Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
710 FXUS61 KLWX 021416 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1016 AM EDT Tue Jul 2 2024 .SYNOPSIS... Dry conditions, seasonable temperatures, and low humidity look to continue through Wednesday as surface high pressure slowly pushes offshore. A frontal boundary will approach the area and stall to the northwest Thursday before crossing the area this weekend. Heat and humidity will return as a result for the Independence Day holiday along with increased chances for thunderstorms. && .NEAR TERM /THROUGH WEDNESDAY/... Broad 1027-1028 mb high pressure over Finger Lakes of New York will continue to wedge it`s way south along the eastern face of the Appalachians today before shifting toward the New England coast late tonight and into Wednesday. Dry conditions are expected as a result along with low humidity and seasonable temperatures. Highs today will be a touch warmer than Monday with ridging/rising heights aloft. Highs will range from the mid to upper 70s over the mountains with mid to upper 80s east of the Alleghenies. Passing stratocumulus is likely throughout the afternoon with subtle moisture noted in the low levels between 850-1000 mb per the 12z KIAD sounding (Low Level RH 71% and Mid Level RH 3%). PWATS are also down around 0.52" signaling the dry air which is evident across much of the Eastern Seaboard on the current water vapor imagery. Winds will turn from the north early this afternoon to the east and eventually southeast later this evening and into tonight as high pressure shifts offshore. This will allow for a subtle uptick in moisture heading into Wednesday. Even with that said, enough dry air should remain to keep low temperatures in the upper 50s and low to mid 60s across the region. Broad high pressure will continue off the New England/Mid- Atlantic coast Wednesday morning into Wednesday afternoon. Moist southeast flow off the Atlantic will return as a result allowing for a subtle boost in humidity across the area. Dry conditions are expected with mostly sunny to partly cloudy skies expected. High temperatures Wednesday will run a few degrees above normal with highs near 90 degrees east of the Alleghenies (low to mid 80s mountains). && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... Wednesday will start out dry with mostly sunny skies. However, an approaching cold front will bring increased cloud cover and and a slight chance of showers and thunderstorms to those west of I-81 Wednesday night into Thursday. Most locations will remain dry though with increasing mugginess. Warming trend continues for the 4th of July, as upper level ridging pivots off the east coast. An approaching frontal boundary and pre-frontal pressure trough will lead to scattered to numerous showers and thunderstorms, mainly that afternoon and into the early evening. High temperatures will soar into the mid 90s most with heat indices reaching triple digits for some. Instability increases throughout the day with SBCAPE values exceeding 1500 J/Kg. However, there still remains a good bit of uncertainty regarding any convection on Independence day with weak lapse rates (<6 C/km) and Bulk Shear(<30 knots). Overnight low temperatures will be in the 70s for most. && .LONG TERM /FRIDAY THROUGH MONDAY/... The end of this week and start of the weekend look to be active as a weak surface frontal boundary is stalled over the area. Aloft, southwesterly flow prevails as the region is in between a slow moving upper trough over the Great Lakes, and a ridge over the Deep South. Deep moisture from the Gulf of Mexico works its way north into our area, bringing PWATs over 2" and dew points in the low to mid 70s. Scattered to widespread afternoon showers and thunderstorms are expected each day Friday and Saturday, especially along and east of the Blue Ridge. A few strong to severe storms are possible given the ample instability and moisture present. Afternoon highs reach the low to mid 90s, with peak heat indices between 102-107 east of the Blue Ridge, and 97-102 west of the Blue Ridge. The upper trough over the Great Lakes slides northeast as a weak surface high builds over the OH Valley. The weak frontal boundary over the area is pushed southward, with drier air moving at least into the northwestern half of the CWA. A tight moisture gradient is likely to be present. Isolated to scattered showers/storms focus mainly in Central VA to southern MD. A slight dip in temperatures to the upper 80s to low 90s, though less humidity as heat indices remain below 100 Sunday. This break in convection/humidity is short lived as the frontal boundary lifts north over the area as a warm front Monday. Unsettled weather with scattered afternoon thunderstorms return for the start of next week. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... Prevailing VFR conditions are expected today through Wednesday night with high pressure in place. Winds remain light and shift to southeasterly throughout the day today. High level clouds are expected throughout the day with some low level clouds this afternoon. Winds remain light and southerly on Wednesday, with MRB, BWI and MTN seeing the strongest gusts of up to 15 knots. VFR conditions continue for the most part on Thursday with southwesterly winds in the morning shifting to westerly in the afternoon. Scattered to numerous showers and thunderstorms are expected in the afternoon and could cause conditions to deteriorate to sub-VFR. Scattered to widespread showers and thunderstorms are likely across the area each afternoon Friday and Saturday. Any thunderstorm moving over a terminal will be capable of producing brief periods of sub- VFR conditions, in addition to gusty winds and lightning strikes. Thunderstorm activity could linger into the evening at IAD, DCA, BWI, and MTN, then clear out overnight. Outside of convection, VFR conditions are expected. && .MARINE... Mild and dry conditions are expected across all waters today as high pressure pivots overhead. Southeasterly winds remain below SCA criteria through tonight. Winds shift to southerly on Wednesday with channeling resulting in SCA criteria gusts in the afternoon and evening. On Thursday, winds remain out of the south/southeast with SCA criteria gusts possible in the southern portions of the waters. SMWs may be needed during showers and thunderstorms that afternoon. A weak frontal boundary in place over the local waters will result in at least scattered thunderstorms each afternoon Friday and Saturday. These storms will be capable of producing wind gusts in excess of 35 knots and frequent lightning strikes. Special Marine Warnings may be needed as storms move across the waters. Thunderstorm activity diminishes in the evening, though a storm or two could last into the night. Outside of thunderstorm activity, southerly winds around 10- 15 knots are expected. && .TIDES/COASTAL FLOODING... Tidal anomalies are forecast to steadily rise through the week as southeast to south winds prevail. No coastal flooding concerns today as most, if not all, sites remain below Action Stage. However, by Wednesday morning some sensitive locations will reach Action Stage, and Annapolis is the most likely to go into minor flooding Wednesday morning. Additional periods of coastal flooding are possible during the morning high tide Thursday and Friday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...EST NEAR TERM...EST SHORT TERM...AVS LONG TERM...KRR AVIATION...AVS/KRR MARINE...AVS/KRR TIDES/COASTAL FLOODING...