textproduct: Wakefield

WHAT HAS CHANGED

Updated TAF/Aviation discussion for 06z.

KEY MESSAGES

1) Gusty showers and isolated thunderstorms are possible along a strong cold front tonight into Saturday morning. Much cooler with steady light to moderate rain on Saturday.

2) Much cooler temperatures arrive this weekend, with frost possible Sunday morning, mainly in the Piedmont.

3) There is still quite a bit of uncertainty for next week with a potential strong coastal system lingering offshore or retrograding back towards the local area.

4) Long Duration coastal flood event expected starting as early as Sunday afternoon, but potentially continuing into mid week. Coastal flood watches issued for the Lower Chesapeake Bay and Lower James River with expansion of coastal flood watches likely to other areas tonight or Saturday.

DISCUSSION

As of 300 PM EDT Friday...

KEY MESSAGE 1...Gusty showers and isolated thunderstorms are possible along a strong cold front tonight into Saturday morning. Much cooler with steady light to moderate rain on Saturday.

Warm and humid weather prevails this afternoon ahead of an approaching cold front over the central Appalachians and northern Mid-Atlantic. Strong low pressure is tracking east over the St Lawrence Valley, with a sharpening upper trough over the mid-MS River Valley/Midwest. A broken line of gusty showers and a few tstms have developed just ahead of the front from WV to central PA. Locally, temperatures are in the lower-mid 80s with mid 60s dew pts. Instability is meager with only a few hundred J/kg of MLCAPE. The front continues to move SE toward the FA this evening before crossing the area tonight. Am still expecting a line of shallow convection to cross the area with the front, which is what most of the CAMs predict. The most likely timing for tstms is between 7 PM-1 AM. While widespread 30-40 mph gusts are likely with the line, the nighttime timing and limited instability (MLCAPE ~500 J/kg or less) should keep the overall severe threat low for a majority of the area. Will need to keep an eye on far northeastern portions of the area (MD Eastern Shore) where there may be slightly better kinematics (though less in the way of thermodynamics as sfc heating has been less here). Temps remain in the 70s with a quick drop to around 60F shortly after the FROPA.

The front moves well to our southeast Saturday morning while the upper trough becomes a closed low as it tracks into western VA. A large area of light to moderate rain develops ahead of that trough and tracks across the area during the day. Rain likely ends by midday inland, but may linger through the late aftn/early evening near the coast. Additionally, a secondary, stronger surge of CAA will cross the area from mid to late Saturday morning. Therefore, Daytime highs will be achieved during the early morning hours, with temperatures struggling to get out of the mid 50s by the afternoon (and could even fall to around 50 where it is raining). So, 24 hour temperature changes could be in the neighborhood of 30-35+ degrees from this afternoon-Saturday afternoon! Deep mixing in the wake of the front will promote breezy N winds, with gusts of 25 to 35+ mph inland and 40 to 50 mph along the immediate coast. A Wind Advisory has been issued for VA Beach/Eastern Currituck starting at noon Saturday.

KEY MESSAGE 2...Much cooler temperatures arrive this weekend, with frost possible Sunday morning, mainly in the Piedmont.

Strong NW flow aloft in the wake of the cold front will usher in the coolest airmass of the season Saturday night into Sunday. Strong sfc high pressure builds east from the OH Valley, but there will likely be a decent pressure gradient locally, especially closer to the coast. With the surface high forecast to be 1035mb+, kept the theme from the previous forecast and undercut NBM lows by a few degrees in the northern Piedmont where decoupling is more probable closer to sunrise (lows into the mid 30s). Depending on dewpoints, at least patchy frost will be possible there. Closer to the coast, lows will range from the upper 40s to mid 50s. Mostly sunny Sunday (potentially more clouds in the SE) with highs about 10 degrees below normal, in the upper 50s to lower 60s. Additional frost potential is possible Sunday night into Monday morning across the northern Piedmont with temperatures again dropping back into the 30s.

