Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Gaylord Michigan
700 PM EDT Tuesday Jul 22 2014

issued at 349 PM EDT Tuesday Jul 22 2014

Showers and thunderstorms are possible through the late afternoon
and evening as a cold front crosses the area. Cooler and much less
humid conditions are expected Wednesday through the end of the
week...with rain chances expected to return as we head into the


Short term...(this evening through tonight)
issued at 349 PM EDT Tuesday Jul 22 2014

..a little convection possible through early evening...

High impact weather potential: a very low end threat for severe
convection through early evening...otherwise nothing later tonight.

Pattern summary: broad upper trough in place along the northern
tier...with an embedded Delaware-amplifying shortwave shearing out across
Northern Lake Superior. A cold front as of 19z lies from about Luce
County down toward the Nebraska/Kansas border. Airmass ahead of this
feature is fairly unstable across northern Michigan...with combo of
middle 80s temperatures and dew points well into the 60s beneath a plume of
steeper 850-650mb lapse rates providing MLCAPE values up around
1500-2000 j/kg. However...things are strongly capped down
low...courtesy of an axis of +18c air folding in just ahead of the
frontal boundary. Quite the robust axis of linear convection an hour
or two ago along the leading edge of the weakening upper vorticity...with
one or two healthy cores working on all that instability. However...
those have weakened considerably recently as they encounter a much
more capped environment...and the upper forcing is quickly waning.

Pushing into early evening...questions remain about just how much
additional convection we can achieve. Certainly it doesn't help that
we are losing our upper forcing...instead having to rely more on
frontal convergence to help try to break the cap. Per satellite
analysis...there appears to be a bit of a better defined vorticity tail
just ahead of the boundary...which may just help our cause a tad the
next couple hours...helping activity unzip southward just ahead of
the actual cold front. However...still not overly sold on widespread
activity for any one location...and will continue with a scattered
wording through about 03z...before the front clears the County Warning Area and
drier air gradually works into the picture.

From a severe weather standpoint...the needed instability is certainly
there...along with at least modest wind shear...with effective shear
values up around 30-35 knots...though largely sandwiched below
500mb. Can't rule out an isolated stronger wind gust given some 40
knots through the 850-700mb layer. In addition...any stronger cores
should be able to squeeze out some sub-severe hail...with a very
warm environment (freezing levels above 15kft) serving to modulate
that threat. Have already seen this in action...with an earlier
storm over Beaver Island (50dbz up to around 45kft) producing only
nickle sized hail. Still something to watch closely into early
evening but confidence is just not very high that any widespread
severe weather threat exists (or that many spots will get rain across
northern lower for that matter).

Active weather should quickly wind down no later than 03z with the onset
of drying aloft as the front passes. From a pattern recognition
standpoint...looks like there is a window for lower stratus
development as strong sub-850mb cooling kicks into gear beneath
lingering warmth aloft. Saw quite a bit of this upstream behind the
front this morning and see little reason there won't be some pesky
stratus up through sunrise...likely slowly decaying from the north
after 09z as markedly drier air works into the region. A mild start
to the evening with lots of 70s/lower 80s...but things should cool
off quite nice later tonight.

Long term...(wednesday through tuesday)
issued at 349 PM EDT Tuesday Jul 22 2014

..cooling back down for the next several days...

Overview: a four-wave hemispheric pattern in place today with low
amplitude troughing in the Gulf of Alaska and western Atlantic.
Somewhat zonal flow across noam with the main belt of westerlies
across Canada and large middle level dome of high pressure across the
southern states. Maximum temperatures well into the 80s and 90s common across
the Continental U.S. Yesterday. But potent short wave energy and associated surface
low now moving through the far northern Great Lakes/Ontario with a
trailing cold front pushing through the Great Lakes. This system
will force buckling/troughing in the overall flow across the Great
Lakes/NE states through the balance of the week and and drag cooler
air into the region. Beyond that...good agreement among the Euro/GFS
solutions shifting the long wave ridge back into the western Continental U.S..
one more piece of strong energy gets dislodged from the Gulf of
Alaska by this weekend and eventually carves out deeper troughing
across the Great Lakes/New England region early next week. This
signals the potential for another July cool down squashing daytime
temperatures back down through the 60s.

