Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 170750
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
350 AM EDT Wed May 17 2017

.NEAR TERM...(Today through Tonight)
Issued at 350 AM EDT Wed May 17 2017

...Warm and unsettled through tonight...

High Impact Weather Potential...Periodic thunderstorms will impact
far northern and western parts of the CWA through tonight.
Marginal risk for severe storms.

Pattern Synopsis/Forecast...Broad upper level ridge axis now sits
through the eastern Great Lakes this morning...downstream of long
wave troughing through the western CONUS and SW flow through the
Plains and Midwest. Strong short wave impulse and upper jet streak
noted over NW Texas lifting into the plains. At the surface...high
pressure is anchored offshore of the SE states pumping warm/humid
air into the eastern CONUS. Elongated low pressure/trough stretches
from the front range of the Rockies into the western Great Lakes
and has becoming the focus for several ongoing convective systems
spanning from Texas...through the plains and into western/central
upper Michigan. A few showers and decaying storms have made it
into eastern upper Michigan during the course of the night.

Meanwhile...surface warm front stretches from central upper
Michigan down through the straits/tip of the mitt and into Lake
Huron. High and dry across lower Michigan at the moment...within
the somewhat capped warm sector...with overnight temperatures more
akin to full-on summertime.

Strong short wave impulse and attending surface low will advance
quickly through the plains and into the Midwest today...before
lifting up through the western Great Lakes tonight. Elongated
surface trough remains draped up through the western and central
U.P. and will remain the main focus for shower/storm development
through the day. Arrival of short wave trough and attending
surface low/cold front tonight will finally kick showers/storms
into lower Michigan tonight through Thursday...followed by an
abrupt cool down (back to near normal) heading into Friday.

Primary Forecast Concerns...Shower/thunderstorm chances and
timing through tonight. Perhaps a marginal risk for severe storms
late tonight-Thursday morning.

Today: As mentioned above...main focus for showers/storms today
and a good part of tonight will reside from the plains up through
Wisconsin and the western half of the upper peninsula...along the
nearly stationary elongated surface trough running up through that
area. Eastern upper Michigan (and possibly a skiff of NW lower
Michigan) will see periodic shower/thunderstorm chances through
the day as ongoing activity continues to ride northeastward along
and just ahead of the trough.

South of the bridge...a warm but somewhat capped atmosphere
remains intact through the day and should prevent any convection
from firing or migrating into the region through the day. So very
warm temperatures are on tap under partly-mostly sunny skies and
a bit breezy with highs spanning the 80s...warmest readings
anticipated across NE lower Michigan/tip of the mitt area due to
downsloping SW flow. Record highs for today run the upper 80s to
low 90s and are probably safe...although it might be close for a
few spots.

Tonight: Short wave impulse/attending surface low lifts up into
northern Michigan by morning...surface low tracking up through NW
lower Michigan and the straits...before cold front kicks through
the region on Thursday. Ongoing showers/storms will finally get
pushed into northern lower Michigan...mainly overnight into
Thursday morning.

Severe storm potential: 40 to 50 knot mid level flow and some
modest instability advecting into the region will present a
marginal severe storm threat into eastern upper Michigan today.
Slightly better probabilities for severe storms later tonight
into Thursday across the CWA as mid level flow further increases
to 50 to 60 knots and better instability advects into the region
ahead of the low/cold front.


&&

.SHORT TERM...(Thursday through Friday)
Issued at 350 AM EDT Wed May 17 2017

...Thunder and turning colder during Thursday dry Friday...

High Impact Weather Potential...Thunderstorms Thursday morning.

Pattern Synopsis/Forecast...Models are in agreement for the cold
front to push through the forecast area during the day. Models also
suggest that the high will occur in the morning and cool through the
afternoon. So, looking at the SREF idea, there is decent mean MLCAPE
(around 1000J/kg) and mean Effective Shear (45-50 knots) at some of
the forecast points. The GEFS plumes look even better. Therefore, it
looks like there is the possibility of some severe storms at least
early in the day, as the front moves through. Once the front moves
through, the instability is lost and the chances begin to fall off.

After 00z/Fri, the sfc low moves NE out of the forecast area, and
the 850 mb RH drop precipitously (RH<10%). This remains through the
day as the high sits over the region with the core of it up near
James Bay. Winds remain light and with 850 mb temperatures of +5C
will expect temperatures around 60F for the highs. While the
temperatures don`t get warm enough or the winds high enough for fire
weather issues, the dry air could pose a bit of an issue, so lowered
the RH and dewpoints for the afternoon significantly. The dry air
remains in place as the 500 mb ridge axis remains over the region at
the same time as the sfc ridge. So will expect that the temperatures
will drop a little lower over night as well.

Primary Forecast Concerns...thunderstorms will be an issue in the
morning as the front moves through as outlined above. The spread on
this isn`t very large, so the models look like they are onto
something at this point.

High temperatures on Thursday could be overdone as the Superblend
gave the 70s, but the actual MET and MAV numbers are around 60 and
mid 60s respectively at GLR. This is all a timing issue with the
cold front. This could affect the thunderstorm issues in the morning
as well, if the front moves through the region early. There is a
high bust potential for this forecast.

Friday, the low RH idea looks like it should work out. The SREF
Dewpoints (at least in the plumes) show that we bottom out around 30
on the driest member, but then again, these models in these mixing
situations don`t typically handle the spring pre-greenup dryness.

&&

.LONG TERM...(Friday night through Tuesday)
Issued at 350 AM EDT Wed May 17 2017

High Impact Weather Potential...None.

Extended (Saturday through Tuesday)...The models are in agreement
with the next system moving into the region during Saturday evening,
bringing thunderstorm chances. The thunderstorm chances remain
through Sunday, when the front moves through the region. Monday is
dry. Next system moves through Monday night and Tuesday as 500 mb
low drops into the Upper Great Lakes. This will put us into the
below normal temperature territory for the early part of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1154 PM EDT Tue May 16 2017

VFR. LLWS tonight, and again Wed night.

Occasional mid/high clouds will persist thru Wednesday, while best
chances for rain remain in upper MI. Precip chances will be
picking up again into Wed evening, as a cold front moves in from
the nw. Still expecting VFR conditions.

Southerly surface winds; these will become gusty on Wednesday.
LLWS tonight, with strong sw-erlies just off the surface. Similar
for Wed night.


&&

.MARINE...
Issued at 350 AM EDT Wed May 17 2017

...Small craft advisory conditions through Thursday night...

Breezy SW flow will be felt on the Great Lakes today with small
craft advisory gusts and waves on a good portion of Lakes Michigan
and Huron. Winds veer into the west and eventually NW through the
day Thursday as a strong cold front passes through the region.
Gusty winds persist behind the front into Thursday
night...diminishing heading into Friday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY until 6 AM EDT Thursday for LMZ323-344>346.
     SMALL CRAFT ADVISORY until 6 PM EDT this evening for LMZ341-342.
LS...NONE.
&&

$$

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



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