1014 
MN QOuUN TAINS 
AN 
yin 
¢ 
Lo Madiferd Sretee 
oh Sa deenvelia Fe? an 
Oo Grante Peee Srer an 
¢ Sohlead S¥e ham 
SF Pew paw 
Raglk sm fer % rhea sned 
Fig. 2. 
here when the Northwest is occupied by 
low pressure; in fact, when a rain fore- 
cast would seem more legitimate than a 
frost warning, as on the night of the 6th 
of April; but this is an uncommon con- 
dition. Under such conditions the barom- 
eter may show no fluctuation worth 
speaking of,.the surface currents may be 
from the south, in fact nothing to war- 
rant a frost warning being issued except 
the fact of a clearing sky and a sharp fall 
in temperature. 
The forecaster has then to determine 
whether the wind is to remain light and 
the sky clear, and this is an extremely 
precarious undertaking. Perhaps the 
daily rise in the barometer occurring at 
the time his decision is being made adds 
to the difficulty; and he must be able to 
distinguish to a certain extent between 
the periodic and the unperiodic move- 
ment, for it is the latter upon which he 
depends in a large measure to foretell 
the condition of the sky. Under such 
conditions, and unless the forecaster is 
sure of his position, it is wiser to place 
on their guard those who wish to protect 
their orchards, for the growers would 
rather be warned a few times unneces- 
sarily than to have freezing temperatures 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
Mal Lead 
OCantradforat 
. 
-~ t x 
= Odeon . 
oo aur dant = 
~— 2 x Be 
° = 
Sraboonuille 
we uy A, 
V aly “, 
MOUNTAINS 
SPP dog ep 
“wo ere ” 
“ef 
Rogue River Valley Fruit District. 
—After Recd. 
descend on their orchards without fore- 
warning. 
The freeze occurring on the morning of 
April 6, 1911, when the temperature at 
North Yakima dropped to 25 degrees, 
could scarcely be foreseen, either from 
the weather map or from local observa- 
tions, but it is a type of local freeze 
which should be studied and for which 
the local observer should be constantly 
on guard. 
The ensuing freezes, which occurred 
with unusual frequency and severity for 
this section, were more easily foreseen. 
Between the inclusive dates of April 5 
and 15 nine heavy frosts were recorded 
in North Yakima, and during the first 
half of the month there were more than 
this number in the neighborhood of Moxee 
and on the low ground below Union 
Gap. Seven times the minimum temper- 
ature dropped to 28 degrees or lower at 
the North Yakima station. The severest 
freeze of the entire period occurred on the 
morning of the 13th of April. The 
North Yakima station registered 24 de- 
grees; in Moxee 16 degrees was reached, 
and the temperature in the lower valley 
ranged from 17 degrees at Sunnyside to 
28 degrees at Parker Heights. 
