Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 210554 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 154 AM EDT THU AUG 21 2014 .SYNOPSIS... SLOW MOVING LOW PRESSURE WILL BRING UNSETTLED WEATHER OVERNIGHT AND THURSDAY FOR MAINLY NORTHERN NEW YORK AND THE WESTERN HALF OF VERMONT. DRIER WEATHER WILL DEVELOP ON FRIDAY AS HIGH PRESSURE STARTS TO MOVE INTO THE AREA. THAT HIGH WILL STICK AROUND, GIVING US A LONG STRING OF DRY AND WARM WEATHER THAT WILL LAST FROM THE WEEKEND INTO THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 7 AM THIS MORNING/... AS OF 144 AM EDT THURSDAY...COMPOSITE RADAR LOOP SHOWING MOST OF THE RAIN SHOWER ACTIVITY CONFINED TO NORTHERN NEW YORK AT THIS TIME ...WITH SOME WIDELY SCATTERED SHOWERS DEVELOPING ACROSS WESTERN VERMONT AT THIS TIME. BASED ON LATEST RADAR TRENDS HAVE LOWERED POPS ACROSS VERMONT OVERNIGHT AND RAISED OVER NORTHERN NEW YORK. BASED ON LATEST SURFACE OBSERVATIONS AND THE LATEST GFS LAMP GUIDANCE HAVE RAISED MIN TEMPERATURES UP A DEGREE OR TWO OVERNIGHT. && .SHORT TERM /7 AM THIS MORNING THROUGH FRIDAY NIGHT/... AS OF 330 PM EDT WEDNESDAY...AFOREMENTIONED UPPER LOW WILL CONTINUE TO BE THE PRIMARY DRIVER OF NORTH COUNTRY WEATHER THROUGH THURSDAY NIGHT. NAM/GFS ALL IN GOOD AGREEMENT THAT UPPER LOW OPENS UP/WEAKENS AS IT PROGRESSES ACROSS THE NORTH COUNTRY THURSDAY INTO THURSDAY NIGHT. EXPECT SHOWERS TO ONCE AGAIN BE PRIMARILY FOCUSED ACROSS NORTHERN NY /LIKELY POPS/ ON THURSDAY...THOUGH THE BEST CHANCE FOR PRECIPITATION ACROSS VT IS ON THURSDAY. AIRMASS STILL IS FAIRLY MOIST WITH PWS AROUND 1.5" WITH 12Z NAM SHOWING CAPE VALUES SUPPORTIVE OF THUNDER. THE THUNDER RISK FOR THURSDAY IS LIMITED GIVEN EXPECTED EXTENSIVE CLOUD COVER AND ALSO LOSING BETTER DYNAMIC FORCING GIVEN WEAKENING UPPER LOW. THEREFORE I`VE ONLY GONE WITH SHOWERS THURSDAY. DESPITE 850 TEMPS OF +11 TO +13C...OVERCAST WILL ONLY KEEP TEMPS IN THE MID 70S. OVERALL DECREASING TREND IN POPS FOR THURSDAY NIGHT AS UPPER DISTURBANCE PIVOTS SOUTH OF THE NORTH COUNTRY. LARGE GRADIENT IN STORM TOTAL QPF /SPANNING WEDNESDAY AFTN THROUGH 12Z FRIDAY/. AMOUNTS RANGE FROM NIL ACROSS THE NORTHEAST KINGDOM...UNDER 0.5" FOR THE CHAMPLAIN VALLEY...TO UP TO 1.25" FOR THE ADIRONDACKS AND ST. LAWRENCE VALLEY AREAS. BY FRIDAY...AN AMPLIFIED UPPER RIDGE WILL BUILD SOUTHWARD TOWARD QUEBEC AS THE UPPER LOW PASSES INTO THE NORTH ATLANTIC AND WEAKENS TO AN OPEN WAVE. SOME INSTABILITY SHOWERS STILL POSSIBLE ON FRIDAY BUT SUBSIDENCE FROM BUILDING UPPER RIDGE WILL WIN OUT BY LATE IN THE DAY INTO THE EVENING. NOT MUCH CHANGE IN THERMAL PROFILES FOR FRIDAY...BUT MORE BREAKS IN CLOUDINESS SHOULD ALLOW FOR HIGHS TO TOP OUT IN THE MID TO UPPER 70S WITH 50S TO AROUND 60 FOR LOWS. