####018003383#### FXUS65 KBOI 051011 AFDBOI Area Forecast Discussion National Weather Service Boise ID 411 AM MDT Sun May 5 2024 .SHORT TERM...Today through Tuesday night...Precipitation will wrap around a closed low as it tracks through northern NV today. This will put the focus of heavier precipitation across the w-central mtns early this morning and over SE Oregon through the day and into this evening. Cold air on the backside of the low is quickly dropping snow levels across SE Oregon and the Owyhee mtns this morning, setting up potential for accumulating snow down to 4kft MSL. Expect 3 to 8 inches above 5000 feet and over a foot possible across Steens Mtn. In SW Idaho snow levels will remain between 4500 feet along the ID/NV border to 5500 feet over the w-central mtns through this evening. The precipitation on the backside of the low will shift eastward tonight as the low crosses the Rockies. This will bring a break to the rain/snow across SE Oregon while increasing precipitation coverage and lowering snow levels across SW Idaho zones. By Monday morning snow levels of 3500-4500 feet could bring a mix of rain/snow or brief changeover to snow in the Snake Plain east of Boise. Low temperatures will remain above freezing so valley sites below 4500 feet will stay wet. Mountains will pick up additional snowfall overnight and see a further boost as a trailing upper wave brings another round of valley rain and mtn snow Monday into Tuesday. Westerly flow aloft will bring breezy winds each afternoon through Tuesday. The western Magic Valley will see the strongest winds and could be inline for a Wind Advisory on Tuesday. Temperatures are 10-15 degrees below normal through Tuesday. .LONG TERM...Wednesday through Sunday...An upper level trough will remain over the western US through Thursday, keeping temperatures cooler than normal. Temperatures will be around 10 degrees below normal on Wednesday before warming to near normal by Thursday. An upper level ridge is forecast to build over the Pacific NW and southwest Canada on Friday into the weekend. Record breaking temperatures possible over portions of the Pacific NW, but the center of the ridge will be north and west of our area, where the warmer temperatures are. Temperatures raise to around 5-10 degrees above normal for Saturday and Sunday. A weak trough lingers over the Great Basin Saturday and Sunday, with a threat of afternoon thunderstorms and slightly cooler temperatures. Forecast confidence is low on the strength of the trough and the placement. && .AVIATION...Generally MVFR to IFR with mountain obscuration in rain and snow. Snow levels 3500-4500ft, lowest over central OR, except 5500-6500ft MSL over central ID mountains. Surface winds: NW-SW 10- 20kt. Winds aloft at 10kft MSL: variable 10-20kt becoming W-NW 20- 30kt by 00z/Mon. KBOI...VFR thru 16z/Sun then MVFR to IFR conditions at times in rain showers. Surface winds: SE 5-10kt thru 16z/Sun becoming W-NW 5-15kt. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...DG LONG TERM....KA AVIATION.....KA ####018008750#### FXUS61 KAKQ 051012 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 612 AM EDT Sun May 5 2024 .SYNOPSIS... Off and on showers are expected to continue through Sunday night. Summerlike conditions return to the area for next week with daily chances of showers and storms. && .NEAR TERM /THROUGH TONIGHT/... As of 320 AM EDT Sunday... Early morning wx analysis indicates Friday's backdoor cold front now pushing back N as a warm front, draped across the southeastern portion of the FA as of 3am. This is evident not only from the winds having turned to the SE, but also the temperature gradient across the area this morning. Latest obs show upper 60s in the SE with dewpoints also in the 60s and low 50s in the NW for both temps and dewpoints. As the front continues northward, temps will remain stable in the SE and rise a few degrees elsewhere. Aloft, a weak shortwave is traveling across the region, aiding in the continuation of showers. Latest radar shows widespread, light precip W of I-95 and isolated- scattered showers elsewhere. Heavier showers near the RIC metro have dropped 1.0-1.5" of rain tonight, spurring a Flood Advisory just south of RIC. These heavier showers have weakened, though, and moved to the ENE. Shortwave energy within the SW flow aloft as well as the front advancing N will lead to additional rounds of showers and tstorms today. Expect the highest coverage will stay in the piedmont through the morning, then expand to all areas W of the bay (~70% PoP) this afternoon. Coverage is then expected to decrease later in the evening and into tonight as the main axis of precip progresses E. Chnc PoPs then continue E of I-95 through the night. Instability of 600-700 J/KG (mean HREF SCAPE) means there will be a decent chance for thunder. Regarding QPF, expecting widespread 0.25-0.5" with higher amounts of 1.0-1.5" within heavier showers/storms. Highs today will be in the mid- upper 70s in the SE and upper 60s-low 70s elsewhere. Remaining mild overnight with lows in the mid-60s. