northern MI. This will result in Sunday night being
the most efficient period of moisture transport, and warm cloud
depths approaching 3.5 km will promote efficient rainfall over all
of northern MI. Marginal elevated instability will come into play
over northern MI late Sunday afternoon into Sunday night with 200-
300 J/kg of MUCAPE, so some embedded thunderstorms are definitely
plausible given the strong lift that will be in play.

The best instability and lift will push east of the area by late
Monday morning as the dry slot encroaches, bringing an end to the
steady, heavier rains. CAA will strip out the deeper moisture by
midday, though there will be enough lingering low level wrap-around
moisture to allow for scattered afternoon showers as low level lapse
rates steepen. This will also lead to breezy conditions Monday
afternoon with gusts to around 30 mph.

Primary Forecast Concerns...Models have been in pretty good
agreement with the track of this system and generally consistent
with the axis of heaviest precipitation laying out from Chicago to
northeast Lower MI. They remain split on actual precip amounts,
however, with the NAM (as an outlier) generating more than 5" of
rain across central Lower MI from Saturday night through Monday
morning. The GFS and ECMWF are more conservative (and believable)
with 2 to 3" over northern Lower. The Canadian had higher amounts
more in line with the NAM but backed off a bit with the 29.00Z run,
now more in line with the GFS/ECMWF. Additionally, GEFS and SREF QPF
plumes are showing less spread and greater clustering around their
respective means...roughly 2 to 3" across northern Lower and 1 to
1.5" over eastern Upper. Highest totals will generally fall
southeast of a line from Cadillac to Alpena.

&&

.LONG TERM...(Monday night through Friday)
Issued at 315 AM EDT Sat Apr 29 2017

High impact weather potential...None.

Intense occluded low will lift from the western Upper Peninsula into
southern Ontario Monday night. CAA will be ongoing with wrap-around
showers continuing Monday night into Tuesday. Breezy conditions will
develop again on Tuesday on the back side of this departing system.
Much drier air will start to filter into the region Tuesday night,
bringing an end to any lingering showers (though a few wet
snowflakes could mix in Tuesday evening as temperatures drop through
the 30s). High pressure and a dry airmass will allow for quiet
weather across the region for Wednesday and probably most of
Thursday. However, a system that should largely pass to our south on
Thursday could perhaps brush northern Michigan if it favors a more
northern track shown by the 29.00Z ECMWF. Temperatures will be on a
gradual warming trend through the period, climbing back above
seasonal normals by Friday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1137 PM EDT Fri Apr 28 2017

...VFR conditions through Saturday...

A period of lower cloud cover (remaining VFR) will slide across
northern lower Michigan tonight, as a small area of low pressure
moves through. Some light rainfall is possible, but nothing
substantial. Precip ends and cloud cover thins out for Saturday.

&&

.MARINE...
Issued at 315 AM EDT Sat Apr 29 2017

Winds and waves will remain below SCA criteria today and this
evening as surface ridging builds overhead and then pushes north of
Michigan. Conditions will begin to strengthen to SCA criteria late
tonight and Sunday as deepening low pressure slowly lifts NE toward
the Western Great Lakes region. Widespread precip will develop
tonight and will continue into Sunday and Sunday night as deep
moisture surges northward into Michigan ahead of this system.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...MLR
SHORT TERM...MEK
LONG TERM...MEK
AVIATION...TBA
MARINE...MLR

NWS APX Office Area Forecast Discussion