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JUNE 2-7, The general storm of June 2-7, 1921, was the only storm of record that caused severe floods and unusually high water in nearly all parts of Colorado. The daily weather maps for the first week in June 1921 show that an area of high pressure exceeding 30.5 inches appeared June lover the Province of Alberta. By June 2 it had displaced a low pressure area over the upper Missouri Valley, and on June 3 it was over Manitoba and the northern part of North Dakota. Between June 3 and 4 the movement of the high pressure area was very slow, and it advanced only as far as northeastern :Minnesota. By June 5 it had reached a point over the Great Lakes. During this period an area of low pressure, 29.7 inches, had de- veloped over western Arizona and remained over the southern Rocky :Mountain plateau for several days.12 Warm, moist air from the southern States and the Gulf of ~Jexico was drawn into the low- pressure area. 'When this moist air met the cold front from the north it was forced upward, and being cooled, its moisture was released as precipitation. The effect of the cold front was increased by the foothills, especially in the vicinity of Pikes Peak, v,rhich is a semi- detached mountain mass rising abruptly from the plains. The following table shows the rainfall during the period June 2-7 along the foothills and the Pil\:es Peak region. Stations are listed from north to south. 1\1 - l\1ETEOl{ULUGIC co::\ DIUO);'S 1921 ..... . and Total Ln LM ~~ ~a L. 1.n Ln ~~ ~u ~~ ~~ ~42 LW ~~ ~M ~M ~M ~~ ~M L~ L~ U. s; GooI June 3-5, 1921 llood of River ,. Follansbee, R'obert. and Jones, E. E., The Arkansas Survey, Water.Supply'Paper 487. pp; 11-12, 1922. ., 1911 2.88 3.42 3.52 272 ~25 R.16 3.82 4.83 1.62 .47 2.23 1. 79 2. 51 2.45 Total Oct.~ 2 and Oct. 4-8, Total co"......+ I}I) -o~Ci -1-1-1-1- .13 '-Ti-:'- .49 O.~ 15 20 01 M vi) v~ 2W 2~ 2W 2m 4.~ &~ L~ L~ LM .n L71 I.M 200 2W Oct 1.16 .72 .19 .20 .11 .15 3.M 08 37 02 50 21 \"uLUlliUJU in the San Juan region, Sept. 22 to v, 1. 75 3,60 5,36 3.80 5.04 2.04 4.15 3.99 Lll 2.()3 3.~ 3,69 2.55 Altitude (fee 7,610 6,589 8,300 8.900 9,400 10,400 7,108 10,015 7,035 10.000 8,824 8,756 7,500 9,800 L\ LLUVU;:' EXPDSl'd to southwes Fort Lewis_h_u hh.h Durango_________ ___uu__._ Terminal Dam_h _____.h_h______.. Cascade__________ ___________.h_____ Sih-erton_ _.______ ____._h.h___. .00. Gladstone_. ______ __U__h__.n.___.. Pagosa Springs_ __ ___ '__ ___ ____.____00.00_ Cumbres_. _ _h _ _ _ _._ ____._ _00 _. _h' ____ 00 Sheltered from southwest: 2Ilaneos.. _ _ _ _. h" _._ __ _ __ nc_ 00__ _ ____'h ~r:;~_~::::::::::::::::::::::::::: ::~::::: Te Huride. _ _ _. hh_h.. __h ___ _ 00_ __00._ Chromo_. ______h.h .___.h.h_____.___ Iron ton...._ _ _ _ __ _ _ _ _h_ _ _ _ h ___. hhh_ Xortbeastern Slope of San Juan l\Iounmins: Wagon Wheel Gap Experiment Station_ 1'la10ro_________ h'__ ~ in.es, Statio,! J.0 precipitation, 2,65 3.34 The San Juan Mountains in southwestern Colorado are much higher than any mountains southwest of them, hence the moist air was deflected upward and, on cooling; deposited much of its moisture in that region. The amount of precipitation was influenced not only by altitude but by the degree of exposure to the storm. :Mancos is sheltered by Mesa Verde; and Eureka, although on the south slope of the San Juan Ivfountains, is in a deep, narrow valley cut off by high mountains. :r~ orth and east of 04 1. 