FXUS63 KMPX 192304
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
604 PM CDT Thu Jul 19 2018
.UPDATE...For 00Z Aviation discussion below
.SHORT TERM...(This evening through Friday)
Issued at 327 PM CDT Thu Jul 19 2018
At 2pm this afternoon, the surface low is currently located over the
border of MN and SD and is gradually progressing east-southeastward.
A band of showers and weak thunderstorms lifted through Minnesota
this afternoon, providing about 0.5 to 2.0 inches of rain from West
Central MN to South Central MN. Forcing from the warm front and
upper trough initiated a few thunderstorms this afternoon in
Southwestern and South Central MN. Due to lack of instability and
effective shear, we did not see any organized supercells. However, a
few funnel clouds developed due to ambient vorticity, low LCLs
around 500 m, and 150 m2s2 0-1km SRH. The threat for funnel clouds
has decreased with the low-level helicity and shear decreasing
across South Central MN.
Scattered weak thunderstorms may still be possible this afternoon,
otherwise we expect shower activity to continue through today and
overnight. The surface low is expected to reach the Iowa/Illinois
border by 12Z Friday. Shower activity will thus progress eastward
with Western MN expected to be mostly dry by Friday afternoon. A
few thunderstorms may be possible in the cyclonic flow across
Central MN through Western WI with near 500-1000 J/kg of MUCAPE
due to daytime heating. Severe weather is not anticipated with the
bulk of the forcing will be with and downstream of the surface
low in Illinois. Temperatures will remain mild in the mid to upper
70s due to the northwest flow and extensive cloud cover.
.LONG TERM...(Friday night through Thursday)
Issued at 327 PM CDT Thu Jul 19 2018
By Friday night, the low pressure system will be over the southern
Great Lakes, with the western extent of cyclonic flow extending west
across WI and MN. A few showers and possibly isolated thunder will
linger into the evening hours, but dissipate as the night
progresses. The low will essentially stall out across southwestern
MI, keeping us in northwest flow and mostly cloudy to overcast skies
for western WI and eastern MN. Much drier air will begin pushing
into western MN from the Dakotas Saturday afternoon, and push across
the area by Sunday morning.
After a pleasant weather day on Sunday, the next feature to watch is
a cold front expected to move through on Sunday. This front will be
extending southward from a low pressure system in northern Manitoba,
so we'll be very far removed from the low. There will be a chance
for thunderstorms to develop along the front, but limited
instability along the front will limit the potential for strong or
The Manitoba low will translate eastward in the following days and
bring a stronger cold front through our area on Wednesday. With a
dry airmass in place, the chance for precipitation along this front
looks limited. Cooler temperatures will follow for the end of next
week as we remain in northwesterly flow behind the front.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 604 PM CDT Thu Jul 19 2018
Low-end MVFR and IFR ceilings will prevail through Friday morning,
along with occasional showers producing visibility reductions to
between 2SM and 5SM. The thunder threat is pretty minimal, with
the exception of east central MN and west central WI sites again
on Friday afternoon as we get a bit of daytime heating. Any
occurrences would be isolated however. Ceilings should gradually
improve to VFR from west to east on Friday afternoon/evening,
although most locations will stay cloudy into the next TAF period.
Scattered showers will be possible through Friday morning, with
the heaviest concentration after daybreak Friday as the upper low
shifts into Wisconsin. Could see thunder in the vicinity late
Friday morning and early afternoon. Expect evening MVFR cigs to
reduce to IFR overnight, with improvement to VFR around 00Z Sat.
/OUTLOOK FOR KMSP/
Sat...VFR. Wind N 10kts.
Sun...VFR. Wind NE 5kts.
Mon...VFR. Wind vrbl becoming NW5kts.
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