805
FXUS63 KAPX 191124
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
724 AM EDT Sun May 19 2019

.NEAR TERM...(Today through Tonight)
Issued at 222 AM EDT Sun May 19 2019

High impact weather: Potential severe storms in northern lower
Michigan this afternoon and early evening. Damaging winds the
primary threat.

Pattern synopsis and forecast:

Low pressure was working into the mid and upper Mississippi valley
early this morning, with a warm front extending eastward across the
nrn IL/srn WI border and srn lower Michigan. The system cold front
was draped off to the south into western MO and eastern OK/KS. The
convection associated with the cold front has waned with loss of
heating, while a large pocket of showers and embedded thunderstorms
was across the IA/MN/WI border. This was associated with good DPVA,
upper divergence from a jet rounding a negatively-tilted Central
Plains trough, and LLJ theta-e advection, within a lapse rate
gradient aloft. Instability in this region was less than impressive
however, with MUCAPES on the order of several hundred j/kg. So,
decent rains, but nothing severe. For nrn Michigan, some of the
ejected shortwave energy/vorticity from the upper trough, combined
with the eastern extent of the theta-e advection, has resulted in
periodic light showers.

Heading through late tonight into this morning, the aforementioned
shortwave and associated sfc low pressure lift into the western
Great Lakes, with increasing DPVA with stronger shortwave activity,
combining with continued theta-e advection and the arrival of upper
divergence from the upper jet, leading to more widespread showers
and possible embedded non-severe thunderstorms. This will all be
occurring north of the warm front (we`ll be in cool easterly flow
into early afternoon). The system cold front approaches the western
CWA late in the afternoon and cross nrn lower through early evening,
while the warm front, based on latest data, suggests it`ll still get
to M-32 in nrn lower. The cold Lakes and easterly flow may prevent
this far of a northward push, keeping the low levels quite cool, and
the warm front further south. As a matter of fact, fcst soundings
still suggest (for 3 days in a row), that low clouds (pure
saturation of the low levels), will be locked in for the day. This
would prevent any daytime destabilization ahead of the approaching
cold front, resulting in less of a severe threat. Most of the
instability will be aloft in this scenario, and despite strong sfc-
6km shear of 55-60kts, doubt any severe winds will be able to punch
through to more stable ground level. Only the RUC is suggesting
there is a possibility of some sort of BL mixing to maybe warm up
enough to support a severe threat. It suggests as much as 1000-1200
j/kg of SBCAPE for areas along and south of M-72 in nrn lower, in
line with the latest SPC Day 1. So, the severe threat is not
impossible, but confidence remains low for severe storms. Also, this
time of year in nrn Michigan, it`s difficult to destabilize at the
sfc. Am expecting some decent rainfall totals with mainly just some
embedded thunderstorms, some possibly strong. Gusty winds and some
hail expected, but again, the severe threat seems less than
advertised. Eastern upper will be out of a thunderstorms threat,
with much less instability, but widespread rains are expected over
all of nrn Michigan. Rainfall totals of 1" to 1.75" expected across
most of nrn Michigan, with the greatest amounts still projected to
reside along and north of a line from Cadillac to Alpena. Deeper
moisture strips out behind the front, leading to possible periods of
drizzle for most areas, especially in the higher terrain of interior
nrn lower. Maybe there will still be deep enough moisture across
eastern upper for a more bona-fide light rain to taper off.

Highs today will be tough, if the low clouds can mix out across the
srn CWA. This scenario would result in upper 40s in eastern upper to
the lower 70s closer to Saginaw Bay. If low clouds hold tough, the
gradient will not be so tight. Could be upper 40s in eastern upper
to the lower 60s south. Difficult for sure. Lows tonight in CAA
behind the cold front, readings will range from the lower 40s
north, to the middle 40s closer to Saginaw Bay.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 222 AM EDT Sun May 19 2019

High Impact Weather Potential...Minimal.

