![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
045 FXUS61 KBOX 192319 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 719 PM EDT Fri Jul 19 2024 .SYNOPSIS... High pressure will build southeastward tonight into early on Saturday. While this will bring a modest increase in cloud cover for Saturday, dry weather, seasonably warm temperatures and lower humidity levels through the weekend. Pattern then turns more active again next week, with humidity levels on the rise. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 7 PM Update... Forecast remains on track. No changes in the latest update. 200 PM Update: Beautiful midsummer afternoon underway across Southern New England under surface ridge of high pressure. Current temps are in the upper 70s to the lower 80s under full sunshine, but also with low humidity levels (dewpoints commonly in the 50s). High pressure will continue to be in control for tonight as well. Will have more of an increase in high clouds with some higher level moisture advecting in from the SW late tonight and overnight but dry weather is expected. Used MOS for nighttime lows in the mid 50s to lower 60s for most, with mid 60s for the Cape and Islands and the urban corridors. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... 200 PM Update: Saturday and Saturday Night: High pressure to our south will bring a SWly flow to the region for Saturday, with a passing cool front well to our north in northern portions of VT/NH/ME for Saturday evening. The increasing higher level cloud cover from tonight will continue to increase further on Saturday as well, towards a filtered sun or at worst a mix of clouds and sun. A few models were generating some QPF in portions of western CT associated with a low-amplitude 500 mb disturbance in the SW flow, one which is also expected to shearing out and weaken; with drier air in the lower atmosphere, opted for dry weather to prevail. Though cloud cover decreases more into Saturday evening, still will be a partly cloud evening. Dewpoints also start to rise back into the mid 60s, so turning a touch more humid but nothing like we saw for much of last week. Highs Saturday in the mid to mid/upper 80s (upper 70s to low 80s coasts), with lows in the mid 60s to around 70. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Highlights * Dry and quiet weather Sun and for much of Mon. Humidity levels beginning to climb on Mon. * Active pattern returns Tue through Fri with opportunities for showers and thunderstorms. Humidity levels turning uncomfortable once again. Sunday through Monday... Not much of a change from 24 hours ago. Will initially have a ridge axis extend from the Carolinas into the OH Valley and troughing over Quebec. This keeps us under cyclonic flow. The ridge builds into the Mid Atlantic/eastern Great Lakes by early Mon, but flattens out as the day progresses as a shortwave rides on top of the ridge. A weak surface trough/cold front slides through on Sun into Mon. A weak high builds in behind this front on Mon. Generally expect dry and quiet weather to prevail throughout this timeframe. At this point haven`t deviated from the NBM as it looks quite reasonable. There does appear to be an opportunity late on Mon where portions of the interior could see an isolated shower/storm. This is a result of the ridge breaking down and a weak shortwave sliding in. Given the position of the high by later on Mon we will see a return to southerly flow, which will bring more moisture into our region. However, there really a lack of a trigger mechanism for this activity other than perhaps diurnal heating as low level lapse rates increase to 7-9 degrees Celsius. Thus the isolated shower/thunder chance fine at this point. Not anticipating severe weather as mid level lapse rates are very meh and MUCAPEs of a few hundred J/kg. Though will be something to keep an eye on as deep layer shear around 30-40 kts in the 0-6 km layer. Highs in the mid to upper 80s on Sun. Still in the 80s on Mon, but should be a few degrees cooler than Sun. Tuesday through Friday... More active pattern setting up during this timeframe. Will be stuck under cyclonic flow with a couple of shortwaves sliding into/through our region. Confidence in the specific timing of these waves is somewhat uncertain and how things evolve convectively. Due to this have stuck with the NBM at this point. Unsettled with opportunities for showers and thunderstorms during this period. Given the pattern will have a somewhat stalled out frontal boundary nearby/overhead. Will continue to see moisture levels increase with dew points climbing into the upper 60s and lower 70s. Expect PWATs to increase to roughly 1-2 STD above model climo per the NAEFS, while the EPS is a bit more juiced up as we climb to roughly 1.5 to 2.5 STD. Could have PWATs of 1.5 to 2+ inches. Should have warm cloud layer depths of 2.5 to 4.5 km. Though the higher warm cloud layer depths come mostly in the Wed-Fri timeframe. Given this set up could have some heavy downpours. This matches WPCs latest Day 5 ERO and CSU ML guidance UFVS in the Tue- Wed period. Cannot rule out some stronger storms as well as will have increasing deep layer shear and instability. Do have hints at the risk with CSU ML guidance indicating low probs (5-15%) in the Wed-Thu timeframe. Something to keep an eye on. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight through Saturday...High confidence. VFR, with increasing mid to high clouds late tonight into Saturday. Winds become light southerly tonight in all areas, with SW speeds Saturday daytime around 5-10 kt (gusts 15-20 kt Cape and Islands). Saturday Night...High confidence, though moderate on fog development. VFR for most; PVD and the Cape/Islands could see patchy fog, but uncertain if it develops. SW winds around 5 kt. KBOS TAF...High confidence in TAF. VFR thru the period. SE seabreezes to shift to light S winds by 00-01Z, then increasing to around 5-10 kt on Sat and shifting to SW. KBDL TAF...High confidence in TAF. VFR thru the period. Variable winds shift to SW at 5-10 kts by Sat afternoon. Outlook /Sunday through Wednesday/... Sunday through Monday: VFR. Monday Night: VFR. Slight chance SHRA, isolated TSRA. Tuesday: VFR. Chance SHRA, isolated TSRA. Tuesday Night: Mainly VFR, with local IFR possible. Chance SHRA. Wednesday: Mainly VFR, with local IFR possible. SHRA likely, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 200 PM Update: Through Saturday Night: High confidence. Favorable boating conditions for mariners with light north winds early tonight becoming a light southerly (speeds 10 kt or less). Will turn a little breezy on Saturday especially over the nearshore waters, with SW speeds around 15-20 kt during the daytime hrs; decreasing to 10 kt or less Saturday evening. Seas 3 ft or less all waters. Dry weather to prevail, although there is a low chance for patchy fog Saturday evening on the southern waters. Outlook /Sunday through Wednesday/... Sunday through Monday Night: Winds less than 25 kt. Tuesday: Winds less than 25 kt. Slight chance of rain showers, isolated thunderstorms. Tuesday Night: Winds less than 25 kt. Chance of rain showers. Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Loconto/BL NEAR TERM...Loconto/BL SHORT TERM...Loconto LONG TERM...BL AVIATION...Loconto/BL MARINE...Loconto/BL