Area Forecast Discussion
Issued by NWS Gaylord, MI

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770
FXUS63 KAPX 210010
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
810 PM EDT WED JUL 20 2016

.SHORT TERM...(This evening and overnight)
Issued at 343 PM EDT Wed Jul 20 2016

Overview...High pressure at the sfc is centered over the Atlantic
seaboard this afternoon, and is spread as far west as the Upper
Great Lakes. The return flow is mainly to the west in Wisconsin,
where the thunderstorms are currently riding along the 500 mb flow.
This has produced hazy, hot, and humid conditions over the region.

Also to the west is a flat ridge in the N Plains which will factor
into our thunderstorm concerns overnight.

Tonight...Timing for the thunderstorms overnight is uncertain, as
the models are giving somewhat differing solutions for the timing
and extent overnight. The GFS has a complex that fires up around
21z, in N Wisconsin, and continues into C Upper overnight, bringing
showers to the E Upper and possibly NW Lower by 06z which then
freeze over Upper Michigan through the night before descending
across the Straits around 12z. The ARW/NMM/NAM and ECMWF, all fire
off some thunderstorms late this afternoon/early evening, before
diminishing for a time. The NAM/NMM/RAP and ECMWF continue with
minimal showers through 12z. The ARW, is reorganizes thunderstorms
around 09z bringing a complex into NW Lower by 12z. So, have trended
toward the mode of the models with lower to no pops in E Upper and
NW Lower. The outliers are the ARW and the GFS, with rain getting
into the forecast area before 12z, so have held off on pushing pops
into the N Lower until after 12z.

.LONG TERM...(Thursday through Wednesday)
Issued at 343 PM EDT Wed Jul 20 2016

High impact weather potential:  Severe storms possible Thursday
afternoon and evening.  Hot and humid weather on Thursday with heat
index values between 95 and 100 degrees.

Complex but potentially high impact weather for Thursday, with
severe possibilities hinged on the evolution of earlier convection.
Expect some form of convective complex to be ongoing Thursday
morning over Wisconsin/Western Upper Michigan, with this activity
diminishing during the morning as it leaves better dynamics.  How
much debris cloudiness lingers across the area and the placement of
outflow boundaries always difficult to pinpoint in these types of
scenarios. Elevated mixed layer will spread east into Northern
Michigan over the top of a surge of low level moisture with
strengthening low level flow.  Incredible PWAT`s on the order of 2
to 2.5 inches working into the Great Lakes, which would be on the
order of 150-200% of normal. Despite some potential lingering
cloudiness associated with morning decaying convective complex,
plenty of juice for the afternoon with MUCAPES on the order of 2-3k.

Models paint new storm development over Upper Michigan into
Northeast Wisconsin Thursday afternoon in the proximity of weak cold
front and leftover outflow boundaries from the morning complex.
This activity will then push east/southeast into Lower Michigan
through the afternoon/evening hours.  Combination of strengthening
low-mid level veering flow and strong instability support strong
updraft development with organized convective complex producing
damaging winds and large hail.  Strongly veered flow and high
surface based instability point toward the possibility of right
moving supercells with isolated tornadoes possible.  Will highlight
severe potential in graphics, HWO and Top News web story.

Much quieter weather Friday and Saturday, with slightly lower
humidity levels behind the departing shortwave.  May have some
morning cloudiness on Friday over southern areas, but that should
give way to lots of sunshine as drier air aloft pushes in from the
northwest. Plenty of heat, with 850mb temperatures of 18-20c
yielding high temperatures in the upper 80s to lower 90s.  Little in
the way of convection with developing mid level capping inversion.
So just hot and dry - a good couple of days to stay in the air
conditioning or close to the water.

Extended Forecast July 20 2016 (Saturday through Tuesday)

A trough at 500mb begins to push east Sunday through southern
Manitoba into Lake Superior by Monday. The accompanying surface low
and cold front will bring increased rain and thunder chances during
the day Sunday. High pressure filters in quickly behind the exit of
the cold front Monday, making the area much more comfortable through
the remainder of the extended period. Temperatures will fall to the
low 80s Sunday, but will remain humid due to high dewpoints until
the overnight hours Sunday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 810 PM EDT Wed Jul 20 2016

Evolution of showers/storms over the next one to two days is the
main forecast problem.

High pressure over the mid Atlantic coast will remain in control
of northern Michigans weather through most of tonight, with solid
VFR conditions persisting. Upstream, lots of warm/unstable stretches
up through the plains to subtle surface low pressure in the
Dakotas. Several clusters of thunderstorms are now developing in
that region and up into Canada. Some of that activity may spread
into northern Michigan Thursday morning through midday. Additional
thunderstorm development is possible Thursday afternoon and into
the evening, but will depend on how things evolve. Right now, best
chances at the terminal sites for shra/tsra appear to be late
morning through mid afternoon. Otherwise, conditions will remain
VFR.

&&

.MARINE...
Issued at 343 PM EDT Wed Jul 20 2016

Tonight Through Friday...Overnight should be relatively quiet with
the winds out of the south to southwest below small craft criteria
with the inversion. However, as the inversion breaks down and mixes
out, the winds will increase at the tightening gradient and the
winds will begin to gust over small craft around 15z in Lake
Michigan. This lasts into Thursday evening, but by 06z we should be
down with the wind and waves. Friday, looks to be back to quiet
weather again as high pressure builds back into the region.


&&

.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

SHORT TERM...JSL
LONG TERM...Keysor/TJL/SML/BPH
AVIATION...Adam
MARINE...JSL



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