Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
352 FXUS61 KLWX 261347 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 947 AM EDT Thu Jun 26 2025 .SYNOPSIS... A ridge of high pressure overhead will maintain hot conditions through this evening. Daily chances for showers and thunderstorms will increase through the end of the week. A weak frontal boundary will slowly drift southward in time before stalling nearby through Friday. This system gradually lifts northward away from the area this weekend. A stronger cold front may cross the region by early next week. && .NEAR TERM /THROUGH TONIGHT/... Current observations across the region show a cooler start to the day today. This is likely, at least partially, due to the convection yesterday really working over the atmosphere. Temperatures this morning are running a few degrees cooler, and dew points are also a couple degrees cooler than this time yesterday. Mostly sunny skies being observed for now, but expect that to change quickly by mid-late morning. The 12z IAD RAOB shows a significantly more moist column this morning, with PWATS already exceeding two inches. A weak cap is in place, with CIN values around 100 J/kg in the mixed layer, but expect that to quickly mix out as we warm into the low 90s by around noon. A robust cu field will likely develop as a result, with convective initiation strictly from the diurnal heating and orographic influences happening perhaps around noon or shortly thereafter. This would be most likely for areas further west to start, with areas further east initiating an hour or two later along any remnant outflow boundaries and/or bay/river breezes. Additionally, a stalled surface boundary across northern Pennsylvania/Ohio is expected to sag southward in time today, eventually pushing into our area later this evening. As this occurs, enhanced frontal lift coupled with perturbations in the mid/upper atmosphere will favor an increasing risk of showers and thunderstorms. With afternoon high temperatures rising into the low/mid 90s and continued humid conditions, instability profiles remain quite robust. Forecast surface-based CAPE values rise into the 2,500 to 3,500 J/kg range, but with rather weak deep-layer shear (averaging around 10 knots). This lack of vertical shear suggests disorganized convection while focusing more intently on mesoscale boundaries (i.e., river and bay breezes, as well as old convective outflows/cold pools). Compared to yesterday, there are a few notable differences that suggest that the high-end wind gust potential should be lower today. Surface to min Theta-e values are substantially lower today than this time yesterday, and favor a more isolated damaging wind threat. Secondly, as previously mentioned, there is a lot more moisture in the column today, thus we have a lot less DCAPE to work with (albeit still conducive to some severe gusts). Lastly, mid-level lapse rates are a bit weaker than yesterday as well. So, in short, thinking storms may have a slightly harder time getting well established and extremely tall like we saw yesterday. However, do think there will be a few that are able to overcome these issues and we will probably see at least a few damaging wind gusts. Additionally, with wet ground from storms yesterday and again today, it may not take severe winds to blow down trees, so would expect to see a good bit of that today as well. Lastly on the thunderstorm threat, storms today will again be prolific lightning producers given the level of instability. As was mentioned earlier, with precipitable water values around 2 inches, slow cell motions, and the potential of repeat convection firing along erratic outflows, flash flooding is possible this afternoon/evening. The Weather Prediction Center has painted a Slight risk for flash flooding across areas east of the Catoctins and Blue Ridge. The overnight HREF actually has some highlights along the I-95 corridor for potential of 3"+ of rainfall in 3 hours. This is rather concerning, so a Flood Watch is being considered at this time for this area. Once 12z guidance comes in, a final decision can be made on that a little later this morning prior to CI. Most high-resolution models depict activity waning after midnight so any severe/flood threat should wane at that point. Besides the convective threats, continued above average temperatures and high humidity levels will carry heat indices into the 102 to 107 degree range. Furthermore, Heat Advisories extend over a bulk of the area outside the mountains from 11 AM until 7 PM this evening. Continue to find ways to stay cool in the heat by taking plenty of breaks from the outdoors, staying hydrated, and wearing light clothing. Heading into the overnight hours, the influence of rain-cooled air should help carry lows into the upper 60s to low 70s (low/mid 60s in the mountains). && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... While the placement of the frontal zone is uncertain and likely re-positioned by convective-scale processes, this system should be in the vicinity of the Mid-Atlantic region on Friday. Not only will this carry an additional risk for showers and thunderstorms, but also comes with a challenging temperature forecast. For those in the cool sector to the north, highs in the mid/upper 70s are likely. Off to the south, the warm/moist sector will support temperatures well into the 80s to near 90 degrees. The