Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 220834
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
334 AM CDT FRI JUL 22 2016

.SHORT TERM...(Today and tonight)
Issued at 334 AM CDT Fri Jul 22 2016

One last day of hot and humid conditions will occur today, primarily
across southern Minnesota but as far north as the Twin Cities, where
dewpoints will still be in the low to mid 70s. Elsewhere, surface
temps will reach the lower 90s, but lower dewpoints in the low/mid
60s will translate to heat indices in the low/mid 90s. Therefore,
the heat warning will only be maintained for areas generally along
and south of a Montevideo to Twin Cities to Durand Wisconsin line.

There are a few showers across far east central MN into west central
Wisconsin early this morning, but otherwise dry weather is expected
until late tonight as a warm front lifts north toward the area. Have
included a chance for showers and thunderstorms after 06Z Saturday
for areas generally along and west of Interstate 35, where moisture
transport ramps up notably overnight. Given the anticipated increase
in clouds and precipitation tonight, expected temperatures to remain
elevated from 65 to 75 degrees.

.LONG TERM...(Saturday through Thursday)
Issued at 334 AM CDT Fri Jul 22 2016

The main concern in the long term is the threat for severe weather
Saturday afternoon and night. This has been well advertised by
the deterministic models the past few nights and now has come to
fruition in the various CAMS that go into Saturday evening.

Moisture and instability will be building across the region on
Saturday as a warm front across SD and IA lifts northeast into MN
during the afternoon. Scattered showers and thunderstorms are
possible during the day, especially across west central through
south central MN. This plays havoc with the high temperature
forecast with MET/MAV MOS forecasting highs in the upper 80s to
lower 90s. This seems plausible with 850 mb temperatures progged
to rise into the +22 to +24 deg C range. Therefore, increased
highs a few degrees over the previous forecast but still a tab
below MOS values due to the uncertainty on how much convective
activity occurs during the day.

By late Saturday afternoon, a cold front will be approaching
western MN. Some model solutions show a surface low near KAXN by
evening with the cold front extending to the southwest while the
warm front curves southeast towards the Twin Cities. The surface
low then moves across central MN during the evening. There is
plenty of shear indicated, both low level and deep layer from
central MN on northward. This is where CWASP values are the
highest. In addition, conditional probabilities for a significant
tornado are above 70 percent through the evening across central MN
which is logical given the shear/instability and boundaries.

CAM output is in pretty good agreement on a line of storms
developing by evening ahead of the cold front and then racing
southeast across the FA. Damaging wind signatures are seen in the
simulated radar reflectivity. DCAPE values are shown to be above
1500 J/KG which is what we saw early Thursday morning across
central/northern MN and northern WI. So, it`s possible when the
storms first develop that we could have a tornado or two before
the system congeals into a bowing line/QLCS. Of course there
could be spin-ups along the QLCS as it heads southeast. Likely
POPS were expanded out some to account for the extensive line
developing. There is also a threat for heavy rainfall with PWATS
progged to around 2.30 inches from a blend of models. This would
be near a record PW value for MPX. Even though the CAMS show the
line advancing rather quickly to the southeast, any training
could cause flooding concerns.

A pleasant period is then forecast for Sunday and Monday as cooler
and less humid air arrive with a system of high pressure. High
temperatures will remain seasonal with readings in the lower to
middle 80s. The dry period is brief as a wave is indicated to
pass across the region on Tuesday with scattered showers and
thunderstorms. A more substantial wave is seen deepening over and
to the south of us from Wednesday into Thursday with more chances
for showers and thunderstorms.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1052 PM CDT Thu Jul 21 2016

Very few aviation concerns as the earlier convection over
southwest MN has diminished while the activity over northeastern
Iowa will continue moving away to the southeast. No further
convection is expected over central and southern MN into wets
central WI. High SCT clouds will remain throughout the period.
Winds will generally remain 5kt or less with varied directions.

KMSP...No significant weather concerns.

/OUTLOOK FOR KMSP/
Sat...VFR early then chances increase for MVFR-IFR late. TSRA
likely late. Wind SE 5-10 kt.
Sun...VFR. Winds NW 10-15 kt.
Mon...VFR. Winds NW 5-10 kt.

&&

.MPX Watches/Warnings/Advisories...
WI...Excessive Heat Warning until 7 PM CDT this evening for WIZ024-
     026.

MN...Excessive Heat Warning until 7 PM CDT this evening for MNZ054-
     056-060>070-073>078-082>085-091>093.

&&

$$

SHORT TERM...LS
LONG TERM...RAH
AVIATION...JPC



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