Aviation Weather Services

AIRMET MTN OBSCN…ME NH VT MA NY PA Washington, for a defined area from Seattle to Portland to FROM CAR TO MLT TO CON TO SLT TO SYR TO CAR Eugene to Seattle. It calls for occasional severe clear air MTNS OCNLY OBSCD BY CLDS/PCPN/BR. CONDS turbulence between FL280 and FL350 due to the location of CONT BYD 02Z THRU 08Z the jet stream. These conditions will begin after 0200Z and continue beyond the forecast scope of this SIGMET of 0530Z. Explanation: AIRMET SIERRA was issued for the Boston area at 1945Z Convective Significant Meteorological Information on the 21st day of the month. SIERRA contains information (WST) on IFR and/or mountain obscurations. This is the third A Convective SIGMET (WST) is an inflight weather updated issuance of this Boston AIRMET series as indicated advisory issued for hazardous convective weather that affects by “SIERRA UPDT 3” and is valid until 0200Z on the the safety of every flight. Convective SIGMETs are issued 22nd. The affected states within the BOS area are: Maine, for severe thunderstorms with surface winds greater than 50 New Hampshire, Vermont, Massachusetts, New York, and knots, hail at the surface greater than or equal to ¾ inch in Pennsylvania. Within an area bounded by: Caribou, ME; diameter, or tornadoes. They are also issued to advise pilots to Saint Johns, New Brunswick; to 150 nautical miles east of embedded thunderstorms, lines of thunderstorms, or of Nantucket, MA; to Newark, NJ; to Ottawa, Ontario; thunderstorms with heavy or greater precipitation that affect to Caribou, ME. The effected states within Caribou, ME 40 percent or more of a 3,000 square mile or greater region. to Millinocket, ME to Concord, NH to Slate Run, PA to Syracuse, NY to Caribou, ME will experience ceilings Convective SIGMETs are issued for each area of the below 1,000 feet/visibility below 3 SM, precipitation/mist. contiguous 48 states but not Alaska or Hawaii. Convective Conditions will continue beyond 0200Z through 0800Z. SIGMETs are issued for the eastern (E), western (W), and central (C) United States. Each report is issued at 55 minutes SIGMET past the hour, but special Convective SIGMETs can be SIGMETs (WSs) are inflight advisories concerning non- issued during the interim for any reason. Each forecast is convective weather that is potentially hazardous to all valid for 2 hours. They are numbered sequentially each day aircraft. They report weather forecasts that include severe from 1–99, beginning at 00Z time. If no hazardous weather icing not associated with thunderstorms, severe or extreme exists, the convective SIGMET is still issued; however, it turbulence or clear air turbulence (CAT) not associated with states “CONVECTIVE SIGMET…NONE.” thunderstorms, dust storms or sandstorms that lower surface or inflight visibilities to below three miles, and volcanic ash. Example: SIGMETs are unscheduled forecasts that are valid for 4 hours MKCC WST 221855 unless the SIGMET relates to a hurricane, in which case it CONVECTIVE SIGMET 20C is valid for 6 hours. VALID UNTIL 2055Z ND SD A SIGMET is issued under an alphabetic identifier, from FROM 90W MOT-GFK-ABR-90W MOT November through Yankee. The first issuance of a SIGMET INTSFYG AREA SEV TS MOVG FROM 24045KT. TOPS is designated as an Urgent Weather SIGMET (UWS). ABV FL450. WIND GUSTS TO 60KTS RPRTD. Reissued SIGMETs for the same weather phenomenon are TORNADOES…HAIL TO 2 IN… WIND GUSTS TO sequentially numbered until the weather phenomenon ends. 65KTS POSS ND PTN Example: SFOR WS 100130 Explanation: SIGMET ROME02 VALID UNTIL 100530 Convective SIGMET was issued for the central portion of OR WA the United States on the 22nd at 1855Z. This is the 20th FROM SEA TO PDT TO EUG TO SEA Convective SIGMET issued on the 22nd for the central OCNL SEV CAT BTN FL280 AND FL350 EXPCD United States as indicated by “20C” and is valid until 2055Z. DUE TO JTSTR. The affected states are North and South Dakota, from 90 CONDS BGNG AFT 0200Z CONTG BYD 0530Z . nautical miles west of Minot, ND; to Grand Forks, ND; to Aberdeen, SD; to 90 nautical miles west of Minot, ND. An Explanation: intensifying area of severe thunderstorms moving from 240 This is SIGMET Romeo 2, the second issuance for this degrees at 45 knots (to the northeast). Thunderstorm tops will weather phenomenon. It is valid until the 10th day of the be above FL 450. Wind gusts up to 60 knots were reported. month at 0530Z time. This SIGMET is for Oregon and 13-12