Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
102 PM CDT Wed Jul 4 2018

.UPDATE...
Issued at 1255 PM CDT Wed Jul 4 2018

Downgraded the heat earning to advisory. Looks like clouds/periods
showers/thunder will be good enough to hold indices to 95 to 100.
May not reach this in far western area, but will leave the
coverage area as is for now.

Updated to include 18z aviation discussion below.

&&

.SHORT TERM...(Today and tonight)
Issued at 441 AM CDT Wed Jul 4 2018

Surface analysis early this morning shows a surface low crossing
from northwest SD into central ND with a leading warm front
extending ESE over the Twin Cities and into southern WI with a
trailing cold front sagging SSW into northern Nebraska. Plenty of
warm and moist air resides in the warm sector of this system.
Aloft, solid southwest flow prevails between a deep southeastern
CONUS ridge and a compact trough progressing eastward over western
NOAM.

The main issue is the evolution of ongoing convection over the
Dakotas, how it progresses into Minnesota, and potential re-
development this afternoon-evening. The current storms are
reaching the point of outrunning the cold front and hence into a
slightly more stable airmass well ahead of the cold front. Thus,
the storms to the west of the WFO MPX coverage area are expected
to lose some steam and potentially dissipate and/or lift off to
the northeast this morning. As the front pushes east and plunges
the entire coverage area into a highly unstable airmass (MLCAPEs
around 4000 j/kg), mid-level capping is expected to erode which
will allow convection to become re-invigorated from the southwest
of the area. As such, this looks to allow another round (and
possibly 2) of convection to progress through the coverage area
late this afternoon into early this evening (with possibly
another round late this evening into the early morning hours
Thursday). Strong low-mid level jetting plus veering profiles
would suggest storms may produce strong/damaging straight-line
winds and possibly hail, while tornadic thunderstorms are not
expected.

The overall tricky part is trying to determine placement of storms
while knowing that there is a high likelihood of storms throughout
the coverage area. As such, confidence is not all that high,
especially given the high variance of the operational HRRR run-
to-run and the differences it has shown in comparison to other
HRRR experimental runs, the SREF, the NAM and the RAP. As such,
have capped pops in the chance range but used areal wording to
emphasize storm coverage rather than probability wording.

In addition, not only is there the potential for severe storms,
but the deep moisture profile in such an unstable atmosphere will
also promote storms containing frequent lightning and potentially
mod-heavy rain. Will maintain the areal flood warnings as they are
currently delineated and will also bring attention to the outline
that WPC has placed much of the WFO MPX coverage area within a
Slight Risk of Excessive Rainfall due to the combination of highly
saturated soils (a.k.a. low flash flood guidance) and the
possibility of storms containing heavy rain.

And, finally, the warm sector will aid max temperatures in rising
to around 90 degrees for much of the eastern half of the coverage
area. With dewpoints into the mid 70s, this combination will
easily put heat index values to around 100 and potentially up to
around 105. As such, have converted the excessive heat watch to a
heat advisory for much of the area east of a line from Sherburne
county to Martin county, with an Excessive Heat Warning for
Hennepin/Ramsey counties due to the lower thresholds for the Twin
Cities.

.LONG TERM...(Thursday through Tuesday)
Issued at 441 AM CDT Wed Jul 4 2018

Precipitation is expected to continue exiting the southern and
eastern portion of the CWA late Thursday morning. Dry conditions
will then resume with surface high pressure progressing into the
High Plains as ridging develops over the Western CONUS with
northwest flow over the Western Great Lakes region. The drier air
mass will allow for dew points to be in the 50s to low 60s which
will be 10 to 15 degrees lower than Wednesday's dew points.

Surface high pressure will gradually shift east through the end of
the week and allow for return flow on Saturday. Thus, surface
dewpoints are expected to rise into the upper 60s to low 70s. The
upper ridge is expected to flatten on Sunday. Weak impulses along
the westerly flow aloft as well as a frontal boundary extending
from a low over Canada will bring storm chances Sunday into
Monday. Afterward, the upper level ridge is expected to amplify
Tuesday with surface high pressure over the Great Lakes. A warm
front looks to lift through MN Tuesday into Wednesday, so while
the forecast looks to be mostly dry Tuesday into Wednesday, the
chance for thunderstorm development in association with warm air
advection will have to be monitored.

