Marine Weather and Tide Forecast for Lancaster, PA

NEAR TERM /THROUGH TONIGHT/
Very little DTD change from Sunday's overcast skies and target area for convection being across far SW PA. A light easterly llvl flow will help to maintain thick/low-based cloud cover with daytime temperatures of 5 to 8 deg F below normal

Localized visibility drops will be possible across Schuylkill County (along the I-81 corridor where the greatest orographic lift will occur) and the south-central mountains through the mid morning hours.

Temperatures to start the day will be quite uniform, ranging from the mid 50s to around 60F.

SHORT TERM /TUESDAY/
Stationary front will begin to lift north as a warm front tonight and Tuesday, which will act to expand the threat for Flash Flooding from heavy rain/repeat showers and thunderstorm over the SW Half of the CWA What's been a very low probability for CAPE to exceed 500 J/KG Sunday and again today, will ramp up significantly Tuesday across the Western Mtns and possibly even a little east of the I-90 corriodr.I

In addition, an increasing and veering wind field aloft Tuesday afternoon and evening will lead to 0-1 KM EHI values increasing to several small areas of 1.5-2 M2/S2. Wouldn't be surprised to see either a MRGL or SLGT introduced by SPC for DY2 (limited to the Western half of PA) where the warm front will help to focus CI and enhance the depth of Updrafts.

High temperatures today will bounce back to just several deg F below normal.

PWAT values begin to increase Tuesday morning into Wednesday with best forcing overhead as a surface boundary warm front moves into South Central Pennsylvania and the Pocono Mtns.

Relatively warmer air will work into the western half of the forecast area, allowing for slightly more instability in place on Tuesday to allow for thunderstorm mentions across the western highlands, with some clearing on Wednesday allowing for enhanced destabilization. From a hydrology perspective, rainfall is expected to be efficient across western Pennsylvania (where PWAT values approach 1.75") which will bring into account flooding concerns, outlined by WPC's D3 MGRL ERO across the western half of the area, with the SLGT risk clipping Somerset/Elk counties. Severe threat on Wednesday remains fairly minimal, with the best shear in place across northern Pennsylvania where cloud cover will likely limit destablization.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
Influence of the upper-level trough continues into the long-term period before gradually drifting eastward by Friday. Period of most interest in the long-term will be Thursday, especially in the afternoon/evening hours with some severe potential in the cards across much of central Pennsylvania. Low pressure stationed across southern Canada with warm front stretched into the northern Atlantic and a cold front stationed across the Ohio Valley will allow for some residence time in the warm sector ahead of an afternoon approach by a surface cold front.
Ample moisture will remain in place, with dew points in the upper 60s to lower 70s across the eastern half of the forecast area. This threat is also noted in the Storm Prediction Center D5 Severe Outlook, with a 15% contour. Do want to highlight that some uncertainty does remain with regards to frontal passage time; however, model guidance is continuing to indicate that ingredients will be in place for some severe potential across central Pennsylvania on Thursday.

Cold frontal passage brings in relatively dry conditions for Friday with upper-level heights beginning to increase. Diurnal showers and thunderstorms will remain in the cards for the weekend, as temperatures trend well-above seasonal averages with relatively humid conditions. Sunday will remain the hottest day of the long-term with forecast high temperatures reaching into the mid-to-upper 80s across the northern tier to the lower 90s across the south-central mountains, with heat index values pushing close to the century mark late Sunday PM. HeatRisk values on Sunday outline the warm temperatures/heat index values, with widespread moderate (level 2/4) risk conditions with areas of the south-central mountains and western highlands reaching into the major (level 3/4) risk for heat-related impacts.

AVIATION /15Z MONDAY THROUGH FRIDAY/
High confidence in low-end MVFR to LIFR cigs persisting into Tuesday morning across Central PA, thanks to a moist low-level east/southeasterly flow off the Atlantic Ocean.

Patchy light rain and drizzle is possible as well, with cigs hovering near or below alternate minimums.

Outlook...

Tue.. MVFR/IFR with AM low clouds/fog; showers and afternoon thunderstorms are possible.

Wed...VFR/MVFR with showers and thunderstorms possible.

Thu...Predominantly VFR, with strong PM t-storms possible and a cold frontal passage.

Fri...VFR with a slight chance of rain showers.

CLIMATE
Astronomical Summer (solstice) officially arrives on Friday, June 20, at 10:42 p.m.

CTP WATCHES/WARNINGS/ADVISORIES
None.