Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 132231 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 631 PM EDT Wed Mar 13 2024 .SYNOPSIS... Continued dry and clear weather through tomorrow with a outside chance for an isolated shower late tonight. Tomorrow will feature mild temperatures away from the coasts where sea breezes will keep temperatures cooler. A more unsettled weather pattern develops Friday into the weekend, with rainy conditions for Fri and again on Sunday. Temperatures trend above normal through this weekend, with a cooling trend toward more seasonable temperatures by early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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630PM Update Forecast remains on track at this hour. Made some slight adjustments to near term forecast to reflect latest observations, but forecast is overall unchanged. KBOX radar is showing some modest returns along the MA/NH border. However, surface obs are revealing dewpoint depressions of nearly 30 degrees or in some cases higher, thus would be surprised if any precip is reaching the ground. Left slight chance PoPs in the forecast for this evening as showers may have better lucking reaching the ground across eastern MA where a sea-breeze earlier afternoon has supported an air mass that isn`t quite as dry across the interior. Either way, any showers would be modest with accumulations ranging from a trace to maybe .01 inches. See previous discussion for additional details. Previous Discussion Mainly dry conditions overnight outside of a low chance for an isolated shower/sprinkle associated with a weak mid level shortwave and cold front. Very narrow moisture axis around 850mb with dry air both above and at the surface will make it very difficult for any rain to reach the ground, thus capped POPs at 20%. With a mid level cloud deck around, radiational cooling conditions wont be perfect, but temps overnight will drop into the mid 30s with below freezing possible if skies stay clear. Winds tonight will be southerly less then 5mph.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Weak mid level ridge builds back in with continued high pressure at the surface. Skies remain mostly sunny again tomorrow setting the stage for another warm day. With 925mb temps jumping from roughly +7C to +11C range, high temps away from the coasts will likely reach the low to mid 60s, with a good chance at 70F for the CT river valley. Near the coasts, seas breezes will develop again, and with ocean temps in the low 40s, high temps will struggle to top the low 50s. Winds tomorrow turn light NW for the interior less then 10mph. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Highlights * Rain Thursday night into Friday * Drying out on Saturday with partial sunshine and seasonable temperatures * More unsettled weather Sunday into Monday will be followed by a period of dry but cold and blustery conditions through the middle of next week. Thursday night and Friday A modest and progressive low-pressure system will move over The Northeast Thursday night into Friday. Overall forcing associated with the system is modest, so not expecting any significant impacts. Most of the region should see a decent soaking of rain with PWATs up to an inch supporting rainfall amounts between a quarter and half an inch. Currently expecting the steadier/heavier precip to be focused north of the I-90 corridor where stronger forcing and enhancements from the left jet exit region aloft should allow for more efficient rainfall processes. Steady southeast winds ahead of the low on Friday morning will transition to a north/northwest flow into Friday afternoon as the low moves overhead. With this will come drier air that will bring precip to an end. Could be some breaks of sun mid to late afternoon, but generally expect overcast skies for much of the day. Temperature forecast is a bit uncertain on Friday as it will depend on the track of the low. As it stands now, a west to east track along I-90 is expected to support warmer south of I-90 in the mid to upper 50s with upper 40s/low 50s more common north of that mark. A north/southward shift in the track would support a shift in observed temperatures as well. Saturday and Sunday Drier air settles in behind the departing low pressure system on Saturday supporting some clearing over the region. This is expected to result in some sunshine and seasonable high temperatures in the low to mid 50s Saturday afternoon. Cloudiness returns Saturday night into Sunday as a low-pressure system over Canada drags a cold front through the region with another round of modest precipitation. Timing a bit uncertain at this time range, but most recent suite of model guidance supports showers clearing out of the region sometime Sunday night. Next Week Much of the first half of next week looks to be on the cold and blustery side as model guidance supports a persistent period of cyclonic flow positioned to our northeast. This is expected to support a persistent period of a dry deep northwest flow and CAA over southern New England. With CAA supporting deep diurnal mixing during the afternoon hours between Monday and Wednesday, we are likely to experience gusty winds during the afternoon and perhaps during the overnight hours as well. How strong wind gusts will be depends on the strength of the pressure gradient in place which remains uncertain at this time range. Ensemble guidance doesn`t support anything eye popping at this time, but periods of 30 to 40 mph gusts are in the realm of possibility on Tuesday or Wednesday of next week. As previously stated, temperatures will be cold as well with temps at 925 hPa forecast to remain below 0 Celsius for much of the first half of next week. This would translate to high temps in the low to mid 40s during the afternoon and upper 20s to low 30s during the evenings. More details to follow as we get into the weekend. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Rest of Today...High Confidence. VFR. Light and variable winds switching from northerly to southerly. Sea breezes kick back out between 21-23z this afternoon Tonight...High Confidence. VFR with light and variable winds. Thursday...High Confidence. Light NW winds across the interior with sea breezes developing along the coast around 13-15Z. KBOS TAF...High confidence in TAF. Sea breeze kicks out between 21-23z and winds could turn SSW briefly before turning light SSE overnight. Sea breeze develops again tomorrow morning by 14z, but winds will already be SE. KBDL TAF...High confidence in TAF. VFR with light and variable winds. Outlook /Thursday Night through Monday/... Thursday Night: VFR. Chance RA. Friday: VFR. Breezy. Chance RA. Friday Night: Chance RA. Saturday: Saturday Night: Breezy. Slight chance RA. Sunday through Sunday Night: Breezy. Chance RA. Monday: Breezy. Slight chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight through Thursday...High Confidence. a weak pressure gradient will keep winds/seas below small craft advisory thresholds today through Thursday with good vsbys. Low chance for an isolated shower over the waters tonight. Outlook /Thursday Night through Monday/... Thursday Night: Winds less than 25 kt. Slight chance of rain. Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain. Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain. Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas locally approaching 5 ft. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...RM/KP NEAR TERM...RM/KP SHORT TERM...KP LONG TERM...RM AVIATION...RM/KP MARINE...RM/KP

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