Alert archive / Utah / Mesoscale Discussions in 2012
Mesoscale Discussion 30
The Storm Prediction Center issued this mesoscale discussion at Jan 18, 2012, 10:48 AM MST for 6 counties in Utah. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 18, 2012, 10:48 AM MST (17:48 UTC)
- Expired
- Jan 18, 2012, 3:45 PM MST
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
Counties Morgan County, UT, Salt Lake County, UT, Summit County, UT, Utah County, UT, Wasatch County, UT, Weber County, UT
The radar
The Salt Lake City radar (KMTX), 113 km from the middle of the area, began a volume at 17:48 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
Salt Lake City I, UT (KSLC), launched 12:00Z, 5.8 hours before the alert went out and 46 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2831 m above ground
- 0-6 km bulk shear
- 113 kt
- 0-1 km storm-relative helicity
- 364 m²/s²
- 0-3 km storm-relative helicity
- 484 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
023
ACUS11 KWNS 181748
SWOMCD
SPC MCD 181748
UTZ000-WYZ000-182245-
MESOSCALE DISCUSSION 0030
NWS STORM PREDICTION CENTER NORMAN OK
1148 AM CST WED JAN 18 2012
AREAS AFFECTED...NRN UT
CONCERNING...HEAVY SNOW
VALID 181748Z - 182245Z
HEAVY SNOWFALL IS EXPECTED TO DEVELOP THIS AFTERNOON/EVENING ACROSS
PORTIONS OF NRN UT. SNOWFALL RATES AOA 1 INCH PER HR OVER ERN
PORTIONS OF THE SALT LAKE VALLEY AND WRN FOOTHILLS OF THE WASATCH
MTNS...TO NEAR 2 INCHES PER HR OVER THE WASATCH MTNS...ARE FORECAST
TO OCCUR.
WATER VAPOR LOOP SHOWS A WEAK IMPULSE /CURRENTLY POSITIONED OVER
SWRN ID/ AND ATTENDANT PLUME OF MIDLEVEL MOISTURE EMBEDDED IN FAST
UPPER FLOW TRANSLATING ESEWD TOWARDS THE ERN GREAT BASIN. ALTHOUGH
17Z SFC OBS FROM KSLC REFLECT A RELATIVELY DRY BOUNDARY
LAYER...PERSISTENT MOISTENING ASSOCIATED WITH MIDLEVEL MOISTURE
ADVECTION...MODERATE LOW-LEVEL UPSLOPE FLOW ALONG THE WRN EDGE OF
THE WASATCH MTNS...AND WEAK ISENTROPIC UPGLIDE WILL RESULT IN
SATURATION THROUGH THE LOWER TROPOSPHERE. WET-BULB COOLING WITHIN
THE BOUNDARY LAYER WILL EVENTUALLY LEAD TO SUBFREEZING COLUMNAL
TEMPERATURES AT MOST LOCALES...FAVORING A P-TYPE OF PRIMARILY
SNOWFALL /AS SUPPORTED BY 12Z WRF-NMM AND 15Z WRF-HRR/...ALTHOUGH
MIXED P-TYPES MAY BE OBSERVED AT TIMES IN THE LOWEST ELEVATIONS AS
TEMPERATURES ARE FORECAST TO BE NEAR OR JUST ABOVE FREEZING.
NAMKF/GFS POINT FORECAST SOUNDINGS INDICATE SOME WARMING WILL OCCUR
IN THE 700-500 MB LAYER BETWEEN 18-21Z...RESULTING IN A SHRINKING
DENDRITIC GROWTH LAYER...BUT ANY EFFECT ON SNOWFALL RATES SHOULD BE
OFFSET BY STRENGTHENING LOW-LEVEL OROGRAPHIC LIFT/ISENTROPIC UPGLIDE
IN RESPONSE TO PRESSURE FALLS OVER NRN WY. THUS...SNOWFALL RATES
NEAR 1 INCH PER HR OVER THE ERN SALT LAKE VALLEY...APPROACHING 2 IN
PER HR OVER THE HIGHER MTN PEAKS OF THE WASATCH RANGE...APPEAR
PROBABLE BY LATE AFTERNOON.
..ROGERS.. 01/18/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...SLC...
LAT...LON 40031074 39791118 39931169 40751209 41191221 41461206
41511149 41031106 40541073 40031074Nearby
Mesoscale Discussions in Utah, 2012Every 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.