Wednesday/Wednesday night...transitional day on Wednesday. Surface cold
front will be pushing S/east through the lower Great Lakes early
Wednesday morning with surface high pressure building into the western
Great Lakes Wednesday afternoon through Wednesday night. Northerly
flow over the northern Great Lakes will drag cooler and drier air into
the region. But...think there will be a fair amount of stratus
across northern Michigan by morning as cooler air undercuts a relatively
warm/moist boundary layer that will take a good part of the morning
to thin out. Even then...forecast soundings reveal a fairly deep surface
based mixed layer for the afternoon (near 6k feet) and room for some
cumulus/stcu to linger. So...will start the morning cloudy...
transitioning to partly sunny for the afternoon. Daytime highs will
run below normal once again...upper 60s to middle 70s with the
warmest spots in the southeast counties.

Thursday through ridging develops across The Rockies
and into the northern plains while surface high pressure slowly works its way
southeast through Michigan and down through the Ohio Valley through Friday.
This will set the stage for dry weather to wrap-up the work week. A
good amount of sunshine for Thursday but a bit more middle and high
level clouds on Friday in advance of a system that will impact US
this weekend (see below). Temperatures...rebounding back into the 70s for
Thursday and Friday...especially Friday as SW flow redevelops across
the region.

Saturday through Tuesday (extended periods)...a couple pieces of
short wave energy break free from the Pacific northwest...advance through the
northern plains before digging out a substantial trough across the Great
Lakes into New England early next week. The overall weather trend
will certainly be cooler and more unsettled through this stretch of
the forecast...although details remain a bit fuzzy at this point
given varying solutions among the medium range guidance over the
exact evolution. Gem/GFS solutions drag a weaker lead short wave and
surface low/warm front across the region as early as Saturday suggesting
a decent shot at some showers/storms. Euro keeps this system
suppressed across the Midwest with high pressure remaining largely
in control of northern Michigan. Inherited Chancy probability of precipitation for Saturday
and Saturday night and will keep it that way for now...although
I/M not convinced. But all guidance pulls a stronger wave down
through the Great Lakes Sunday into Monday carving out our
aforementioned cool/deep trough that will then linger for a good
part of next week and bring chances for showers...especially
Sunday and Monday. So...back to below normal temperatures once again.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 700 PM EDT Tuesday Jul 22 2014

VFR conditions will diminish to MVFR ceilings later this evening as an
area of low clouds spreads into northern lower Michigan in the wake of a
cold front. In the meantime...a few showers and an isolated
thunderstorm remains possible along and ahead of this front...but
the chance is too small to include in the tafs for now. MVFR ceilings
will lift and mix out into scattered cumulus by Wednesday afternoon. SW
winds gusting to 20 kts will shift to the northwest later this evening
behind the front...and then to the north on Wednesday. Gusts of 20
to 25 kts will remain possible through the entire taf forecast


issued at 349 PM EDT Tuesday Jul 22 2014

Gusty southwest winds will continue through early evening ahead of
an approaching cold front...shifting northwest and then north later
tonight. Small craft advisories will continue through the
night...with winds expected to slowly subside into Wednesday and
especially Wednesday night as high pressure arrives. Light west
winds should be the rule into Thursday...perhaps increasing back
toward 15 knots or so out of the southwest by Friday ahead of a
series of weak low pressure systems slated to arrive for the


Apx watches/warnings/advisories...
LH...Small Craft Advisory until 2 PM EDT Wednesday for lhz345>349.
Lm...Small Craft Advisory until 2 PM EDT Wednesday for lmz323-341-342-
Ls...Small Craft Advisory until 2 PM EDT Wednesday for lsz321-322.


short term...Lawrence
long term...Adam

National Weather Service Glossary of Abbreviations