Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 261045

Area Forecast Discussion
National Weather Service Gaylord MI
645 AM EDT Sat May 26 2018

.NEAR TERM...(Today through Tonight)
Issued at 343 AM EDT Sat May 26 2018

...Very warm, more humid with possible storms...

Primary Forecast Concern...Pops and severe weather potential.

Zonal to weakly cyclonic flow through the period with weak short
waves moving through the flow at times (one of which is evident on
water vapor imagery over northwest Wisconsin). This in combination
with very warm temperatures and a decently moist airmass in place
(pw/s in the 1 to 1.5 inch range) will likely spark afternoon
showers and thunderstorms. Models have between 1000 and 2000 j/kg of
mixed layer cape and soundings don`t show much of a cap so with the
heating of the day expect scattered to numerous coverage on storms.
The potential for severe overall still looks low with little shear
in evidence (0-6 km bulk shear generally under 30 knots) but can not
totally rule out damaging winds from a pure downward momentum
standpoint. Freezing level is around 11,000 feet but wet bulb zero
heights are only about 9,500 feet which supports the possibility of
marginally severe hail.

Today...Ongoing convection centered over Lake Michigan should
generally fizzle out over the next couple of hours with the loss of
the nighttime low level jet. This should lead to a lull in activity
for a few hours until we heat up later this morning into this afternoon
likely bringing in showers and storms as mentioned above. Highs
today ranging from the upper 70s north to the middle 80s south.

Tonight...Expect any lingering convection to diminish by late
evening. This will be followed by chances for additional showers and
storms which would likely originate to our west over eastern
Wisconsin. Muggy with lows ranging from the middle 50s north to the
lower 60s south.


.SHORT TERM...(Sunday through Monday)
Issued at 343 AM EDT Sat May 26 2018

...Still very warm with small rain chances...

High Impact Weather Potential...A few thunderstorms possible on
Sunday afternoon.

Pattern Synopsis/Forecast...An active pattern develops well upstream
on Sunday with a cutoff low rotating over the Rockies and a building
ridge over the Plains. A few pieces of energy breaking off from that
cutoff low will ride the northern periphery of the ridge into the
Upper Great Lakes through Memorial Day, providing continued small
chances for showers and storms at times.

Primary Forecast Concerns...Continued small chances for showers and
thunderstorms. Also persistent heat for interior northern Lower.

Despite surface high pressure weakly building in from the south and
rising heights aloft, weak periodic disturbances rippling around the
northern periphery of the upstream ridge may be sufficient for
additional shower/storm chances at times, particularly on Sunday.
Sunday`s heat combined with dew points in the low to mid 60s should
yield favorable diurnal instability with MLCAPE perhaps in excess of
1500 J/kg. Cloud cover should also be limited, which would further
promote increased daytime instability. However, wind shear will
still be rather weak, with only a few transient pockets of 30-40 kt
0-6km bulk shear. At any rate, Sunday`s forcing looks to be weaker
than Saturday, so have limited PoPs to ~30% or less mainly for areas
east of I-75. It appears the gradually increasing subsidence should
serve to limit overall rain chances on Memorial Day. The NAM and GFS
both show a decaying MCS over the Upper Peninsula Monday morning,
pretty much dying out before reaching our doorstep. Will have to
monitor this potential, but the rest of the day looks pretty dry.

Sunday and Monday will continue to be hot for portions of interior
northern Lower. 925mb and 850mb temperatures will be 2 to 3 standard
deviations above the mean over northern Michigan, and guidance would
suggest some areas getting into the lower 90s both afternoons.
Humidity looks to be restrained enough so as to keep heat indices
generally in the upper 80s to low 90s across interior northern
Lower, though.

.LONG TERM...(Monday night through Friday)
Issued at 343 AM EDT Sat May 26 2018

High Impact Weather Potential...Some thunderstorms possible
Wednesday and Thursday afternoons.

A weak cold front dropping in late Monday will bring a slight
reprieve from the heat heading into Tuesday, but temperatures will
still remain above normal through the rest of the work week. Strong
Canadian surface high pressure passing by to our northeast on
Tuesday will provide more dry weather. Increasing return flow on the
back side of this system combined with an approaching shortwave over
the Northern Plains will promote shower/storm chances heading into
Wednesday and Thursday. Medium range guidance then diverges
significantly heading into Friday, but it looks like an unsettled
pattern may continue.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 642 AM EDT Sat May 26 2018

Mainly vfr conditions are expected at all four taf sites through
the period. Scattered showers and possibly thunderstorms forecast
for this afternoon and evening. The best chance of thunder is at
kapn. No precipitation is expected late tonight/early Sunday.


Issued at 343 AM EDT Sat May 26 2018

Winds will be mainly light, mostly out of the south/southwest
through Sunday. The north end of Lake Huron will be the exception,
with winds Saturday afternoon out of the southeast/east roughly
as you get north of Thunder Bay. Chances for scattered
thunderstorms will continue through the weekend, which could
produce some small hail and some localized gusty winds.




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