As we reach late Wednesday into Thursday, there are large
discrepancies between the ECMWF and GFS. A cold front looks to
pass through the region during that time frame with the GFS having
it progress slower than the ECMWF would. This boundary will likely
cause shower and thunderstorm activity across MN and WI, but
there still is low confidence in the timing and intensity.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1255 PM CDT Wed Jul 4 2018

Convective trends difficult to discern initially but appears the
greatest threat of convection will be mainly early through about
00z or so over the east and south. Will continue to mention this
threat into the evening far east with overall drying trend
remainder of the area. Should see VFR outside of any convection
through the evening. Then VFR trend remaining through the rest of
the period. Winds SE-S and gusty around thunder with winds
becoming more w-nw with fropa into the evening.

KMSP...Appears one more through of thunder moving through before
00z. then VFR drying trend expected thereafter into tonight with
outside chance of shra/tsra through about 06z.

/OUTLOOK FOR KMSP/
Thu night...VFR. Winds NW at 5-10 kts.
Fri...VFR. Winds E at 5-10 kts.
Sat...VFR. Winds S at 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory until 8 PM CDT this evening for WIZ023>028.

MN...Heat Advisory until 8 PM CDT this evening for MNZ051-059>063-
     066>070-074>078-082>085-091>093.

&&

UPDATE...
SHORT TERM...JPC
LONG TERM...AMK
AVIATION...DWE

Hazardous Weather Outlook...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1140 AM CDT Wed Jul 4 2018

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
051100-
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-
1140 AM CDT Wed Jul 4 2018

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

.DAY ONE...This Afternoon and Tonight

Scattered thunderstorms will move across the area this afternoon,
but it is uncertain how much severe weather there may be. If
there is severe weather, the most likely area would be from south
central Minnesota into west central Wisconsin. Some storms may
also produce heavy rain.

Heat and humidity will build back in later this afternoon, after the
morning and midday storms. Peak heat indices in the middle and
upper 90s are possible over east central and southern Minnesota
into west central Wisconsin.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation may be needed, mainly from south
central Minnesota into west central Wisconsin.

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1112 AM CDT WED JUL 4 2018

MNZ091-041700-
Martin-
1112 AM CDT WED JUL 4 2018

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

At 1112 AM CDT, a strong thunderstorm was located over Alpha, or near
Jackson In Jackson County, moving northeast at 45 mph.

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

Locations impacted include...
Fairmont, Sherburn, Truman, Trimont, Welcome, Ceylon, Granada, East
Chain, Northrop, Dunnell, Ormsby and Fairmont Airport.

This includes Interstate 90 between mile markers 82 and 112.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in The Twin Cities.

LAT...LON 4385 9485 4384 9425 4351 9425 4350 9485
TIME...MOT...LOC 1612Z 245DEG 37KT 4365 9490

JLT

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1135 AM CDT WED JUL 4 2018

MNZ082-083-091-092-041715-
Blue Earth-Watonwan-Martin-Faribault-
1135 AM CDT WED JUL 4 2018

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN FARIBAULT...
NORTHEASTERN MARTIN...SOUTHWESTERN BLUE EARTH AND SOUTHEASTERN
WATONWAN COUNTIES...

At 1135 AM CDT, a strong thunderstorm was located over Trimont, or 13
miles northwest of Fairmont, moving northeast at 45 mph.

Wind gusts of 50 to 55 mph and dime size hail are possible with this
storm.

Locations impacted include...
Lake Crystal, Winnebago, Truman, Trimont, Welcome, Amboy, Vernon
Center, Lewisville, South Branch, Northrop, Ormsby and Odin.

This includes the following highways...
 Interstate 90 between mile markers 92 and 96.
 U.S. Highway 169 between mile markers 20 and 33.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in The Twin Cities.

LAT...LON 4366 9465 4385 9478 4412 9421 4377 9413
TIME...MOT...LOC 1635Z 243DEG 38KT 4376 9469

JLT

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1209 PM CDT WED JUL 4 2018

MNZ083-084-091-092-041815-
Waseca-Blue Earth-Martin-Faribault-
1209 PM CDT WED JUL 4 2018

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN FARIBAULT...
NORTHEASTERN MARTIN...BLUE EARTH AND WESTERN WASECA COUNTIES...

At 1209 PM CDT, a strong thunderstorm was located near Vernon Center,
or 21 miles southwest of Mankato, moving northeast at 45 mph.

Wind gusts of 50 to 55 mph and dime size hail are possible with this
storm.

