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<br />played in the surface and 500-millibar synoptic maps below and 2) ~he <br />vertical time cross sections discussed nore fully in section E. In <br />addition to the two-dimensio~al display, the availability of snyoptic <br />data is relevant to the farecasting of the storm periods in the Jemez <br />area en an operational basis. L~e forecast will depend on the data <br />available by phone from Albilquerque, ap-d the local surface and radiosonde <br />observations interpreted with knowledge cf overall synoptic patterns <br />in the area. <br />Since all aspects of weather data are ultimately interrelated, <br />the period of synoptic analysis has been limited to coincide with the <br />period or rain gage network operations in the Jemez Mountain area (approx- <br />imately 5 January, 1968 to 15 March, 1968). With limited synoptic data <br />available, no claim is made for all inclusiveness of winter storm patterns. <br />The observed situations are generalized somewhat and are based on the <br />experience of a professional forecaster. Five surface systems, and <br />four SOO-mb systems which have a definite relationship to stormy weather <br />periods are discussed below. <br />1. Frontal Systems, The Pacific Front (see FiRure 1) <br />A surface cold front approaches the area from the west or north- <br />west, which is usually characterized by a few hours of precipitation <br />followed by ra?id clearing. Surface winds shift from southwesterly <br />to northwesterly while surface pressure changes from a falling ten- <br />dency to a rising tendency during the passage of the front. Some <br />drop in surface temperature is usually observed with this type of <br />frontal passage. A 500-rnb trough passage generally accompanies this <br />type of front which was associated with the storm periods in the <br />experimental area during 11 January, 28 January, 31 January, 18 Feb- <br />ruary, and 8 March, 1968. This is probably the most frequent type <br />of surface weather pattern, but is often completely "dry" after having <br />traversed all the mountainous western states prior to reaching the <br />Jemez area. <br />2. Frontal Systems, The Canadian Front (see Figure 2) <br />A surface cold front approaches the target area from the north, <br />northeast or east. This system is often "dry", not because it has <br />passed over extensive ranges of mountains, but because the origin of <br />this storm (central Canada) is not an adequate source of moisture. <br /> <br />-7- <br />