Sunrise 6:08 AM   Sunset 7:54 PM Moonrise 7:59 PM   Moonset 5:18 AM

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FXUS61 KCTP 242356 AFDCTP

Area Forecast Discussion National Weather Service State College PA 756 PM EDT Wed Apr 24 2024

SYNOPSIS
Widespread frost and freeze conditions are expected tonight and Friday morning, with high pressure providing dry and mostly sunny conditions. Clouds increase late Friday leading to a chance of showers Friday night and into the weekend before it turns much warmer for Sunday and Monday.

NEAR TERM /THROUGH THURSDAY/
Clouds are being pretty stubborn over the NE and wrn NY.
Therefore, we've slowed down the clearing expected there this evening and early tonight, but kept the clearing similar by the end of the night. Will watch this evolution closer over the next few hours to see if mins (and any headlines) need to be changed.
SHRA continue as expected, and seem to be diminishing slowly.
Haven't seen any LTG thus far, and not expecting more than a strike or two before these SHRA die.

Prev...
500mb trough axis swinging offshore this afternoon with residual trailing isold-sct shra traversing central PA mid to late afternoon. This activity will dissipate with loss of diurnal heating and decreasing deep layer moisture as the 5h axis moves farther offshore.

Main focus tonight on cloud cover and light winds as high pressure builds, and resultant minimum temperatures on Thursday morning in areas where the growing season has begun. Consensus is for clearing to occur from NNE to SSW from late tonight through 12z Thu, with a light northerly breeze keeping up in most areas. Widespread freezing temps expected along and north of I-80, and upgraded to Freeze Warning from the earlier Watches in these areas. Farther south, temps of 33F to 36F will be widespread from northern parts of the Laurel Highlands through the Ridge and Valley Region, but the light northerly winds may limit frost to the most sheltered locations. Given these temperature ranges and critical time in the growing season, opted for wider goalpost frost messaging/headline and to message the light wind potentially as a mitigating factor in preventing frost.

1030+mb Canadian high pressure with origins over northern Manitoba will drift southward to a position north of Lake Ontario overnight. Frost/freeze risk outside of the headline areas is highlighted in the HWO.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/
Chilly/cold start Thursday followed by mostly sunny conditions allowing temps to warm into the mid 50s to around 60F. Very dry air/below normal pwats ~0.20 inches combined with HRRR ens min and mixed Td sounding signal suggests a floor for minRH as low as 10-15% across the northern tier. The abnormally dry air and favorable radiational cooling conditions will support renewed frost/freeze concerns tomorrow night into AM Friday. This risk is highlighted in the HWO.

The sfc high strengthens to +2SD or ~1035mb as it drifts over interior New England to Long Island by 12Z Saturday. Rain free wx conditions will continue through the end of the week/Friday with sun mixing with high clouds and max temps trending warmer into the upper 50s to lower 60s.

Showers along a warm front are likely to reach western PA by daybreak Saturday based on latest operational model/ens consensus. No frost/freeze concerns for Friday night into AM Saturday with increasing clouds and fcst lows 38-45F.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
The weekend appears somewhat unsettled, with a warm front arriving Saturday and warm sector struggling to overspread central PA. It won't be raining all the time, but a couple of showers are likely on Saturday with a t-storm possible on Sunday.

Upper ridging should eventually win out by early next week, allowing for drier wx and much warmer temps with highs surging through the 70s and perhaps topping 80F across the south on Sunday. The warmest day of the extended period will be Monday as temperatures soar into the 80s areawide. A bit humid as well with fcst Td around 60F. This could support overnight lows near record levels next week (near 60F).

Precipitation will be tough to come by in the extended period without much gulf moisture sourcing. Decaying systems that bring severe weather to the Plains will struggle to stay together and 7-day precipitation forecasts show very little rainfall across southeast PA through the middle of next week with amounts only approaching 0.75" in northwest PA.

AVIATION /00Z THURSDAY THROUGH MONDAY/
A northwesterly flow continues to gust 15-20 kts this evening.
Borderline IFR/MVFR cigs were observed across NW PA (BFD), with borderline MVFR/VFR cigs down the western highlands into JST and predominantly VFR conds elsewhere.

JST should see cigs drop to solidly MVFR overnight, while the IFR cigs at BFD are expected to eventually scatter out. Expect predominantly VFR conds to persist at the other central PA TAF sites overnight. Wind gusts will diminish, although a light northerly sfc flow should persist in most areas.

Skies will clear areawide on Thursday, with widespread VFR conds and a light northeasterly sfc flow of 5-10 kts expected.

Outlook...

Thu-Fri...Predominantly VFR conds under high pressure.

Fri night-Sat...Patchy rain developing from west to east.

Sun...Isold SHRA/TSRA possible.

Mon...Predominantly VFR.

CTP WATCHES/WARNINGS/ADVISORIES
Freeze Warning from 2 AM to 8 AM EDT Thursday for PAZ004-005- 010-011-017>019-045-046-049>053.
Frost Advisory from 2 AM to 8 AM EDT Thursday for PAZ024>028- 056-057-059.

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Market Street Bridge
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Wed -- 02:32 AM EDT     6.64 feet High Tide
Wed -- 06:09 AM EDT     Sunrise
Wed -- 06:16 AM EDT     Moonset
Wed -- 09:51 AM EDT     0.56 feet Low Tide
Wed -- 02:55 PM EDT     5.86 feet High Tide
Wed -- 07:48 PM EDT     Sunset
Wed -- 08:51 PM EDT     Moonrise
Wed -- 09:57 PM EDT     0.91 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Market Street Bridge, Schuylkill River, Pennsylvania, Tide feet

Philadelphia
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Wed -- 02:58 AM EDT     6.85 feet High Tide
Wed -- 06:09 AM EDT     Sunrise
Wed -- 06:16 AM EDT     Moonset
Wed -- 10:00 AM EDT     0.58 feet Low Tide
Wed -- 03:21 PM EDT     6.04 feet High Tide
Wed -- 07:48 PM EDT     Sunset
Wed -- 08:51 PM EDT     Moonrise
Wed -- 10:06 PM EDT     0.94 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Philadelphia, Pennsylvania, Tide feet

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