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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
701 am CDT Tuesday Jul 7 2015

Short term...(today and tonight)
issued at 407 am CDT Tuesday Jul 7 2015

A fine weather pattern in the short term as a 1022mb high over the
northern plains passes across the upper Mississippi Valley. The
fire smoke that caused surface visibility problems on Monday in
the wake of the cold front has moved east and south of the forecast area
early this morning. National oceanic and atmospheric administration air quality forecast guidance indicates
that a band of surface based fire smoke will extend from Nebraska
on northward through the central Dakotas today. The smoke will
remain in place today then begin to dissipate tonight as low
level southerly winds increase on the backside of the surface
high. The vertical smoke integration forecast shows that some high
level smoke and a milky sky will return from the west during the
afternoon and cover much of the region tonight.

The day ahead has a few other concerns. A low level thermal trough
will be dropping south across Minnesota and WI today. A rather extensive
area of stratocumulus over The Arrowhead and northwest WI has been
moving slowly south overnight. Some dissipation has been noted on
the forward edge...which lines up well with the strong downglide
noted on the NAM 290k Theta surface. However...with the thermal
trough moving over eastern Minnesota and WI today...more low cloud
development will likely occur as indicated with the rather
negative cumulus rule from the NAM/rap this morning. Sky condition in
the eastern County Warning Area should be no worse than partly cloudy for a time
this morning...but some short term cloudy periods can/T be ruled
out in west central WI. Sunny conditions will occur across western
Minnesota.

Highs today from mix-down at 850 mb were lower than the various
short term guidance products. Therefore...trended lightly today
with highs about 2 degrees either side of 70. This is some 12 to
14 degrees below normal. Used mix-down for the afternoon dew
points which brought them back down into the middle 40s. Continued
with lows tonight in the upper 40s across portions of central Minnesota
and adjoining areas of west central WI with around 50 to the lower
50 elsewhere. Introduced some patchy late night fog in WI with the
cross-over temperature being met. Indicated most of the fog in the
areas that experienced the heaviest rain Sunday night/Monday
morning.

Long term...(wednesday through monday)
issued at 407 am CDT Tuesday Jul 7 2015

Not a lot of concerns in the extended until we get to the
weekend...when details of the forecast will hinge on when a warm
front arrives and how far north it makes it.

We will start the long term with high pressure centered over WI
Wednesday morning. As this high works east...the return of srly
winds will result in a gradual warming of temperatures and increase
in dewpoints Wednesday into Thursday. For both days...favored the
high forecast more toward a European model (ecmwf)/Gem blend...as low level thermal
profiles look to warm a bit to quickly with the NAM/GFS.

Thursday...the cold front that is in the process of stalling out
around Oklahoma will begin lifting back north across the plains as a
warm front. We are seeing timing differences on when this front gets
up here...with the GFS being the most aggressive bringing it into
the area Friday night...while the European model (ecmwf) is about 24 hours slower.
Doing a dprog/dt of both models show that both have been
slowing the progression of the front over the last few runs...with
the European model (ecmwf) being the most aggressive with the slowing. This slowing
makes sense...as there will likely be a large complex of
thunderstorms that will develop on the leading edge of the low level jet to
the north of the warm front Friday night...likely slowing its
progress north. Interestingly...when looking at the cips analog
guidance for Saturday...all 15 of the top matches for what the GFS
has forecast for Saturday show a healthy burst of quantitative precipitation forecast occurring to
the north of a warm front...so confidence is pretty high we will see
a large complex of thunderstorms develop Friday night to the north
of the warm front...its just a question of where. Based on how the
GFS/European model (ecmwf) Orient the low level jet and associated moisture transport...the
most likely region for seeing a complex Friday night at the
moment would be from southeast Minnesota to northeast Illinois.

After Friday...its a matter of where will the front end up. Both the
GFS/European model (ecmwf) say we should see a northwest-southeast oriented boundary over/near the
mpx area while also sitting on the northern/eastern periphery of a
subtropical ridge that will be building from the southeast Continental U.S. Up
into the northern rockies/plains by early next week. In other words...we
have a ring of fire pattern potentially setting up for the weekend
into early next week.

The one model that was avoided...at least for temperatures this
weekend was the GFS...as its low level thermal fields are nothing
short of unrealistic. Still...the more realistic European model (ecmwf) has 850 mb
temperatures of nearly 25c coming up behind the warm front...which would
support highs in the low 90s. Right now...Sunday looks to be the day
that has the greatest potential to produce widespread highs in the
90s...as even the southern European model (ecmwf) shows the warm front getting up to I-94
by then. Beside these temperatures...both the GFS/European model (ecmwf) show
dewpoints climbing into the middle 70s this weekend...so we will likely
see oppressive levels of humidity. In fact...the probability of the
maximum heat index exceeding 100 degrees with the cips guidance for
Saturday reaches 60 percent in SW Minnesota...so beside the
thunderstorm/heavy rainfall threat...we will have to keep an eye on
potential heat issues this weekend as well.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 701 am CDT Tuesday Jul 7 2015

Broken-ovc045 will push southward across west central WI and far
eastern Minnesota this morning...associated the low level thermal trough
moving through. Scattered conditions for the afternoon. Kmpx upper air
profile this morning showing 15-20 knot winds off the surface
that will likely mix-down this morning. Hence...added some gusts
for kmpx...krnh and Keau. Otherwise...high pressure over the
Dakotas will move over the taf sites tonight. Some MVFR fog
possible at krnh and Keau. The fog at Keau will likely be river
fog with a light NE wind near daybreak. Conditions could be much
worse than forecast...ie vlifr for an hour or two. No reduction in
the surface visibilities expected today with the National oceanic and atmospheric administration air
pollution guidance forecasts showing it to the south and west.
There will likely be high level smoke spread in from the west this
afternoon according to the aforementioned forecast.

Kmsp...the western edge of bkn045 will brush the Twin Cities this
morning with clear-scattered conditions this afternoon. Some gusts to
15-18 knots this morning as well in the north-northeast flow. Light winds and
clear skies tonight.

/Outlook for kmsp/

Wednesday...VFR. Winds S 5-10 kts.
Thursday...VFR. Winds S 5-10 kts.
Friday...VFR. Winds southeast 5-10 kts.

&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Short term...rah
long term...mpg
aviation...rah

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