Spot Forecast
Issued by NWS Boston, MA
Issued by NWS Boston, MA
Versions:
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945
FNUS71 KBOX 211818
FWSBOX
Spot Forecast for Mustard Gas...Winchendon MA Fire Dept.
National Weather Service Boston/Norton MA
218 PM EDT Tue Jul 21 2026
Forecast is based on forecast start time of 1500 EDT on July 21.
If conditions become unrepresentative, contact the National
Weather Service.
.DISCUSSION...
Showers and thunderstorms will become numerous Tuesday afternoon
and evening across Winchendon, MA, then slowly diminishing
overnight. Some of the storms will contain very heavy downpours
and possibly strong winds. A second round of showers and
thunderstorms are expected Wednesday, however not as widespread
or as strong as Tuesday. Southeast winds Tuesday afternoon will
become south to southwest Tuesday night, then westerly Wednesday
afternoon.
.REST OF TODAY...
Sky/weather.........Mostly cloudy. Showers likely late in the
afternoon, then showers and chance of
thunderstorms late in the afternoon.
CWR.................45 percent increasing to 67 percent.
Chance of pcpn......80 percent.
Chance of thunder...7 percent.
Max temperature.....Around 77.
Min humidity........72 percent.
Dewpoint............68.
Surface winds (mph).South winds 10 to 12 mph with gusts to around
23 mph.
Mixing height.......3100 ft AGL.
Smoke dispersal.....Good (36700 knot-ft).
Smoke dispersal.....Good (36700 knot-ft).
CEILING (KFT).......3.7 decreasing to 1.4.
Visibility..........9 decreasing to 6 late in the afternoon.
Transport winds.....South 18 to 21 mph.
LVORI...............5.
ADI.................1 to 38.
TIME (EDT) 3PM 4PM 5PM
Sky (%).........88 76 90
Weather cov.....LKY DEF DEF
Weather type....RW RW RW
Tstm cov........ CHC CHC
CWR.............50 60 70
Chc of pcpn (%).70 80 80
Chc of thdr (%).10 10 10
Temp............74 75 72
Dewpoint........68 69 69
RH..............82 81 89
Surface wnd dir.S S S
Surface wnd spd.12 12 10
Surface wnd gst.23 23 22
Mix hgt (kft)...3.1 2.9 2.3
Transp wind dir.S S S
Transp wind spd.21 21 18
LVORI...........6 6 4
ADI.............1 1 38
Vrate kt-ft/1K..55 53 37
Ventrate Cat....FR FR PR
SDspl kt-ft/100055 53 37
Ceiling (kft)...3.7 2.6 1.4
Visibility (sm).9 6 6
.TONIGHT...
Sky/weather.........Cloudy. Showers and chance of thunderstorms in
the evening, then chance of showers and
isolated thunderstorms after midnight. Patchy
fog early in the morning.
CWR.................83 percent increasing to 93 percent early, then
decreasing to 72 percent decreasing to 41
percent decreasing to 29 percent decreasing to
11 percent early in the morning.
Chance of pcpn......100 percent.
Chance of thunder...13 percent.
Min temperature.....Around 62.
Max humidity........100 percent.
Dewpoint............67 decreasing to 64 early in the morning.
Surface winds (mph).South winds 5 to 9 mph with gusts to around 20
mph shifting to the southwest 5 to 7 mph after
midnight.
Mixing height.......400 ft AGL.
Smoke dispersal.....Fair (16900 knot-ft) early in the evening
decreasing to poor (4300 knot-ft) late in the
night.
Smoke dispersal.....Fair (16900 knot-ft) early in the evening
decreasing to poor (4300 knot-ft) late in the
night.
CEILING (KFT).......0.9 decreasing to 0.7 early in the evening,
then decreasing to 0.5 early increasing to 0.6
late in the evening increasing to 0.7
decreasing to 0.6 increasing to 0.7 decreasing
to 0.5 after midnight decreasing to 0.4
decreasing to 0.3 early in the morning.
Visibility..........2.89 increasing to 4 around midnight.
Transport winds.....South 10 to 14 mph.
LVORI...............7.
ADI.................7 to 22.
