FXUS61 KAKQ 250730 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 330 AM EDT Sun Jul 25 2021 .SYNOPSIS... High pressure will remain offshore for the remainder of the weekend, allowing for diurnally driven showers and thunderstorms today. A weak cold front crosses the most of the area on Monday, resulting in scattered numerous thunderstorms from Monday afternoon through Monday night. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM EDT Sunday... Early morning wx analysis shows upper ridging anchored over the central/srn Plains, while NW flow aloft continues to prevail over the Mid-Atlantic. Surface high pressure has shifted well offshore of the local area. A shortwave aloft is tracking to our north toward New England and this feature is responsible for the isolated to scattered showers (w/ brief heavy rain) that are tracking across the Lower MD Ern Shore from W-E. Elsewhere, it is mainly dry with S-SSW winds and temperatures mainly in the low 70s. Will keep slight chc-chc PoPs over the Lower Ern Shore through 12z. Not expecting much in the way of thunder on the Ern Shore, given that there is no surface-based instability present (with only a small amount of elevated CAPE). It will be noticeably warmer (and a bit more humid) today than it has been during the past few days due to increasing low level SSW flow, as upper ridging continues to build over the central/srn Plains. Dry wx is expected from ~8 AM through early-mid aftn. Isolated to widely scattered tstms are progged to initially develop to our NW along a sfc trough this aftn and move into our NW zones (mainly from Farmville to Tappahannock and NW) by late aftn/early evening. Rain chances spread E-SE to northern neck and eastern shore by 00z...with even a slight chc of a tstm as far SE as the Richmond metro). Highs today mainly upper 80s to low 90s. While widespread severe wx is not expected, cannot rule out a couple near-severe wind gusts that down a few trees across our far NW zones from late aftn-evening. Effective shear values will be a bit less than they were yesterday, given sfc winds out of the SSW instead of the SSE. The low-end severe threat should diminish by 9-11 PM with the loss of surface heating. However, an approaching cold front and a nocturnal southwesterly ~30kt 925mb jet may be enough to keep at least isolated showers/tstms going (mainly N of I-64 and E of I-95) through much of the night. Have 15-30% PoPs through 12z Mon to account for this. Early morning lows Monday AM range from the upper 60s to low/mid 70s. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 330 AM EDT Sunday... For Monday, a WNW-NW flow aloft continues to prevail across the region as the above mentioned weak cold front continues to approach from the NW and drops through the local area late in the day and overnight into Tue morning. Meanwhile, deep-layer moisture continues to increase across the area, with PW values rising to 2.0-2.4" across the SE two-thirds of the area by Monday aftn. In addition, a shortwave trough aloft is progged to cross the area late Monday into Monday night. Instability parameters become fairly impressive by 18z Mon (1500-2500 J/kg of MLCAPE) as temperatures rise to around 90F with low-mid 70s dew points. However, the models continue to forecast only minimal shear. Nevertheless, suspect that there will be some chance for at least isolated strong to severe storms (main threat will be localized damaging wind gusts) Mon aftn/evening. It appears the greater threat may be locally heavy rain/flooding given the above mentioned PWs and also the relatively slow expected motion (MBE velocities are only 10-15kt from Mon aftn-Mon evening as per 00z NAM/GFS). Greatest threat for localized flooding appears to be across southern VA and into NE NC (main concern would be the urban areas of Hampton Roads given relatively high FFGs elsewhere). Even though it is at the end of its forecast period (48-h), it is worth noting that the 00z HREF has 30-50% probabilities of 3"/3 hours in these areas from 21z Mon-00z Tue. WPC has maintained a MRGL Risk for Excessive Rainfall from Mon-Mon night across most of the area. Have nudged the highest PoPs (60-70%...from 18z Mon-06z Tue) a bit to the south given the trend in the 00z/25 guidance. Have chc PoPs (mainly during the aftn/evening) across nrn zones. Tstms will be most numerous during the aftn/evening (with the highest coverage along and S of I-64). These tstms are progged to gradually move SE during the evening and overnight. Convection will wane/exit the area during the latter part of Mon night. Forecast highs Mon are in the upper 80s to around 90F, with lows in the upper 60s-low 70s Monday night. The front stalls/weakens across NC on Tue. Will keep high chc PoPs across the south Tue aftn, with a slight chc of aftn tstms into most of central/E-central VA. Highs in the upper 80s to lower 90s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 330 AM EDT Sunday... The middle to late portion of this week will be characterized by near to slightly above normal temperatures and seasonally moderate levels of humidity, as the heat ridge remains anchored in place across the central CONUS with continued W-NW flow aloft across the local area. Timing of rain chances in this type of pattern will be dependent on timing and location of numerous shortwave disturbances in the flow aloft (and a cold front that potentially approaches by late next week). Overall, will have only 10-20 PoPs Wed-Thu, with PoPs 20-30% for Fri as the next cold front moves through, with 10-20% PoPs Sat. The timing of the front is somewhat uncertain so a faster solution (like the 00z GFS/GEM) could lead to higher PoPs than currently forecast as early as Thu evening/Thu night. The slower ECMWF solution would imply that the highest PoPs hold off until Fri aftn. Summerlike heat and humidity is expected with highs 90-95F and lows mainly 70-75F Wed-Fri. Sat looks a little cooler with less humidity at this time. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... As of 115 AM EDT Sunday... VFR conditions are expected to prevail through the 06z TAF period with S-SSE winds becoming SW 5-10kt this morning, then increasing to 8-12kt with a few gusts approaching 20kt by afternoon. There is a ~30% chc of showers (with perhaps a rumble of thunder or two) at SBY from 08-12z, which could produce brief MVFR/IFR VSBYs in heavy rain. However, confidence is still not high enough to include a TEMPO group in the TAF. Otherwise, any isolated showers/tstms are expected to remain NW of RIC and SBY this afternoon, but could approach SBY (and even RIC) by this evening. However, PoPs are only 20-30% at RIC/SBY this evening, so will hold off on mentioning pcpn in the TAFs. Isolated to widely scattered showers (and perhaps a tstm or two) are possible tonight at SBY, while PoPs are no higher than 20% at the VA/NC terminals. Prevailing conditions likely remain VFR through tonight. Outlook...The chc for afternoon/evening showers/tstms increases to 30-60% on Monday, as moisture pools ahead of an approaching frontal system. Mainly VFR conditions Tuesday with isolated to widely scattered showers and tstms potentially bringing brief degraded flight conditions in the afternoon and evening. The chc for afternoon and evening showers and tstms is 20% or less by Wednesday and Thursday. && .MARINE... As of 300 AM EDT Sunday... Try as I might, can't seem to find gusts aoa 20 kts across the Ches Bay except from Tangier Isl on north. Latest model guid not as bullish with 20 kt gusts either, so dropped the SCA on the Bay south of Windmill Point. Will leave the SCA up for ANZ603 though. Minimal SCA's cont for the nrn cstl waters, expecting gusts arnd 25 kts and 4-5 ft seas later today/tonite. Diminishing winds Mon as the pressure gradient relaxes. A weak front approaches then crosses the region Mon aftrn into Tues. The boundary lingers/washes out just south of the local area Tues into Wed. Sub- SCA conditions expected thru mid week. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 10 AM this morning to 4 AM EDT Monday for ANZ650-652-654. Small Craft Advisory until 4 PM EDT this afternoon for ANZ630. && $$ SYNOPSIS...ERI/LKB NEAR TERM...ERI SHORT TERM...ERI/LKB LONG TERM...ERI/LKB AVIATION...AJZ/ERI MARINE...MPR