RAP: Temperatures

We have three major temperature issues for Rapid City today:

1. What will the temperature be at 06Z tonight?
2. What will the temperature be during the day tomorrow?
3. What will the temperature be at 06Z tomorrow night?I'll tackle the first one first. If the front does not arrive by 06Z, what will happen?

Back to the hourlies. I guess they'll mean something for the forecast after all. I've extracted some of the overnight observations below.

KRAP 110255Z 15007KT 10SM CLR 14/07 A2973 RMK AO2 PRESFR SLP060 T01440067 58017= 

KRAP 110355Z 17004KT 10SM CLR 13/07 A2971 RMK AO2 SLP049 T01330072= 

KRAP 110455Z 12013KT 10SM CLR 14/07 A2965 RMK AO2 PRESFR SLP025 T01440067=

KRAP 110555Z 15005KT 10SM CLR 13/07 A2963 RMK AO2 SLP015 T01280067 10200 20122 58027= 

KRAP 110655Z 15007KT 10SM CLR 12/06 A2961 RMK AO2 SLP008 T01220061 402610050= 

KRAP 110755Z 15009KT 10SM CLR 14/08 A2959 RMK AO2 SLP998 T01390083= 

KRAP 110855Z 14009KT 10SM FEW095 15/10 A2957 RMK AO2 RAB45E55 SLP989 P0000 60000 T01500100 56019= 

Last night at 06Z, the temperature was 12.8 C, or 55 F. The winds are a bit stronger today than yesterday, which ought to keep the temperature warmer at night. I also happen to know from experience that right in front of a cold front, the temperature has a hard time dropping at night, and sometimes it goes up at night before the front comes through! On the other hand, there's rain on the way. But the latest observation:

KRAP 111955Z 19012G18KT 10SM CLR 26/12 A2938 RMK AO2 SLP925 T02560122=

shows a dewpoint of 12.2 C (54 F). Rain typically cools the air 1/2 to 2/3 of the way down to the dew point, so rain by itself won't drive the temperature down much at RAP. I'm going to say that if the front doesn't come through, the temperature will be about 58 F. And since I already forecasted that the front would not come through til after 06Z, and since the daytime temperatures behind the front are in the 40s, that's my maximum temperature forecast: 58.

I am inserting this paragraph after having looked at what actually happened. It turned out that I was too slow with the front, for reasons I will mention later. So here's an opportunity to do some forecasting for yourself, and to beat me: if the front comes through RAP around 00Z, six hours before the start of the forecast period, what do you think the temperature will be in RAP at 06Z? Remember, conditions behind the front are cloudy, so that air probably won't cool off much from its current afternoon temperatures. Make a forecast for the 06Z temperature, then continue.

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