The Forecasting Process, page 18 of 20

SDZ013-014-025>027-030>032-041>044-112100-
BENNETT-CENTRAL FOOT HILLS-CUSTER PLAINS-FALL RIVER-HAAKON-JACKSON-
MEADE-NORTHERN FOOT HILLS-PENNINGTON PLAINS-SHANNON-SOUTHERN FOOT HILLS-
ZIEBACH-
INCLUDING THE CITIES OF...FAITH...DUPREE...STURGIS...RAPID CITY...
HOT SPRINGS...WALL...EDGEMONT...PINE RIDGE...KADOKA...MARTIN
920 AM MDT SAT OCT 11 1997

.TODAY...PARTLY CLOUDY WITH A 30 PERCENT CHANCE OF SHOWERS OR
THUNDERSTORMS. HIGH IN THE MIDDLE 70S. SOUTHEAST WIND 10 TO 20 MPH.
.TONIGHT...WINDY WITH RAIN LIKELY. LOW IN THE LOWER TO MID 40S. WIND
BECOMING NORTH AND INCREASING TO 20 TO 35 MPH THIS EVENING. CHANCE OF
RAIN 70 PERCENT.
.SUNDAY...VERY WINDY AND MUCH COLDER WITH A 50 PERCENT CHANCE OF RAIN.
NEARLY STEADY TEMPERATURES IN THE LOWER TO MID 40S. NORTHWEST WIND 25 TO
40 MPH.

A check of the zone forecast shows no useful guidance on the maximum temperature. They don't say when they think the front will come through, so I'm stuck with my 58. (If I had more time, I would read the forecast discussion; usually they're more explicit about fronts in the discussion.)

They seem to agree with my estimate of the daytime high tomorrow. But they don't say what the forecast is for tomorrow night. I guess it's too far in the future to show up in the zone forecast. The longer-range forecasts are given in the state forecasts, so I go to STATE in Weather and get the state forecast for South Dakota:

FPUS1 KFSD 110901
SFPSD
SDZ001>071-112100-

STATE FORECAST FOR SOUTH DAKOTA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
400 AM CDT SAT OCT 11 1997

.TODAY...MOSTLY CLOUDY WITH A CHANCE OF SHOWERS AND THUNDERSTORMS. WINDY
CENTRAL AND EAST. HIGHS IN THE MID 60S TO MID 70S.
.TONIGHT...THUNDERSTORMS LIKELY EAST. RAIN LIKELY WEST...POSSIBLY MIXED
WITH OR CHANGING TO SNOW IN THE NORTHWEST AND BLACK HILLS. WINDY. LOWS
AROUND 40 NORTHWEST TO NEAR 60 SOUTHEAST.
.SUNDAY...WINDY AND MUCH COLDER WEST WITH A CHANCE OF RAIN. RAIN MIXED
WITH OR ALL SNOW IN THE NORTHWEST AND BLACK HILLS. WINDY EAST WITH
SHOWERS AND THUNDERSTORMS LIKELY. NEARLY STEADY TEMPERATURES FROM THE
LOWER 40S NORTHWEST TO THE MID 60S SOUTHEAST.

.EXTENDED FORECAST...
.MONDAY...CHANCE OF SHOWERS...MORE LIKELY NORTH. COOL. LOWS IN THE
UPPER 20S TO LOWER 30S. HIGHS IN THE UPPER 40S TO LOWER 50S.
.TUESDAY...DRY AND CONTINUED COOL. LOWS IN THE MID 20S TO LOWER 30S.
HIGHS IN THE LOWER TO MID 50S EAST...LOWER 60S WEST.
.WEDNESDAY...DRY. LOWS IN THE 30S. HIGHS IN THE 50S EAST AND 60S WEST.

                               DAY 3         DAY 4         DAY 5
SIOUX FALLS   73/59/61       L30/45-50     25-30/L50      N30/M50
RAPID CITY    73/46/46       30-35/M50     25-30/L60      L30/M60
ABERDEEN      75/57/58        U20/M40       M20/N50       N30/L50
PIERRE        77/54/56        L30/U40       U20/M50       L30/N60

The state forecast says 30-35 for the min tomorrow night, a bit colder than I had expected. I'll hedge down my minimum temperature forecast a bit as a result, to 37. The text of the forecast gives the impression of being rather rainy, so I'll stick with my category 4. Thus, my final forecast is 58 37 4.

Second thoughts. Climo is 0.02 to 0.03 for precip per day. That's only about 3/4 inch for the entire month, on average! Do I dare forecast that much precipitation for a single day? No, I don't. Make that 58 37 3.

Third thoughts. The wind will be from the northwest. That's downslope, which tends to cause downward motion and inhibits precipitation. Perhaps I should go category 2? Nah, I don't want to deviate from the computer model that much without a solid reason. But there is a good reason, the Black Hills are too small to be properly represented in the model. I've talked myself into it: 58 37 2.

I could lose a lot of points on the precip, and I could lose a lot of points on the max. If that front speeds up (and it's still developing), my max will be way too high. I ought to hedge downward, but I've done enough hedging for one day. I'm sticking to my forecast.

Questions or Comments

Scientific: E-mail John Nielsen-Gammon < n-g@tamu.edu >
Technical: E-mail John Fulton < jdfult@nimbus.met.tamu.edu >