143 FXUS61 KLWX 072003 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 303 PM EST Sun Nov 7 2021 .SYNOPSIS... Low pressure offshore will continue to progress out to sea as high pressure builds in from the west for the early to middle portions of the week. && .NEAR TERM /THROUGH TONIGHT/... 12z IAD sounding shows a very dry profile in the low-mid levels, with a little bit of moisture around jet level. A bit of cirrus is forming within the jet entrance region of a jet streak positioned off to our northeast. These cirrus clouds are confined to primarily along/SE of I-95. Elsewhere, skies are sunny this afternoon. These high cirrus clouds will move out tonight as the aforementioned jet streak lifts off to our north and east. Winds will decrease a bit overnight, but light flow will likely be maintained within the pressure gradient between an area of low pressure off the NC coast and high pressure centered over the Ohio Valley. Lows tonight will be in the 30s to lower 40s for both. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... Mid-upper level ridging will progress overhead on Monday, with primarily zonal flow on Tuesday. At the surface, a large area of high pressure will slowly drift from the Ohio Valley to the southern Appalachians. This will lead to continued dry conditions, along with a warming trend. Highs will be in the upper 60s for most tomorrow, with temperatures in the upper 60s to lower 70s on Tuesday. Skies will be sunny tomorrow, with increasing clouds late Tuesday into Tuesday night as a disturbance passes to our north. No precipitation is expected however. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Our long period of quiet weather comes to an end towards the end of the week, as a strong storm system approaches from the west. For Wednesday though, quiet conditions will persist as high pressure begins to push off to the east, and a weak cold front and upper- level disturbance move across the region. This system brings only a slight cool down (mid to upper 60s) to the region. Otherwise, expected to just be a dry frontal passage. These quiet conditions persist into Wednesday night and most of Thursday. Overnight lows on Wednesday will be well above average into the mid 40s, owing to cloudy skies amidst onshore flow. For Thursday, dry conditions expected through at least the early part of the afternoon with high temperatures again in the mid 60s. Thursday night into the weekend is where the forecast becomes a lot more interesting though. Guidance is all over the place, but all tend to show one common feature...that being a very strong upper- level trough exiting the central CONUS and moving towards the east coast. A strong surface low underneath this trough will push northeastward into the upper midwest and then into Canada, with a dying cold front pushing across our region Friday into Saturday. Showers are expected ahead of the cold front on Friday, but shouldn't see much of a severe threat there given that the primary trough is still off to the west, with little shear over our region. For Saturday and Sunday though, the forecast grows very complicated. The upper-level pattern becomes very complex, with the primary trough somewhat weakening, then a strong surge of shortwave energy diving south out of the midwest towards the southeastern U.S. Timing on this varies greatly amongst the available guidance at this time, by as much as 24 hours. The key feature this will interact with will be the aforementioned cold front, which should be setup as a coastal front at this point. If this surge of shortwave energy is more progressive, thus interacting with the existing frontal boundary sooner, this could result in a powerful coastal low just off the Mid- Atlantic coast. However, if the slower guidance pans out, this interaction happens further offshore, bringing a coastal low more into the northeastern U.S. with less impacts in our region. Several things to iron out with this system, and not all pieces are even in place just yet, so have to wait for more data to see how these upper- level features start to set up. This is towards the end of the forecast period, so a lot can change between now and then. Given that there could be multiple rounds of potentially moderate to heavy rainfall for portions of the area, flooding could be a concern by late weekend into early next week. Do want to stress again that this is a very dynamic forecast, just something to watch closely at this time. Severe weather is also not out of the question with a trough this strong. Couldn't nail down timing at this point, because it is all going to depend how quickly the trough progresses. If the fropa coincides with a favorable trough position, could see some severe weather. However, instability is always an issue with setups like these, so look for that to be an inhibiting factor. Lastly, can not rule out the potential for some snow in the higher elevations, should some of the more bullish guidance pan out and take a low right up the Mid-Atlantic coast as a cool upper trough moves overhead. Again, confidence very low at this time, and have not included snow in the forecast at this time, but certainly can't rule it out late weekend into early next week. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... VFR conditions are forecast at the terminals through Tuesday. Winds will be out of the north both today and tomorrow, with winds turning lighter and switching around to the west to northwest on Tuesday. Some early morning fog can't be ruled out on Tuesday. Generally VFR expected Wednesday and Thursday. Light winds Wednesday will become a bit stronger from the south on Thursday, possibly gusting up to 20 knots. && .MARINE... SCAs remain in effect through tomorrow in northerly flow. Winds start to decrease and gain slightly more of a westerly component late Monday into Tuesday as high pressure approaches from the west. Light winds likely prevail Wednesday behind a weak front. However, approaching stronger front from the west on Thursday may bring winds up to SCA levels by late in the day or at night. && .TIDES/COASTAL FLOODING... Anomalies remain elevated, but northerly flow combined with a reduction of onshore flow at the mouth of the bay as the storm to the south moves out to sea should allow anomalies to start diminishing. We are starting to see that at a few sites already this afternoon. Water levels will be close to minor flood this afternoon/evening at both Straits Point and DC, so we'll continue to monitor that potential. Anomalies are building up at the mouth of the bay (anomaly of over two feet at Norfolk), so there may be some potential for snapback tides as winds decrease tomorrow night into Tuesday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until noon EST Monday for ANZ531-532-536- 539-540. Small Craft Advisory until 6 PM EST Monday for ANZ533-541-542. Small Craft Advisory until 9 PM EST Monday for ANZ534-537-543. && $$ SYNOPSIS...KJP NEAR TERM...KJP SHORT TERM...KJP LONG TERM...CJL AVIATION...RCM/CJL/KJP MARINE...CJL/KJP TIDES/COASTAL FLOODING...RCM/KJP