Mesoscale Discussion 111

Issued

Feb 20, 2011, 4:35 AM CST (10:35 UTC)

Expired

Feb 20, 2011, 10:30 AM CST

In force

6 hr

Issued by

the Storm Prediction Center

The Quad Cities radar (KDVN), 72 km from the middle of the area, began a volume at 10:37 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.

358 
ACUS11 KWNS 201035
SWOMCD
SPC MCD 201035 
INZ000-MIZ000-ILZ000-WIZ000-IAZ000-MNZ000-201630-

MESOSCALE DISCUSSION 0111
NWS STORM PREDICTION CENTER NORMAN OK
0435 AM CST SUN FEB 20 2011

AREAS AFFECTED...NRN IA...SRN MN...SRN WI...NRN IL AND NRN IND

CONCERNING...FREEZING RAIN 

VALID 201035Z - 201630Z

ZONE OF CONVECTIVE PRECIPITATION WILL CONTINUE TO EXPAND N-NEWD
THROUGH MID MORNING ACROSS NRN IA/SRN MN SEWD ACROSS SRN WI/NRN IL
AND NRN IND. THE SHIELD OF PRECIPITATION MAY YIELD FREEZING RAINFALL
RATES IN EXCESS OF 0.03 IN/HR AS ELEVATED WARM NOSE IS MAINTAINED
ABOVE SUB-FREEZING SURFACE TEMPERATURES.

AT 10Z...A ZONE OF CONVECTIVE PRECIPITATION WAS LOCATED ALONG A DSM
TO MLI LINE OVER IA...AND THEN EXTENDED SEWD ACROSS CNTRL IL.
PRIMARY FORCING MECHANISM FOR THIS ACTIVITY IS STRONG LOW-LEVEL
WAA/ISENTROPIC UPGLIDE OCCURRING WITHIN THE EXIT REGION OF 40+ KT
GREAT PLAINS LLJ. SHORT-TERM MODEL GUIDANCE INDICATES THIS ASCENT
WILL PERSIST THROUGH MID-MORNING AS THE LLJ SHIFTS EWD TOWARD THE
MID MS VALLEY REGION...THUS SUSTAINING CONTINUED SHOWER/THUNDERSTORM
DEVELOPMENT ACROSS NRN IA/SRN MN SEWD ACROSS SRN WI/NRN IL AND NRN
IND. NAM/RUC FORECAST SOUNDINGS N OF ONGOING PRECIPITATION INDICATE
A LAYER OF DRY AIR EXISTS FROM THE SURFACE UP TO 700 MB.
HOWEVER...AS HEAVIER PRECIPITATION RATES MOVE ACROSS THE DRIER
BOUNDARY LAYER AIR...WET BULB COOLING WILL LEAD TO RAPID SATURATION
OF THE COLUMN AND AID IN MAINTAINING FREEZING TEMPERATURES NEAR THE
SURFACE. MEANWHILE... WAA ABOVE THE SURFACE IS FORECAST TO MAINTAIN
A 2 DEG C WARM NOSE AT AROUND 700 M AGL. THIS TEMPERATURE PROFILE IS
EXPECTED TO YIELD A THREAT FOR FREEZING RAIN WITH RATES POSSIBLY IN
EXCESS OF 0.03 IN/HR. IN ADDITION...MIDLEVEL LAPSE RATES ARE
FORECAST TO STEEPEN THROUGH THE MORNING...WHICH WILL AID IN THE
DEVELOPMENT OF MUCAPE VALUES FROM 100-200 J/KG ROOTED NEAR 700 MB.
GIVEN THIS DESTABILIZATION...A TRANSITION TO SLEET WILL BE POSSIBLE
WITH STRONGER THUNDERSTORM CORES.

..GARNER.. 02/20/2011

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

ATTN...WFO...IWX...IND...LOT...MKX...DVN...ARX...MPX...DMX...
FSD...

LAT...LON   41759039 42559332 42889561 43709590 44159489 44059157
            42868788 42108633 40938541 40448591 40428704 41298918
            41759039

Mesoscale Discussions in Iowa, 2011Mesoscale Discussions in Illinois, 2011Mesoscale Discussions in Indiana, 2011Every mesoscale discussion in 2011

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.