Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 162

February 28, 20129 counties in Iowa; Jackson County, Nobles County, Rock County, Minnesota; 4 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2012, 6:18 AM CST for 9 counties in Iowa; Jackson County, Nobles County, Rock County, Minnesota; 4 counties in South Dakota. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Feb 28, 2012, 6:18 AM CST (12:18 UTC)
Expired: Feb 28, 2012, 11:15 AM CST
In force: 5 hr
Issued by: the Storm Prediction Center

Counties Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sioux County, IA, Jackson County, MN, Nobles County, MN, Rock County, MN, Clay County, SD, Lincoln County, SD, Minnehaha County, SD, Union County, SD

The radar

The Sioux Falls radar (KFSD), 83 km from the middle of the area, began a volume at 12:20 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 0.3 hours before the alert went out and 207 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1601 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 441 m²/s²
0-3 km storm-relative helicity: 433 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

117 
ACUS11 KWNS 281219
SWOMCD
SPC MCD 281218
MNZ000-IAZ000-NEZ000-SDZ000-281715-

MESOSCALE DISCUSSION 0162
NWS STORM PREDICTION CENTER NORMAN OK
0618 AM CST TUE FEB 28 2012

AREAS AFFECTED...NWRN IA/SERN SD/SWRN MN

CONCERNING...FREEZING RAIN

VALID 281218Z - 281715Z

FREEZING RAIN IS EXPECTED TO DEVELOP THIS MORNING ACROSS NWRN
IA...SERN SD AND INTO SWRN MN.  RATES OF 0.05-0.1 INCH/3-HOUR ARE
LIKELY BETWEEN 15-18Z...WITH SOME RATES LOCALLY EXCEEDING 0.1 INCH/3
HR.  AFTER 18Z...FREEZING RAIN SHOULD CHANGE TO RAIN AS SURFACE
TEMPERATURES RISE ABOVE 32 F.

INITIAL COOLER VERTICAL THERMODYNAMIC PROFILES WITHIN THE AIR MASS
OVER NWRN IA/SERN SD/SWRN MN UNDERGOING SATURATION HAVE BEEN
SUPPORTING PRIMARILY LIGHT SNOW AND OCCASIONAL SLEET.  SURFACE
TEMPERATURES HAVE BEEN SLOWLY RISING OVERNIGHT...AND AT 11Z WERE IN
THE UPPER 20S TO NEAR 32 F.  HOWEVER...WHILE THE SURFACE WET BULB
ZERO C LINE HAS ALSO BEEN MOVING NWD...AT 11Z IT RESIDED FARTHER S
OF THE DISCUSSION AREA FROM THE SRN TIER OF NEB COUNTIES INTO
NWRN-EAST CENTRAL MO.  GIVEN THE HORIZONTAL DISTRIBUTION OF THE 0 C
SURFACE/WET BULB TEMPERATURES...FURTHER EVAPORATIVE COOLING IN THE
BOUNDARY LAYER THIS MORNING WILL TEND TO OFFSET WAA AT THE SURFACE.
STRONG LOW LEVEL WAA /PER A 40-50 KT SSWLY LLJ/ WILL BE MAINTAINED
TODAY FROM THE CENTRAL PLAINS THROUGH THE MID MO/UPPER MS VALLEYS.
THIS WARMING ABOVE THE SURFACE WILL RESULT IN THERMODYNAMIC PROFILES
FAVORABLE FOR FREEZING RAIN AS SURFACE TEMPERATURES REMAIN BELOW 32
F THROUGH 18Z.

AT 12Z...REGIONAL RADAR IMAGERY SHOWED SHOWERS INCREASING IN AREAL
COVERAGE ACROSS EAST CENTRAL/SERN NEB...WITH THE TIMING OF THE
RELATIVELY STRONGER REFLECTIVITIES REACHING THE DISCUSSION AREA
BETWEEN 14-15Z.  AN INCREASE IN LOW LEVEL WAA AS THE PLAINS LLJ
STRENGTHENS LATER THIS MORNING...AND INCREASING UVVS AS EXIT REGIONS
OF SWLY MID AND UPPER LEVEL JETS SPREAD INTO NWRN IA/SWRN MN/SERN SD
SHOULD SUPPORT GREATER PRECIPITATION RATES.  IN ADDITION...GIVEN THE
STRENGTH OF THE LOW LEVEL WAA...FORECAST SOUNDINGS SHOW ELEVATED
CAPE DEVELOPING AFTER 15Z WITH THE POTENTIAL FOR TSTMS FURTHER
ENHANCING PRECIPITATION RATES THROUGH 18Z.

..PETERS.. 02/28/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MPX...DMX...FSD...OAX...

LAT...LON   42519562 42489660 42739710 43329715 43659685 43949598
            44049536 43749491 43119475 42579502 42519562

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 28, 11:43 AM CST	Mesoscale Discussion	SPC	Lyon, Osceola	5 hr
Feb 28, 2:40 PM CST	Mesoscale Discussion	SPC	Anoka, Benton, Carver, Chisago, Dakota, Dodge and 18 more	4 hr
Feb 28, 2:43 PM CST	Mesoscale Discussion	SPC	Becker, Clay, Crow Wing, Douglas, Grant, Morrison and 6 more	5 hr

Nearby

Mesoscale Discussions in Iowa, 2012 Mesoscale Discussions in South Dakota, 2012 Mesoscale Discussions in Minnesota, 2012 Every mesoscale discussion in 2012

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.