Area Forecast Discussion
Issued by NWS Burlington, VT

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999 FXUS61 KBTV 251718 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 118 PM EDT Sun Jun 25 2017 .SYNOPSIS... Scattered showers and thunderstorms are expected to develop later this morning and afternoon across the North Country. Gusty winds and small hail will be possible with any of the thunderstorms. The showers and storms will taper off tonight...but the potential for additional showers or storms will develop once again Monday afternoon. High temperatures will be right around seasonal normals today and a few degrees below normal on Monday. && .NEAR TERM /THROUGH MONDAY/... As of 1020 AM EDT Sunday...Forecast remains in good shape and no changes needed as of 1000 am. Approaching robust shortwave across the eastern Great Lakes still on track to arrive later today forcing scattered showers and storms, a few of which may be strong. Best forcing along PVA axis to occur across northern tier of counties this afternoon. Have a great day. Prior discussion...Deep layer shear has developed over the area and will persist through tonight...and even into Monday for that matter. Instability is expected to develop as temperatures warm into the 70s and temperatures aloft cool a couple of degrees. This will create a nearly dry adiabatic lapse rates in the 850-500 millibar layer...thus producing sufficient instability for convection. Meanwhile dynamic support will also be increasing over the area as a pronounced shortwave trough moves out of the eastern Great Lakes and into our area tonight. These conditions will all be sufficient to create scattered showers and thunderstorms later this morning and afternoon across the area. Forecast soundings show low wet bulb zero values and drier air in the sub cloud layer. As a result...the potential for gusty winds and small hail will exist and will include in the forecast from midday into early evening. For tonight...convection will decrease in areal coverage toward midnight as we lose instability and dynamic forcing shifts north and east of the area. Should be relatively dry during the overnight hours. Deep layer shear remains over the area on Monday and instability should develop during the afternoon hours. Temperatures will be a few degrees cooler than Sunday...thus instability will not be as favorable as Sunday. And there will be less of a forcing mechanism on Monday...thus looking at only a chance for showers or storms during the afternoon hours. Activity should not get organized enough to become no enhanced wording at this time. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 325 AM EDT Sunday...not much change in the overall forecast for this period - still more unsettled weather. The first half of Monday night will have a weak shortwave push across the region. Models all show some disorganized convection associated with the shortwave lifting southwest to northeast through 08z, so have aligned the PoPs with a blend of some of the hi-res models to show the evolution. One little feature to see if it comes to pass will be the potential for a little bit of lake effect showers come off Lake Ontario into the St Lawrence Valley area first thing Tuesday morning thanks to some cooler air aloft. A stronger upper trough approaches the area Tuesday. Although there will be plenty of clouds and temperatures on the cool side (upper 60s to lower 70s), the temperatures aloft (around 500mb) are rather cold (near -22C), so that should result in some instability to produce another round of afternoon/evening showers and perhaps a few t-storms. With the cold air aloft, wet bulb zero heights are quite low (7000-8000ft), so chance for some small hail in any deeper convection. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 325 AM EDT Sunday...00z model suite still pointing toward a continued lengthy stretch of unsettled weather. Not that it will be cloudy and rainy continuously, rather we will see short dry periods of 12-18 hours followed by 12-18 hour long periods where scattered showers and t-storms will be around. At upper levels, we will be in a region of fast mainly zonal (west to east) flow with embedded shortwaves zipping through. It will be these shortwaves, combined with daytime heating, that will be the primary triggers for the convection. Given the uncertainty in timing these shortwaves, it`s best to take a bit more of a general approach to the forecast and use a model blend for day- to-day PoPs. At this point, I don`t see anything indicating any widespread severe weather through Friday. GFS and ECMWF continue to show a more significant upper trough develop to our west on Saturday, resulting in a deeper southerly flow which brings in some very moist air (precipitable water closes in on 2.0"). If this does come to pass, we could have some hydro related issues by then, especially if we have enough convective activity repeat across the same areas during the week. Just something to watch at this point. In general, temperatures will be slightly below normal through much of the week though trending closer to normal late week as the more southerly flow develops. Again, stuck with model blend for temperatures, and there is considerable error potential if we end up having much more sunshine than currently expected. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Through 18Z Monday...Mainly VFR through the period with scattered showers and thunderstorms through early evening. Shortwave pushing across the area this evening driving scattered showers and thunderstorm activity across the area. No severe weather is expected though a few of the more robust storms could produce small hail, gusty winds into the 30-40 mph range, enhanced low level turbulence and brief MVFR/IFR conds. Coverage of storms to wane this evening and overnight with loss of surface heating and as shortwave exits east. Winds west to southwesterly 6 to 12 kts and occasionally gusty into the 15-20 kt range through sunset, abating to light overnight. After 12Z Monday VFR continues, but with an increasing threat of showers and thunderstorms once again as we approach the 18Z time frame. Given this will occur toward the very end of this forecast cycle have omitted specific mention at this point. Winds continue light west/southwesterly 5 to 10 kts. Outlook... Monday Night: VFR. Chance SHRA...Slight Chance TSRA. Tuesday: VFR. Chance SHRA...Slight Chance TSRA. Tuesday Night: VFR. Slight Chance SHRA...Slight Chance TSRA. Wednesday: VFR. Chance SHRA...Slight Chance TSRA. Wednesday Night: VFR. Slight Chance SHRA. Thursday: VFR/MVFR. Likely SHRA. Thursday Night: MVFR. Likely SHRA...Slight Chance TSRA. Friday: VFR/MVFR. Chance SHRA...Slight Chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson/JMG SHORT TERM...Nash LONG TERM...Nash AVIATION...JMG is the U.S. government's official web portal to all federal, state and local government web resources and services.