Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 241844 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 244 PM EDT Sun Mar 24 2024 .SYNOPSIS...
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High pressure will gradually build into the region through tonight and hold through the first half of the week. A weak cold front will cross the area Thursday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Continued sfc ridging/cool wedge anchored on a 1040+ mb high pressure center over the center of Quebec will remain over the area through the first half of the week. This will keep sfc temps quite cool today and below normal through Tue. Winds will gradually diminish through the day, but it will be quite cool and brisk for late March standards despite full sunshine. Cold tonight under very dry air mass and light winds. Lowered temps below NBM guidance given favorable pattern for radiational cooling. For those with vegetation interests, another hard freeze is likely outside of the DC metro and southern Maryland. Would not be surprised with the typical cooler valley locales being in the upper teens to near 20F.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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Ridging will hold through at least Tue keeping fair weather conditions. Some moisture return is expected Tue night which may result in a few showers Tue night, but it`s likely that any showers will hold off until Wednesday. Have increased winds along/west of the Allegheny Front Monday night into Tuesday morning where downslope winds are forecast to gust to 30-40 kts. H85 winds are not at the best orientation for most of the wind to make it to the sfc, but will continue to monitor. Looks like the greatest threat is just west of the FA at this time.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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Split flow persists across the country with a closed low pivoting across southeastern Canada while a southern stream feature pushes toward the Carolinas. Within the latter area of interest, models are consistent in developing a wave of low pressure which is to strengthen as it exits off the Atlantic coast. At this point, the best chance for any rainfall would be east of the Blue Ridge, particularly for those along and east of the I-95 corridor. The associated shield of rainfall begins to exit into the Delmarva Peninsula by Thursday night. In the wake, expect increasing northwesterly winds as gradients tighten due to deepening low pressure over the western Atlantic. Friday`s wind gusts could push up to around 30 to 35 mph, locally a bit higher across the higher elevations. Despite the frontal passage, a downsloping component to the flow should offset the results of cold advection effects. To finish out the work week, high temperatures should be seasonable, generally into the mid 50s to low 60s (40s across the mountains). Over the weekend, ensembles agree on a further warming trend as heights build. A weak frontal zone approaches, but expect a mainly dry weekend. Forecast winds shift to westerly with afternoon gusts up to 15 to 20 mph, with 25 to 30 mph across the higher terrain.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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N winds gusting up to 20 kt will be main impact to terminals this afternoon, gradually decreasing through the evening. Winds become less than 10 kt tonight. P6SM SKC continuing. Continued VFR conditions Monday with a light southeast wind gusting to 5-10 kts. With some precipitation impacting terminals on Thursday, restrictions are possible at times, particularly for locations east of the Blue Ridge. Expect dramatic improvements into Friday and the weekend as VFR conditions are expected. The bigger story will be the gusty northwesterly winds, particularly on Friday. Afternoon gusts could approach 25 to 30 knots, before falling to around 15 to 20 knots on Saturday as winds turn westerly.
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&& .MARINE...
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SCA conditions for all of Potomac and Chesapeake Bay south of Bay Bridge through sunset. SCA conditions will persist into the overnight across the southern Potomac and Chesapeake. Added back in middle and northern Chesapeake for late in the overnight into the first part of Monday AM as most guidance has a renewed puff of wind moving over the waters through ~14Z. Wind fields increase across the waterways during the second half of Thursday. This is in response to a coastal low pressure system which passes off to the southeast. Small Craft Advisories will likely be needed by Thursday afternoon. Northerly winds increase in earnest late Thursday with near gale force winds possible over the lower waters. These gusty winds persist through Friday afternoon while turning more northwesterly in nature. Although winds decrease a bit toward Friday night, Small Craft Advisories may be needed into the night.
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&& .FIRE WEATHER...
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Dry conditions are expected today as high pressure builds in from the west, but temperatures will be below normal with gusty winds. The high will remain to the north Monday into Tuesday as temperatures warm closer to normal. A slow moving front will bring increasing chances of rain showers Wednesday into Thursday. Recent wetting rains should keep fuel moistures somewhat elevated for the next few days, but wind gusts of 20 to 30 mph out of the north are likely today, turning more northeast during the afternoon. Lighter winds are expected Monday through Wednesday, although higher ridges above 2000 feet could start seeing some stronger gusts greater than 20-35 mph Monday night. Relative humidity values will drop to 25 to 35 percent this afternoon. RH is expected to recover to 60 to 80 percent tonight, and 70 to 90 percent Monday night, with minimum afternoon values of 25 to 35 percent Monday afternoon, and 35 to 55 percent Tuesday afternoon. Mixing and smoke dispersion should be fair to excellent this afternoon, becoming poor to fair with lighter winds tonight through Monday night. Improving smoke dispersion is likely on Tuesday..
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&& .TIDES/COASTAL FLOODING...
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Northerly flow started to let up a bit and turn more northeasterly as of early this afternoon. After dropping to around or just below 1 ft MLLW on the northern part of the Chesapeake Bay, tide levels have already begun to show a bit of a rebound heading into mid afternoon. Low water issues may persist in the far northern bay into early this evening, but should abate shortly thereafter. The tidal rebound (snap-back) was outpacing ETSS a bit, but was not nearly as pronounced as the very aggressive CBOFS (more in line with ESTOFS/P-ETSS/SFAS). Anomalies were running 1-1.5 ft above normal over the lower part of the bay, and this excess water should slosh north over the next 12-24 hours. This would result in near minor flooding of vulnerable shoreline as early as Monday afternoon. There are hints of a period of enhanced northeasterly winds tonight, and this could cause anomalies to rise a bit quicker than currently forecast if it`s a little stronger or longer than anticipated. The east to northeasterly flow will persist through Tuesday, piling water into the mouth of the Chesapeake Bay. Anomalies are expected to continue to rise through Tuesday, then surge more readily Tuesday night into Wednesday as flow turns southeasterly to southerly. This should push anomalies into the 2-2.5 ft range, and cause near moderate tidal flooding for vulnerable shoreline locales; widespread minor flooding is most likely elsewhere through Wednesday night. There is uncertainty in the exact timing of a wind shift following a frontal system/area of low pressure late Wednesday night into Thursday, but flow is expected to eventually turn offshore causing a notable decrease in tide levels by late Thursday into Friday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 11 AM EDT Monday for ANZ531>533-539>541. Small Craft Advisory until 6 PM EDT this evening for ANZ532- 533-535-536-540>542. Small Craft Advisory until 11 AM EDT Monday for ANZ534-537-543.
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&& $$ SYNOPSIS...LFR NEAR TERM...CPB SHORT TERM...CPB LONG TERM...BRO AVIATION...BRO/CPB MARINE...BRO/CPB FIRE WEATHER...CPB TIDES/COASTAL FLOODING...DHOF

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