TIME (EDT) 6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........89 91 97 96 93 89 93 94 93 91 89 93
Weather cov.....DEF DEF DEF DEF DEF CHC CHC CHC CHC SCH SCH SCH
Weather type....RW RW RW RW RW RW RW RW RW RW RNF RNF
Tstm cov........CHC CHC CHC CHC CHC ISO ISO ISO ISO ISO
CWR.............80 80 90 90 70 40 30 30 10 10 10 10
Chc of pcpn (%).90 90 100 90 80 40 30 30 30 20 20 20
Chc of thdr (%).10 10 10 10 10 10 10 0 0 0 0 0
Temp............72 71 68 67 68 68 68 66 66 66 63 65
Dewpoint........69 69 68 67 68 68 68 66 66 66 63 65
RH..............91 94 100 100 100 100 100 100 100 100 100 100
Surface wnd dir.S SE S S S S S SW SW SW SW SW
Surface wnd spd.9 8 7 6 5 5 5 5 5 5 6 7
Surface wnd gst.20 18 15 14 13 12 12 12 13 13 14 16
Mix hgt (kft)...1.4 1.1 0.7 0.5 0.5 0.5 0.5 0.5 0.4 0.4 0.5 0.5
Transp wind dir.S S S S S S SW SW SW SW SW SW
Transp wind spd.14 14 12 10 10 12 13 12 12 13 14 12
LVORI...........4 5 8 9 9 8 8 8 8 8 8 9
ADI.............22 18 8 7 7 8 8 8 8 8 9 7
Vrate kt-ft/1K..17 13 7 4 4 5 5 5 5 5 6 5
Ventrate Cat....PR PR PR PR PR PR PR PR PR PR PR PR
SDspl kt-ft/100017 13 7 4 4 5 5 5 5 5 6 5
Ceiling (kft)...0.9 0.7 0.5 0.6 0.6 0.7 0.6 0.7 0.5 0.4 0.4 0.3
Visibility (sm).4 3 3 2.9 4 4 4 4 5 5 4 4
.WEDNESDAY...
Sky/weather.........Cloudy then becoming partly sunny. Slight
chance of showers and thunderstorms in the
morning, then chance of showers and
thunderstorms in the afternoon. Patchy fog
early in the morning.
CWR.................11 percent increasing to 32 percent early in
the afternoon, then decreasing to 22 percent
late in the afternoon.
Chance of pcpn......40 percent.
Chance of thunder...6 percent.
Max temperature.....Around 79.
Min humidity........62 percent.
Dewpoint............66 increasing to 69 in the late morning and
early afternoon, then decreasing to 65 late in
the afternoon.
Surface winds (mph).Southwest winds 7 to 10 mph with gusts to
around 21 mph shifting to the west around 10
mph late in the afternoon.
Mixing height.......4000 ft AGL.
Smoke dispersal.....Poor (5900 knot-ft) early in the morning
increasing to excellent (60300 knot-ft) in the
afternoon.
Smoke dispersal.....Poor (5900 knot-ft) early in the morning
increasing to excellent (60300 knot-ft) in the
afternoon.
CEILING (KFT).......0.5 increasing to 8.0.
Visibility..........5 increasing to 9 through early afternoon.
Transport winds.....Southwest 13 to 18 mph.
LVORI...............3.
ADI.................14 early in the morning increasing to 85 in the
afternoon.
TIME (EDT) 6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........88 66 74 66 59 52 51 48 60 56 51 43
Weather cov.....SCH SCH SCH SCH SCH SCH SCH SCH CHC CHC CHC SCH
Weather type....RNF RNF RW RW RW RW RW RW RW RW RW RW
Tstm cov........ SCH SCH SCH CHC CHC CHC
CWR.............10 10 10 10 10 10 10 10 30 30 20 20
Chc of pcpn (%).20 20 20 20 20 20 20 20 40 30 30 20
Chc of thdr (%).0 0 0 0 0 0 0 0 10 10 10 0
Temp............65 65 68 71 73 74 76 77 77 77 78 77
Dewpoint........65 65 68 70 71 71 70 69 68 67 66 64
RH..............100 100 100 97 93 90 82 75 73 70 66 65
Surface wnd dir.SW SW SW SW SW SW SW SW W W W W
Surface wnd spd.7 7 7 7 8 9 9 10 10 10 10 10
Surface wnd gst.15 15 15 16 16 17 18 20 20 21 20 20
Mix hgt (kft)...0.5 1.0 1.3 1.9 2.4 2.9 3.3 3.8 3.6 3.7 3.8 4.0
Transp wind dir.SW SW SW SW SW SW W W W W W W
Transp wind spd.13 14 15 16 17 18 17 18 17 18 17 17
LVORI...........5 5 5 4 4 4 3 3 3 3 1 1
ADI.............14 18 23 30 36 66 70 85 45 82 78 82
Vrate kt-ft/1K..6 13 17 26 36 46 50 60 55 59 57 60
Ventrate Cat....PR PR PR PR PR FR FR GD FR FR FR GD
SDspl kt-ft/10006 13 17 26 36 46 50 60 55 59 57 60
Ceiling (kft)...0.5 0.6 0.6 1.0 1.5 1.6 2.3 2.9 3.6 5.1 6.5 8.0
Visibility (sm).5 6 9 9 9 9 9 9 9 9 9 9
$$
Forecaster...Nocera
Requested by...EMD Winchendon
Type of request...HAZMAT
.TAG 2617883.0/BOX
.DELDT 07/21/26
.FormatterVersion 2.0.0
.EMAIL gwante@winchendon-ma.gov