Pattern Synopsis/Forecast...Monday, the sfc low moves to the east of
the Upper Great Lakes, and Michigan. if there are any showers from
the moisture, then they will probably be done by 15z/Mon. High
pressure builds into the region by the afternoon. As the drier air
continues to infiltrate into the Upper Great Lakes, skies will be
clear overnight. With the clear skies and light wind overnight from
the high pressure, temperatures are expected to drop into frost
freeze territory for N lower again, and it looks like as we get into
Tuesday, we should remain dry enough for the relative humidity fall
during the afternoon. The GFS has qpf for late Tuesday afternoon,
into the evening with the warm front again. ECMWF does not. Looking
at the GFS soundings for MBL during that time, think that the ECMWF
has a better forecast. Models amplify the ridge, pushes the rain
back to the west until 12z/Wed.

Primary Forecast Concerns...A few issues for the upcoming couple of
days. 1) Do we get any rain showers in the morning, and if we do how
long does it take for the clouds to clear out. With the LRQ of the
500 mb jet moving into the region and the sub freezing 850 mb
temperatures out by 21z/Mon it could be a self destruct sunshine day
over N lower, but probably without the rain. 2) skies don`t look
like they clear out until after sunset as the better subsidence and
dry air moves into the region. So current forecast is for around 32F
give or take a degree, especially in NE Lower. There is some support
for this within the models, and the bias corrected MOS numbers, so
will lean cold on this and look at the pot frost grids. 3) Current
Min RH in the forecast for Tuesday afternoon is about 30-35% but
with the amount of dry air and the amount of mixing expected,
especially over NE Lower, where there is more sand, think that Rh by
18z-21z/Tue will be maybe 25-30%, especially in the light of the low
temperature start for the day.

.LONG TERM...(Tuesday night through Saturday)
Issued at 222 AM EDT Sun May 19 2019

High Impact Weather Potential...Thunder possible on Wednesday.

Extended (Wednesday through Saturday)...Wednesday, a vigorous speed
max at 500 mb moves through the region in the afternoon/evening,
which would produce thunderstorms with the weak warm front that is
moving through Upper Michigan. Thursday, begins the repeat of the
current situation, as the low moves into the Northern Plains and the
warm front/500 mb jet is stretched over N Lower. Rain, is expected,
although the GFS would suggest more thunder, and the ECMWF is
backing off of the extended rain. Friday,The GFS has what looks like
a solid line of showers/thunderstorms, and the ECMWF has a very
broken line, with the the main forcing north and south of the
forecast area. The GFS qpf field looks like it could be broken, so
will make sure that the pops are lower for that time if they aren`t
already. Saturday looks like dry, although the GFS has little short
wave troughs and some moisture kicking off showers, while the ECMWF
is dry the whole day. will try to make sure that any pops will
remain low as well.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 724 AM EDT Sun May 19 2019

Sfc low pressure and a warm front lift into the region today, before
exiting this evening, along with the system cold front. Widespread
showers and embedded thunderstorms will blanket northern Michigan,
along with an expectation for widespread IFR/MVFR CIGS and reduced
VSBYS. A few of these storms may be severe, mainly south of M-72,
but confidence is not very high for severe weather, as there is an
expectation for the low levels to remain in low clouds (MVFR), thus
limiting destabilization of the atmosphere. While showers taper off
into tonight, solid MVFR/IFR CIGS are expected to continue, along
with periods of potential drizzle.

&&

.MARINE...
Issued at 222 AM EDT Sun May 19 2019

Sfc low pressure and a warm front lift into the region today, before
exiting this evening, along with the system cold front. Advisory
level easterly winds for the Straits region and far nrn sections of
Lake Michigan and Huron are still expected through early to mid
afternoon, before the gradient relaxes. Winds may go southerly in
many of the srn nearshore waters, before winds gradually turn more
SW, then NW through the day Monday with many nearshore waters
possibly needing additional advisories. Higher pressure and lighter
winds then move in Monday night.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 4 PM EDT this afternoon for
     LHZ345>347.
LM...SMALL CRAFT ADVISORY until 4 PM EDT this afternoon for LMZ341-
     342.
LS...SMALL CRAFT ADVISORY until 4 PM EDT this afternoon for LSZ321-
     322.
&&

$$

NEAR TERM...SMD
SHORT TERM...JL
LONG TERM...JL
AVIATION...SMD
MARINE...SMD

NWS APX Office Area Forecast Discussion