Locations impacted include...
Mankato, North Mankato, Eagle Lake, Janesville, Mapleton, Winnebago,
Madison Lake, St. Clair, Minnesota Lake, Good Thunder, Amboy and
Vernon Center.

This includes the following highways...
 U.S. Highway 14 between mile markers 133 and 148.
 U.S. Highway 169 between mile markers 20 and 45, and between mile
markers 52 and 54.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in The Twin Cities.

LAT...LON 4374 9427 4397 9437 4402 9437 4424 9384
      4424 9377 4420 9377 4420 9374 4386 9354
TIME...MOT...LOC 1709Z 243DEG 38KT 4392 9425

JLT

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1247 PM CDT WED JUL 4 2018

MNZ076-077-083>085-092-093-041845-
Steele-Le Sueur-Waseca-Blue Earth-Rice-Freeborn-Faribault-
1247 PM CDT WED JUL 4 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN
FREEBORN...EASTERN FARIBAULT...LE SUEUR...STEELE...EASTERN BLUE
EARTH...RICE AND WASECA COUNTIES...

At 1245 PM CDT, radar indicated strong thunderstorms were located
along a line extending from Kasota to Mankato Airport to near St.
Clair to near Wells to Frost. Movement was east at 40 mph.

Winds in excess of 40 mph and half inch hail are possible with these
storms.

Locations impacted include...
Mankato, Owatonna, Faribault, Northfield, Albert Lea, St. Peter,
Waseca, Lonsdale, Montgomery, Le Center, Eagle Lake and Wells.

Those attending the events near St. Peter, Elysian, and Waseca are
in the path of these storms and should prepare for the expected
weather conditions.

This includes the following highways...
 Interstate 35 between mile markers 8 and 70.
 Interstate 90 between mile markers 129 and 167.
 U.S. Highway 14 between mile markers 131 and 181.
 U.S. Highway 169 near mile marker 58, and between mile markers 62
and 65.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4375 9387 4402 9391 4422 9403 4428 9402
      4434 9393 4438 9396 4454 9335 4447 9328
      4440 9315 4421 9306 4394 9305 4364 9319
      4350 9393 4350 9404
TIME...MOT...LOC 1745Z 250DEG 33KT 4429 9400 4420 9390 4405 9383 4377
9379 4356 9394

JLT

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
107 PM CDT WED JUL 4 2018

MNZ076-077-084-041900-
Le Sueur-Waseca-Rice-
107 PM CDT WED JUL 4 2018

...A STRONG THUNDERSTORM WILL AFFECT LE SUEUR...RICE AND NORTHERN
WASECA COUNTIES...

At 105 PM CDT, a strong thunderstorm was located over Lake
Jefferson, or 13 miles northeast of Mankato, moving northeast at 35
mph. The Mankato regional airport had a wind gust of 55 mph at 1:02
pm with this storm.

Wind gusts of 50 to 55 mph and half inch hail are possible with this
storm.

Locations impacted include...
Faribault, New Prague, Lonsdale, Montgomery, Le Center, Waterville,
Webster, Morristown, Elysian, Warsaw, Cleveland and Bridgewater.

This includes Interstate 35 between mile markers 52 and 74.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in The Twin Cities.

LAT...LON 4412 9374 4417 9377 4423 9377 4424 9382
      4439 9392 4455 9355 4454 9330 4451 9328
      4447 9328 4447 9325 4425 9310
TIME...MOT...LOC 1805Z 234DEG 30KT 4427 9377

JLT

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
130 PM CDT WED JUL 4 2018

MNZ060-062-068>070-041930-
Dakota-Hennepin-Carver-Ramsey-Scott-
130 PM CDT WED JUL 4 2018

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN HENNEPIN...WESTERN
DAKOTA...SCOTT...EAST CENTRAL CARVER AND SOUTHWESTERN RAMSEY
COUNTIES...

At 128 PM CDT, a strong thunderstorm was located near Marystown, or
21 miles northwest of Northfield, moving northeast at 30 mph.

Winds in excess of 40 mph and half inch hail are possible with this
storm.

Those attending the fourth of july events around the Twin Cities are
in the path of this storm and should prepare for the expected
weather conditions.

This includes Interstate 35 between mile markers 75 and 80.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

If you are on area lakes across the Twin Cities metro area, get out
of the water. Remember, lightning can strike out to 10 miles from
the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

LAT...LON 4486 9359 4507 9310 4455 9299 4454 9352
      4455 9360
TIME...MOT...LOC 1828Z 228DEG 24KT 4464 9349

JLT