KEY MESSAGE 3...There is still some uncertainty for next week with a potential strong coastal system lingering offshore or retrograding back towards the local area.

There is still a decent amount of uncertainty with respect to the track and strength of coastal low pressure late this weekend into early next week. Sunday will most likely be dry and cool as the low deepens 100-200 miles east of the NC coast while strong high pressure wedges down from the north. Guidance continues to struggle with how close this coastal system remains to the shoreline, though most of the ensemble solutions show the low meandering around 100- 200 miles off the southern VA or NC coast. However, there are still hints (especially from the deterministic GFS and Canadian) that it could retrograde back towards the local area on Monday before moving a bit back out to sea by mid to late week. Precipitation chances have increased on Monday (especially near the coast) and have kept at least some PoPs in the forecast through much of next week. The 50th percentile GFS/Canadian Ensemble QPF is 0.25-1.00" across much of the area on Monday, though the EPS has noticeably less rain. Again, it is important to emphasize that that there is uncertainty and the forecast will change. Breezy N to NE winds will likely persist through much of next week, with the highest gusts along the immediate coast. The Wind Advisory for VA Beach/Eastern Currituck is in effect until 8 PM Sunday and will likely need to be extended. As winds become more NE Sunday/Monday, the Advisory may need to be expanded as well. Near to slightly below average temperatures are currently in the forecast for next week.

KEY MESSAGE 4...Long Duration coastal flood event expected starting as early as Sunday afternoon, but potentially continuing into mid week. Coastal flood watches issued for the Lower Chesapeake Bay and Lower James River with expansion of coastal flood watches likely to other areas tonight or Saturday.

North winds to gale force will allow water levels to build first over the lower Bay and Lower James River as early as Sunday afternoon. This will allow for tide anomalies to be 2 to 3 feet above normal astronomical tide. Fortunately, we are currently on the low end of the tide cycle. Even so, moderate flood stage is forecast at Lynnhaven, Jamestown and Smithfield with the Sunday high tide. As the winds turn slightly more northeast and increase Sunday night into Monday, expect the anomalies to build and impact the ocean front, as well as other areas in the lower and middle Chesapeake Bay. By Monday, many sites south of Windmill Point and along the ocean front are forecast to be into moderate flooding, including Sewells Pt. Lynnhaven, Jamestown and Smithfield are forecast to major tidal flooding on Monday. Considerable beach erosion is also expected with seas building to 10 to 15 feet. With little change in wind direction and only a slight decrease of wind speed on Tuesday or Wednesday, expect moderate to major tidal flooding to continue into mid week. Note that there is still considerable uncertainty in the tide forecast especially early next week as the exact placement of the low will be very important in what the actual tide values will be. PETSS still has a significant range of solutions for many sites so users need to pay very close attention to the forecasts through the weekend.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

As of 130 AM EDT Saturday...

A cold front is quickly dropping south across the region and is currently on the doorstep of ECG. In the wake of the front, winds shift to the N-NW, rain chances increase, and MVFR CIGs will overspread the local area. CIGs may approach IFR at the SE terminals (ECG, ORF, PHF) later this morning into the afternoon. In addition, moderate rain across the SE terminals may result in occasional IFR VSBYs later this morning. Rain tapers off from NW to SE later this morning at SBY, by midday/early afternoon at RIC, but will likely linger through late afternoon at PHF and possibly even until early evening at ORF/ECG.

Winds briefly diminish post-frontal, but quickly ramp back up with onset of cold air advection, especially between 12-15Z. Expect winds to frequently gust to 30-35 kt at ORF/ECG, and 25-30 kt elsewhere.

Outlook: Conditions become VFR inland later this afternoon with gradually diminishing winds, and should remain VFR through Sunday. Closer to the coast, periodic sub-VFR CIGs may re- develop Sunday and continue through Monday-Tuesday, along with continued breezy conditions (winds gusting to at least 25-30 kt) as a nor'easter develops offshore.

MARINE

As of 300 PM EDT Friday...

