Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 221132

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
632 AM CDT Thu Jun 22 2017

Issued at 617 AM CDT Thu Jun 22 2017

Updated to include 12z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Thu Jun 22 2017

Today and tonight...

Surface analysis early this morning shows a surface low over west-
central Manitoba province with a trailing cold front extending
southeast into north-central MN, curving southwest into
southeastern SD and northern NE. Its associated warm front extends
east from a triple point over southwestern MN into northeastern
IA and through the Ohio River Valley. The surface low is under a
deepening H5 low while upper level flow flattens out considerably
over the Upper Mississippi River Valley, running rather zonal over
the region. This stacked low is expected to drift to the east
over the next 24-30 hours, repositioning itself to over south-
central Ontario province, while dragging with it a potent trough
axis through the Dakotas into MN/WI tonight into tomorrow. This
movement aloft will help nudge the cold front eastward while the
warm front lifts slightly north, allowing for some warm-sectoring
to occur today into this evening over eastern MN into western WI.

The rather unstable airmass in advance of the cold front (MUCAPEs
in the 2000-3000 j/kg range and diminishing CINH) plus steep
mid-level lapse rates have contributed and are contributing to
scattered convection overnight through this morning. Some of the
storms have become surface-based and that is expected to continue
in mainly southern MN as the day progresses. In addition, the loss
of capping with the northward-moving warm front plus diurnal
heating over an area that has not been overly worked over will
allow for additional coverage of showers/thunderstorms later today
into this evening. Have indicated as such with pops increasing
into the categorical range for southern and eastern portions of
the WFO MPX coverage area. Aiding the convective development in
these southeastern portions will be highs that climb to near 80
degrees plus dewpoints into the low-mid 60s. The main hazards
continue to be large hail and damaging winds with storms that will
take the form of clusters and/or MCCs.

The precipitation will steadily wind down and shift off to the
east with the cold frontal passage this evening. This also
coincides with the passage of the potent shortwave aloft. Slightly
drier air along with weak high pressure will fill in behind the
front for the remainder of the overnight hours. This will be
reflected in lows for early Friday morning which will drop to the
low-mid 50s along with dewpoints falling to the upper 40s to lower

.LONG TERM...(Friday through Wednesday)
Issued at 330 AM CDT Thu Jun 22 2017

The longer term concerns remain the highly amplified pattern with
the cold trough affecting the eastern conus through early next

Northwest flow aloft becomes entrenched across the area Friday.
Cooler with a small chance of showers will be found over the
northeast portion of the cwa. Should see quite a bit of clouds
cover with the cooler air as well. This should limit highs in the
65 to 70 degree ranges. Some 10 to 15 degrees below normal.

Both deterministic long term models drive a couple of short waves
through the region over the weekend. This will affect mainly
about the eastern half of the area. The GFS is farther west with
the initial wave...and seems a bit overdone. Some instability
ahead of this feature so will include slight chance thunder for
Saturday afternoon to the east. This may also occur into Sunday
afternoon as the next wave arrives. This may be even
more isolated with even colder air aloft expected to arrive.

The last wave exits east of the region Monday and this leaves cool
and dry conditions through at least Tuesday. Models do try and
develop a somewhat flatter more zonal upper air pattern to the
area later in the period. The GFS tries and draw warmer air for
the Pacific Northwest while the ECMWF remains not as robust with
the warm air return. We should still see temperatures warm through
the end of the week...closer to or slightly above normal. Along
with the warmer air...another frontal system is expected to
arrive by the end of the work week bringing another chance of
showers and thunderstorms.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 617 AM CDT Thu Jun 22 2017

Showers and thunderstorms expected to increase in coverage as the
day progresses in advance of a cold front due to pass over the
region today. Conditions dropping to MVFR likely in heavier
storms, IFR possible but low confidence to include at this point.
Conditions will improve tonight into tomorrow as the cold front
exits and weak high pressure arrives. Light/variable winds will
eventually swing around to NW with speeds in the 5-10 kt range but
could be higher in and near thunderstorms.

KMSP...Showers look to move into the MSP area early on in the
22/12z TAF but best thunder chances hold off until midday. Have
gone as low as MVFR for now but that could change depending on
radar trends.

Sat-Sun...Mainly VFR. Slight chc -TSRA/MVFR. Wind NW 5-10 kts.
Mon...VFR. Wind NW 5-10 kts.




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