Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 172336 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 736 PM EDT Thu May 17 2018 .SYNOPSIS... A frontal boundary stalls across northern portions of the forecast area through Friday, bringing periodic showers and thunderstorms, with the likelihood for heavy rainfall. Somewhat drier air arrives during the weekend as the upper level low pressure system weakens. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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As of 730 PM EDT Thursday... ...Flood Watch in effect through Friday evening for much of the area... Flood advisories are currently in effect for locations north of the RIC metro, from Louisa/Fluvanna County east to Caroline County and the Northern Neck. The steadiest/heaviest rain on the radar is currently over the aforementioned areas where rain amounts have been up to 1-2" per hour (nearest a stalled frontal boundary). Elsewhere, rain is lighter and more sporadic which is good news given the soggy conditions as of late. Have aligned PoPs through the remainder of the evening to show best chances (~90-100%) across our northern counties (mainly N of RIC), tapering to chc PoPs (50%) across the southern tier counties, where the radar is quieter. Hi-res guidance, including the HRRR, show the current batch of moderate/heavy rain lifting north/waning thru 02Z before the next round of moderate/heavy rain ramps up to the south and lifts north through the FA overnight. The synoptic setup is one for heavy/excessive rainfall through tonight (and Fri). Deep layered southerly flow will continue transporting highly anomalous moist over the local area (with a nearly stationary sfc boundary draped across far nrn tier of the FA). Best forcing/UVM overnight is expected to be across central/wrn and nrn locations of the FA. Flood Watch will remain in effect for average rainfall of a few inches possible in numerous SHRAS and ISOLD-SCT tstms. Threat will continue for localized flash flooding in heavier bands of SHRAS/tstms that do develop. Kept areas of FG near/over coastal areas along the MD ern shore. Lows tonight from around 60F on the lower MD ern shore to 65-70F elsewhere.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... As of 315 PM EDT Thursday The pattern featuring a trough over the Mid-South and a stalled frontal boundary over the Mid-Atlantic will continue into Fri night. A deep feed of subtropical/tropical moisture will persist on the ern side of the trough (PW generally +2 to occasionally +3 st dev) bringing periodic showers/tstms. 12Z/17Z models are targeting a window of another surge of concentrated +RA possible over central portions of the FA during Fri. Will have Flood Watch continue through midnight Fri night for now...though axis of highest/deepest moist and potential +RA may shift to ESE portions of VA and NE NC Fri eve/night. Highs Fri from the l-m60s on the lower MD ern shore to the 70s elsewhere. Most if not all of the FA is expected to get back into the warm sector Sat as axis of deepest moist shifts to the coast/offshore. So...highs Sat will genly be in the u70s-l80s (l-m70s on most of the eastern shore). Some potential for stronger tstms exists by Sat aftn/evening though much uncertainty remains. Storm total QPF through Sat night ranges from 2.00"-2.50" SE to 3.00"-5.00" NW. Due to the convective nature of this event, there will likely be localized areas of higher amounts, but also some areas that receive less. Sun will be warm and moderately humid w/ VRB clouds/partly sunny conditions. Will have PoPs 20-40% (highest over far SE VA- coastal NE NC)...primarily for afternoon/eve SHRAS/tstms. Highs from the u70s-l80s on the ern shore to the m80s inland. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 100 PM EDT Thursday Unsettled wx expected to continue early in the extended forecast period then a trend toward drying/improving wx now highlighted mid week. A gradual break down of the moist SSW flow expected as westerlies aloft strengthen and finally push a (and more significant) cold front through the region (Wed). Keeping PoPs above climo Sun night through Tue (mainly 30-50%) for SHRAS...mainly diurnally driven tstms. Lowering PoPs to aob 15-30% Wed-Thu. Highs each day mainly in the 80s...w/ lows in the 60s-70F. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/... As of 700 AM EDT Thursday... Sfc frontal boundary is still positioned over far N/E sections of the CWA as of 18z. Currently, VFR/MVFR conditions are being observed at all terminals, as IFR ceilings that were observed this morning have lifted. Scattered showers (some w/ heavy rain) have developed throughout the CWA and will persist through the evening hours. Showers will be most numerous in the northern/western CWA, and brief IFR visibilities are possible in heavy rain through the evening hours. Went with SHRAs with 3-6 mile visibilities at all sites, as forecaster confidence is low regarding a precise time range for IFR visibilities. Left thunder out of the TAFs as little to no lightning has been observed with these showers. Scattered showers continue as the frontal boundary slowly sags southward tonight. Therefore, flight restrictions will become more widespread after 06Z (especially north of the boundary) with IFR ceilings likely (LIFR possible at SBY) at all sites except ECG. The boundary will likely stall just north of RIC on Friday as moisture continues to stream into the area from the S. This will result in periodic showers/tstms, which could bring MVFR and brief IFR vsby in heavy rain on Friday. OUTLOOK... The boundary will gradually lift N by Saturday, but shower/tstm chances will continue. Somewhat drier conditions potentially arrive by Sunday. Patchy early morning MVFR/IFR stratus will be possible on both Saturday and Sunday. && .MARINE...
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As of 720 PM EDT Thursday... A frontal boundary will remain stalled across the northern portions of the marine area this evening/tonight and even into Friday. This will result in winds remaining E or NE 10-15 kt or less off the MD coast and over the upper Bay. SE winds will persist over the middle to lower Bay and the remainder of the coastal waters through Fri night. Seas generally 2-4 ft; waves 1-2 ft. A breif uptick in wind speeds to around 20 kt is possible north of Chincoteague Friday aftn/eve. Wave guidance is also showing the potential for seas to reach 5 ft out past 10 nm north of Parramore Island Friday night. SCA looks marginal at best so will defer to next shift to asses whether a headline will be needed. The pressure gradient tightens on Sat resulting in an increasing southerly flow to 15 to 20 kt especially over the coastal waters. SCA conditions will be marginal for the Bay Sat/Sat night and an SCA may be needed. Potential exists again for seas to build to 5 ft out around 10-20 nm on the coastal waters. Flow becomes a little more SW Sun as a front drops down across northern VA and stalls. Bermuda high pres well offshore will keep winds SW around 15 kt through Tue with some higher gusts possible. Models suggest an area of low pressure may pass across New England Tue into Wed which could increase winds a little more with SCA possible for a time Tue and Wed.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Flood Watch through Friday evening for MDZ021>025. NC...None. VA...Flood Watch through Friday evening for VAZ048-060>062-064>069- 075>090-092-509>522. MARINE...None. && $$ SYNOPSIS...ALB/LKB NEAR TERM...ALB/JDM SHORT TERM...ALB/LKB LONG TERM...ALB AVIATION...ERI/LKB MARINE...JDM/JAO

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