####018002808#### FXXX12 KWNP 181231 DAYDIS :Product: Forecast Discussion :Issued: 2024 May 18 1230 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # Product description and SWPC contact on the Web # http://www.swpc.noaa.gov/wwire.html # # Forecast Discussion # Solar Activity .24 hr Summary... Solar activity reached high levels following an M7.2/2b flare from Region 3685 (S13E49, Esi/beta-gamma). Associated with the flare was Type II (425 km/s) and Type IV radio sweeps as well as a CME first observed in SOHO/LASCO C2 imagery at 17/2124 UTC off the E limb. Initial analysis indicated a potential glancing blow late on 20 May. Slight growth was observed in Region 3685 and Region 3683 (S23W39, Dri/beta). The rest of the spotted regions were either stable or slightly decaying. .Forecast... Solar activity is expected to be low with a good chance for further M-class flares (R1-R2/Minor-Moderate) and a slight chance for an X-class flare (R3/Strong or greater) on 18-20 May. Energetic Particle .24 hr Summary... The greater than 10 MeV proton flux was slightly elevated, but well below S1 (Minor) levels. The 2 MeV electron flux was at normal to moderate levels. .Forecast... There is a slight chance for the greater than 10 MeV protons reaching S1 (Minor) levels on 18-20 May due to the flare potential of Region 3685. The greater than 2 MeV electron flux is expected to remain at normal to moderate levels through 20 May. Solar Wind .24 hr Summary... Solar wind parameters reflected the likely arrival of the 14 May CME. The arrival at 17/1245 UTC resulted in stronger enhancements than anticipated, with total field reaching a peak of 17 nT, Bz seeing a maximum southward deflection of -15 nT, and solar wind speeds mostly in the 450-500 km/s range. After 18/0000 UTC, solar wind speed began to decrease to the 400-450 km/s range and total field decreased to under 10 nT after 18/0600 UTC. Phi angle was mostly negative. .Forecast... Solar wind parameters should continue to decrease through the rest of 18 May. Further enhancements are likely on 19-20 May, due to glancing influences of additional CMEs. Geospace .24 hr Summary... The geomagnetic field reached G1-G2 (Minor-Moderate) storm levels late on 17 May following the arrival of the anticipated 14 May CME. Quiet to active levels were observed through early on 18 May. .Forecast... The latter half of 18 May should see a return to quiet to unsettled levels as CME effects diminish. By 19-20 May, conditions are expected to increase back to unsettled to active levels, with a chance for G1 (Minor) storming, due to glancing CME effects from the 15 and 17 May CMEs. ####018002290#### FXXX10 KWNP 181231 DAYTDF :Product: 3-Day Forecast :Issued: 2024 May 18 1230 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # Product description and SWPC contact on the Web # http://www.swpc.noaa.gov/wwire.html # # 3-Day Forecast # A. NOAA Geomagnetic Activity Observation and Forecast The greatest observed 3 hr Kp over the past 24 hours was 6 (NOAA Scale G2). The greatest expected 3 hr Kp for May 18-May 20 2024 is 4.00 (below NOAA Scale levels). NOAA Kp index breakdown May 18-May 20 2024 May 18 May 19 May 20 00-03UT 3.67 3.33 2.67 03-06UT 3.33 3.33 2.33 06-09UT 2.33 4.00 3.67 09-12UT 3.33 4.00 3.00 12-15UT 3.00 2.67 3.00 15-18UT 1.67 2.33 3.33 18-21UT 1.67 2.00 4.00 21-00UT 2.33 2.67 4.00 Rationale: There is a chance for G1 (Minor) geomagnetic storm conditions on 19-20 May due to possible glancing blows from CMEs that left the Sun on 15 and 17 May. B. NOAA Solar Radiation Activity Observation and Forecast Solar radiation, as observed by NOAA GOES-18 over the past 24 hours, was below S-scale storm level thresholds. Solar Radiation Storm Forecast for May 18-May 20 2024 May 18 May 19 May 20 S1 or greater 10% 10% 10% Rationale: There is a slight chance for the greater than 10 MeV protons reaching S1 (Minor) levels on 18-20 May due to the flare potential of Region 3685. C. NOAA Radio Blackout Activity and Forecast Radio blackouts reaching the R2 levels were observed over the past 24 hours. The largest was at May 17 2024 2108 UTC. Radio Blackout Forecast for May 18-May 20 2024 May 18 May 19 May 20 R1-R2 40% 40% 40% R3 or greater 10% 10% 10% Rationale: Solar activity is expected to be low with a good chance for further M-class flares (R1-R2/Minor-Moderate) and a slight chance for an X-class flare (R3/Strong or greater) on 18-20 May.