Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 251438 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1038 AM EDT THU AUG 25 2016 .SYNOPSIS... High pressure moves farther offshore today. Warm and more humid conditions return ahead of a cold front Friday, which may lead to a few showers or thunderstorms. Large high pressure will crest across New England this weekend, bringing dry and somewhat less humid conditions. Another front will slowly move across the region late Sunday night and Monday with a chance for showers and thunderstorms. Conditions for Tuesday and Wednesday look dry for now. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure axis from our offshore waters to the Deep South. This brings a southwest flow to tne New England states. Morning soundings show a mixed layer to at least 830 mb with winds temps 15-17C and winds near 20 knots in the layer. Expect these to mix to the surface. Satellite images show mid and high clouds moving into our western areas. Thicker clouds along/west of a line UCA-BGM-AVP moving east to the CT River Valley 1-2 pm...Worcester 2-3 pm...Boston/Prov 4 pm. Showers in NY have been drying as they moved east. Soundings look rather dry, so expect this trend to continue. Best chance of any showers reaching our area would be along/west of the CT River 3-6 pm. Will go with 12-18 percent, highest near the VT border. Observed dew points in the mid 60s should continue, so humidity should be noticeable but not oppressive. Temps in the mixed layer suggest max sfc temps mid to upper 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Subtropical moisture plume moves into southern New England ahead of a cold front with precipitable water values approaching 2.00". The forcing continues to be rather weak, although mid level lapse rates should become a bit more supporting of thunderstorms. Not expecting an all-the-time washout everywhere. However, wherever showers and thunderstorms develop, there will be the possibility for a torrential downpour. Humidity continues to increase tonight into Friday. As such, temperatures tonight are not expected to drop much below 70 at most places. It will likely be muggy sleeping weather. The heat continues to build Friday. A cold front should move through or region by late Friday, which should bring an end to the rainfall chances. The humidity will take longer to drop off. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Highlights... * Shower and thunderstorm chances Friday evening and late Sunday night into Monday * Expect a warm and somewhat less humid but dry weekend * Lower confidence for sensible weather conditions Tue/Wed Overview and model preferences... Overall upper level pattern across the northern tier of North America appears to remain essentially the same with a nearly zonal flow aloft into this weekend. Do note a weak short wave in this flow, with its associated frontal system that pushes through Friday night. Large high pressure builds east out of central Canada to the Great Lakes by Saturday, then shifts eastward through the weekend as high amplitude H5 ridge builds but remains progressive. With higher H5 heights, will still see temperatures across the region running 5 to 10 degrees above seasonal normals through the weekend, though somewhat lower humidity will make it feel comfortable. As the northern strong ridge builds toward the Maritimes later Sunday, noting another H5 short wave in the flow. Big question will be how far S the energy from this short wave will work as the surface front moves along in the upper flow for late Sunday night into Monday. Appears what energy and moisture will be mainly across central and northern areas, but not much of either to be had at this point. Most models and their ensembles all signaling the storm track across the northern stream appears to be retreating into southern Canada early next week. Looks to be difficult to get any moisture or instability to work in, as it appears the front crossing the region during Monday tries to wash out as it shifts S. It may linger as it stalls near or S of the region by the middle of next week. With mid level subsidence allowing for capping, will not see much in the way of convection. Models having their issues in the timing and placement of any precip that may develop for into the middle of next week. Most guidance is trying to keep any moisture that may organize across SW New England, mainly N CT into RI, near or just N of the stalled front. Then there`s what could happen with the tropical wave 99L as well as Hurricane Gaston. For now, appears only effects that will be felt from Gaston will be mainly across the coastal waters, and that will be dependent upon its track well E of Bermuda at this point. As for 99L, that appears to be a southern U.S. concern, but still needs to be monitored. Details... Friday night...May see isolated-sct showers/thunderstorms lingering in the evening ahead of cold front as it crosses. The best PWATs have already pushed offshore, so not a lot of moisture to work with. Any leftover precip across southern areas should end. May see patchy late night fog develop in the normally prone inland locations. Expect lows in the 60-65 degree range well inland, coolest in the E slopes of the Berkshires, ranging to around 70 along the S coast. Saturday-Sunday...Large high pressure crosses New England Saturday, settling into Maine and the Maritimes during Sunday. With the center of the high N of the region, will see mainly