textproduct: Burlington

WHAT HAS CHANGED

As of 249 PM EDT Sunday...

No significant changes from the previous forecast.

KEY MESSAGES

As of 249 PM EDT Sunday...

1. Warm Monday, hot and humid on Tuesday with when significant heat is likely, localized fire weather concerns on Wednesday.

2. Precipitation chances increase early this week. A sharp cold front will pass through the region late Tuesday into Wednesday bringing a chance for thunderstorms, some of which could be strong to severe.

3. Seasonable conditions are generally expected for the latter half of the week into the weekend, with a few chances for showers possible.

DISCUSSION

As of 249 PM EDT Sunday...

KEY MESSAGE 1: The low level air mass will warm a bit compared to recent days for Monday as flow turns southerly ahead of a shortwave trough. While light rain may cool temperatures a bit later in the day, think enough sunshine will be present to boost temperatures back into the 80s areawide.

Much hotter and more humid air remains on track to surge into the region on Tuesday. Have noted the air mass that will be advecting into the region may be more humid and less hot than what the current blend suggests, with low to mid 70s dew points common in eastern North Dakota and western Minnesota this afternoon with temperatures surging into the 90s. Have trended heat index values a touch higher with this forecast with maximum values mainly in the 92 to 99 range at elevations 1000 feet and below, but overall the idea of significant heat building in Tuesday is unchanged. Full sunshine/little cloud cover will support dangerous heat for outdoor activities during the afternoon hours especially. We also continue to expect unusually breezy conditions to accompany the heat, although this hot wind will not bring much relief. The magnitude of the winds don't appear to be significant from a utilities standpoint, but deep mixing above 850 millibars during peak heating could lead to some gusts approaching 35 MPH in many locations, especially in northern New York and eastern downslope/foothills in Vermont with the westerly flow.

Behind a cold front passing through early Wednesday, drier air will make for more comfortable conditions, although the deep mixing of still rather warm air should still lead to above normal temperatures. We will also be monitoring potential for gusty winds given low relative humidities, posing a fire weather risk in areas that will have seen little to no meaningful rainfall in more than a week across portions of south central Vermont and southern Champlain Valley.

KEY MESSAGE 2: A trough will bring an increase in clouds and chance for light rain showers during the day. Perhaps the combination of moistening of very dry air near the ground and the aforementioned shortwave will be enough to support a heavier shower or even an isolated thunderstorm late in the day, but risk appears to be quite low.

Much more meaningful thunderstorm chances remain for Tuesday night. Unfortunately, the predictability of the hazard impacts (the important when and where questions) have not become any more clear in this forecast cycle. Mesoscale convective complexes are inherently difficult to forecast other than the ingredients to suggest their development. So confidence remains high in the formation of strong to severe thunderstorms in southern Canada Tuesday afternoon/evening but not the specific timing and location. There is some consensus, especially among convection allowing models, that the cap will remain strong through sunset with a low chance of thunderstorms in our region through that time. Thereafter, solutions split quite a bit with the track of clusters of thunderstorms, tracking south/southeastward through either or both of southern Ontario towards northern New York, and southern Quebec tracking into northern Vermont, roughly between 8 PM and 2 AM. Given the high shear environment and instability that will be in place, ample storm relative helicity will support well- organized storm modes with a combination of supercell and linear segments expected. Earlier timing of storms reaching our area will support a higher risk of severe storms There also is potential for torrential rainfall rates given very high PWAT and warm cloud depths with sufficiently high MUCAPE. Additionally, heavy rainfall footprints/training of storms could occur given anomalous deep moisture transport and convergence along a boundary oriented from west-northwest to east-southeast.

KEY MESSAGE 3: Thursday looks to be a pleasant summer day across the region as dry mid-level and incoming cooler air bring seasonable conditions. High temperatures are expected to climb into the upper 70s to mid 80s, feeling quite enjoyable with dewpoints in the 50s. A shower or two may be possible across northern Vermont as a shortwave moves through, but given the abundance of dry air meaningful precipitation is not expected. As we head towards the very end of the week into the weekend, there is increased uncertainty in the weather pattern and what to expect. Given the colder air mass and influence of an upper level troughing centered over the Canadian Maritimes, seasonable temperatures are expected, with some days possibly below normal. Precipitation chances are more uncertain, with model guidance all over the place in regards to the timing of any boundaries and limited moisture available. The current forecast shows some slight chances for showers throughout the week, particularly on Saturday into Sunday when more guidance supports a frontal boundary moving through the region, but trends may change as we progress through the week.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday...VFR conditions will continue to prevail across all terminals throughout the forecast period. Mostly clear skies will continue through the afternoon, with some fair weather cumulus continuing to develop off the higher terrain, with cloud bases generally between 5000 and 7000 ft AGL. Winds this afternoon are generally north to northwesterly, less than 10 knots, although wind direction has been variable at times. Winds overnight will generally trend calm or terrain influenced. After another dry day, fog potential is even more limited overnight than the previous days, so have left any mention of fog out of the forecast for now.

Outlook...

Monday Night: VFR. NO SIG WX. Tuesday: VFR. Windy with gusts to 30 kt. NO SIG WX. Tuesday Night: VFR. Chance SHRA, Slight chance TSRA. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. Slight chance SHRA. Thursday Night: Mainly VFR, with areas MVFR possible. NO SIG WX. Friday: Mainly VFR, with local MVFR possible. NO SIG WX.

CLIMATE

High temperatures on Tuesday will be hot, but we are at the climatological warmest part of the year. Therefore, it is far from a certainty that any records will occur. At this time, PBG, MPV, and MSS are the more likely long-term climate sites to set a record. See below for current records:

Max Temp Records Date BTV MPV MSS PBG SLK 07-14 100|1995 94|1952 92|2012 95|1952 95|1934

High Min Temp Records DatePBG 07-14 70|1974

BTV WATCHES/WARNINGS/ADVISORIES

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