Area Forecast Discussion
Issued by NWS Wakefield, VA

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583 FXUS61 KAKQ 190824 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 424 AM EDT Fri May 19 2017 .SYNOPSIS... A cold front moves south across the area tonight and stalls over the Carolinas on Saturday. This front will lift back north as a warm front on Sunday. Another cold front is expected to cross the Mid Atlantic Region on Monday. && .NEAR TERM /THROUGH TONIGHT/... Sct high clouds streaming in from the SW as Atlantic and Gulf moisture rotate in around mid-upper ridging off the Southeast and FL coasts. A lee trough is becoming more prominent early this morning (as expected) in advance of a cold front progged to drop down from the north later this evening. A warm start to the day will give way to highs generally in the upper 80s with pockets around 90F inland VA. Ample daytime heating plus increasing moisture/dewpoints will allow aftn cumulus to develop. As the lee trough continues to build into the area, expect thunderstorms to develop along/west of the trough axis late this aftn into this evening. Shear is not all that impressive (0-6km bulk shear is 25kt or less), however inverted-V profiles are present with ample CAPE in the hail growth zone. The main challenge today will be achieving enough lift for either of these components to be an issue. That being said, the lee trough could provide just enough lift for a few strong storms to develop prior to the loss of daytime heating. Main storm-type should be unorganized pulse storms with the primary threat being wind, however hail cannot fully be ruled out based on sounding profile data. Bulk of thunderstorms should occur between 500-1000PM. One of the bigger changes in model solutions has been to focus storms generally along/north of the Interstate 64 corridor with isolated to scattered storms possible across far swrn counties. Given weakly sheared environment and a small amount of uncertainty in precip placement based on 00Z model runs, have limited to POPs to 30-40% through early evening and then 30-50% late this evening as the cold front drops into the area and creates somewhat of a squeeze play with the lee trough...thus squeezing out more widespread showers (again mainly along/north of the Interstate 64 corridor) during this timeframe. In addition, periods of moderate to heavy rainfall will be possible as Pwats approach 1.35-1.40 inches based on actual upstream observations at 19/0000Z, which is about 150-175 percent above normal. Isolated thunder may continue into the overnight hours invof the cold front as it drops southward and starts to stall in NC late tonight. Clouds and evaporational cooling from precipitation will be the main reason overnight lows cool due to negligible cold air advection behind the front. Expect lows in the low-mid 60s north and upper 60s south. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Showers will taper off from north to south as the cold front exits the area and stalls over the Carolinas during the day. Thunderstorms may re-fire along/south of the VA/NC border in the aftn due to daytime heating. All precip should end by late aftn/early evening. Temperatures could be tricky as the combination of clouds, evaporational cooling from recent rains, and decent onshore winds over the cooler waters (15-20 mph with gusts to 25-30 mph immediate coast) should hamper daytime heating even though 850mb temps only cool a few degrees. For inland areas, expect highs in the low-mid 70s north and mid-upper 70s south. for locations closer to the coast, expect highs in the 60s to around 70F. The stalled frontal boundary washes out into a warm front Saturday night. Although wind speeds at the coast are expected to diminish after midnight, return flow along the warm frontal boundary could pull enough moisture over the warm front and allow isolated light rain showers to develop overnight into Sun morning. Lows in the upper 50s north to lower 60s south (low-mid 50s possible MD Lower Eastern Shore). The warm front slowly lifts northward through the area on Sunday as a cold front approaches the region from the west. A slight chance for rain showers will continue into Sunday invof the front until the warm sector south of the boundary and ahead of the cold front can take hold. Held onto similar temperatures as Saturday with highs generally in the 70s (mid 60s to lower 70s immediate coast), however temps could end up being several degrees warmer if the warm front can shift north faster than anticipated. The region should be within the warm sector by Sunday night, and lows in the mid-upper 60s will be common (low-mid 60s possible inland MD Lower Easter Shore). && .LONG TERM /MONDAY THROUGH THURSDAY/... Models a few hours quicker with the moisture ahead of the strong cold front still progged across the FA during Monday afternoon/early evening. Plenty