Area Forecast Discussion

WHAT HAS CHANGED

Updated 12Z aviation discussion.

Confidence in rain chances and QPF has increased late Thursday into Friday, with 1-2+" possible across portions of the area.

KEY MESSAGES

1) Dry and unseasonably warm conditions continue today.

2) Widespread moderate to locally heavy rainfall is expected Thursday night through Friday, with a few thunderstorms possible.

DISCUSSION

As of 230 AM EST Wednesday...

KEY MESSAGE 1...Dry and unseasonably warm conditions continue today.

Surface analysis shows the area of high pressure that has been in control of our weather for the last several days now centered offshore. It will be pushed further offshore throughout the day today ahead of an approaching cold front, but the high will extend back west enough to give us another dry and unseasonably warm day today. Another round of patchy dense fog is occurring as of this writing, especially along the Eastern Shore and closer to the coast in SE VA/NE NC. Guidance tries to spread it westward over the next few hours, so it could be a foggy morning commute. The fog will quickly dissipate after 8/9am and give way to a mostly sunny start to the day. With upper level ridging overhead, temperatures will be able to warm a few more degrees than yesterday. Highs are forecast to reach the mid to upper 70s, with the warmest spots being east of I-95. These temperatures are 10-12 degrees above normal for early November. Additionally, some light southerly breezes are likely this afternoon. Cloud cover will start to move in from the west this afternoon as the aforementioned cold front approaches the western edge of the state. These clouds will keep overnight lows rather mild, only dipping to around 60 degrees for most everyone. Hi-res guidance is holding onto a low-end chance for a few scattered showers for western locations overnight into Thursday morning.

The first part of Thursday will be cloudy and mostly dry as we await the arrival of the slow-moving cold front. Again, there could be an isolated shower or two passing through during the day, but the majority of us will stay dry until late. Southerly winds will keep the warm temperatures around again, as highs top out in the mid to upper 70s. There could even be a few 80 degree readings in SE VA and NE NC. After a prolonged period of dry weather, dewpoints will rise into the mid to upper 60s throughout the day, so this increase in moisture will likely feel noticeable if you step outside. The dry pattern will come to a temporary end Thursday night.

KEY MESSAGE 2...Widespread moderate to locally heavy rainfall is expected Thursday night through Friday, with a few thunderstorms possible.

Confidence has increased as models have come into better agreement regarding a period of moderate to locally heavy rainfall Thursday night into Friday. The cold front will slowly move eastward as low pressure strengthens over the Great Lakes. This will result in rain developing across our western locations late Thursday night/early Friday morning, then expanding east by daybreak. Both the GFS and ECMWF depict a southwest to northeast axis of enhanced QPF extending from south-central VA up to the MD Eastern Shore. This locally heavy rain could be generally stationary over the same locations for most of the day, potentially dropping localized rainfall amounts of 2+". Confidence in exactly where those maximums will occur keeps shifting, but the possibility is definitely worth noting. However, the 00Z ECMWF is noticeably more east with the heavier rainfall than the GFS.

Regardless, anomalously high moisture will accompany this system, with PWATs forecast to surge to 200%+ of normal for this time of year. There is also a slight chance of embedded thunderstorms on Friday, especially from mid/late morning through the early afternoon hours ahead of the cold front. Guidance is indicating 500-800 J/kg of MUCAPE alongside 40-50kt of shear during this timeframe, which could further enhance the areas of localized heavier rainfall due to the thunderstorms. The band of rainfall will shift to coastal locations Friday evening before the front moves offshore in the early morning, bringing the rainfall to an end. Regarding high temperatures, the cloud cover and persistent rain will keep most of the area from getting above 70; however, if the rain doesn't reach SE locations until the afternoon, then they may see another day in the upper 70s.

A closed low pressure will drop into the northern Mid- Atlantic/southern New England region on Saturday, reinforcing our northwesterly flow. This will allow drier and cooler air to fill into the area, dropping high temperatures back to more seasonable values. Highs this weekend will be in the mid to upper 60s on Saturday and low to mid 60s for Sunday. Overnight lows will drop into the mid to upper 30s (low 40s by the coast) each night. We look to remain seasonable and dry heading into the start of the new work week. Big model differences return late Tuesday.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

As of 530 AM EST Wednesday...

Patchy dense fog continues across the area as of this writing. VIS has been wildly up and down between MVFR and LIFR at most terminals, so left TEMPOs in for possible brief VIS reductions to 3/4SM through 13Z. Fog will then quickly dissipate giving way to FEW250 skies. More clouds gradually build in from west to east late this afternoon. Winds remain S 5-10 kt through the period. Hi-res guidance shows a low-end chance of a light SHRA overnight, but impacts would be minimal. Can't totally rule out patchy fog again Thursday morning.

Outlook: Rain chances increase Thursday night into Friday, with widespread showers and isolated thunderstorms potentially resulting in periods of sub-VFR conditions. Conditions improve Friday night into Saturday, with VFR conditions generally anticipated for the weekend.

MARINE

As of 230 AM EST Wednesday...

Key Messages:

- Sub-SCA winds prevail through the weekend despite a frontal passage on Friday. The next potential solid SCA event is not until early next week when a stronger front potentially crosses the waters.

Early morning weather analysis shows broad high pressure centered well offshore, with low pressure tracking through the northern plains. Benign, sub-SCA marine conditions prevail with light and variable winds and 2-3 ft seas. Winds become SE at ~10 kt by late today as that high moves farther offshore. As the low in the northern plains moves eastward on Thursday, a cold front will approach from the west. Winds become S and increase to 10-15 kt by late Thu/Thu night as the pressure gradient increases slightly. S winds of 10-15 kt persist on Friday. By late Friday/early Saturday the cold front will have finally pushed through the area shifting winds out of the NW. These northwesterly winds are progged to persist through the weekend but are likely to remain a few knots below SCA criteria on the bay. The only chance for SCAs appears to be from Thu night-Fri across the ocean as seas may briefly reach 5 feet. Looking far into the extended (early next week) there are hints of a stronger frontal system that could bring more solid SCA conditions back to the waters. However, confidence is low at this time on exact details.

AKQ WATCHES / WARNINGS / ADVISORIES

MD...None. NC...None. VA...None. MARINE...None.