Near term - through 9pm this evening -
...Skies are starting off partly to mostly cloudy with a dense layer of altostratus across the region. This is in association with a warm front stretched from northern Ontario southeast into southern Quebec. Scattered showers are moving SE along the boundary from northern New York into southern New Hampshire and southern Maine. The area of scattered showers has recently moved out of the Boston area, so skies will soon clear there. In Keene, the southern edge of the high clouds is moving northeast and will clear the area by 8:20AM. Skies will become mostly sunny across most of central New England by 11AM. Daytiem heating will allow for moderate instability. The 06z NAM shows lifted indices between -2 and -4 this afternoon. A short wave, currently entering southern Quebec, will move along the warm front boundary later this afternoon, and will be the focus for isolated showers and thunderstorms mainly after 2pm. Some of the storms could become strong with gusty winds and/or small hail. The convective threat will end around 9pm with the loss of daytime instability.

Temperatures this morning started out at 55 in Keene with 50's and 60's across the region. 850mb temperatures will range between 14 and 17C across New England, with clear skies allowing for near maximum heating into the 80's to near 90 with the best chances of 90 from south-central NH into southern MA and most of CT away from the coast. For some areas today may be the start of a 3 to 4 day heat wave.

Short term - Tonight through Tuesday night -
...Dew points will slowly be on the rise through today and tonight. 850mb temperatures at 15 to 17C coupled with dew points around 60 will keep temperatures in the 60's tonight, with a low around 61 tomorrow morning. Skies will remain partly cloudy. Patchy fog may develop after 2am tomorrow.

On Tuesday, early morning sun will burn off any fog before 8am, as temperatures start off on a long rise into the 90's. 850mb will approach 20C tomorrow, and with maximum heating, surface temperatures will reach 93 by 3pm. The record high in Keene for 6/26 is 96, so that is a long shot. A frontal boundary will slowly sink south out of Quebec. Scattered showers and thunderstorms, some strong to severe, will develop across Maine and northern New Hampshire in the afternoon. These storms will not reach Keene, however a few airmass storms cannot be ruled out across central and southern New England, with the NAM forecasting lifted indices from -4 to -8.

Skies will be partly cloudy Tuesday night. A decent amount of radiational cooling will allow for temperatures to fall below 70, with lows reaching the mid 60's by early Wednesday morning.

Long term - Wednesday through Sunday 7/1 -
...While it appeared before that Tuesday would be the hottest day this week, Wednesday is threatening to take the title. MOS forecasts are split between the two, and it may be that the deciding factor will be when thunderstorms arrive on Wednesday. 850mb temperatures will be up near 20C again, and temperatures will get a faster start, with 93 possibly reached around 2:30pm. If heating continues, 95 is a possibility. The record for 6/27 in Keene is 94, so the chance is small but there. The best shot for record breaking will be in the I95 corridor, where winds will be off the land. The record in 6/27 record for Boston is 96. Highs will range between 94 and 97. The main story however, will be very high dew points, the first of the year, exceeding 70 across most of southern and central New England, with low to mid 70s in the I95 corridor. Heat indices could exceed 100 for more than 2 hours there (Heat Advisory criteria). In Keene, dew points will range between 68 and 72, with 2 hour heat indices around 95 possibly spiking near 100. Backdoor cold front will move slowly south Wednesday afternoon. Scattered thunderstorms will affect the area between 3pm and 9pm. The air will be very unstable so any thunderstorms that develop could become strong with a few severe. In addition to hail and winds, very heavy rainfall is possible as PWAT values reach or exceed 2.0 inches. Flash flooding could be a concern in a few larger storms.

Wednesday night, skies remain partly cloudy, a slight chance of showers will stick around through the early morning. It will be our first real uncomfortable night of the year, with temperatures not dropping below 70. MOS forecasts present a bit of a range here, from upper 60s to mid 70s. Right now, looking at low temperatures Thursday morning around 72 or 73.

Thursday, humidity stays through the afternoon, however no where near the same amount of heating, as front crosses early. Highs will reach the low to mid 80's. Further east, where the front crosses later in the day, there is a shot at 90, which would conclude a 3 to 4 day heat wave. A little bit of a timing issue with the front, as GFS is about 3 hours later than the rest of the model guidence. Right now, looks like showers and thunderstorms will cross the area around noontime. While these thunderstorms will very likely be strong to severe, as the strong boundary cuts through a very unstable airmass, the early timing may save Keene from the worst of the storms as peak heating is far from reached. Main threat will be for areas to our east.

850mb temperatures will be falling through the day, dropping back to aournd 10C by Thursday night. Lows will fall down into the low to mid 50's, along with dew points down around 50. Drier and cooler air moves in at the surface for Friday, Saturday, and Sunday. Skies will be mostly sunny to sunny, with temperatures held back to the mid 70's and lows in the lower 50's.

The one point of interest beyond day 4 is Saturday, as a short wave moves southeastward behind the departing storm. Cold air aloft could provide for enough instability for showers and thunderstorms, some with gusty winds and small hail. Another cool down moves in on Sunday with highs only in the lower 70's.

&&

Forecaster: SL
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Weather history:
6/25 in Keene, NH:
average high is 78, record is 95
average low is 54, record is 33

Astronomy:
Sunrise: 5:11AM Sunset: 8:32PM
Moonrise: 4:12PM Moonset: 1:29AM
Length of visible light: 16 hours 31 minutes
Length of day: 15 hours 21 minutes
-Tomorrow will be 18 seconds shorter

6/25 across the United States:
1749 - A general fast was called on account of drought in Massachusetts. It was the year of the famous dry spring in which fields and villages burned. (David Ludlum)

1925 - The mercury hit 101 degrees at Portland, OR, their earliest 100 degree reading of record. (Sandra and TI Richard Sanders)

1953 - The temperature at Anchorage soared to 86 degrees, their hottest reading of record. (The Weather Channel)

1987 - Afternoon highs of 97 degrees at Miami, FL, 107 degrees at Medford, OR, and 111 degrees at Redding CA were new records for the date. It was the third of six straight days of record heat for Miami. Thunderstorms produced wind gusts to 70 mph at Austin, and gusts to 75 mph at Tulsa OK. (The National Weather Summary) (Storm Data)

1988 - Fifty-two cities in the central and eastern U.S. reported record high temperatures for the date. Highs of 100 degrees at Erie, PA, and 104 degrees at Cleveland OH established all- time records for those two locations. Highs of 101 degrees at Flint, MI, 105 degrees at Chicago, IL, and 106 degrees at Fort Wayne, IN, equalled all-time records. Thunderstorms in Idaho produced wind gusts to 100 mph west of Bliss and north of Crouch, injuring 29 persons. (The National Weather Summary) (Storm Data)

1989 - Tropical depression Allison, the remnants of what was earlier Cosme (a hurricane over the Pacific Ocean which dissipated as it crossed northern Mexico), began to spread heavy rain into southeast Texas and southwest Louisiana. (The National Weather Summary)

Yesterday (6/24):
Keene: H 75, L 48
State extremes: Nashua high of 80, Mt Washington low of 37