####018005854#### FXAK68 PAFC 110042 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 442 PM AKDT Fri May 10 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... A large vertically stacked low situated over the southern Alaska Peninsula looks to push towards southern Alaska over the next couple of days. The storm system will be slow moving, with the low drifting into the western Gulf Saturday afternoon. A series of short-waves rounding the low will provide plenty of lift and produce some hefty precipitation totals for Kodiak Island and the coastal zone of Southcentral. Drier conditions for interior Southcentral as well as Anchorage and western Kenai Peninsula. Snow is still possible at higher elevations. Marginally warmer temperatures are expected across much of Southcentral Saturday and Sunday, with values reaching into the mid-50's for interior Southcentral. Gusty winds will continue across the Kenai Peninsula and eastern Turnagain Arm through Saturday. Southeasterly gap winds will slowly diminish through tonight for the Copper River and Knik River Valley. The low weakens by Sunday and the upper level trough will lift northwards across Southcentral. Steady moderate to heavy precipitation will fade to lighter rain showers, primarily around Prince William Sound and the north Gulf coast. && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... The weakening vertically stacked low over the Alaska Peninsula continues to move eastward. Moisture from the Gulf of Alaska will be carried in with the persistent southerly flow, providing rain and wet snow for much of Southwest. This will continue to occur through Sunday morning before the low further dissipates and moves into the gulf. Some breaks in the clouds and shift to southerly flow will help bring temperatures back up closer to normal for this time of year. Highs should be up closer to the 50s inland with coastal areas getting into the 40s. The increased temperatures will support increased instability which could result in showers to occur in the late afternoon hours tomorrow and Sunday. Gusty conditions on the north and west side of the low over the Bering will continue as well, producing gale force gusts between the Pribilofs and AKPen. Over the Aleutians, another low currently located south of Shemya will brush by the central Aleutians through Sunday morning. Much of the impacts will remain either over the Aleutians or for the North Pacific, with small craft winds and gale force gusts forecast. Precipitation in the form of a rain/snow mix or all rain is expected as the low moves eastward, with high temperatures getting into the upper 30s or low 40s. The track of the low continues to move slightly south over the last few model runs, bus some impacts over the Aleutian are still likely. The next system will start to enter the western Bering midday Monday, with widespread precipitation and gustier winds possible as the front of the low moves eastward. -BS && .LONG TERM FORECAST (Days 4 through 7: Tuesday through Friday)... The Alaska weather map opens with an elongated and somewhat fragmented positively tilted trough extending from the Arctic over the Eastern Mainland. The trough then curves back to the South of the Alaska Peninsula. The Northern portions drifts into the Canadian Provinces through Wednesday, while the Southern portion links up with a second system moving out of the Russian Far East. The trough becomes negatively for Thursday, with an increasing negative tilt through Friday. A ridge builds over the ALCAN border through Friday. Model agreement is good through midweek, but falls apart afterwards, as the flow pattern across the region weakens. The extended forecast opens somewhat quietly as North Pacific low moves the active weather into Southeast Alaska. Locally heavy rain over Prince William Sound and the Copper River Basin dissipates Tuesday. In the far West, the Northern Kamchatka low and front brings gusty winds and precipitation starting as snow, but quickly changing to rain across the Aleutians and Bering. The front brings locally heavy precipitation over the Central and Eastern Aleutians, AKPEN and Western Alaska. Some of this will be mixed precipitation over Western Alaska into the Interior, and trailing through Wednesday before diminishing over the AKPEN Thursday. Locally heavy rainfall moves moves over Kodiak Island and Southcentral Alaska for Thursday and across Prince William Sound and Copper River Delta through Friday. Lesser amounts of rainfall from the South reaches the Alaska Range for Friday. - Kutz && .AVIATION... PANC...VFR conditions will persist through the TAF period. Southeast winds out of Turnagain Arm will continue out ahead of a frontal system in the southwestern Gulf of Alaska. Winds peak later this this evening coincident with the greatest amount of instability present. Southeast winds may gust as high as 30 mph before the down inlet flow strengthens by the evening hours and persists into Saturday. This will help to keep the southeast winds over Turnagain Arm and out of the terminal with northerly winds prevailing this evening through Saturday. LLWS will likely develop later this evening as the winds over Turnagain Arm and the Anchorage Hillside remain southeasterly. The majority of precipitation will remain along the coast and the eastern facing slopes of the coastal mountain ranges due to the downslope drying effects of the southeasterly flow. -CC && $$ ####018008520#### FXUS62 KRAH 110042 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 840 PM EDT Fri May 10 2024 .SYNOPSIS... A cold front will move off the coast of the Carolinas this evening. High pressure will follow and extend across the Southeast and Middle Atlantic through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 235 PM Friday... Severe storms remain possible across our S half and far E portions of the central and southern Coastal Plain through early evening. Large hail and damaging straight line winds are the primary threats. A severe thunderstorm watch is in effect for this area until 9 PM. As the morning convection-allowing models strongly indicated, we've seen initiation of deep convection across our SW and in the Coastal Plain, along the prefrontal trough marking the transition between the 60s dewpoints to the S/SE and the 40s/50s values to the N/NW. We've managed to blow through this morning's elevated inversion, with steep mid level lapse rates nearing 7.5 C/km along with increasingly favorable mid level flow to 50 mph, while SBCAPE has risen to 1000-2000 J/kg in the watch area and will likely inch up a bit higher. The fairly straight and decently long hodographs with this buoyancy support a large hail threat, along with damaging straight line wind gusts, as the existing cells are likely to merge and congeal into short lines or bowing segments. Can't rule out a secondary line of convection back with the synoptic cold front, which is still to our NW, as it pushes SSE through mid-late evening. This activity should push SE of our area by 9 pm, followed by mostly clear skies overnight as lower dewpoints surge into the area. Lows in the upper 40s to mid 50s. -GIH Earlier discussion from 1010 AM: Forecast tweaks this morning focused on slight spatial and timing adjustments to hourly precip chances today into the evening. 