Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
501 FXUS61 KLWX 011408 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1008 AM EDT Mon Jul 1 2024 .SYNOPSIS... Behind a cold front, a strong area of high pressure settles over the area through Tuesday before drifting offshore by Tuesday night. A warm front nears the region by mid-week yielding a warming trend. A cold front approaches from the west late in the week. This system briefs stalls to the west before lifting northward as a warm front into New England. && .NEAR TERM /THROUGH TONIGHT/... A thin layer of moisture not resolved well in computer models has resulted in a transient area of broken to overcast stratocumulus. These clouds should continue to drift southwest and scatter out by the afternoon, although there may still be more clouds around than previously advertised due to cold advection across the eastern Great Lakes. Wind gusts have also been notable, with gusts to around 30 mph in some locations. Some adjustments to dew points have also been made toward lower guidance due to efficient mixing, ranging from the mid 40s to mid 50s. Previous discussion: The positively-tilted upper trough is slated to exit the Eastern Seaboard by this afternoon with some gradual building of heights in the wake. In response to the exiting system, surface pressures really begin to increase as a 1024-mb ridge tracks from the Great Lakes toward the northeastern U.S. Relative to early July climatology, the pressure of this anticyclone will be around 1.5 to 2 standard deviations above average. Overall, expect a day with low humidity and high temperatures in the upper 70s to low 80s (60s in the mountains). The center of the surface ridge settles over the northeastern U.S. late tonight into early Tuesday. Mostly clear skies persist with weakening gradients supporting much less wind. Forecast low temperatures will be in the 50s for most, with low/mid 60s more likely along and east of I-95. A few areas of patchy fog cannot be ruled out in low-lying valley locations. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Throughout the day, the anomalous surface high will slowly push from interior New England toward the Atlantic coast. As this occurs, winds begin to shift from northerly to more east/southeasterly. In response to the wind shift, low-level moisture will creep up allowing dew points to rise back into the low 60s for areas east of I-95. Mid/upper heights are expected to continue increasing as a southern to southeastern U.S. ridge expands northward. 24-hour mid-level height rises will be on the order of 6 to 8 dm. Consequently, high temperatures rebound back into the mid 80s, accompanied by mostly sunny skies. A light southerly wind should yield a milder night across the area, particularly west of the Blue Ridge. Low temperatures rise by about 5 to 8 degrees from the previous night. Wednesday marks the next possible 90 degree day as heights further build over the area. The northeastern extent of the 594-dm height line infringes on the I-64 corridor. Its northward progression generally halts at that point which keeps the Mid- Atlantic region along a more active portion of the storm track. This becomes evident as shower and thunderstorm chances return by late Wednesday into the night. Continued southerly flow further moistens the lower troposphere as dew points creep back into the low/mid 60s late in the day. This comes with afternoon gusts of 15 to 20 mph at times. Nighttime conditions come with increasing cloud cover and storm chances. Low temperatures range from the mid 60s to low 70s over the area. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Upper level ridging will be pushing offshore as an upper level trough tracks eastward across the central Plains to start out the long term period. At the surface, an area of low pressure located over the plains looks to track northeast across the Great Lakes and into Eastern Canada through the weekend. The associated cold front will stall to our west Thursday and Friday before tracking across the forecast area on Saturday. This will lead to daily shower and thunderstorm chances, peaking each afternoon. Sunday will have the lowest chances of precipitation of the period, with PoPs ranging from 25-35 percent that afternoon. High temperatures Thursday through Saturday will be in the upper 80s to mid 90s with higher elevations staying in the upper 70s to low 80s. High temperatures on Sunday will be a few degrees cooler with temperatures in the mid 80s to low 90s. To highlight Independence Day, the aforementioned front will be located to our northwest providing the area with a chance of showers and thunderstorms. Showers and thunderstorms are likely for those west of the Blue Ridge as they are closer to the frontal boundary. While high temperatures will top out in the mid 90s primarily for those east of the Blue Ridge, dew points in the mid 70s will lead to heat indices exceeding 100 degrees for some. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... VFR conditions are expected through mid-week as high pressure dominates the pattern through late Tuesday. A transient area of ceilings around FL040 is currently affecting MRB, IAD, and DCA, but it does appear these should scatter out by afternoon. The main impacts to the terminals will be the wind shifts. A gusty northerly wind persists through the late afternoon (with gusts to 25 kt) to early evening today before weakening after dark. Light northerly winds give way to an east to southeasterly wind on Tuesday. As the high fully departs offshore, a return to southerlies are expected on Wednesday with afternoon gusts to around 15 to 20 knots. Some late evening/night showers may approach from the west. However, at this time, these should stay west of the terminals. Prevailing VFR conditions are expected at all terminals Thursday and Friday. Showers and thunderstorms are possible both days at all terminals with the greatest chances being for KMRB. During any precipitation, sub-VFR conditions are possible. && .MARINE... In the wake of a strong cold front, a gusty northerly wind persists through much of day. Small Craft Advisories are in place for these gusts which may reach 25 to 30 knots at times. Winds slowly begin to fall below advisory levels by early in the evening as a strong ridge approaches from the Great Lakes. Depending on observational trends, some of the more southern waters could see a brief extension in such advisories. Wind gusts remain in the 5 to 10 knot range on Tuesday given high pressure over the waters. Winds begin to shift to east to southeasterly as the high slowly drifts toward the New England coast. By Wednesday, southerlies pick up in earnest which may lead to some channeling effects. Small Craft Advisories could be warranted during the afternoon/evening period, especially over wider portions of the Chesapeake Bay. This may persist into portions of Wednesday night as well. Winds stay below SCA criteria both Thursday and Friday across all waters. Showers and thunderstorms could lead to possible SMWs each afternoon and into the evening. && .TIDES/COASTAL FLOODING... Tidal anomalies will continue to fall through Tuesday with northerly winds expected. As snapback occurs, a few tidal sites are expected to hit Action Stage including Baltimore, Annapolis, and Solomons Island, and Straits Point. No minor flooding is expected at this time. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ530- 531-535-536-538-539. Small Craft Advisory until 6 PM EDT this evening for ANZ532>534-537-540>543. && $$ SYNOPSIS...BRO NEAR TERM...ADS/BRO SHORT TERM...BRO LONG TERM...AVS AVIATION...ADS/AVS/BRO MARINE...ADS/AVS/BRO TIDES/COASTAL FLOODING...AVS