000 FXUS61 KALY 262057 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 457 PM EDT Tue May 26 2020 .SYNOPSIS... Wednesday will be hot and more humid with chance for showers Thursday as a disturbance approaches from the south. More widespread chances for storms come Friday as cold front approaches. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Isolated showers and thunderstorms developed across the higher terrain of the southern Adirondacks this afternoon. With very weak flow they will be slow movers with brief downpours. The convection will dissipate with loss of peak heating. The strong 500 mb ridge, 590 dm, will crest over the region tonight. It will be milder and muggier with lows only down in the 60s with light winds. These readings are 10 to 15 degrees above normal. Once again, there could be some patchy low stratus clouds and/or patchy fog due to the weak southerly flow and humid air mass in place. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... The upper ridge will begin to gradually shift eastward with the ridge axis off the coast by Thursday. Wednesday will feature similar conditions to today with large scale subsidence across the region. Guidance continues to show some instability mainly over the western Adirondacks, so have kept mention just a slight chance of a thunderstorm there and across the higher terrain of the southern Green Mountains otherwise dry. It will remain very warm and humid, with temperatures and dewpoints very similar to today with highs in the 80s. Mild and muggy Wednesday night with lows mainly in the 60s. A disturbance will move northward up the west side of the upper ridge bringing increasing clouds and chances for showers to the area especially during the afternoon and evening. Hence it will not be a warm but still humid. Looking at highs in the 70s with lower 80s in the upper Hudson Valley. Only mention for any thunderstorm will be across basically Herkimer County where some minor instability is expected. The storms will be capable of producing brief downpours with anomalously high precipitable water values across the area. Warm and muggy conditions continue with lows in the 60s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Main highlight for the long term period will be potential thunderstorms on Friday associated with an approaching cold front and upper level trough. Then, temperatures should cool down heading into the final days of May as a chilly Canadian air mass with 850hPa isotherms 1 to 2 standard deviations (as per 12 UTC GEFS) below normal pushes into the Northeast. In fact, morning lows Sunday and Monday morning should be quite cool, falling into the 40s throughout eastern NY/western New England. High temperatures Monday may just barely reach 70. Next chance for showers then returns middle of next week. Our long term discussion will focus on the thunderstorm potential Friday as that will be our next chance for strong to severe weather. Warm temperatures Friday in the mid to upper 80s will be compounded by high humidity levels (dew points well into the 60s) leading to apparent temperatures readings or the "feel- like" temperatures in the low 90s. While guidance shows dew points in the upper 60s to low 70s and this may be a little overdone, the positively tilted upstream trough extends into the Tennessee Valley States which should allow for a fetch out of the Gulf of Mexico. This explains why PWATS are 2 to 3 standard deviations above normal. So, we kept the dew points in the mid to upper 60s but limited any 70F+ mention. Dew points will be an important factor in our prediction of instability values with latest GFS and NAM guidance showing 2000J/kg+ of SB CAPE after 18 UTC Friday. That caught our attention. Wind shear is another vital ingredient when looking possible severe weather. We will positioned in between a strong ~585-590dm ridge over the western Atlantic and a shortwave trough moving through the Great Lakes. 500hPa wind flow over the Northeast looks to range 45-50kts which our local severe weather studies shows is sufficient for strong to severe weather. Guidance shows 0-6km shear is about 40kts Friday afternoon which again is sufficient for organized convection. Main lifting mechanism looks to be a pre-frontal trough Friday afternoon well ahead of the main cold front which lags way behind and does not arrive until late Friday night. This means the pre-frontal trough will likely be the main forcing mechanism for thunderstorms. Storm mode will be something to monitor over the coming days as well but with southwesterly flow in place through most of the column, we should mainly see a linear storm mode. We do note the lowest levels of boundary layer on BUFKIT profiles maintain a south to southeast flow regime through most of Friday which should provide some directional shear. SPC Convective outlook does not include Friday at this time but we will be monitoring the potential for strong storms Friday. Should instability values be as high as guidance shows, frequent lightning and heavy downpours will be hazards to monitor in addition to possible damaging winds. We included chance thunder in the latest forecast from 18 UTC Friday to 06 UTC Saturday. We did not include any enhanced wording such as damaging winds given we are 4 days out and also because mid-level lapse rates are meager at only 5 - 5.5C/km due to a warm air mass through most of the column. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... Subsidence amid a strong mid/upper level 588-591 dam ridge overhead will allow for VFR conditions to dominate much of the TAF period. Clouds will be far and few in between during the daytime hours due to the environment being capped. Overnight tonight around 7z or 8z is when we could see stratus clouds emerge once again as light southerly winds allow for moist marine layer to advect into the area. This could bring MVFR cigs back into the equation for the terminals. Clouds should once again begin to burn out and dissipate between 13z and 16z across the area giving way to a return to VFR conditions. Overall, winds will range from calm to variable or light out of the south at around 5 kts during the TAF period. Outlook... Wednesday Night: No Operational Impact. NO SIG WX. Thursday: Moderate Operational Impact. Breezy. Chance of SHRA. Thursday Night: Moderate Operational Impact. Chance of SHRA. Friday: High Operational Impact. Likely SHRA...TSRA. Friday Night: High Operational Impact. Likely SHRA...TSRA. Saturday: Moderate Operational Impact. Chance of SHRA. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Wednesday will be hot and more humid with chance for showers Thursday as a disturbance approaches from the south. More widespread chances for storms comes Friday as cold front approaches. && .HYDROLOGY... Very warm and humid conditions will persist through Wednesday night, with just an isolated thunderstorm possible during the afternoon and early evening hours. Scattered showers will be possible Thursday into Thursday night, as a disturbance approaches from the south. A more widespread rainfall is expected Friday into Friday night, as a cold front gradually moves across the region. There will be the potential for locally heavy rainfall within any persistent thunderstorms. However, due to dry antecedent conditions widespread hydro issues are not expected. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...IAA NEAR TERM...IAA SHORT TERM...IAA LONG TERM...Speciale AVIATION...Evbuoma FIRE WEATHER...IAA HYDROLOGY...IAA/JPV