Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 202332 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 632 PM EST Mon Feb 20 2017 .SYNOPSIS... A brief return to cooler weather today continues into Tuesday with high pressure in control. High pressure off the mid Atlc coast combined with a series of low pressure systems moving through the Great Lakes will result in an extended period of unseasonably mild temperatures Wednesday through Saturday, with near record warmth possible Thursday. A strong cold front will cross the region Saturday, likely bringing some rain, followed by blustery and more seasonable conditions Sunday and Monday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 630 PM update... SKC across SNE with diminishing wind will result in a sharp temp drop this evening across typically colder locations. Adjusted T/Td grids for current trends, otherwise forecast on track. Previous discussion... Mid level closed low over Nova Scotia will continue to circulate a dry cool airmass into New England tonight. Last short wave pinwheeling around this large circulation at late afternoon is moving across western sections of Gulf of ME and Georges Bank. As a result winds have shifted to the NW across northern MA along with the back edge of the cloud shield now east of Cape Cod and continuing to move seaward. As this last short wave moves farther offshore this evening mid level heights begin to rise across the region and in response surface ridge advects over the area later tonight. So with diminishing winds, mostly clear skies and low dew pts, ideal radiational cooling conditions will support temps free falling with sunset. Min temps tonight were derived from the coldest MOS guid along with shaving a few more degs off the typically cooler locations such as the CT river valley and interior eastern MA. Lows here in the mid to upper teens, 20s elsewhere. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Tuesday... Fairly high deep amplitude ridge over the region in the morning and afternoon provides deep layer subsidence and abundant sunshine. However as ridge continues to slide east, mid and high clouds will begin to invade from the western horizon during the afternoon. Chilly start to the day but despite shallow blyr mixing and light winds from 1027 mb high overhead, temps will climb into the 40s regionwide. Coolest readings will be along the immediate coast as winds become onshore in the afternoon off the chilly near shore waters with SSTs in the upper 30s. Tuesday night... High pressure moves offshore with WAA pattern overspreading the region. Increasing clouds will give way to the risk for some showers with highest pops...chance across western section of MA/CT. Only wrinkle here is that shallow cold air may linger long enough across northwest MA for a low risk of freezing rain. Temps around freezing across interior eastern MA are some concern however precip may dry up before reaching this area. Overall risk is low given marginal cold airmass (temps near freezing vs temps in the 20s) and precip possibly drying up as it moves eastward. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Highlights... * Mild conditions Wed with near record warmth possible Thu * A backdoor front may bring cooler temps Fri but low confidence * Mild with widespread showers likely sometime Sat/Sat night * Blustery and cooler Sun/Mon Overview... Guidance in general agreement on amplifying trof moving into the Rockies and Plains toward the end of the week with building downstream ridge along the east coast. This will result in a period of unseasonably mild temps into the weekend, but will have to watch a northern stream shortwave which could allow a backdoor front to cool things off around Friday. Models agree on mid level low lifting across the Great Lakes Sat with inside runner and strong cold fropa likely bringing a period of rain, although timing and details are uncertain. More seasonable and blustery conditions follow for Sun/Mon as broad trof develops across the NE. Details... Wednesday into Thursday... Pronounced warming trend as high pres sets up south of New Eng with SW flow of mild air into SNE. There may be some clouds to contend with Wed as weak shortwave moves through with low risk of a few showers and isold fzra early in the morning interior N MA, but expect partly sunny skies in the afternoon as mid level drying develops from the north. Highs should reach into the 50s Wed with upper 50s possible in the coastal plain if there is sufficient sunshine. On Thursday, continued SW flow will push 925 mb temps to near 12C which supports highs well into the 60s away from the south coast with partly sunny skies. Even GEFS mean 925 mb temps around 10C so above average confidence of temps above 60 Thursday with potential for some upper 60s with sufficient sunshine. Could see near record highs at some of our climate sites. See climate section below. Friday... Low confidence temp forecast as a backdoor front will be nearby and may slip south of the region. GFS and GGEM push front to the south with cooler temps while ECMWF hold the front to the north with temps in the 60s again. Expect more cloud cover Fri along with a risk of a few showers as deeper moisture moves into the region, but forcing for ascent is limited so most of the time should be dry. Saturday... Timing uncertain but widespread showers likely to move into the region sometime Sat into Sat night depending on the timing of the cold front. Pre-frontal southerly low level jet should result in more unseasonably mild temps. Sunday into Monday... A return to more seasonable temps with blustery W/NW winds as the low pres moves into the Maritimes. && .AVIATION /23Z MONDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/... Tonight... VFR. Diminishing winds becoming light. Tuesday... More of the same, VFR with dry weather and light winds. Tuesday night... VFR to start then MVFR with chance of a few showers except probably remaining dry over RI and southeast MA. Interior MA will have to watch the potential for some -FZRA with temps near freezing. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Wednesday through Saturday/... Wednesday...Moderate confidence. Leftover MVFR/IFR conditions possible in the morning, then improving to VFR. Thursday...Moderate confidence. Mainly VFR. Friday...Low confidence. Potential for easterly flow and MVFR cigs if backdoor front slips to the south. However, VFR with SW winds if front remains to the north. Saturday...Moderate confidence. Potential for widespread MVFR/IFR conditions with rain overspreading the region. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/... Tonight...High confidence. Lingering marginal small craft wind gusts/seas across our eastern waters this evening should diminish after midnight as high pressure builds in from the west. Tuesday...High confidence. High pressure overhead will result in light winds and flat seas. Tuesday night...High confidence with winds becoming south. Chance of showers and patchy fog late may reduce vsby at times. Outlook /Wednesday through Saturday/... Wednesday into Thursday...High confidence. Mainly SW flow with gusts to 20 kt. A few gusts to 25 kt possible Thu afternoon. Friday...Low confidence. Winds will depend on location of a backdoor front. Easterly flow if the front moves to the south, but continued SW flow with gusts to 20-25 kt possible if front remains to the north. Saturday...Moderate confidence. Increasing southerly flow with SCA gusts likely. Vsbys reduced in developing rain and fog. && .CLIMATE... Record Highs for Thu Feb 23 BOS...65/1990 BDL...68/1990 PVD...60/1990 ORH...61/1990 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ231- 232. Small Craft Advisory until 6 AM EST Tuesday for ANZ250-254-255. && $$ SYNOPSIS...KJC/Nocera NEAR TERM...KJC/Nocera SHORT TERM...Nocera LONG TERM...KJC AVIATION...KJC/Nocera MARINE...KJC/Nocera CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.