Scientific Forecaster Discussion
fxus63 kmpx 182002
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
302 PM CDT Tue Jun 18 2019
Short term...(this evening through Wednesday night)
issued at 250 PM CDT Tue Jun 18 2019
The short term period will be relatively quiet with temperatures
slightly cooler than normal. Very little chance of precipitation
through tomorrow night.
A widespread cumulus field developed this morning across the area
and will remain in place through the remainder of the daytime hours.
A few very isolated showers made in into central Minnesota near Mille Lacs
Lake in association with the pv Max moving across northern Minnesota. Do
not anticipate the showers to make it much farther south as they
should be confined to near the vort Max.
Clouds should dissipate tonight, leaving mostly clear skies in place
across the region. There could be patchy fog in low lying areas as
wind speeds remain very light tonight. High clouds will spill into
the region tomorrow ahead of an approaching system from the west.
Guidance is in good agreement that precip will stay west of the area
through tomorrow night, before the weather turns more active locally
during the long term period.
Long term...(thursday through tuesday)
issued at 250 PM CDT Tue Jun 18 2019
The end of this week into the start of next week will feature a
rather unsettled pattern, mainly due to a slow-moving low pressure
system in conjunction with deep moisture and a split flow aloft.
The period will commence with a low pressure system over the
Dakotas, with its warm front extending into southern Minnesota. Aloft, a
lumbering cutoff low will be slowly rotating eastward over south-
central Canada with an additional low/trough feature over the
southwestern Continental U.S.. the surface low is expected to slowly shift
east through the weekend, dropping into South Dakota Friday then push east
into northern Minnesota Saturday, on its way into western Ontario
province on Monday. The cold/occluded front of this system will
slowly be dragged eastward across Minnesota/WI during this time. The
isentropic lift in advance of this system Thursday-Friday followed
by a more convective precipitation scheme Saturday-Sunday will
produce periods of showers/thunderstorms for much of the region.
While the best chance for any severe weather will be to the south
of Minnesota/WI, and more into Iowa and points south, some of the storms
may well contain heavy rain as pwats climb to around 1.5" and quantitative precipitation forecast
through the weekend may well reach 2-3" for some locations. Too
early to determine exactly where but it can be said with moderate
confidence that heavy/excessive rainfall may develop across the
area and this is already highlighted in the day 3 excessive
rainfall outlook from wpc. As for storm strength, there is
potential for some phasing of the northern and southern streams
across the upper Mississippi River valley region Saturday into
Sunday, which may increase deep layer shear to the 40-50kt range.
In addition, the deep moisture and warm-sectoring may push MLCAPES
into the 3000-4000 j/kg range. However, exactly where this may
occur is still too early to determine with any certainty so will
overall need to see how this scenario develops before discussing
more severe potential for MN/WI.
The frontal system will finally be east of the area Monday with
the trailing cold front remaining to the south and east of the
area during the start of next week. High pressure will fill in
behind the front, allowing for a dry start to the next workweek.
As for temperatures, the slow progression of the cold front will
allow temperatures and dewpoints (and, hence, humidity levels) to
increase through the weekend. Highs will climb through the 70s
Thursday-Saturday then reach the lower 80s Sunday. Even with the
frontal passage, no cold air advection is expected behind the
front so high temperatures are expected to remain in the lower 80s
into early next week.
Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1250 PM CDT Tue Jun 18 2019
A widespread cu field has developed as was anticipated. Ceiling
heights in the 4-5 kft range will continue to gradually lift this
afternoon, so expect VFR conditions throughout. Very isolated
showers are possible this afternoon across central Minnesota, but chances
for any particular site were too low to include in the taf. Cu
will scatter out this evening, with mostly clear skies expected
for tonight. More cumulus could develop tomorrow, especially
across western Minnesota. Northwest winds around 5-10 knots will persist
this afternoon, and will gradually shift to a NE wind by
tomorrow, but speeds will remain relatively light.
Kmsp...afternoon showers should stay to the north of msp. VFR
conditions expected throughout the period.
/Outlook for kmsp/
Thu...VFR with MVFR/-tsra likely late. Wind southeast 5-10 kts.
Fri...MVFR or lower with -tsra possible. Winds southeast 5-10 kts.
Sat...MVFR or lower with -tsra possible. Winds west 5 kts.