584 FXUS61 KLWX 270755 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 355 AM EDT Sun Apr 27 2025 .SYNOPSIS... As an earlier cold front pulls further away from the Atlantic Seaboard, Canadian high pressure will build into the area through Monday before moving offshore. A warm front moves through Tuesday while another frontal system will waver across the Mid-Atlantic during the middle to latter portions of the work week. A cold front sweeps through on Friday with high pressure returning for next weekend. && .NEAR TERM /THROUGH TONIGHT/... The cold front which moved through last afternoon and evening currently stretches from just offshore of the Delmarva Peninsula down into the eastern Carolinas. In the wake, a much drier air mass is in place as dew points have fallen by around 20 to 30 degrees over the past 24 hours. Despite the cold advection pattern, temperatures have not really plummeted due to the elevated wind fields. Although northwesterly winds are not quite as gusty as last evening, current gusts are currently running between 15 to 25 mph. Consequently, 07Z/3 AM temperatures are mainly in the mid 40s to low 50s. GOES-19 nighttime satellite imagery shows some stable wave clouds persisting across areas along and west of U.S. 15. These largely consist of overcast skies around 5,000 feet, while being lower in nature across the Allegheny Front. An upper low currently spinning over upstate New York is forecast to continue an eastward push toward coastal New England today. A cyclonic flow regime over the northeastern U.S. will favor further cooling today with temperatures near to slightly below average for late April. Given these mid-Spring solar insolation angles, vertical mixing should be rather deep in this post-frontal northwesterly flow environment. Forecast soundings over the region indicate mixing up to around 850-825 mb. With 850-mb temperatures around 5-6C, dry adibatic mixing would carry high temperatures into the upper 60s to low 70s. As these regimes can often underdo the level of drying at the surface, favored some the driest guidance available. This would carry afternoon relative humidities into the 20 to 25 percent range. Accompanying this dry air mass will be a gusty northwesterly wind which may reach 30 to 35 mph at times. However, this all occurs underneath sunny skies owing to ample subsidence in the troposphere. Broad Canadian high pressure currently centered over Lake Michigan will advance eastward today. As this anticyclone nears, winds should quickly drop off after dark. This sets the stages for a decent night of radiational cooling effects given continued clear skies. Forecast low temperatures are likely to fall into upper 30s to 40s, with mid 30s possible over the I-81 corridor and points westward. Depending on how this all evolves, some patchy frost cannot be ruled out in areas that fully decouple. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... The influence of Canadian high pressure persists into the start of the work week. After a chilly start to the morning, another day full of sunshine should allow for a quick recovery to milder afternoon conditions. Compared to previous days, winds will be much weaker in nature given lighter gradients around the dome of high pressure. Forecast highs are to push into the mid 70s, with upper 60s to low 70s over mountain locations. Eventually this area of high pressure moves offshore by the evening allowing for return southerly flow to ensue. This shift in the winds will bring a noticeable rise to Monday night`s temperatures. The current forecast calls for widespread upper 40s to mid 50s. Tuesday will carry a marked rise in temperatures as an upper ridge tracks eastward from the Mississippi Valley. Characterized by 500-mb height anomalies around 1 to 1.5 standard deviations above average, this ridge will allow for a vast warm up through the week. Ensemble temperature spread is rather low so fairly confidence in the area seeing low/mid 80s on Tuesday. Even those in the mountains can anticipate readings into the 70s. The passage of the surface warm front during the morning hours puts the Mid-Atlantic region squarely into an expanding warm sector. Some shortwave energy rounds the top of this ridge which may spark some showers and thunderstorms on Tuesday afternoon and evening. The main risk for severe weather is currently confined to far western Maryland and points westward. Some convective activity may persist into Tuesday night across areas west of I-95. Overall temperatures will be very mild, generally holding steady in the low/mid 60s. Current records for such overnight warmth are in the upper 60s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Flow aloft will turn zonal on Wednesday, causing an initially southward moving cold front to slow its forward progress and potentially stall out. Most guidance favors this occurring across southern portions of the forecast area (generally from Central Virginia to Southern Maryland, or potentially even further south), but uncertainty in the positioning of the frontal boundary remains. With the frontal boundary lingering nearby, an afternoon thunderstorm can`t be ruled out, but the bulk of the day should remain dry. Temperatures will be dependent on the positioning of the frontal boundary, with locations to the south of the front making a run at 90 degrees, while locations further north would likely have highs in the 70s. A shortwave trough is expected to track northeastward from the Southern Plains toward the Mid-Mississippi Valley on Thursday, before interacting, and potentially phasing with a larger trough moving southeastward out of the Northern Plains toward the Great Lakes. Regardless of how this interaction between upper level features shakes out, low pressure of an undetermined strength is expected to track off to our northwest into the Great Lakes Thursday into Friday. This will cause the aforementioned frontal boundary to lift back northward through the area as a warm front, leading to an increase in temperatures and low-level moisture. The combination of increasing low-level moisture and height falls associated with the system passing to our northwest will lead to the development of surface based instability, and increasing chances for showers and thunderstorms on Thursday and Friday. With flow aloft and resultant deep layer shear also increasing, some of these storms could potentially be strong. The system`s cold front is expected to move through the area Friday night into the day Saturday, causing cooler and drier air to filter back into the area. As a result, mostly sunny skies and seasonable temperatures are forecast for Saturday. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... VFR conditions are expected for today and into early portions of the work week. However, the big story today will be the gusty northwesterly winds which continue through early this evening. Although early morning gusts have dropped to around 20 knots, another ramp up is likely once diurnal heating commences. Expect gusts to around 30 knots today, occasionally up to 35 knots during the gustier periods. However, approaching Canadian high pressure should quickly reduce wind speeds after dark and into the overnight hours. This dome of high pressure moves offshore Monday evening allowing for a return to southerly winds during subsequent days. Winds are on the light side on Monday before ramping up to 15 to 20 knots gusts by Tuesday. Prevailing VFR conditions are expected on both Wednesday and Thursday, although a passing shower or thunderstorm can`t be ruled out either day. Uncertainty remains with respect to the wind direction on Wednesday with a stalled front nearby. Winds are expected to turn out of the south on Thursday. && .MARINE... While Gale Warnings remain in effect across all of the waters through 6 AM this morning, only the more southern waters are currently seeing gale-force gusts. Other locations could see such headlines converted over to Small Craft Advisories. Gusty northwesterly winds continue today which will warrant Small Craft Advisories for all waters today. Occasional gales may impact the southernmost waters, but these should not be persistent in nature. The peak in the winds will be this morning into the early afternoon with gusts up to 25 to 30 knots. These gradually decrease later in the day before falling to sub- advisory levels by late this evening. Canadian high pressure should keep winds on the lighter side tonight through Monday. As this ridge retreats offshore, winds return to southerly by Monday evening. Some channeling effects may occur on Tuesday which would warrant additional Small Craft Advisories for portions of the waters. Sub-SCA level winds are expected on both Wednesday and Thursday. Uncertainty remains with respect to the wind direction on Wednesday with a stalled front nearby. Winds are expected to turn out of the south on Thursday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Gale Warning until 6 AM EDT early this morning for MDZ008. VA...None. WV...None. MARINE...Gale Warning until 6 AM EDT early this morning for ANZ530>543. && $$ SYNOPSIS...BRO NEAR TERM...BRO SHORT TERM...BRO LONG TERM...BRO/KJP AVIATION...BRO/KJP MARINE...BRO/KJP