National Weather Service Twin Cities Area Forecast Discussion

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163
FXUS63 KMPX 191945
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
245 PM CDT Thu Sep 19 2019

.SHORT TERM...(This evening through Friday night)
Issued at 245 PM CDT Thu Sep 19 2019

Temperatures and humidity levels continue to be abnormally warm for
this time of year across the Upper Midwest. These readings are more
typical for August vs. mid September. Latest satellite imagery this
afternoon depicted the remnants of the decaying thunderstorm complex
across eastern Wisconsin. In the wake of this complex, very little
change in the atmosphere was noted along the Iowa border. There is
even a gradient line noted in the local radar across far southern
Minnesota where low clouds lingered through the afternoon.

The main forecast concern is how widespread or isolated will the
convection become later tonight, and on Friday.

There is a subtle wave noted across central Nebraska this afternoon.
Models have this feature moving northeast across eastern Nebraska,
and into northwest Iowa/southwest Minnesota late tonight. Moisture
advection associated with this feature is weak, but I wouldn`t be
surprised to see a few showers or storms develop along it late
tonight. This feature will likely continue to enhance a few showers
or storms across southwest/south central Minnesota after sunrise
Friday. It may even continue to spread northward Friday afternoon,
but typically an increasing inversion should keep most of the
activity isolated at best. The latest CAMs suggest that most of the
activity will be isolated with the main concentration of storms
across the Dakotas.

Late Friday night should see an increase in showers and
thunderstorms activity, especially in western Minnesota as the
frontal boundary nears, and the upper level energy moves closer to
the region. Still, the bulk of the precipitation should hold off
until after 12z Saturday.

.LONG TERM...(Saturday through Thursday)
Issued at 245 PM CDT Thu Sep 19 2019

The longer term concerns remain convective potential Saturday
along with cooling temperatures.

Saturday continues to indicate severe potential, especially if
morning convection/cloud cover remains sparse and we get
heating/destabilization ahead of the surface cold front. Timing
would bring the front into central MN Saturday afternoon and will
be the focus for any real convection. Models indicate around 2500
J/kg MLCAPE and around 35kts shear associated with boundary as it
moves through. Better lift will move across central/northern MN
and there are some indications of a secondary wave traveling
farther south over IA/MO region. This may split forcing, but still
looks like there will be a severe threat for much of the central
and eastern CWA Saturday afternoon/night.

This system exits the region Sunday morning leaving clouds and
cooler air moving into the area on breezy west/northwest winds.
There may be some showers over the northeast CWA into Sunday
afternoon in the CAA/cyclonic flow remaining behind exiting cold
front.

Timing of the next frontal boundary remains in question with the
deterministic models bring it through in the Tue/Wed time frame.
We will retain the smaller end PoPs for this at the moment and see
if models come into better agreement on timing. Also, the ECMWF
shows indicating of split flow developing with cutoff circulation
travels south of MN ate next week. The GFS continues to develop
the trough to west but builds the southeast CONUS ridge well into
the central Mississippi River valley. This would leave MN/IA
region close to the surface boundary and susceptible to more
prolonged heavy rain threat. Will need to monitor model trends
through next week.

High temperatures will cool through the 70s early next week, with
highs possible struggling to reach 70 by the end of next week. No
significant signal for frost seen through at least the next seven
days.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1220 PM CDT Thu Sep 19 2019

No aviation concerns this afternoon or evening as low cigs/vsbys
and chc of TSRA will be south of MPX Taf area. After 6z,
cigs/vsbys will likely deteriorate across eastern Minnesota, and
into west central Wisconsin. LIFR cigs/vsbys will be possible near
KEAU. Otherwise, a small chc of TSRA late tonight as a frontal
boundary moves northward across southern Minnesota. The best
chance of TSRA will occur after 18z/20.

KMSP...

No additional concerns through 6z. After 6z, there is an
increasing chc of MVFR/IFR conditions. Chc of TSRA are low at this
time before 18z/20, but increase during the afternoon.

/OUTLOOK FOR KMSP/

Fri evening...VFR. MVFR/IFR in TSRA. Wind SE 10G20 kts.
Sat...AM MVFR/TSRA likely. Wind SW 15G25 kts.
Mon...VFR. Wind W 10G20 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...JLT
LONG TERM...DWE
AVIATION...JLT

NWS MPX Office Area Forecast Discussion