Key Messages:

- A strong cold front to pass through the waters tonight. A brief period of gale force winds possible immediately behind the front this evening and overnight.

- Widespread northerly gale force conditions start Saturday and continue through Monday and likely beyond as coastal low pressure develops off the coast.

- There is the potential for storm force wind gusts on Monday as the low pressure moves north and deepens.

Winds are currently steady at SW 10 to 15 kt across the waters this afternoon with gusts to 20 kt. However, they are expected to increase even more this evening ahead of the cold front. Have opted to start the SCA in the bay/rivers with forecast issuance this afternoon due to the gusts to 20 kt. Winds will quickly shift to the NW behind the front which should enter the northern waters around 11pm this, then exit the southern waters by 4am Sat morning. The high res guidance suggest that a brief surge to near gale force winds may occur immediately behind the front, which is not unexpected with these type of strong Autumn cold fronts. However, this wind will be short lived and will likely relax before the stronger and more widespread gales move in Saturday morning. If this does occur, we will likely handle with Special Marine Warnings since it will be less than 3 hours in duration.

The main change in the model guidance is to ultimately come into better agreement with the coastal low developing off the NC coast later Saturday into Sunday. Before this happens, there will be a period of moderate Gales starting Saturday morning and continuing into Sunday. The winds are expected to diminish some on Sunday, especially across the far northern waters depending on how far south the low develops. However, will continue to keep gales in place in all zones and in fact extend the gales into Monday night.

Regarding early next week, the low is then expected to meander offshore on into Sunday before moving northward (and possibly westward) into Monday. There are still important differences which will be critical to the forecast for late this weekend and especially early next week. The GFS brings the low further north earlier, which would bring potentially a round of storm force gust conditions to at least the central and southern coastal waters Sunday night into Monday. Meanwhile, the ECMWF is slower and further south, which would likely delay any storm force gusts during the day on Monday and into Monday Night and keep them even further offshore. Will trend toward the ECMWF and NBM which show the strongest winds Monday into Monday night but keep gusts just below storm force for now. Still, storm watches may need to be issued this weekend if this trend continues. Both models show the low will then meander offshore for several days into mid week with the ECMWF being the closest to the coast and the model that would bring the worst impacts to the local area. GFS keeps the low further offshore but still gale force conditions through mid week and continued high surf/coastal flooding. Needless to say this is now looking like a long duration event with gales likely continuing into mid week if not beyond.

CLIMATE

- Record High Temperatures set today Fri 10/16:

- RIC: no record set. - ORF: 87 *ties (2008). - SBY: no record set. - ECG: 86 *ties (2008)

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...High Surf Advisory from noon today to 6 PM EDT Monday for NCZ102. Wind Advisory from noon today to 8 PM EDT this evening for NCZ102. VA...High Surf Advisory from noon today to 6 PM EDT Monday for VAZ098. Wind Advisory from noon today to 8 PM EDT this evening for VAZ098. Coastal Flood Watch from Sunday afternoon through Tuesday morning for VAZ089-090-524-528. Coastal Flood Watch from Sunday afternoon through Tuesday morning for VAZ097-098-529>531. MARINE...Small Craft Advisory until 7 AM EDT this morning for ANZ630>632-634-650-652-654-656-658. Gale Warning from 7 AM this morning to 7 AM EDT Sunday for ANZ630-631. Gale Warning from 7 AM this morning to 6 AM EDT Tuesday for ANZ632-634-652-654-656-658-680-682-684-686-688. Small Craft Advisory until 10 AM EDT this morning for ANZ633- 639. Gale Warning from 10 AM this morning to 6 AM EDT Tuesday for ANZ633-639. Small Craft Advisory until 6 PM EDT this evening for ANZ635>637. Gale Watch from this evening through Sunday morning for ANZ635- 636. Gale Warning from 6 PM this evening to 7 AM EDT Sunday for ANZ637. Gale Warning from 7 AM this morning to 1 PM EDT Sunday for ANZ650.