Forecast for Friday, May 20

Issued: Tuesday, May 17 Launch Weather Officer: Capt. Paul Lucyk, 30th Weather Squadron Synoptic Discussion: Vandenberg is currently under the influence of low pressure exiting the area to our east. Expect an upper-level ridge of high pressure to move in today and continue through Wednesday. This will keep our weather dry with warm temperatures and overnight low clouds and fog. A low pressure system is poised to move through the Pacific Northwest on Thursday bringing a broad, weak trough and tighter surface pressure gradient to central and southern California. This will again bring breezy conditions for tower roll efforts by early evening. The forecast calls for sustained northwesterly winds in the 15-20 knot range with gusts to 25 knots in the afternoon and evening hours. The wind will taper off slightly after sunset, but we expect continued high teens gusting in the low twenties through 2300 local. By T-0, expect northerly winds from 15-20 knots and temperature in the low to middle 50's. Visibility will be 3 miles with light fog in the area and we will have scattered to broken stratus and cirrus clouds overhead. The upper level winds will be west-southwesterly with maximum of 72 knots at 43,000 feet. 24 Hour Scrub Forecast: The forecast for Friday afternoon and Saturday morning brings a significantly tighter pressure gradient and associated gusty winds. The maximum gusts are forecast from the north at 33 knots followed by 20-25 knots by T-0. This will present a significantly more challenging day for tower roll/exposure and booster preparations. Expect clear skies and unrestricted visibility with temperatures in the upper 40's to lower 50's. Upper level winds are forecast to remain from the west-southwest and decrease to 42 knots at 44,000 feet. Clouds: Stratus at 500 feet with 5/8ths sky coverage tops at 1,700 feet; Cirrus at 27,000 feet with 6/8ths sky coverage tops at 32,000 feet Visibility: 3 miles Launch Pad Winds: Northwesterly from 330-360 degrees at 15 to 20 knots Temperature: 50 to 55 degrees F Probability of Violating Weather Constraints at T-0: 20 percent Concerns: Launch pad winds

24-hour Delay Forecast

Saturday's Probability of Violating Constraints at T-0: 40 percent Concerns: Launch pad winds