of moisture along with decent instability to keep the likely pops. A few strong tstms with heavy downpours are possible, depending on how much heating can occur. Highs in the upr 70s to lwr 80s. ECMWF has come around to a GFS solution with respect to how fast this system moves off the coast. Will keep likely pops eastern zones Mon night and then taper off to chc after midnight. Lows mid 50s nw to low-mid 60s se. A brief reprieve Tue as weak high pressure builds into the area from the west. Kept it dry under pt sunny skies. Highs in the mid to upr 70s. Mstly cldy with sct shwrs returning Tue night. Lows in the upr 50s nw to mid 60s se. Upr level low moves ne across the Gt Lakes region Wed with the trailing cold front progged across the area late in the day and night. Likely pops most areas Wed, chc pops Wed evening as the front pushes offshore. Highs Wed in the mid to upr 70s. Lows in the mid 50s to lwr 60s. Upr level moisture rotates around the low to the north. This keeps Thursday rather unsettles with mstly cldy skies with chc shwrs. Highs in the low to mid 70s. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Sct high clouds this morning will give way to aftn cumulus as a lee trough builds into the area. Thunderstorms are expected to develop along/west of the trough axis this aftn/evening; mainly between 19/2000Z-20/0200Z. Latest model trend is to keep precipitation focused along/north of the Interstate 64 corridor during this timeframe. Precipitation becomes more widespread late this evening as a cold front drops south and interacts with the lee trough. Locally strong winds, brief periods of moderate to heavy rainfall, and isolated hail will be the primary threats. Brief periods of MVFR CIGS/VIS should also be anticipated under stronger storm cores. The cold front pushes south through the area tonight and shunts precip southward during Saturday as the front begins to stall over the Carolinas. Breezy NE winds develop late tonight into Saturday behind the cold front with gusts of 15-25kt along the coast. Showers should end by late Saturday aftn/early evening with winds diminishing after midnight as the cold front washes out into a warm front. This boundary is expected to slowly lift northward on Sunday. Return flow/moisture along this boundary should allow light rain showers to develop late Saturday night into Sunday and may persist into the day due to the slow movement of the frontal boundary. Another cold front approaches from the west Sunday night and is anticipated to cross the area on Monday. && .MARINE... Latest sfc analysis shows sfc high pressure centered well off the southeast coast near Bermuda with a cold front pushing southeast of the Great Lakes. SW winds remain elevated this morning at around 15 kt with some gusts to 20 kt over the lower Bay and coastal waters, though will not have any headlines as these winds are marginal for SCA and should see diminishing trend late this morning into the aftn. This as the gradient weakens this aftn and will tend to see wind directions shifting more to the S or SE across the lower Bay and southern coastal waters and S to SSW farther N in the marine area. Tstms will be possible later this aftn and especially this evening and will be capable of producing locally higher winds, but outside of convection winds will avg around 10 kt or less. Have raised SCA headlines for all zones except the upper James and York/Rappahannock River (where it will be more marginal and will allow day shift to determine if it will be needed). These headlines begin early Sat morning across the N and by later Sat morning or early Sat aftn across the S. This due to a surge of colder air and pressure rises of 4-6 mb/hr on Sat as high pressure builds from the eastern Great Lakes to off the mid-Atlc coast by Sat night/Sun morning. Seas build to 4-5 ft on avg and waves in the Bay will avg 3- 4 ft. The event is fairly short in duration, with winds diminishing by Sat evening as high pressure builds a little farther south and easterly winds diminish to 10-15 kt. Seas will remain elevated into Sat night on the coast so headlines there have been issued through the 4th period/Sat night. Seas on Sun avg 3-4 ft. Winds shift to the SSE later Sun into Mon. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 7 AM to 10 PM EDT Saturday for ANZ632-634. Small Craft Advisory from 1 PM to 10 PM EDT Saturday for ANZ633. Small Craft Advisory from 4 AM to 4 PM EDT Saturday for ANZ630- 631. Small Craft Advisory from 7 AM to 7 PM EDT Saturday for ANZ638. Small Craft Advisory from 4 AM Saturday to 4 AM EDT Sunday for ANZ650-652-654. Small Craft Advisory from 10 AM Saturday to 6 AM EDT Sunday for ANZ656. Small Craft Advisory from 1 PM Saturday to 6 AM EDT Sunday for ANZ658. && $$ SYNOPSIS...BMD NEAR TERM...BMD SHORT TERM...BMD LONG TERM...MPR AVIATION...BMD MARINE...LKB

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