Area Forecast Discussion
Issued by NWS Gaylord, MI

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205
FXUS63 KAPX 201518
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1118 AM EDT WED JUL 20 2016

.UPDATE...
Issued at 1050 AM EDT Wed Jul 20 2016

High pressure is over the region. Main areas of clouds and
convection is well to the west in the Upper Mississippi Valley and
moving SE. So the expectation is for nothing but sunshine and warm
temperatures today.

&&

.SHORT TERM...(Today and tonight)
Issued at 335 AM EDT Wed Jul 20 2016

High pressure remains over much of the Great Lakes region early this
morning...the center of which is in the process of sliding east of
Michigan. Dry weather continues across all of Michigan at this
hour...but mainly high clouds are increasing across Upper and
Northern Lower Michigan from an area of dissipating upstream
convection over Northern Minnesota. This area of convection
developed along a warm front associated with low pressure developing
to the lee of the Rockies...but is rapidly falling apart with loss
of diurnal instability and diminishing moisture with eastward
progress.

Warmer air will begin to lift northward into Michigan today as low
level southerly flow/WAA starts to strengthen ahead of low pressure
developing over the Northern Plains. Low level moisture will also
gradually increase today...resulting in a steady increase in
instability from west to east thru tonight. However...strongest
instability and as well as 850 mb theta e ridging will remain west
of our CWA over the Upper Mississippi Valley...Western Upper
Michigan and Wisconsin thru 12Z Thursday. This will maintain focus
for convective development within this region...leaving our CWA
generally high and dry today thru this evening. Latest NAM12 and
RAP13 show MCS development will take place upstream of our CWA this
afternoon and evening during peak instability...the remnants of
which will make a run at the NW half of our CWA overnight. Will
remove all POPs across our CWA thru 00Z Thursday...and will keep
chance pops for the NW half for late evening and overnight. MCS
should be diminishing by this time with loss of diurnal instability
and with eastward progress away from better upstream moisture.
Thus...do not expect severe storms thru 12Z Thursday.

Strengthening WAA and partly to mostly sunny skies should boost
temps well into the 80s this afternoon. Increasing clouds tonight
with ongoing WAA will limit diurnal cooling...with overnight lows
only falling into the mid 60s to around 70 degrees.

.LONG TERM...(Thursday through Tuesday)
Issued at 335 AM EDT Wed Jul 20 2016

...Severe Thunderstorms Possible Thursday...

The well advertised strong ridge of high pressure centered to our
south will remain across the region into the weekend. This will
result in unseasonably warm and humid conditions (essentially a heat
wave). In addition...periodic upper level waves will top the ridge
and bring chances for showers and thunderstorms to northern Michigan
from time to time. The best shot at storms looks to be Thursday into
Thursday evening and again Saturday night into Sunday. There is even
the potential for severe storms to form, especially Thursday
afternoon and evening. Not as warm nor as humid conditions move in
for early next week. The main forecast concerns revolve around the
severe weather potential Thursday.

Thursday into Thursday evening...Much warmer and more humid
conditions continue to spread into the region. Models increase
precipitable waters to a remarkable 2 to 2.50 inches with surface
dewpoints pushing into the upper 60s and lower 70s. A short wave
evident on water vapor imagery over Washington state will top the
ridge and track east southeastward possibly spawning severe storms
Thursday afternoon and evening (maybe in the form of a mesoscale
convective system). Although many questions remain about the
initiation, timing and placement of storms there are many favorable
ingredients in place. Wind fields look impressive with 0-6 km bulk
shear of 40 to 50 knots and moisture is extremely impressive as
noted above. There is also a decent amount of directional shear so
an isolated tornado can not be ruled out...although damaging winds,
large hail and torrential downpours appear to be the primary threats
for the afternoon and evening hours. Highs of well into the 80s to
the lower 90s with heat indexes pushing into the lower and middle
90s.

Overnight Thursday into Saturday...Slightly less humid air advects
in behind the departing short wave. However, it will remain hot and
humid. Models have a decent capping inversion as well an absence of
deep moisture at mid and upper levels so do not expect much in the
way of convection to form. Lows in the muggy 60s to lower 70s and
highs in 80s to lower 90s.

Saturday night into Sunday...A decent trough tracks from the Pacific
across southern Canada and eventually drags a cold front into the
region (likely during the day on Sunday). Decent shot at another
round of showers and thunderstorms. Lows in the muggy middle and
upper 60s and highs ranging from the upper 70s far north to the
upper 80s southeast.

Monday and Tuesday...The trough moves by to the east allowing for
high pressure to build in. Only slight chance pops...though chances
are most spots will be dry. Less humid with highs in the
seasonable middle 70s to lower 80s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 645 AM EDT Wed Jul 20 2016

VFR conditions will persist at all Northern Lower Michigan TAF
sites through tonight as strong high pressure continues to slide
east away from Michigan. S/SW low level winds will begin to advect
warmer air into the region today...but wind speeds will remain AOB
10 kts thru tonight. There is a small chance of showers and
thunderstorms late tonight...but the chance is too small to
include in the TAF for now.


&&

.MARINE...
Issued at 335 AM EDT Wed Jul 20 2016

Conditions will remain below SCA criteria thru tonight...although
some strengthening in southerly flow will bring warmer air into the
region. Further strengthening of southerly flow ahead of low
pressure developing over the Northern Plains will produce SCA
conditions for our Lake Michigan nearshore areas on Thursday.
Chances of showers and storms will also increase late Wednesday
night into Thursday as moisture and instability builds ahead of that
upstream system.


&&

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

$$

UPDATE...JSL
SHORT TERM...MLR
LONG TERM...Sullivan
AVIATION...MLR
MARINE...MLR



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