12z surface analysis shows a low E off the tip of the Delmarva with a trailing trough into NE NC, a second trough (dewpoint discontinuity with shift of weak winds) along the NC Foothills into N GA, with the actual synoptic cold front still back across central and SW VA, E TN and N AL/MS. RAP- based mesoanalyses of SBCAPE and the 12z GSO sounding show well the shallow surface-based stable layer over the area (contributing to persistent stratus in our SW) with another inversion around 800 mb, topped by some decently steep (7.0-7.5 C/km) lapse rates through the mid levels that are also noted upstream. With heating expected to erode the surface stability, we're still expecting convection to develop, grow upscale and become organized into a W-E then WSW-ENE line, starting first in our SW then spreading across our SE third (where dewpoints will be around 60 or higher) through the afternoon before exiting by mid evening. A wrench in this scenario is the mature MCS to our S over SE GA and N FL. The recent CAM runs did not depict the southern bowing portion racing so far eastward, currently off the SAV coast while most models have the front edge of this complex about 150-200 m slower/ further W. This system, and its effects on the regional wind field through ageostrophic adjustments, may play into the evolution and strength of storms further N over our area, as low level jetting into our SE could be disrupted, although this actually seems less likely based on the faster MCS movement, allowing time for air mass and pressure field recovery in its wake as heating takes place. As the surface trough shifts ESE today, lower dewpoints will spread into much of the Piedmont and W Sandhills, limiting the northward extent of deep surface-rooted convection. Have adjusted pops and weather to depict lower chances of mainly just showers over the N Piedmont, transitioning to good chance to likely pops for showers and storms, some possibly strong to severe across our far S and SE, peaking in the late afternoon then shifting to our SE in the early/mid evening. Highs in the upper 70s to lower 80s. -GIH && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... As of 1225 PM Friday... Shortwave ridging will give way to a shortwave digging southeastward into the Great Lakes, OH valley and northern Mid-Atlantic. While most of the energy with the trough will remain to our north in VA, height falls will promote some weak lift in the mid to late evening hours across our northern counties. At the surface, high pressure will give way to a lee trough. A secondary cold front or surface trough will then move through in the evening and overnight hours. Highs will be some 5-9 degrees below normal in the low to mid 70s, comfortable for early May. WAA in a return SW flow aloft Sat night between 850-700 mb will aid some weak (~100 J/kg) instability in the mid to late evening hours ahead of the trough passage. While most areas will see more dry time than showers, we introduced a slight chance of isolated showers across mainly the northeast Piedmont and northern Coastal Plain, roughly along/north of a line from Raleigh to Rocky Mount. Any showers will exit by late evening, with lows dipping a few degrees below seasonal normals into the upper 40s to mid 50s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 115 PM Friday... A period of dry weather and clear skies Sun into early Mon as a broad shortwave trough will be pivoting across the Northeast and Mid- Atlantic Sun morning and slide towards the Northeast coast by Sun evening. Strongly convergent flow aloft will favor strong subsidence on the backside of the departing trough and transient high pressure over the area before shifting offshore by Mon morning. Mostly clear skies and calm conditions will support steep surface inversions and pockets of radiational cooling and have trended down minimum temperatures, especially in the typical cool spots (mid 40s to low 50s). The next chance for rain will be right around the corner as the flat shortwave ridging and 850 anti-cyclone over the Southeast shift offshore Mon evening into Tues. A surge in deep southwesterly flow off the Gulf driven by a closed low spinning through the Mid-MS Valley will spread anomalous moisture (PWAT 1.3 to 1.6, 90th percentile) and waves of 700 to 850mb WAA through the southern Mid- Atlantic. Deep layer moisture appears to be maximized over the area on Tues, best chance for periods of showers/storms, while Wed may be a bit more uncertain. A tongue of dry air from 700mb and up will round the southern side of the shortwave and overspread portions of the Southeast and southern Mid-Atlantic. Where this dry pocket sets up will depend on the track of the aforementioned shortwave, which there area still timing differences on its departure Wed into Thurs. Nevertheless, will continue to highlight chance to likely PoPs during this time given the potentially favorable track and associated synoptic forcing and increased instability, but coverage may be more limited during this time. Temperatures will be coolest on Tues (5 to 10 degrees below normal), otherwise highs/lows will be near to slightly above normal through the remainder of the extended. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 835 PM Friday... A cold front and accompanying showers/storms has now cleared all cntl NC TAF sites and will move offshore through ~02-03Z. In its wake, nnwly surface winds may remain strong and gusty at times especially at INT/GSO for a couple of more hours this evening, as cooler and drier air surges in. VFR conditions, and light and variable surface winds, are otherwise expected through Sat, as high pressure builds across the Southeast. Outlook: A band of rain/showers, from clouds based around 5-6 thousand ft AGL, and with a risk of brief flight restrictions, will move across cntl NC Sat evening. Rain and IFR-MVFR restrictions, lowest over the Piedmont at INT/GSO, will overspread cntl NC Tue morning, with a following chances of showers/storms Tue afternoon through Wed. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...Hartfield SHORT TERM...Kren LONG TERM...Swiggett AVIATION...MWS