light N-NE winds with sea breezes especially on Saturday, then winds become more S-SE during Sunday. With the high mid level heights, temperatures will remain warm. Expect highs both days in the lower-mid 80s with some upper 80s across the lower CT valley. Inland locations will see drier dewpts, mainly in the mid-upper 50s, but will be somewhat muggier along the coast with the onshore winds. Sunday night-Monday...Another front approaches. Best PWATs, on order of 1.7 to 1.8 inches, cross the region Sunday night and push offshore by 12Z Monday. So, best shot for any precip will be later Sunday night through about midday Monday. Not a lot of QPF expected with any precip. Looks like best shot will be near and north of the Mass Pike but will be light. Will be another warm day on Monday with highs mainly in the 80s, though a bit cooler along the immediate S coast. Tuesday-Wednesday...Lower confidence due to possible waves along stalled front S of the region that may influence sensible weather across N CT/RI and possibly into SE Mass. For now, kept forecast mainly dry, but much uncertainty. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/... This afternoon...High confidence. VFR with cigs 5-10k ft moving in across western New England during the afternoon. SW gusts to 20-25 kt, especially along the S-SE coast this afternoon. Tonight...Moderate confidence, mainly due to timing issues. Mainly VFR cigs, but areas of MVFR cigs possible. A few SHRA possible with isolated TSRA. Friday...Moderate Confidence, mainly due to timing issues. Scattered SHRA/TSRA, mainly across N/W portions of southern New England. Possible TEMPO MVFR-IFR impacts with any storms. Breezy S/SW winds with gusts up to 25 kts. KBOS Terminal...Will hold winds out of the S/SW with the terminal with the possibility of gusts of around 25 kts this afternoon. KBDL Terminal...S winds increasing with gusts up to 25 kts possible. Outlook /Friday Night through Monday/... Friday night...Moderate to high confidence. May see leftover isolated SHRA/TSRA across RI/SE Mass Friday evening with brief local MVFR conditions. Otherwise, mainly VFR. May see areas of MVFR-IFR CIGS/VSBYS lingering along S coastal Mass, Cape Cod and the islands. Patchy fog develops across normally prone inland locations after midnight with MVFR-IFR conditions. Expect light N-NW or calm winds. Saturday and Sunday...High Confidence. VFR. Light N-NE winds with sea breezes along the coast Saturday. E-SE winds as high pressure moves into the Maritimes. May see brief patchy late night/early morning fog in normally prone inland areas both days. Sunday night and Monday...Moderate Confidence. May see scattered SHRA/isolated TSRA move into N Mass mainly north of the Mass Pike after midnight Sunday night with brief local MVFR conditions. Otherwise, mainly VFR conditions. Brief patchy fog with local MVFR-IFR VSBYS after 05Z Sunday night, improving 11Z-12Z. Isolated SHRA/TSRA may linger across central and northern areas through early-mid afternoon on Monday, then should dissipate. W-SW winds around 10 kt or less. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/...High confidence. Increasing S/SW winds ahead of a cold front through Friday. Seas should generally remain less than 5 feet. Cannot rule out some higher seas across the outer coastal waters, particularly tonight and Friday. The main issue will be the potential of 25 kt gusts at times, particularly near shore where better mixing should occur. Increasing risk for scattered showers and thunderstorms tonight into Friday ahead of a cold front. Southwest winds and more humid conditions could also lead to some fog across the southern coastal waters with reduced visibility. Outlook /Friday Night through Monday/... Friday night...Moderate Confidence. SW winds 10-15 kt Friday evening, with gusts up to 20 kt on the southern waters, shifting to N-NW overnight. Seas 4 ft or less. Patchy fog on the southern near shore waters with visibility restrictions. Saturday and Sunday...High Confidence. Generally light N-NE winds with sea breezes along the near shore waters Saturday, becoming S-SE around 10 kt Sunday. Seas remaining below 5 ft, but may see SE swells increasing during Sunday. Monday...Moderate Confidence. W-SW winds remain light, though may see some gusts up approach 20 kt on the eastern waters Monday morning. SE swells from distant Hurricane Gaston may build to around 5 ft on the eastern waters as well as east and south of Cape Cod and Nantucket. && .CLIMATE... As we wind down August, we looked at the annual precipitation to date. As dry as we have been lately, there have actually been drier January to August periods. Here is how we rank at each of the climate sites: Boston: 1. 16.30" (1965) 12. 20.26" (2016)* 13. 20.28" (1950) 14. 20.45" (1980) Worcester: 1. 17.16" (1907) 17. 23.40" (2016)* 18. 23.46" (1923) 19. 23.50" (1999) Providence: 1. 16.84" (1957) 42. 25.83" (2016)* 43. 25.95" (1945) 44. 25.99" (1912) Hartford: 1. 16.75" (1965) 6. 22.34" (2016)* 7. 22.51" (1921) 8. 22.57" (1980) && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 2 PM this afternoon to 10 PM EDT this evening for ANZ231>237-251. Small Craft Advisory from 2 PM this afternoon to 7 AM EDT Friday for ANZ250-254. Small Craft Advisory from midnight tonight to 7 AM EDT Friday for ANZ256. && $$ SYNOPSIS...Belk/EVT NEAR TERM...WTB/Belk/EVT SHORT TERM...Belk LONG TERM...EVT AVIATION...Belk/EVT MARINE...Belk/EVT CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.