####018002889#### FXXX12 KWNP 201231 DAYDIS :Product: Forecast Discussion :Issued: 2024 May 20 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 moderate levels when Region 3685 (S13E22, Ehi/beta-gamma) produced an M1.9/1N at 19/1344 UTC, an M2.5/1B at 19/1756 UTC, and an M1.6/1n at 19/2159 UTC. Growth was observed in the intermediate spots of Region 3685 and the leader spots of Region 3683 (S24W65, Dai/beta). New Region 3687 (N15W06,Bxo/beta) was numbered. Modelling of a filament eruption CME mentioned in the 19/1230 UTC discussion suggested passage well south of the ecliptic. Analysis and modelling are underway for a halo CME first seen in C2 imagery at 20/0536 UTC. This event is associated with a C6.7 flare at 20/0554 UTC from AR 3683. Early estimated speeds indicate a possible arrival on 22 May. .Forecast... Solar activity is likely to be moderate, with isolated M-class flares (R1-R2/Minor-Moderate) probable and a slight chance for an X-class flare (R3/Strong or greater) on 20-22 May. Energetic Particle .24 hr Summary... The 10 MeV proton flux at geosynchronous orbit had returned to background levels. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 406 pfu. .Forecast... There is a slight chance for the greater than 10 MeV protons reaching S1 (Minor) levels on 20-22 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, with a chanced for high levels, through 21 May. Solar Wind .24 hr Summary... Solar wind speeds slowly decreased from ~400-350 km/s. Total IMF reached 9 nT at 19/1417 UTC. The maximum southward component of Bz reached -8 nT at 19/1254Z and was mostly southward from around 19/00 UTC to 19/19 UTC. Phi was mostly positive. .Forecast... Solar wind enhancements are then expected on 20 May from the CME that left the Sun on 17 May. CME influences are expected to slowly diminish on 21 May. Enhanced conditions are expected on 22 May due to the possible arrival of a halo CME from 20 May. Geospace .24 hr Summary... The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. .Forecast... On 20 May, unsettled to active levels are expected, with G1 (Minor) storming likely with glancing CME effects from the 17 May CME. Mid to late day on 21 May, active levels are expected to decrease to mostly unsettled levels as CME effects gradually diminish. G1-G3 (Minor-Strong) storm levels are possible on 22 May due to the possible arrival of the 20 May halo CME. ####018002301#### FXXX10 KWNP 201231 DAYTDF :Product: 3-Day Forecast :Issued: 2024 May 20 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 3 (below NOAA Scale levels). The greatest expected 3 hr Kp for May 20-May 22 2024 is 6.67 (NOAA Scale G3). NOAA Kp index breakdown May 20-May 22 2024 May 20 May 21 May 22 00-03UT 1.33 4.00 1.67 03-06UT 2.67 3.67 1.33 06-09UT 2.33 3.00 4.67 (G1) 09-12UT 1.67 2.67 6.67 (G3) 12-15UT 4.67 (G1) 3.00 5.67 (G2) 15-18UT 4.67 (G1) 2.67 4.67 (G1) 18-21UT 4.00 2.67 4.67 (G1) 21-00UT 4.00 2.67 4.33 Rationale: G1 geomagnetic storms are likely on day 1 (May 20) from a brush with a transient solar feature that left the Sun on 17 May. G1-G3 storm levels are possible on day three due to transient influences from a CME from 20 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 20-May 22 2024 May 20 May 21 May 22 S1 or greater 10% 10% 10% Rationale: A slight chance for S1 (Minor) or greater solar radiation storms are from Region 3685 is expected through the period. C. NOAA Radio Blackout Activity and Forecast Radio blackouts reaching the R1 levels were observed over the past 24 hours. The largest was at May 19 2024 1756 UTC. Radio Blackout Forecast for May 20-May 22 2024 May 20 May 21 May 22 R1-R2 55% 55% 50% R3 or greater 10% 10% 10% Rationale: R1 (Minor) to R2 (Moderate) radio blackouts are likely from Region 3685 for days 1-2 of the forecast period, diminishing to a chance on day 3 (May 22).