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fxus63 kmpx 200000 

Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
700 PM CDT Thu Sep 19 2019

issued at 630 PM CDT Thu Sep 19 2019

Updated to include 00z aviation discussion below.


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 Minnesota 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 Minnesota
and there are some indications of a secondary wave traveling
farther south over Iowa/MO region. This may split forcing, but still
looks like there will be a severe threat for much of the central
and eastern County Warning Area 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 County Warning Area into Sunday
afternoon in the cold air advection/cyclonic flow remaining behind exiting cold

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 European model (ecmwf)
shows indicating of split flow developing with cutoff circulation
travels south of Minnesota ate next week. The GFS continues to develop
the trough to west but builds the southeast Continental U.S. Ridge well into
the central Mississippi River valley. This would leave Minnesota/Iowa
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


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 630 PM CDT Thu Sep 19 2019

VFR at all sites to start. There is some concern for MVFR-IFR
conditions for kmsp eastward around daybreak for low stratus
and/or fog. Have maintained that thinking in this set of tafs.
Beyond daybreak tomorrow, there are low chances for precip mainly
north of I-94. Have advertised prob30s at sites which look to have
the potentially best chances for precip. Omitted any mention of
cumulonimbus/ts at this point as convective potential is rather low. issues through midnight then some ground fog may move
into the kmsp area close to the time of the Friday morning rush,
and potentially drop conditions to IFR and/or below 1700ft
ceilings. Conditions improve by late morning then chances for
precip increase just enough in the afternoon to warrant mention.

/Outlook for kmsp/
Sat...MVFR/tsra likely. Wind SW 15g25 kts.
Sun-Mon...VFR. Wind west 5-10 kts.


Mpx watches/warnings/advisories...


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