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 330 PM EDT WEDNESDAY...12Z GUIDANCE FROM GFS, GFS ENSEMBLES AND ECMWF ARE ALL IN PRETTY DARN GOOD AGREEMENT WITH EACH OTHER AND THEIR INDIVIDUAL PREVIOUS RUNS, THUS I WOULD RATE MY CONFIDENCE IN THE FORECAST AS ABOVE NORMAL. IN SUMMARY, LARGE SCALE BLOCKING RIDGE DEVELOPS ACROSS THE EASTERN HALF OF THE COUNTRY, RESULTING IN DRY AND WARMING CONDITIONS INTO THE MIDDLE PART OF NEXT WEEK (SUMMER WILL HANG ON NEXT WEEK, WHICH MAKES THIS FORECASTER PERSONALLY HAPPY). WITH THE CLOSENESS AMONG THE MODELS, I SAW NO REASON TO SIGNIFICANTLY DEVIATE FROM THE PURE BLEND BETWEEN THEM ALL. HERE ARE THE DAILY SPECIFICS... SATURDAY...UPPER TROUGH WILL BE PUSHING SOUTH/EAST OF THE AREA. STILL SOME CYCLONIC FLOW ALOFT SO CAN`T RULE OUT AN ISOLATED LIGHT SHOWER OR SPRINKLE ACROSS MAINLY THE HIGHER TERRAIN, BUT IN GENERAL THE FORECAST IS A DRY ONE. CLOSER TO THE SURFACE, HIGH PRESSURE WILL BE SLOWLY NOSING DOWN FROM THE NORTH. THIS WILL RESULT IN A LIGHT EASTERLY FLOW. LUCKILY THIS TIME OF THE YEAR THE ATLANTIC OCEAN WATERS ARE AT THEIR WARMEST SO I DON`T EXPECT ANY ISSUES WITH WIDESPREAD LOW STRATUS DEVELOPING AS WE WOULD SEE IN THE SPRING OR EVEN EARLY SUMMER. HOWEVER IT WILL SET UP AN A TEMPERATURE GRADIENT WHERE IT WILL BE COOLEST EAST OF THE GREEN MOUNTAINS AND WARMEST IN THE ST LAWRENCE VALLEY. WITH 850MB TEMPERATURES RUNNING ABOUT 10-12C (EAST TO WEST), HIGHS SHOULD RANGE FROM THE LOWER 70S IN THE CONNECTICUT VALLEY TO UPPER 70S IN THE ST LAWRENCE VALLEY. SHOULD BE MOSTLY CLEAR SATURDAY NIGHT. VALLEY FOG WILL PROBABLY FORM AS TYPICAL THIS TIME OF YEAR. LOWS GENERALLY IN THE 50S. SUNDAY...DITTO. MONDAY...SURFACE HIGH SHOULD BE PRETTY MUCH ON TOP OF THE AREA ALONG WITH STRONG RIDGING ALOFT. NET RESULT: LOTS OF SUN AND VERY LIGHT WINDS. 850MB TEMPERATURES RISE TO THE 12-13C RANGE AND WITH ATMOSPHERIC MIXING, WE SHOULD REALIZE THE FULL POTENTIAL OF WARMTH WITH HIGHS TOPPING OUT IN THE 70S TO LOWER 80S. MONDAY NIGHT ANOTHER REPEAT OF CLEAR/CALM/PATCHY FOG. TUESDAY...ALMOST IDENTICAL TO MONDAY, EXCEPT THE HIGH SINKS JUST A LITTLE SOUTH OF THE AREA ALLOWING THE FLOW TO TURN MORE SOUTHWESTERLY. IN RESPONSE, TEMPERATURES WILL RISE A DEGREE OR TWO FROM MONDAY. 