Forecast for Friday, May 20

Issued: Thursday, May 19 Launch Weather Officer: Capt. Paul Lucyk, 30th Weather Squadron Synoptic Discussion: Vandenberg is currently under the influence of high pressure exiting the area to our east. 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 at SLC-2 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 northeasterly winds from 12-18 knots with occasional gusts to 22 knots and temperature in the middle 50's. Visibility will be unrestricted and we will have few to scattered stratus and cirrus clouds overhead. The upper level winds will be west-southwesterly with maximum of 58 knots at 45,000 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 33-35 knots followed by 20-25 knots at 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 50's to lower 60's. Upper level winds are forecast to remain from the west-southwest at 40 knots near 45,000 feet. Clouds: Stratus at 700 feet with 3/8ths sky coverage tops at 1,800 feet; Cirrus at 28,000 feet with 2/8ths sky coverage tops at 32,000 feet Visibility: 7 miles Winds at Launch Time: Northerly from 350-040 degrees at 12-18 knots, gusting to 22 Temperature: 53 to 58 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