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 350 AM EDT Sunday... Key messages: - Continued unsettled pattern with on and off rain to start the week - A warming trend expected with above normal temps and humid conditions Mon and Tues mark the start of a summer-like pattern that will persist through the week. Multiple rounds of shortwaves in the (fairly weak) SW flow aloft plus a lee trough will lead to off and on shower/storm chances. These will likely follow a generally diurnal pattern with the best chances in the afternoon through late evening. Temps climb into the low 80s on Monday with dewpoints as high as the upper 60s. HREF mean CAPE shows values over 1000 J/KG, but shear will be weak. Therefore, severe weather is not expected outside of a strong storm or two. Highest coverage in precip on Mon looks to be across the south (roughly S of US-460) during the afternoon hours as of latest guidance. Tuesday is less certain, as models are still showing some disagreement regarding coverage and timing of precip. Highs will be in the mid 80s across the south of low 80s in the north. Lows both nights will be in the mid- upper 60s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 350 AM EDT Sunday... Key messages: -A summer-like pattern will bring unsettled conditions and above-normal temps Wednesday through Friday. -There is the potential for severe weather mid to late week. An unsettled, summertime continues through the rest of the week. A ridge aloft starts to break down Wed. The GFS and ECMWF both suggest stronger 500mb flow of up to 50 kt by Wed-Thurs. Additionally, several waves of weak shortwave energy will pass over the area. As of latest guidance, the strongest of these looks to pass through Thu ahead of an UL trough dropping into the Great Lakes. A stronger system (i.e. cold front) will then cross the area Thu night into Fri. These features along with plentiful daytime heating/instability will allow for daily rounds of showers/tstms. Will be monitoring this time period for severe weather given the support aloft and steep mid-level lapse rates. The CSU Machine Learning Probabilities have picked up on the aforementioned parameter space and suggest at least a slight risk for severe weather Thu for the entire area. Mainly dry weather will return for Sat. Highs will be in the mid 80s to lower 90s Wed and Thu, in the upper 70s to lower 80s Fri, and in the lower to mid 70s Sat. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/... As of 145 AM EDT Sunday... IFR CIGs still prevail at RIC late tonight with MVFR/VFR at SBY/ORF/PHF/ECG. The backdoor cold front that crossed the area Friday will slowly lift back north as a warm front through the period. CIGs improve to MVFR (with occasional periods of VFR) as winds become SE-SSE after the front moves north of a given terminal. It looks like IFR CIGs likely hang on until late morning at RIC. In addition, showers will once again overspread RIC tonight. Showers are likely at all terminals on Sun, with isolated- scattered tstms possible during the aftn/evening. Outlook...Sub-VFR conditions are expected at times from Sunday night- Monday, due to an unsettled weather pattern. Sunday night should be mostly dry, but more tstms are possible Mon aftn-late Mon evening. A warmer, more summerlike pattern returns Tue through Thu, with chances for storms each aftn/evening. && .MARINE... As of 320 AM EDT Sunday... Key Message: - All Small Craft Advisories have been discontinued. Strong sfc high pressure (>1030mb) is centered across Atlantic Canada early this morning, with a stationary front in vicinity of the NC Outer Banks slowly pushing N. E-SE winds prevail, but the wind speeds have generally been under-performing over the past 12 hrs and as such, have decided to cancel all remaining SCA headlines. Conditions today will still be less than ideal for boating as SE winds average 10-15 kt with gusts to ~20 kt and waves of 2-3 ft in the Bay and 1-2 ft in the rivers. Seas are 3-4ft. The stationary front will continue to lift back N as a warm front later today, with winds becoming more from the S at 10-15 kt tonight, and then to the SSW by Monday. Winds will average ~10 kt with gusts less than 20 kt through the week so outside of any tstms, conditions will be sub-SCA. The winds may increase a bit Thu- Fri as the pressure gradient tightens with the approach of a stronger cold front. && .TIDES/COASTAL FLOODING... As of 600 AM EDT Sunday... Key Messages: - Coastal Flood Advisory remains in effect for the northern Neck through late tonight/early Monday for minor flooding. - A new Coastal Flood Advisory is in effect for the high tide cycle late tonight/early Monday for the bayside of the Maryland eastern shore. Ebb tide currents have been stronger over the past 18-24 hrs, leading to a slight lowering of tidal departures in the Bay and tidal rivers (departures are now mainly +1.0 to +1.25 ft above astro tide). The upcoming high tide cycle later this morning/early this aftn will likely fall short of Minor Flood thresholds given the latest obs and trends, with the following cycle late tonight/early Monday morning expected to reach into Minor flood thresholds. This is due to a few extra tenths of a foot of surge (from SSE winds) in tandem with astro tides that will also be a few tenths higher during this timeframe. Coastal Flood Advisories are in effect to cover this period (for the northern Neck the Advisory is also in effect for 1st tide today given the product was already in effect). Water levels are expected to drop off by ~0.5 ft later Monday as winds shift to the SW and water flushes out of the mouth of the Bay. Some nuisance to localized low- end minor flooding will still be possible with the higher diurnal astro tides late Mon night/early Tue AM and again late Tue night/early Wed AM. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Coastal Flood Advisory from 9 PM this evening to 6 AM EDT Monday for MDZ021>023. NC...None. VA...Coastal Flood Advisory until 4 AM EDT Monday for VAZ075>078. MARINE...None. && $$ SYNOPSIS...TMG NEAR TERM...AM SHORT TERM...AM/TMG LONG TERM...AM/TMG AVIATION...AM/ERI MARINE...AJZ/LKB TIDES/COASTAL FLOODING...AKQ