Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 240843 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 443 AM EDT Wed May 24 2017 .SYNOPSIS... Scattered showers and possibly a thunderstorm are possible today mainly over the higher terrain as a weak upper level disturbance crosses the area. A stronger low pressure area will move out of the Ohio valley and bring more widespread rainfall to the North Country Thursday afternoon through Friday. Today will be the warmest day of the week with highs in the low to mid 70s. Clouds, rain, and cool east winds off the Atlantic will all conspire to keep highs in the 60s Thursday, and 55 to 60 on Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 440 AM EDT Wednesday...500 mb vort center moving along Atlantic coastline in southwest flow as closed low digs into base of mean trough centered over central Mississippi valley. Surface low centered off the New Jersey coast moving northeast and set to cross the benchmark today. Area of rain will remain close to the low and may brush southern New England coast but remain outside forecast area. Although this rain will miss us, weak shortwave trough will cross the area during the day, and combination of it an weak low level convergence area along with 200-400 j/kg of surface based cape will provide focus for scattered showers and possible thunder. Pops more widespread compared to yesterday, but still in chance category in the mountains and slight chance in the valleys. Any precip will dissipate toward evening with loss of surface heating. Today will be the warmest with weak ridging and higher thickness values. Highs in the 70s. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... As of 440 AM EDT Wednesday...Region remains in southwest flow tonight and Thursday as 500 mb low deepens over eastern US. Closed low over the Ohio Valley will shift northeast to the eastern Great Lakes through Thursday, while a vort lobe swings through the base of the trough across the gulf states and moves up the coast Thursday and Thursday night. By Friday the Great Lakes low fizzles out and the upper low center shifts to the coastl vort, spinning up a surface low there. For sensible weather rain will spread from southwest to northeast Thursday afternoon and continue Thursday night. For Friday better QG forcing shifts east of the area with the low, however moist easterly flow at the low levels will keep plenty of moisture into the area with showery precip tapering off through the day. Storm total precip for this period 3/4 to 1 inch, with higher amounts in south & east Vermont. As the surface low deepens over Long Island late Thursday a strong low level jet east/southeast jet of 35-45 kts develops with the potential for wind gusts of 30-45 mph along along the downslope communities of the western slopes of the Green Mountains in Chittenden, Addison and Rutland counties. Brief window for gusty winds late Thursday before more stable maritime air moves in. Temperatures will see a cooling trend Thursday and Friday as heights fall under the upper low & low level temperatures cool in easterly flow off the Atlantic. Clouds and rain will also keep any sun at bay. Overnight lows to remain mild however, in the upper 40s to 50s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 321 AM EDT Wednesday...Large scale pattern shows closed 7h/5h circulation and associated 998mb low pres lifting toward eastern Canada by 00z Saturday...with deep layer moisture quickly decreasing from west to east. Have continued to mention low chc pops on Friday Night...as GFS/ECMWF continue to show some 850 to 500mb RH...along with favorable northwest flow. Highest pops VT mtns with any qpf <0.10". Saturday...1015mb high pres builds into our cwa...and should result in a dry day as our region is between systems. Weak energy lobes in the flow aloft...along with a ribbon of enhanced mid level rh...could produce a spot shower...but areal coverage would be very limited. 850mb temps between 7-9c support highs mainly 60s mountain towns to l/m 70s warmer valleys. Sunday...still some uncertainty on timing of moisture associated with warm front lifting across our cwa...along with thermal profiles. GFS is the most aggressive and fastest with 850 to 700mb moisture and embedded 5h vort aloft impacting our cwa btwn 15- 18z...while ECMWF/GEM are 3 to 6 hours slower. In addition...GFS conts to show some weak elevated instability mainly across our southern cwa...along with cape values between 200-400 j/kg. Have continued with previous forecaster thinking with schc to chc pops thru 18z...and chc to likely pops between 18z-00z Sunday. Highest pops will be southern SLV into central/southern VT...based on placement of dynamics/moisture. Also...with some weak instability...continued to mention isolated rumble of thunder possible. Temps are tricky...because of increasing clouds and timing of precip. Have noted latest MEX at BTV jumping to 81F...while the 12z ECE was 71F. Based on slightly warmer 925mb to 850mb thermal profiles associated with southerly winds and low level warm air advection...I have bumped highs into the upper 60s to mid/upper 70s. Have placed 77 in the grids for BTV with some increasing humidity levels during the afternoon hours as the rain showers approach. Monday-Tue...Mid/upper level trof deepens across the central Great Lakes with several embedded 5h vorts in the flow aloft...along with a series of surface boundaries. Have continued to mention likely pops for Sunday night into Monday...with additional rounds of showers on Monday Night into Tuesday. Difficult to determine degree of surface heating and associated instability profiles...for chances of thunder. Best potential of instability with fropa looks to be Monday afternoon across our central/eastern cwa. Temps aloft start cooling on Tuesday with scattered to likely pops...and limited instability. Timing of individual s/w`s and associated boundaries are difficult at this time...along with magnitude of instability...so mainly chc pops of showers for now. Temps mainly at or slightly below normal...especially tues into Weds. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... Through 06Z Thursday...Some patchy fog/br possible overnight at slk/pbg with periods of ifr possible. Otherwise...VFR conditions expected the next 12 to 24 hours with some mid/upper level clouds impacting our taf sites overnight. A weak backdoor front will interact with some weak surface heating/instability to produce scattered afternoon showers with an embedded rumble of thunder. Have mention vcsh at slk/mpv/btv/pbg...with a brief period of mvfr possible in the heavier showers between 17-22z today. Otherwise...light winds overnight...become north 4 to 8 knots today. Outlook... Wednesday Night: VFR. NO SIG WX. Thursday: VFR/MVFR. Windy with gusts to 30 kts. Likely SHRA. Thursday Night: MVFR/IFR. Windy with gusts to 30 kts. Likely SHRA. Friday: MVFR/IFR. Likely SHRA. Friday Night: VFR. Slight Chance SHRA. Saturday: VFR. NO SIG WX. Saturday Night: VFR. Slight Chance SHRA. Sunday: VFR. Chance SHRA...TSRA. && .EQUIPMENT... The WSR-88D at Burlington, VT (KCXX) will be unavailable from Tuesday May 23, 2017 through Friday May 26, 2017. During the outage, radar coverage is available from adjacent radar sites including Montague, Albany, and Buffalo, NY and Gray ME. A new signal processor will be installed, which replaces obsolete technology, improves processing speed and data quality, provides added functionality, and supports IT security. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Hanson NEAR TERM...Hanson SHORT TERM...Hanson LONG TERM...Taber AVIATION...Taber EQUIPMENT...Team BTV

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