Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
719 PM CDT Tue May 8 2018

.Updated for 00Z Aviation Discussion...
Issued at 640 PM CDT Tue May 8 2018

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 300 PM CDT Tue May 8 2018

This afternoon we continue to see shower activity across Central
MN and West Central WI. A Marginal Risk for severe weather
continues for Southwestern and South Central MN. Thunderstorms
have developed along the warm frontal boundary in Southern MN
along 1-90 where there is between 1500 to 2000 J/kg MUCAPE and 45
kt Bulk Shear. Midlevel lapse rates are around 7 degrees C/km or
less, which reduces the potential for strong updrafts.
Precipitable water is near between 1 and 1.3 inches, which has
allowed for a 0.1" to 0.25" per hour rainfall rates.

As low pressure approaches from the west, forcing for ascent will
increase this afternoon. Most high resolution models continue to
show the development of clusters of thunderstorms around 23Z in
West Central MN. There has been cloud clearing in Western MN which
has allowed instability to approach near 1000 J/kg already this
afternoon with still a few hours of daytime heating. Isolated
severe storms may be possible with the gusty winds and hail. An
isolated tornado cannot be ruled out. Thunderstorm strength is
expected to decrease tonight with the loss of heating with shower
activity likely reaching Wisconsin overnight.

As the trough and surface low move overhead, we expect moisture to
be trapt within the inversion below 850 mb. This will cause
widespread low cloud cover and the opportunity for showers through
the overnight hours. Highs on Wednesday will likely in the 60s
with highs reaching the lower 70s in far Western MN where cloud
cover looks to erode Wednesday afternoon.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 300 PM CDT Tue May 8 2018

Overall long term concerns remain heavy rain threat Thursday night
into Friday and handling model differences into early next week.

Models continue to show a good heavy rain signal developing
Thursday night as the next trough moves across the area. The GFS
and NAM have a strong frontal boundary over northern Iowa with
strong FGEN moisture transport lifting north into the southern
third of the cwa. Precipitable water does increase to near 1.5
inches and this should provide enough moisture to generate some
more widespread 1 inch rainfall across the southern cwa Thursday
night into Friday. The ECMWF is a bit farther south with its
forcing and overall QPF and is not as robust. Still, we should
still be able to generate some hefty rains during this period as
the wave moves through. With abundant cloud cover expected,
temperatures will be hard pressed to warm much Friday and
Saturday. We should see widespread 50s for highs both days with
Friday being the coldest.

Models diverge in handling the overall pattern into the weekend.
We will remain close to the baroclinic zone south just south of
the area for Saturday and this could continue the threat of
showers, especially over the southern cwa once again. Following
this, the ECWMF drives much cooler air south across the Great
Lakes through Sunday and this could set up a frost threat to
mainly the northeast cwa Sunday morning. Will have to monitor
overall models trends to see if this does materialize.

Finally, the ECMWF becomes more amplified for the next western
CONUS trough with the GFS remaining a bit more split/flatter in
the upper pattern. The ECMWF would drive much warmer air back
into the area into early next week, with a good chance of strong
thunderstorms developing about the Tuesday timeframe.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 640 PM CDT Tue May 8 2018

VFR conditions with scattered showers and thunderstorms this
evening. Overnight forecast guidance continues to bring in
MVFR/IFR ceilings, and carries them through most of Wednesday
morning. I did raise ceilings a little earlier than guidance since
there will be breezy northwest winds bringing in drier air.

KMSP...
Most of the thunder is trending to the south for the next few
hours, so pushed back the chance for thunder until 04Z when the
parent upper level circulation moves in. Even then the chance for
thunder does appear to be decreasing.

