textproduct: Burlington

WHAT HAS CHANGED

As of 239 AM EDT Thursday...

No significant changes.

KEY MESSAGES

As of 239 AM EDT Thursday...

1. Showers return tonight into Friday.

2. While heat and humidity will gradually build early next week, significant heat is not expected during this period. Isolated or scattered showers and thunderstorms are possible on Tuesday and Wednesday, although the forecast becomes more uncertain towards midweek.

DISCUSSION

As of 239 AM EDT Thursday...

KEY MESSAGE 1: After a few mostly dry days showers will be moving into our region later today in northern New York, and spreading across the rest of the north country overnight. A low pressure system situated in the Great Lakes region this morning will track eastward towards our forecast area. A weak warm front will lift across our area today brining first round of showers. Lift associated with the front should cause stratiform precipitation to spread across the area overnight, with rain heavy at times. As the stratiform precipitation comes to an end, should end with a few areas of weak elevated convection. Then there will be a break in the precipitation before scattered showers and embedded thunderstorms develop Friday afternoon as a cold front approaches from the west with low passing just to our north. During the afternoon there will be around 500- 1000 J of CAPE and 0-6 KM shear around 30-35 KT, so a few strong storms will be possible. However, increasing dry air aloft and relatively weak synoptic dynamics will help minimize the threat. Adequate storm movement and the break between the warm front and the convection will minimize the flood threat. SPC has placed most of our region under general thunder threat, with marginal over southeastern Vermont. WPC has also put most of VT within an excessive rainfall marginal risk since our area has been pretty wet recently. Rainfall totals tonight into tomorrow should range from around just a tenth of an inch in parts of the St Lawrence valley, up to around an inch of rain where the most persistent rain falls and in any areas that have convection Friday afternoon. These types of rainfall totals over 24 hours are unlikely to cause many flooding concerns.

KEY MESSAGE 2: Typical summertime heat is expected on Monday when high pressure will be accompanied by 850 millibar temperatures at about 15 to 16 degrees C. These temperatures are near the 80th climatological percentile and suggestive of high temperatures mainly in the mid to upper 80s when skies are mainly clear and winds light. Then on Tuesday and Wednesday the forecast gets a little more complicated by potential for cloud cover and showers/thunderstorms. On both days, the warmest guidance continues to be warmer than the day before and yet there is almost as much guidance that trends temperatures less hot. Based on the ensemble mean, it is unsurprising forecast highs continue to be hotter than on Monday, but again it should be noted that these highs are more uncertain than early in the week. Overall, the risk of significant heat remains low compared to areas to our south and west with the upcoming weather pattern.

The latest model blend probabilities for thunderstorms have slightly trended downward on both Monday and Tuesday. While Tuesday still looks more promising for thunderstorm chances generally due to greater chance for precipitation, it has continued to trend downward. Better probabilities of thunderstorms currently are on Wednesday and especially over northern New York. Note this is still a week out and the probabilities are fairly low (12 hour thunderstorm chances only as high as 28% within the St. Lawrence Valley). That said, it appears surface winds finally will turn towards the southwest and allow transport of truly humid air (dew points possibly into the 70s) reaching our region that will have been building under a heat dome sitting to our west. This scenario where at least modest northwesterly flow aloft coincides with potentially high amounts (>2000 J/kg SBCAPE) of instability suggests at least some risk of strong to severe thunderstorms on Wednesday.

AVIATION /06Z THURSDAY THROUGH MONDAY/

Through 06Z Friday...VFR conditions will continue across the airspace through most of the period amidst a mix of ceilings ranging from about 8000 feet to 25,000 feet. Chances of MVFR and brief IFR will increase after 00Z, associated with an area of showers with embedded heavier rain pushing in from the south and west. Think most rain initially will have cloud bases remaining VFR, and visibilities will probably drive any category changes to MVFR. However, if heavier rain develops on the earlier side, ceilings will also tend to lower late in the period. Cloud bases below 1000 feet are favored especially at RUT and MPV.

Weak high pressure in place today should lead to only light south or west winds. Concurrent with the area of rain late in the period will an increase in southwest winds aloft, but these look too light to produce LLWS at this time.

Outlook...

Friday: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Friday Night: Mainly VFR, with local IFR possible. NO SIG WX. Saturday: Mainly VFR, with local IFR possible. Slight chance SHRA, Slight chance TSRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.