Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220802 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 402 AM EDT Wed Mar 22 2017 .SYNOPSIS...
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A strong cold front is crossing the region early this morning. High pressure will return this afternoon through Thursday night. A warm front will cross the region Friday. Low pressure may affect the area Sunday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A strong cold front was bisecting the CWA at 3 AM. South of the front, jet energy has resulted in radar returns, but based on obs, this precipitation is likely little more than sprinkles. These showers will exit by daybreak. Wind gusts have been tame and sporadic so far, but expect some of the peak gusts to occur just after sunrise when mixing can improve. These gusts could top out in the 30-40 mph range, diminishing slightly to 20-30 mph in the afternoon as pressure rises relax. Clouds will gradually scatter out through the morning, with clear skies expected by mid afternoon. Cold/dry advection will be strong behind the front. Calendar day highs are likely occurring or have occurred. Daytime temperatures will hold in the 40s, except 50s in central VA where colder air will arrive last. See fire weather concerns below.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
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High pressure will continue to build south tonight, allowing winds to diminish. The center of the high will be centered over PA by Thursday morning. Western valleys will likely decouple, leading to lows in the teens, with 20s elsewhere. The chilly airmass will remain in place for Thursday, with highs once again remaining in the 40s. Thursday night into Friday morning forecast is a bit tricky, as it will start out mostly clear, which will likely allow temperatures to drop to near freezing. Isentropic ascent increases late with next warm surge aloft. ECMWF continues to be farther south with QPF compared to NAM/GFS, although it does have support of some GEFS members. If this solution were to occur, a brief period of freezing rain/and or sleet could occur in the northern quarter of the area, but confidence is very low. Temperatures will quickly warm above freezing though with established southerly flow, reaching the 50s and 60s by Friday afternoon. The area will remain in the warm sector of a low pressure system in the Plains on Friday night, with mostly cloudy and mild conditions expected.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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Reasonable agreement in the long term. A warm front will advance east across the region slowly on Friday. Some rain is possible especially near the Mason-Dixon line and if it arrives early enough, a little freezing rain is possible. Otherwise, southerly flow will develop and some moderation is expected. A wedge may try to persist across parts of the region, but it should erode by early Saturday. That said, the presence of the wedge does make temperatures a little uncertain on Friday, but they should manage to return to normal across most areas - perhaps above where the wedge erodes fastest. Whatever wedge lingers late Friday should completely erode by midday Saturday and the entire region should feel a warm southwest flow as high pressure to the east pumps warmer and more humid gulf air northward. Temperatures should reach the 70s in most of the area. It should stay dry with forcing from fronts and storms keeping their distance. Backdoor cold front may slip south into the area, especially in MD, Saturday night and Sunday, preventing the second day of the weekend from being as pleasantly warm as the first. Add in the approaching system to the west, and Sunday also looks wetter than Saturday, with showers or perhaps a thunderstorm possible. The front may push back north as a warm front later on Monday, as the storm moves eastward into the Atlantic, with a better chance at 70s returning to the region. However, the chance of showers or even a thunderstorm will remain as the system pushes off the coast. By Tuesday, guidance is uncertain, with potential for the front to drop back south and another low to move east into the region. Showers and cooler weather look possible.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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Cold front is pushing through the terminals early this morning, with NW wind gusts expected to increase behind it. Peak gusts of 30-35 kt will be possible just after sunrise, with slightly lower gusts persisting through afternoon. Winds will diminish tonight as high pressure builds in from the north. No issues expected through Thursday evening with the high in control. At this time, light precipitation Friday morning is likely to stay north of the terminals. Southerly flow could be a bit gusty Friday afternoon. VFR conditions expected through Saturday night although clouds will be prevalent. Sub-VFR conditions possible Friday with any rain with warm front. VFR Saturday. Sub-VFR again possible with rain Saturday night into Sunday. Winds becoming south Friday, perhaps a few gusts to 20 knots, continuing Saturday, then becoming more uncertain Sunday.
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&& .MARINE...
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Have upgraded to a Gale Warning for all waters through this morning as peak winds around 35 kt are possible behind a cold front. Since SCA was already in place, have left that unchanged, gradually dropping off this evening. 25-30 kt gusts during the afternoon will diminish tonight as high pressure builds in. Lighter winds are expected Thursday and Thursday night as the high moves overhead and then offshore. SCA conditions in southerly flow will be possible Friday. Small craft advisory conditions possible Friday with increasing southerly winds. Winds mainly sub-SCA Saturday and Sunday.
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&& .FIRE WEATHER...
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Dry conditions and gusty winds expected today following strong cold frontal passage. Relative humidities will drop into the 15-30% range with sustained north to northwest winds from 15 to 20 mph, gusting 30 to 35 mph. However, following recent rain and snow, fuel moistures are currently between 9 and 15 percent, and thus fire weather statements are not needed at this time.
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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 noon today to 8 PM EDT this evening for ANZ530-531-535-536-538>540. Gale Warning until noon EDT today for ANZ530>543. Small Craft Advisory from noon today to 4 AM EDT Thursday for ANZ532>534-537-541>543.
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&& $$ SYNOPSIS...RCM NEAR TERM...ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM FIRE WEATHER...ADS

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