94 3.25 71 05 99 1. 78 9,610 9;WO in inches, along foothills and Pikes Peak region in South Platte Arkansas River Basins, June 2-7, 1921" 2 3 4 5 6 7 _1__1_1_1__1_1_ 051 .4() 18 Tr. ---~!-I-.:-~! .01 .15 .4() _h___ ,:\,r. .'J:I ~60 .m .~ .m .n .~ .U .M .n .n .W .~ ~~ .~ .M .M .m .W .60 .m .M .~ .~ .W .00 0.47 .25 .52 .44 .71 .20 .48 1.60 .52 .95 Tr. 1. 07 .10 82 1.4() 1. 43 1.1i5 h:09' .75 .30 June L~ L~ I.g -g I.W .00 .g 1.~ LM 2M .00 2D W 200 ~~ 2m 2M ~oo I.~ 2M .M ~n I.M l.W ~m .M .W 2M .m .n L~ 2m .W LW .65 253 .03 2_23 1.f>4 .30 .20 0.66 .M .07 .31 ,01 .23 .M .23 .06 .34 06 .16 1.94 Alti. tude (fect) ~~ ~- ~D ~- ~m ~~ ~~ ~~ ~- 8,14() ~m ~- ~~ 7,~ ~- ~~ ~~ ~m ~- ~m ~m Station South Platte River Basin: La Porte_ __.oo_________h h__h 'Fort .Collins.._oooo._h__.__ _hh_ W aterdale__ _h__. 00 _00.__.'_._. __. _ hh_h Longmont___ _ 00 __.. __ _ _ _ _ _00 _._ _. hhh h_ Boulder _ __ .'h_____h_hh___oo _____00_____. Hawthorne__.h _h_ h h h _ _ _.oo. __.oo__ _ h__ ~~~~~~:~::::::::::::::::::::::::::::::::: : Kassler._ ._noo___ _.___. _n_n___ h' _ h____.. 'Elk Creek.'__ 00 ._00 __. oo h ___ n_ _ _ _ _ _ _ h __ ___ Castle Rock_. __.__ _hn.~. .h_ _h :_h h h _ h Cht'€'smaD...._ ~ _ ~ ___ _ _ _ _~ _... _ __ _ ___ __ u_ _ __ _ ___ Aldhurst. . _ _ h_ _h.. _ 00.._ ._... __. n_ __.. ___ Arkansas River Basin: Monument._ _ ._. _h h h_ h __ _h' _h _h __._.. Lake Moraine_ ___ _c._______h__hh_h.h___ Fremont Experiment Statlon.nhh__h____ Victor _ _ h _ _ _ h ____nn_ n' noon. __ n_.._._. Colorado Springs .n.h___.-'..____oooo_______ Pueblo_ ___..n__.hh.____._ __:__00..0000"_ Canon City .. _ __._ h_' _._ .._____. _ ___ __. _n_ Trinldad_ _._ _____h.h__._ _. __n_._.___~..oo Corrected record. Rainfal the san Juan Mountains the precipitation was much less, averaging about 1.5 inches for October 4-6, except along the Sangre de Cristo Mountains, which form the eastern boundary of the San Luis Valley. The part of the San Juan :Mountains forming the western boundary of the valley is not as wide as the northern part in the Silverton region and caused less loss of lllOisture from the air crossing that part. Consequently, when the air currents reached the Sangre de ,Cristo Mountains and were deflected up'Xard, heaVy precipitation resulted., Although no rainfall records for the western slope are available, there is evidence of severe floods on all streams draining that slope; indicating heavy rainfall. At Hermit Lake, at an altitude of 10,000 feet on the eastern slope just below, the crest, the precipitation October 4-6 was 3.68 inches. At La Veta Pass it was 2.01 inches. , The only other record of precipitation in the State that. exceeded 2 inches for the period October 4-6, 1911, was 2.35 inches at Marble, at anaititude of 7,950 feet, on the north slope of the Elk Mountains, a high mountain mass somewhat west of th~ central part of tJ1e State.