Area Forecast Discussion
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220 FXUS61 KBOX 200152 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 952 PM EDT Wed Jun 19 2024 .SYNOPSIS...
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Hot and humid weather continues into Thursday. Another round of thunderstorms is expected Thursday near and north of the Mass Pike, and some could become strong to locally severe. A backdoor cold front moves in from northeast to southwest Friday, though there remains uncertainty how far inland the front tracks. Showers and thunderstorms are likely along the front Friday afternoon. Unsettled and muggy this weekend, while not expecting a washout, there will be periods of rain and thunderstorm activity. A cold front moves across the region on Monday with drying and warming conditions into next week.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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10 PM Update: Convection/thunderstorms have dissipated with just some cloud debris left behind. Warm and humid night ahead, with current dew pts in the 60s to low 70s across northern MA. Previous forecast remains on track, therefore no changes with this update. Earlier discussion below. ================================================================== For the rest of the evening, we should see decreasing cloud cover although it will still be quite muggy with dewpoints in the upper 60s to lower to mid 70s leading to little significant relief. The high humidity levels should also favor potential for marine fog on the southern waters, and some of that fog could make it landward into the south coasts of RI and MA, Cape Cod and the Islands. Lows only in the upper 60s to the lower 70s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... 400 PM Update: Key Points: * Another day of heat and humidity with high heat indices, excessive to those with prolonged exposure. * Scattered strong storms with localized strong/damaging winds, heavy rain capable of street flooding and frequent lightning potentially as soon as early afternoon, decreasing in coverage and strength into early evening. Greatest risk from the Mass Pike northward, with isolated storm coverage to the Hartford-Providence corridor. The sprawling upper level ridge from the mid-Atlantic into coastal Southern New England continues to shift ever so slowly southward Thu and Thurs night. Given the current coverage of t-storms Wed aftn which lies on the northern periphery of the ridge axis, it would seem reasonable to expect a little greater t-storm coverage Thurs and possibly into Thurs night with the upper ridge axis shifting southward. While vertical wind shear is a touch stronger Thurs than today, it still is a pretty weakly-forced large-scale setting for t- storms, one which higher resolution guidance often struggles with. Though it still should be hot and humid Thurs, the coverage and if/when these storms develop now casts a level of uncertainty on how warm we might get; in particular for areas along and north of the Mass Pike. Regarding the heat/humidity, it should again be hot and humid and left heat headlines and heat index values more or less little changed to keep the message simple. As mentioned though, we`ll also be destabilizing as the heat and humidity builds on Thurs and we expect storms to develop near the MA/VT/NH border and sag southward at some point during the afternoon hours. This looks closer to the GFS depiction, although some of the CAMs are faster with development, potentially as soon as early afternoon, while others are later by late-afternoon. So there is a possible outcome where storms develop early in the day and could keep us from reaching Advisory criteria north of the Mass Pike, but for now will leave these heat headlines as is. Thus highs in the 90s, with heat indices into the low 100s away from the south coast. Near the south coast, highs in the upper 70s to lower 80s with heat indices in the 80s. On the t-storm threat for Thurs, it looks as though we`ll see a greater extent of storms toward scattered, with PoPs in the 30-50% range. Moderate to strong instability looks progged with the degree of heat and humidity around, with CAPE values in the 2500-3000 J/kg range, decreasing significantly with southern extent mainly south of the Hartford-Providence corridor. While vertical wind shear is still weak and supporting pulse to multicellular storm clusters, downdraft CAPE should be pretty large by the afternoon. A few storms could pulse to severe limits with localized straight line wind damage being the main severe weather risk. There are signals for re- developing storms/backbuilding potential as we move through the afternoon, which could shift the threat from isolated severe weather to more of heavy rain/localized hydro problems, with less-strong instability as individual storms rain themselves out. After consult with SPC, we think the severe weather potential