/OUTLOOK FOR KMSP/
Thu...VFR with MVFR/-SHRA possible late. Wind N 5-10 kts.
Fri...Chc MVFR with SHRA/TSRA. Wind E 10-20 kts.
Sat...VFR. Wind variable at 5 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

SHORT TERM...AMK
LONG TERM...DWE
AVIATION...JRB

Hazardous Weather Outlook
National Weather Service Twin Cities/Chanhassen MN
1011 PM CDT Tue May 8 2018

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
100315-
Douglas-Todd-Morrison-Mille Lacs-Kanabec-Stevens-Pope-Stearns-
Benton-Sherburne-Isanti-Chisago-Lac Qui Parle-Swift-Chippewa-
Kandiyohi-Meeker-Wright-Hennepin-Anoka-Ramsey-Washington-
Yellow Medicine-Renville-McLeod-Sibley-Carver-Scott-Dakota-
Redwood-Brown-Nicollet-Le Sueur-Rice-Goodhue-Watonwan-Blue Earth-
Waseca-Steele-Martin-Faribault-Freeborn-Polk-Barron-Rusk-
St. Croix-Pierce-Dunn-Pepin-Eau Claire-
1011 PM CDT Tue May 8 2018

This Hazardous Weather Outlook is for portions of central and
southern Minnesota...and west central Wisconsin.

.DAY ONE...Tonight

Thunderstorms will be possible tonight. The risk for severe
weather is low.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Additional chances for thunderstorms exist Thursday night into
Friday morning and again Friday night into Saturday morning. The
threat for severe weather is low, though areas of heavy rain and
localized flooding will be possible with the activity Thursday
night into Friday morning. The greatest risk for heavy rain will
be across southern MN.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation will not be needed.

jrb

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
620 PM CDT TUE MAY 8 2018

MNZ091-090000-
Martin-
620 PM CDT TUE MAY 8 2018

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN MARTIN COUNTY...

At 620 PM CDT, a strong thunderstorm was located over Okamanpedan
State Park, or 11 miles southwest of Fairmont, moving northeast at 45
mph.

Winds in excess of 40 mph and nickel size hail are possible with this
storm.

Locations impacted include...
Fairmont, Ceylon, Iowa Lake, Granada, Fairmont Airport, Imogene and
Wilbert.

This includes Interstate 90 between mile markers 98 and 112.

LAT...LON 4351 9469 4368 9455 4369 9425 4365 9425
      4349 9445
TIME...MOT...LOC 2320Z 229DEG 38KT 4349 9458

jrb

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
859 PM CDT TUE MAY 8 2018

MNZ091-090245-
Martin-
859 PM CDT TUE MAY 8 2018

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN MARTIN COUNTY...

At 859 PM CDT, a strong thunderstorm was located near Superior, or 7
miles northwest of Estherville, moving northeast at 30 mph.

Winds in excess of 40 mph and nickel size hail are possible with this
storm.

Locations impacted include...
Sherburn, Ceylon, Dunnell and Wilbert.

This includes Interstate 90 between mile markers 82 and 91.

LAT...LON 4351 9485 4368 9485 4375 9474 4351 9451
TIME...MOT...LOC 0159Z 230DEG 27KT 4350 9490

jrb

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1210 AM CDT WED MAY 9 2018

MNZ092-093-090600-
Freeborn-Faribault-
1210 AM CDT WED MAY 9 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT FARIBAULT AND FREEBORN
COUNTIES...

At 1208 AM CDT, radar indicated strong thunderstorms thunderstorms
between I-90 and the Iowa border, moving northeast at 25 mph.

Wind gusts up to 40 mph are possible with these storms.

Locations impacted include...
Albert Lea, Blue Earth, Wells, Clarks Grove, Minnesota Lake, Elmore,
Alden, Glenville, Geneva, Emmons, Bricelyn and Hartland.

This includes the following highways...
 Interstate 35 between mile markers 1 and 24.
 Interstate 90 between mile markers 120 and 169.
 U.S. Highway 169 between mile markers 1 and 12.

LAT...LON 4351 9416 4385 9405 4384 9305 4381 9305
      4350 9325
TIME...MOT...LOC 0508Z 225DEG 21KT 4360 9352 4363 9407