850MB TEMPERATURES WILL BE UP AROUND 12-14C, SO LOOK FOR LOWER 80S TO BE MORE WIDESPREAD. STILL DEEP LAYER RIDGING AND A STRONG SUBSIDENCE INVERSION PERHAPS AS LOW AS 7500FT SO ANY DAYTIME CUMULUS THAT FORMS WILL BE VERY SHALLOW. TUESDAY NIGHT ANOTHER REPEAT OF MONDAY NIGHT WHICH IS A REPEAT OF SUNDAY NIGHT WITH IS A REPEAT OF SATURDAY NIGHT. WEDNESDAY...MODELS BEGIN TO DIVERGE SOME. GFS & IT`S ENSEMBLE MEAN KEEP THE UPPER RIDGE STRONG, MEANING LOTS O` SUN. ECMWF FLATTENS THE RIDGE IN RESPONSE TO A STRONG SHORTWAVE PASSING BY TO THE NORTH AND BRINGS IN SOME MOISTURE TO NORTHERN NY LATE IN THE DAY SUGGESTING A FEW SHOWERS/T-STORMS ABOUT. WITH THE BLEND I USED, I LEANED MORE TOWARD THE GFS SOLUTION, BUT PAINTED IN SOME 10-20% POPS IN NORTHERN NY. THE BASIC WORDED FORECAST WILL INDICATE A DRY DAY. 850MB TEMPERATURES RISE TO 14-16C OR SO, THUS EVEN MORE OF THE AREA WILL BE POKING ABOVE THE 80F MARK -- WITH EVEN A FEW LOCATIONS IN THE CHAMPLAIN/ST LAWRENCE VALLEY PUSHING INTO THE MID 80S. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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THROUGH 06Z FRIDAY....CRNT RADAR SHOWS A BAND OF LIGHT TO MODERATE RAIN ACRS NORTHERN NY ATTM...SLOWLY MOVING INTO THE CPV. VIS/CIGS ASSOCIATED WITH THIS PRECIP IS MAINLY VFR WITH SOME MVFR IN THE HEAVIER SHOWERS. ALSO...NOTED SOME MVFR WITH BRIEF PERIODS OF IFR CIGS AT MSS. THINKING THIS RAIN WL ARRIVE AT PBG BY 08Z AND INTO BTV BY 09Z...WITH MAINLY VFR/MVFR CONDITIONS. SOUNDINGS SHOW LLVL MOISTURE INCREASING AT SLK WITH SOME IFR CIGS POSSIBLE BTWN 09Z- 14Z THIS MORNING. HAVE USED A TEMPO GROUP TO COVER THIS POTENTIAL. OTHERWISE...CLOUDS AND 200 TO 400 FT AGL WINDS OF 10 TO 15 KNOTS SHOULD LIMIT FOG POTENTIAL AT MPV OVERNIGHT. FOR THURSDAY...EXPECTING ADDITIONAL SHOWERS WITH SOME PERIODS OF MODERATE RAIN POSSIBLE WITH MVFR VIS BTWN 3-5SM. WL USE TEMPO GROUP TO COVER HEAVIER PERIOD OF SHOWERS AT BTV/RUT. A SLOW CLRING TREND WITH IMPROVING CONDITIONS SHOULD DEVELOP BY 18Z...WITH GENERALLY LIGHT SOUTHEASTERLY WINDS AT 4 TO 8 KNOTS. OUTLOOK 06Z FRIDAY THROUGH MONDAY...VFR CONDITIONS WITH SFC HIGH PRES BUILDING INTO THE REGION. MORNING FOG WL BE LIKELY AT SLK/MPV WITH IFR/LIFR CONDITIONS BOTH SAT AND SUNDAY MORNINGS BTWN 07Z- 13Z. LOOK FOR MAINLY EAST TO NORTHEAST WINDS OVER THE WEEKEND AT 5 TO 10 KNOTS WITH SOME SLIGHTLY STRONGER VALUES AT MSS AND RUTLAND.
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&& .EQUIPMENT... AS OF 144 AM EDT THURSDAY...THE AUTOMATED SURFACE OBSERVING SYSTEM (ASOS) AT SAINT JOHNSBURY VERMONT (K1V4) HAS NOT TRANSMITTED AN OBSERVATION SINCE 1954Z (354 PM EDT) ON WEDNESDAY AUGUST 20TH. AN ELECTRONICS TECHNICIAN WILL CHECK INTO THIS PROBLEM LATER THIS MORNING. NO ESTIMATE IS AVAILABLE AT THIS TIME AS TO WHEN THIS PROBLEM WILL BE FIXED. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...LOCONTO NEAR TERM...WGH SHORT TERM...LOCONTO LONG TERM...NASH AVIATION...TABER EQUIPMENT...WGH

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