seems isolated. Phrased as scattered storms with enhanced wording for gusty winds, heavy rainfall and frequent lightning near and north of the Mass Pike, with more isolated coverage to the Hartford-Providence corridor. The forecast for Thursday night is low-confidence and will hinge on how daytime t-storms develop and evolve. Upper level ridge axis continues to shift slowly southward, with a surface frontal boundary trying to slip southward from NH/VT. Residual showers/storms from the daytime hours should continue to progress southeastward. NAM/GFS each indicate a windshift to N/NNE moving into far northern MA by early Fri AM, which could bring a somewhat cooler air mass to northern and northeast MA. There could be continued clouds and showers around in interior MA/CT/RI into the daytime hrs. Expect there to be adjustments to the forecast moving forward, but there is too much uncertainty to lock into any solution or outcome at this time. It still looks pretty muggy outside of northern MA later in the overnight with lows in the 60s to lower 70s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Highlights: * A backdoor cold front will move northeast to southwest on Friday with cooler temperatures returning, but uncertain how far inland the front will go. In addition, showers and thunderstorms may develop along the backdoor cold front. * Warm and muggy this weekend with rain chances both Saturday and Sunday. * Cold front sweeps across the region on Monday, drier and returning heat into mid next week. Friday: Shift in mid-level pattern, sub-tropical ridge of high pressure "breaking down" and drifting south. As previously mentioned there is a backdoor cold front should move across the region from the northeast to the southwest. That said, there is a bit of uncertainty with the magnitude of the front, and how far inland the cold front will penetrate. Combination of the front and convection will play a significant role in how warm it gets. The Dynamic Ensemble-Based Scenarios for IDSS, or DESI for short, suggests highs greater than 85F are most likely areas west of I-495, with probabilities of 85+ percent for all of the Connecticut River Valley. When increased to greater than 90F, found probabilities between 55% and 70%. Conversely, highs less than 80F, there are probabilities between 20% to 30% along east coast of Massachusetts, with probabilities between 40% to 60% for high temperatures less than 80 degrees across eastern Essex County! Given these stats, opt`d to keep a `Heat Advisory` for northern Connecticut and southern Pioneer Valley of Massachusetts. The aforementioned front provides the necessary lift for development of pop-up thunderstorms, given SBCAPE are between 800 and 1200 J/kg. Don`t expect organized convection due to the lack of shear, though heavy downpours are possible as PWATs are around two inches. WPC kept most of the region highlighted in its day three ERO, the CWA is highlighted within a marginal risk (at least 5%) for excessive rainfall. NAM 3KM now includes Friday into Friday afternoon and suggests areas further inland, where there SBCAPE is greatest and the atmosphere is most unstable. Current thinking, area with greatest risk are central to western Massachusetts, and northern Connecticut. Once again, this will heavily depend on the exact placement of the front. Saturday & Sunday: Mid-level ridge continues to deamplify over the weekend with shower and/or thunderstorm chances both days. Saturday, the aforementioned backdoor cold front becomes quasi-stationary with weak low pressure forming along it, mainly across New York, this provides the lift for showers/thunderstorms. Do think the better chances for any stronger storms will be just west of southern New England. The front is on the move on Sunday, as a warm front with showers/thunderstorms once again. At this point, hesitate to call this upcoming weekend a total washout. But with anomalously high PWATs, heavier downpours are possible within any shower and/or thunderstorm. While it is cooler this weekend, it is still warm and muggy for late June. Saturday likely cooler of the two days, highs lower to middle 80s, but dewpoints are in the middle to upper 60s. On Sunday, highs are a bit warmer, given placement in the warm sector, highs are between the middle and upper 80s, dewpoints in the upper 60s and low 70s. Early Next Week: Mid-level shortwave and cold front sweeps across the region Monday with showers and thunderstorms. The cold front brings a slight reprieve from the humidity Tuesday, but signs for another warmer than normal week continues into mid next week. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z TAF Update: Tonight: High confidence. Localized MVFR/IFR possible at BAF and ORH associated with weakening TSRA, with a short period of VCTS at BDL. Expect by 02z that storms will have ended in these locations, toward VFR for all airports. It now looks like fog on the south coast is less likely. SW winds around 5-10 kt. Thursday: High confidence in TAF/trends, lower to moderate on t-storm timing. VFR at least into the morning hours. While the exact timing is still uncertain, better chance (~ 25-40%) at ISO/SCT TSRA than compared to today from the Mass Pike northward. Storms could develop as soon as 18z but seem more likely around and after 20z. Storms would be capable of frequent lightning, heavy downpours and localized strong gusts. SW winds around 10-15 kt. Thursday Night: Low confidence. Low-confidence aviation forecast Thu night, which will hinge on how Thu daytime SHRA/TS evolve. These SHRA/TS should weaken and shift SE Thu night. Will message VFR but there is continued potential for sub-VFR. Easing SW winds early Thu night could shift to N/NE under 10 kt by daybreak. KBOS TAF...High confidence in TAF. VFR with SW winds around 10-12 kt. VFR for the morning hrs Thurs; better chance at TSRA (~25-40%) on Thurs aftn and messaged as PROB30. Timing uncertain, could begin as soon as 18z but more likely after 20z. SW winds on Thurs continue around 10 kt with nil chance at sea breeze. KBDL TAF...High confidence in TAF. TS to the north near BAF prompted VCTS thru 01z Thurs, but should not directly impact terminal. VFR thereafter with S winds around 7-10 kt. Better chance at TSRA Thurs, although timing uncertain. Could begin as soon as 18z but more likely after 20z. Messaged as PROB30 for now. Outlook /Friday through Monday/... Friday: Mainly VFR, with areas MVFR possible. Chance SHRA, chance TSRA. Friday Night through Saturday: Mainly VFR, with local IFR possible. Chance SHRA, isolated TSRA. Saturday Night: Mainly VFR, with local IFR possible. Chance SHRA. Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance TSRA. Sunday Night: Mainly VFR, with areas IFR possible. Breezy. SHRA likely, isolated TSRA. Monday: Mainly VFR, with local IFR possible. Breezy. Chance SHRA, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 410 PM update... Through Thursday Night: High confidence. High pressure just offshore provides fairly tranquil boating weather this period. An isolated t-storm could develop over the northern MA waters tonight, but better chances for thunderstorms for Thursday. Otherwise, patchy fog may lower vsby 1-3 miles tonight along the southern coastal waters. Winds mainly SW around 15-20 kt through the period, with seas 4 ft or less all waters. Outlook /Friday through Monday/... Friday: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. Local visibility 1 to 3 nm. Friday Night: Winds less than 25 kt. Chance of rain showers. Saturday: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. Saturday Night: Winds less than 25 kt. Chance of rain showers. Local visibility 1 to 3 nm. Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of rain showers. Sunday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Rain showers likely, isolated thunderstorms. Visibility 1 to 3 nm. Monday: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Areas of rough seas. Chance of rain showers, isolated thunderstorms. Visibility 1 to 3 nm. && .CLIMATE...
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All Time June High Temperature Record (Daily) BOS - 100 F (06/06/1925, 06/26/1952 and 06/30/2021) BDL - 100 F (06/26/1952, 06/30/1964) PVD - 98 F (06/25/1943, 06/15/1945 and 06/30/1945) ORH - 98 F (06/26/1952) Most recent day of 100 F (or greater) BOS - 100 F (07/24/2022) BDL - 100 F (07/21/2019) PVD - 100 F (07/28/2020) ORH - 102 F (07/04/1911)* * For ORH this is the only 100+ degree day in its period of record. Daily High Temperature Records... June 19th BOS - 96 F (1923) BDL - 95 F (1995) PVD - 94 F (1923) ORH - 93 F (1923) June 20th BOS - 98 F (1953) BDL - 97 F (2012) PVD - 95 F (1941) ORH - 93 F (1953) June 21st BOS - 96 F (2012) BDL - 96 F (1953 and 2012) PVD - 96 F (1941) ORH - 91 F (Multi-Years) Daily Warmest Low Temperatures Records... June 19th BOS - 73 F (1995) BDL - 72 F (1929) PVD - 70 F (1995) ORH - 72 F (1929) June 20th BOS - 78 F (1931) BDL - 74 F (1931) PVD - 74 F (1931) ORH - 72 F (1931) June 21st BOS - 80 F (2012) BDL - 73 F (1923 and 2012) PVD - 75 F (2012) ORH - 74 F (1923 and 2012)
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert until 11 PM EDT this evening for CTZ002-003. Air Quality Alert from 11 AM to 11 PM EDT Thursday for CTZ002- 003. Heat Advisory until 7 PM EDT Friday for CTZ002>004. MA...Air Quality Alert until 11 PM EDT this evening for MAZ005>007- 010>015. Air Quality Alert from 11 AM to 11 PM EDT Thursday for MAZ007- 010>021. Heat Advisory until 7 PM EDT Friday for MAZ008>011. Heat Advisory until 7 PM EDT Thursday for MAZ002>007-012>019- 026. RI...Air Quality Alert from 11 AM to 11 PM EDT Thursday for RIZ001>005. Heat Advisory until 7 PM EDT Thursday for RIZ001>005. MARINE...None. && $$ SYNOPSIS...Loconto/Dooley NEAR TERM...Loconto/Nocera SHORT TERM...Loconto LONG TERM...Dooley AVIATION...Loconto/Dooley MARINE...Loconto/Dooley CLIMATE...BL