Area Forecast Discussion
Issued by NWS Sterling, VA

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538 FXUS61 KLWX 190758 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 358 AM EDT Wed Oct 19 2016 .SYNOPSIS... A weak cold front will stall out over the area late today into tonight before retreating to the north on Thursday. Another, stronger cold front will cross the area Friday. An upper-level trough will pass through the area Saturday and high pressure will build into the region for Sunday. A reinforcing cold front will pass through the area Sunday night into Monday. && .NEAR TERM /THROUGH TONIGHT/... Surface analysis depicts high pressure centered over the SE CONUS...leading to light S/SW flow across much of the area. Cold front currently approaching the Mid-Atlantic from the N/NW, with light showers along/ahead of it. Aloft...nose of mid-/upper-level ridge extends into southern/central VA. While the showery activity across PA is expected to weaken and dissipate as it slowly works cover near front will gradually work into the area through the day today. This will lead to a tricky temperature cloud cover could temper warming across parts of the area this afternoon. General consensus is for E/W oriented front to be bisecting the northern part of the CWA by afternoon. Thus, while M/U80s are forecast across central VA...locations near the Mason-Dixon line and across northern/central Maryland line could remain in the 70s. There could also be a few showers that develop this afternoon across the Highlands in an area of enhanced convergence near frontal boundary. This scenario is supported by most convective allowing models including many members of NSSL-/NCAR-WRF ensembles as well as the HRRR. While non-zero...thunder chances are low, as elevated warm layer is present near 12 kft which would likely prevent strong updrafts from penetrating into favorable temperature regions for lightning. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Cold front that was draped over the area Wednesday will lift back north as a warm front Thursday...leaving our area in the warm sector. Lack of forcing will leave most areas dry through much of Thursday. Cloud cover across northern portions of the area could again temper warming in these areas. Additionally...H5 heights will be falling during the day as riding breaks down in response to potent vorticity maxima approaching from the west. This should also help to keep most places a few degrees cooler than previous days. Coverage of showers will increase from west to east Thursday night into Friday as a strong cold front approaches. Anafrontal nature of precipitation will likely keep rainfall amounts on the low- end...with most places receiving less than a half an inch during the entire event (greatest totals likely across the higher terrain in the west). && .LONG TERM /SATURDAY THROUGH TUESDAY/... Low pressure will track up toward Nova Scotia Saturday while high pressure builds over Ohio Valley. An upper-level trough will pass through the area during this time. A tight gradient between the departing low and the high to the west will cause windy conditions and the northwest flow will cause much cooler conditions compared to recent days. A bkn stratocu deck is possible Saturday as the trough swings through. A couple showers cannot be ruled out...but much of the day should be blustery and dry. High pressure will Saturday night into Sunday. Dry and chilly conditions are expected Saturday night. Frost in the valleys and a freeze on the ridge tops are possible. Confidence in the frost is low since the gradient wind may be strong enough to prevent radiational cooling. Sunday will remain dry and cool. A reinforcing cold front will pass through Sunday night into Monday and high pressure will build overhead later Monday and Tuesday...bringing more dry and chilly conditions. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Fog potential this morning appears much lower than previous light southerly flow remains at the terminals and dewpoint depressions through the boundary layer are larger than previous nights. Thus, expect VFR conditions to remain at all terminals. VFR will continue through the day today. A stalled frontal boundary will be across the region Wednesday night into Thursday...leading to the possibility of lower ceilings, however flight restrictions are currently not anticipated. Showers increase in coverage Thursday night and sub-VFR conditions are possible into Friday. Gusty NW winds are also possible behind the front through Friday night. Gusty northwest winds are expected Saturday. VFR conditions will persist for Saturday and Sunday. && .MARINE... Southerly winds continue on the waters this morning. A few gusts AOA SCA were noted early this morning as stronger winds aloft were able to mix down due to warmer waters. Thus, issued an SCA to account for this. Winds should diminish near sunrise. Winds then remain below SCA through Thursday afternoon. Winds increase a bit out of the south Thursday night ahead of an approaching frontal system and winds may approach SCA conditions. Cold front moving through the region Friday will very likely bring SCA conditions with gales possible later Friday into early Saturday. Gusty northwest winds are expected behind a cold front for Saturday through Saturday night. A Small Craft Advisory will be needed and a Gale warning may be needed for portions of the waters. Winds may shift to the west and southwest for Sunday. A small craft advisory will likely be needed for portions of the waters during this time. A reinforcing cold front will pass through Sunday night into Monday. More SCA conditions are possible during this time. && .TIDES/COASTAL FLOODING... South to southwest flow will continue over the waters through tonight...with southerly winds Thursday into Friday ahead of a cold front. Elevated water levels are expected at the sensitive sites during this time. DC/Alexandria appears the most vulnerable for minor coastal flooding through tomorrow nights high tide cycle...with the current forecast near minor stage tomorrow night. Otherwise...minor tidal flooding concerns return Thursday night at other sensitive sites (e.g., Annapolis). A potent offshore flow will develop behind a cold front later Friday through the weekend. Blowout tides are possible during this time. && .CLIMATE... A record daily high temperature of 84 degrees was set at Baltimore-Washington International Thurgood Marshall Airport (BWI) near Baltimore MD Tuesday. This breaks the old record of 82 set in 1945...1928 and 1908. Climate records have been kept at BWI since 1950. Additional temperature records for the Baltimore MD area extend back to July of 1872. Two record daily high temperatures were set at Washington Dulles International Airport (IAD) so far this week. A high temperature of 84 degrees Monday broke the old record of 83 set in 1963. A high of 85 degrees on Tuesday broke the old record of 82 set in 2007 and 1963. Climate records have been kept at IAD since November of 1962. Below is a list of record daily warm temperatures for October 19th and 20th. Record daily high temperatures Site 10/19 10/20 DCA 88 (1938) 86 (1969) BWI 82 (1947)* 87 (1969) IAD 83 (1991)* 83 (1969) *also occurred in previous years Record daily warm low temperatures Site 10/19 10/20 DCA 65 (1905) 64 (1885)* BWI 67 (1905) 65 (1910) IAD 60 (2011) 59 (1993) *also occurred in previous years && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 7 AM EDT this morning for ANZ533- 534-537-543. && $$ SYNOPSIS...BJL NEAR TERM...MSE SHORT TERM...MSE LONG TERM...BJL AVIATION...BJL/MSE MARINE...BJL/MSE TIDES/COASTAL FLOODING...MSE CLIMATE...DFH is the U.S. government's official web portal to all federal, state and local government web resources and services.