Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 231747 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 147 PM EDT Wed May 23 2018 .SYNOPSIS... A cold front will cross the region later today through tonight. Dry weather is expected Thursday and Friday under the influence of high pressure. Low pressure over the Gulf of Mexico will gradually bring a return of moisture for the upcoming weekend, especially by Sunday and Monday. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... As of 1110 AM EDT Wednesday... The cold front continues to make southward progress across the Mid-Atlantic States this morning and looking at the observations can see some drier air already moving into NW portion of the area in Louisa and Caroline Counties. There may be a weak leeside trough that is moving through ahead of the main cold front and turning the flow to the NW in advance of the actual front. But with that wind turn and the drier air advancing into the area, seeing the chances for showers and storms diminishing across the northern portion of the County Warning Area. The 12 NAM has continued the trend of showing convection developing later this afternoon after 18z mainly along the VA/NC border and slowly moving southeastward as the front continues its southern progression. So have trimmed the pops across the north, mainly north of Richmond which continued the trend from the previous forecast. Otherwise, pretty much left the forecast intact as temperatures look pretty reasonable and if anything might see highs a degree or two warmer than forecast based on current temperatures and developing NW flow. Prev Discussion... Latest analysis indicates sfc low pressure over the St Lawrence Valley with a cold front extending SW into the OH Valley. Aloft, flow is beginning to increase from the WNW as an upper low is situated over Atlantic Canada with shortwave energy currently pushing ESE from the Great Lakes around the base of this broad upper trough. A few spotty showers linger over the region early this morning, but coverage is now about 20% over SE VA and less elsewhere. An area of tstms is ongoing upstream over WV with the shortwave aloft, but IR satellite imagery shows warming cloud tops and high res models suggest this activity diminishes est of the Mtns as it approaches the AKQ CWA. Thus, expect little if any shower activity over the local area this morning under partly cloudy skies on avg. The surface front will gradually push through the area this aftn, and south of the region by the evening. As a result much of the southern half of the local area will remain south of the front through the mid/late afternoon. This should allow for thunderstorms to once again develop along the front. Winds aloft are only marginal for severe storms in the afternoon with only about 20-30 kt of shear during the afternoon. Could not rule out some line segments with gusty winds but organized severe unlikely and overall it appears like less of a threat compared to Tue. High res models (the last few runs of the HRRR in particular) have also backed off quite a bit on the coverage of aftn convection. With a WNW to NW flow aloft and shortwave energy aloft, did not go quite as dry as some of this new guidance, though did lower the PoPs somewhat, mainly on 20-30% from about metro RIC northward and for most of the eastern shore. Maintained a period of likely PoPs in NE NC where greatest instability Will persist the longest. Hampton Roads area may see the winds shift to the NNE by around 18Z or so and this would tend to push the highest coverage of storms inland and to the south near the VA/NC border. Will continue to highlight the marginal risk per latest SPC outlook, though believe the best chance for any strong storms will reside in NE NC and south central/interior SE VA along the NC border. Highs today will be mainly into the mid 80s, though temperatures look to fall near the coast later in the aftn as flow turns to the N/NE. Will maintain some chance PoPs over the south this evening, otherwise becoming mostly clear overnight as drier air filters in from the NNW. Lows tonight mainly 60-65 F, though the far NW could drop into the upper 50s and SE zones along the coast will avg in the mid/upper 60s. && .SHORT TERM /8 PM THIS EVENING THROUGH FRIDAY NIGHT/... As of 230 AM EDT Wednesday... A needed respite from all of the recent heavy rain will prevail as ~1025 mb sfc high pressure is progged to be centered over the lower Great Lakes by 12Z/Thu, ridging SE into the local area by Thu aftn. Dew pts dropping into the 50-55 F range for most of the region will make for comfortable/pleasant conditions. Highs Thu stay slightly above avg inland with lower-mid 80s, while areas near the coast will be cooler due to onshore low level NE flow (highs there in the upper 70s to around 80 F). Mostly clear and relatively cool Thu night with lows mainly in the mid 50s to around 60 F. This is close to avg but noteworthy as most of the CWA except on the eastern shore and far northern portions have not had a low below 60 F in over 10 days. Mostly sunny and warm and continued dry with dew pts Fri in the 50s and highs ranging from the mid 80s inland to the upper 70s/lower 80s near the coast. Mostly clear and trending a bit warmer Fri night with lows primarily in the 