current forecast calls for this separation of air masses to be between I-70 and I-66. There should be a particular focus for convection in the vicinity of this frontal zone where lift will be augmented. Along and south of this front will yield a severe weather component to the storms where instability is maximized. Additionally, well above average columnal moisture profiles favor further instances of flooding potential. It is difficult to say where this will occur, but the usual focuses would be in the urban corridors and regions hit by previous days of heavy rainfall. Depending on how quickly instability is exhausted, some of the convection could fester into the overnight hours on Friday. With mid/upper height changes being somewhat neutral, it remains to be seen how much northward progress this boundary makes on Saturday. This system could easily linger right near the Mason-Dixon Line which would maintain a more unsettled pattern during the first half of the weekend. The expectation is for this boundary to drift northward in time on Saturday which will help usher highs back into the upper 80s to low 90s. Further, convection would be driven more heavily by instability versus along any particular frontal boundaries. But as mentioned, there is plenty of uncertainty in how this all plays out. Will see Saturday night`s lows be a tad milder than previous nights with readings in the upper 60s to mid 70s. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... The Summertime convection threat continues each day Sunday through Tuesday, mainly in the afternoon and evening hours when it is the warmest. High temperatures will reach the lower to middle 90s each afternoon. A strong upper trough and associated surface cold front is expected to cross the area on Tuesday. This could lead to an active afternoon and evening with multiple rounds of convection and/or severe thunderstorms. High pressure builds in the wake by the middle of next week which favors a return to drier weather. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... With convection in the forecast through the remainder of the work week and into the first half of the weekend, periods of restrictions are looking likely at times. Otherwise, VFR conditions should be commonplace outside of these convective episodes. For this afternoon/evening, remain confident enough in thunderstorm development to have a 3 to 4 hour period of TSRA restrictions roughly between 20-00Z. As some of this may linger after dark, have maintained the PROB30 groups into subsequent hours as inherited by previous shifts. As a frontal zone drifts southward across the area, winds turn more easterly in nature on Friday. Eventually this boundary does return northward as a warm front which would bring a return to south-southwesterlies at some point on Saturday. And as mentioned, restrictions are possible given a decent chance for thunderstorms each afternoon/evening. VFR conditions at all terminals Sunday through Monday night. At times of convection, we could see brief MVFR visibility and/or ceilings. Winds will be light and variable, except higher gusts in strong thunderstorms. && .MARINE... While gradients remain weak enough to keep the waterways free of Small Craft Advisories, the threat of convection will make for hazardous boating conditions at times through at least Saturday. It is difficult to say which day will be the most active in terms of thunderstorm development, but the degree of continued heat and humidity should maintain a daily 30-60 percent chance of storms each afternoon/evening. As usual, frequent lightning is possible in any such storm, with the stronger cells likely requiring Special Marine Warnings. No marine hazards Sunday through Monday night. If thunderstorms move out over the waters, then Special Marine Warnings may be warranted. Winds light and variable through the period, except higher gusts in strong thunderstorms. && .TIDES/COASTAL FLOODING... Tidal anomalies will remain slightly elevated through the next several high tide cycles. This will keep water levels slightly elevated for the more sensitive tidal sites. At this point, only Annapolis is slated to reach Action stage during the next couple of astronomical high tides. && .CLIMATE... Here are some daily high temperature records on June 26, 2025: A `+` sign indicates multiple years currently hold that record. ***THURSDAY, JUNE 26TH, 2025*** LOCATION RECORD HIGH (YEAR) RECORD WARM LOW (YEAR) Washington-National (DCA) 101F (1952) 77F (1952)+ Washington-Dulles (IAD) 99F (2024) 72F (2023)+ Baltimore (BWI) 99F (2024)+ 80F (1952) Baltimore Inner Harbor (DMH) 104F (1998) 83F (1952) Martinsburg (MRB) 102F (1943) 75F (1949) Charlottesville (CHO) 99F (1998) 78F (1952) Annapolis (NAK) 98F (1998)+ 81F (1952) Hagerstown (HGR) 98F (1954)+ 75F (1952) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Heat Advisory until 7 PM EDT this evening for DCZ001. MD...Heat Advisory until 7 PM EDT this evening for MDZ003>006-008- 011-013-014-016>018-502>508. VA...Heat Advisory until 7 PM EDT this evening for VAZ026>031- 036>040-050-051-053>057-501-502-505-506-526-527. WV...Heat Advisory until 7 PM EDT this evening for WVZ050>053-055- 502-504. MARINE...Heat Advisory until 7 PM EDT this evening for ANZ530. && $$ SYNOPSIS...BRO NEAR TERM...CJL/BRO SHORT TERM...BRO LONG TERM...BRO/KLW AVIATION...BRO/KLW MARINE...BRO/KLW TIDES/COASTAL FLOODING...LWX CLIMATE...LWX