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SEPTEMBER 1988 Type'" Date 11 FEB84 15MAR84 07FEB85 26MAR85 15JAN86 29JAN86 02FEB86 12FEB86 14FEB86 16FEB86 07MAR86 09MAR86 0IJAN87 03JAN87 2 08FEB84 23FEB84 13MAR84 16MAR84 24MAR85 04JAN86 14JAN86 23JAN86 3IJAN86 11 MAR86 13MAR86 04DEC86 3 2IJAN84 II FEB85 21MAR85 19JAN86 19NOV86 21NOV86 22NOV86 29NOV86 13DEC86 18DEC86 22DEC86 3lDEC86 MARK F. HEGGLI AND ROBERT M. RAUBER TABLE 1. Summary of storm types (see section 3) 1983/84 through 1986/87 field seasons. Start Hour (UTC) 2230 0430 0430 1030 2230 0730 0430 0130 0130 1630 0430 2230 0130 1030 1630 1630 0730 1630 1330 0730 2230 0430 1930 1930 0430 2230 0130 1330 0130 2230 0130 0430 1330 0430 1630 1030 1330 1030 Zonal Date Stop Hour (UTC) Data+ Type Date 14FEB84 16MAR84 10FEB85 29MAR85 17JAN86 3lJAN86 04FEB86 13FEB86 16FEB86 21FEB86 09MAR86 11 MAR86 02JAN87 04JAN87 IOFEB84 25FEB84 15MAR84 17MAR84 26MAR85 06JAN86 15JAN86 23JAN86 01 FEB86 12MAR86 14MAR86 06DEC86 22JAN84 12FEB85 21MAR85 20JAN86 19NOV86 21NOV86 22NOV86 29NOV86 14DEC86 19DEC86 23DEC86 OlJAN87 1630 1630 0130 0430 2230 1330 0730 1930 1630 1630 2230 1930 0730 0430 1030 1630 0430 1330 0130 0730 2230 1930 1630 2230 1030 1630 0130 2230 1630 1930 1930 1630 1930 1630 2230 1030 1030 0130 P o A A o o P o o o P A o o 4 21FEB84 15DEC84 06JAN85 IOMAR85 17MAR85 14MAR86 19DEC86 Start Hour (UTC) 0130 0730 1030 0730 2230 2230 1030 0130 0130 0130 1930 1030 2230 2230 0730 1630 1030 1630 1030 1630 0730 0130 1630 1030 1630 Meridional Stop 995 Date Hour (UTC) Data 22FEB84 17DEC84 08JAN85 12MAR85 19MAR85 16MAR86 20DEC86 17FEB84 01APR84 29JAN85 02FEB85 04FEB85 20FEB85 02MAR85 05MAR85 08MAR85 06FEB86 08NOV86 26MAR84 26JAN85 3lDEC85 OlJAN86 22FEB86 02MAR86 06JAN87 0730 0130 1030 0130 0130 1630 0730 0130 2230 0430 1030 0430 1030 1030 1330 0130 0730 0730 2230 1930 0130 2230 1630 1330 1630 o o A A A A A P A A A A o A A A A A A A o o o o A '" 1. Developing storm embedded in strong westerly or southwesterly flow; 2. Moderate amplitude short-wave associated with an occluded storm; 3. Split flow in the middle troposphere associated with a dissipating storm; 4. Cutoff low or large amplitude short-wave near 40oN; 5. Large amplitude long-wave pattern producing cold northerly storms; 6. Stonns did not fit above categories, + Data column indicates radiometer data availability for storm: A = all, P = partial, and 0 = no data available. frontal boundary was present at 700 mb over Sheridan. Air above the front was moist but dry below the front prior to 1800. The warm frontal cloud shield extended far ahead of the main precipitating regions of the sys- tem. The cloud shield is evident on the 0100 satellite photograph. With time, as the warm front continued to move over the region, precipitation fell into the drier low-level air, gradually moistening the lower atmo- sphere. At the time of the photograph, the warm frontal surface was still present over Sheridan. Precipitation rates increased steadily as the warm front moved over the region. Supercooled water was present continuously within the frontal clouds, but generally in small quan- 5 15FEB84 31MAR84 28JAN85 0lFEB85 03FEB85 19FEB85 0lMAR85 04MAR85 05MAR85 05FEB86 07NOV86 P A o o A o A P o A A A 6 26MAR84 25JAN85 29DEC85 3lDEC85 21 FEB86 02MAR86 05JAN87 A o o o o o o A P A A A tities (0.10 mm liquid water depth). No significant peaks were present in supercooled water, suggesting that the liquid developed in response to gradual lifting, probably associated with the frontal surface, rather than convection. Two precipitation bands moved across the Sierra Nevada at 0300 and 0420. The latter band was asso- ciated with the cold front. The surface cold frontal po- sition at 0000 was slightly east of the high cloud boundary evident in northwest California in Fig. 4. The surface cold front moved through Sheridan at 0200 (Fig. 5) and over Kingvale at 0445. Reynolds and Ku- ciauskas (1987) have shown that this front possessed