60s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 320 PM EDT Monday... The upper ridge will be gradually weakening on Sat, but it will still be mainly dry with just a 20-30% PoP for widely scattered aftn/evening storms. Highs in the mid/upper 80s. The upper ridge will then erode more significantly through the holiday weekend with a gradual increase in moisture as it appears that another area of low pressure will form in the northeastern Gulf of Mexico by Sunday and push more tropical moisture northward into the region. This could allow for more showers and tropical downpours for Sunday and again on Monday. The big model difference in the models is the handling of a backdoor cold front between the 12z GFS and ECMWF with the GFS pushing the front south through the area and the ECMWF keeping the boundary well north of the area. In either case, the chance for showers and some possibly heavy rainfall exist for the second half of the Holiday weekend. If the GFS is right with the front Monday could be a damp cool rainy day while the ECMWF would lead to more periodic showers with some breaks. At this time of year, seems more likely the for the front to hang north of the area. So have kept the temperatures up more in the low to mid 80s for Sunday and Monday. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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As of 145 PM EDT Wednesday... The cold front continues to make progress through the region having dropped south of SBY and RIC by 18z. The front will continue to drop south through eastern NC by 00z - 3z. There is still a chance for some scattered convection along the cold front this afternoon with ECG the most likely site to see convection. So have added some mvfr conditions with the forecast for ECG, otherwise have not added any other restriction with convection to the forecast. Behind the front just seeing some daytime heating cu field with ceilings between 4K - 6K FT. Once the front clears the area this evening will see drier air pushing south with mainly clear sky. At this point not think that fog will be an issue with the northerly flow and drier air. Quiet conditions/no flight restrictions Thu/Fri with high pressure in place and mostly sunny/clear skies. Increasing moisture returns for the upcoming weekend with scattered showers/tstms possible by Sat aftn/evening. The showers and tstms overall will become more numerous on Sunday and beyond with potential flight restrictions.
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&& .MARINE... As of 355 AM EDT Wednesday... Latest analysis reveals weak quasi-stationary boundary just north of the waters over the upper eastern shore. Obs and buoy reports indicate S-SW winds have nudged up slightly as anticipated over the southern coastal waters, lower Chesapeake Bay and the eastern VA rivers, in association w/tightening pressure gradient between surface ridge oriented just to the south and surface low and associated cool front to the west over the OH/TN valleys. Front drops across the region later this morning through the early evening, with the flow to veer around to the W-NW post-frontal. Only a modest push of cooler/drier air behind the front, and only a short-lived convective surge is expected, likely best handled by SMW/MWS as needed. Once the front clears the area, high pressure will settle over the waters for Thursday into Friday night. This will provide light winds and benign seas through Friday night. On Saturday, the flow will return to the south as the high pressure system slides off the SE US coast. Expect some increase in winds to 10 - 15 KT for later in the day Saturday and Saturday night. Upper ridge slowly breaks down Saturday night through the remainder of the holiday weekend, with model guidance intent on developing yet another low pressure area near the Yucatan, tracking into the east-central Gulf coast by Sunday morning. GFS remains the farthest east of the medium range models, with the ECMWF/Canadian off to the west with the sfc low. The GEFS is likely a good compromise for now. Either way, expect S winds to increase slightly on Sunday and Sunday night in response to this wave of low pressure, with wind wave potentially nudging seas upward to 3-4 ft central and southern waters. && .HYDROLOGY... As of 435 AM EDT Wednesday... Flood warning continues for the Appomattox River basin. Mattoax looks to have crested at 24.8 ft early this morning, just below moderate flood threshold (25 ft). The river level will slowly drop through tonight, dropping below flood stage Wednesday evening. Additional flood warnings continue for portions of the Chickahominy and Mattaponi rivers. See FLWAKQ or FLSAKQ for more details. && .CLIMATE... As of 215 AM EDT Wednesday... * RIC monthly rainfall total through 5/22 is 10.22" which now ranks as the wettest May on record. (breaking the old record of 9.79" in 2016). (Precipitation records date back to 1880). * SBY monthly rainfall total through 5/22 is 8.63" which already ranks as 3rd wettest May on record (wettest is 10.38" in 1948). (Precipitation records date back to 1906). && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...LKB NEAR TERM...ESS/LKB SHORT TERM...LKB LONG TERM...BMS AVIATION...ESS MARINE...MAM HYDROLOGY... CLIMATE...

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