Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
1249 PM CDT Monday Jul 25 2016

Update...
issued at 1240 PM CDT Mon Jul 25 2016

Updated to include 18z aviation discussion below.

&&

Short term...(today and tonight)
issued at 348 am CDT Mon Jul 25 2016

Few concerns in the short term as high pressure along the
Dakotas/Minnesota border early this morning glides southeast to the lower
Great Lakes by Tuesday morning. Abundant sunshine today with
afternoon 850 mb temperatures climbing into the +16 to +22 degree
range from Eau Claire to Alexandria respectively. Mix-down from
this level yields highs in the lower to middle 80s with upper 80s
in the western forecast area where the higher 850 mb temperatures reside.
This agrees well with the observed highs on Sunday to our west
with corresponding 850 mb temperatures.

Low level southwesterly flow will increase Minnesota tonight on the
backside of the high pressure system. 925-850 mb winds rise into
the 35-40 knot range from the Buffalo Ridge on northeast into
central Minnesota by daybreak Tuesday. Elevated instability also develops
during the overnight hours in the eastern Dakotas and pushes into
northern and central Minnesota. The NAM 310k Theta surface shows very
strong upglide spreading across the Minnesota forecast area after 06z. Various cams
do show some widely scattered activity across central Minnesota in the
09z-12z time frame. Concerned this may be underdone due to the
strength of the upglide moisture advection. It's possible that
some of the activity seen in the cams is altocumulus castellanus. At any rate, began
small pops across west central into central Minnesota after 09z.

Raised low temperatures over the previous forecast by a few
degrees tonight due to the increasing low level warm air advection along with
some mid level cloudiness. The lows may still not be warm enough
downwind of the Buffalo Ridge as well as in the Twin Cities where
around 70 degrees was forecast.

Long term...(tuesday through sunday)
issued at 348 am CDT Mon Jul 25 2016

Main source of uncertainty in the extended continues to be with
precip chances Tuesday through Saturday. Though the forecast may
read gloomy with chances for precip day and night through this
period, it will likely just be mostly cloudy most of the time. The
threat for severe weather still looks low, with the period having
the best chance for seeing precip being Wed into Thu.

The culprit for the proliferation of chance pops in the forecast is
a slow moving open trough/wave that will be working across the upper
MS valley Wed and Thu. At the surface, a rather diffuse frontal
boundary will drop down out of northern Minnesota Tuesday and will slowly
wash out across southern Minnesota on Wednesday. This frontal boundary will
serve as a focus for isolated to scattered storms across central Minnesota
Tuesday. Wednesday, moisture pooled into southern Minnesota will create a
diurnally unstable environment, with scattered storms likely on
Wednesday. Thursday, the focus for precip should shift south as a
surface low begins to slowly take shape across northern MO. It still
looks that acitivity will be largely diurnally driven, with limited
low level jet forcing to help sustain activity overnight.

The strength of the low that develops over MO on Thursday will help
determine our precip chances for Fri/Sat. The European model (ecmwf) continues to
develop a stronger wave at the end of the week, which would keep the
mpx area largely dry for Friday and Saturday. The GFS doesn't
really ever develop a surface low to our south, which allows it to
bring another wave and associated precip chances into Minnesota for Friday
and Saturday.

Have continued to cap pops in the chance range with little
discernible focus for storms. Have the best chances Wednesday and
Thursday, with chances dropping for Friday and Saturday thanks to
more drier solutions starting to make an appearance.

Not anticipating any severe weather this week either with shear
looking to be minimal. Hodographs this week reflect this and expect
the activity we see to be of the pulse variety, with only an
isolated hail/wind threat existing.

For temperatures, Tuesday will be our warmest day as a warm nose
gets pulled into southern Minnesota out ahead of the cold front. Highs
Tuesday will be dependent on how much sun we see. If clouds are
minimal, then upper 80s with a few 90s is where we are heading. If
it ends up mainly cloudy, then all we will be able to hit are the
lower to mid 80s. After Tuesday, the combination of increased cloud
cover and slightly cooler 925/850 temps will keep highs comfortably
in the 70s until the weekend when both more sun and the return of
southerly winds will allow highs to start climbing back into the 80s.

&&

Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1240 PM CDT Mon Jul 25 2016

Very few concerns this taf cycle. High pressure will slide off to
the east tonight through tomorrow, allowing clouds to very slowly
increase late tonight. High clouds will filter in first then some
mid-level clouds will follow, including some ceilings in western
Minnesota. During this 24-hour period, only kaxn may be susceptible to
some light -shra from daybreak Onward tomorrow. Northwest winds will
shift to become generally southerly overnight through tomorrow
with speeds below 10 knots.

Kmsp...VFR through the period with no additional concerns.

/Outlook for kmsp/
Wed...mainly VFR. Chance MVFR/tsra. Winds variable 5 kts.
Thu...mainly VFR. Chance MVFR/tsra. Winds NE 5 kts.
Friday...mainly VFR. Chance MVFR/tsra. Winds east 5 kts.

&&

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

$$

Update...jpc
short term...rah
long term...mpg
aviation...jpc

National Weather Service Glossary of Abbreviations