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ANZ530 Chesapeake Bay North Of Pooles Island- 740 Am Est Thu Dec 7 2023
Today..SW winds 5 to 10 kt. Waves 1 ft. Scattered snow and rain showers this morning with vsby 1 to 3 nm.
Tonight..W winds around 5 kt. Waves 1 ft or less.
Fri..S winds around 5 kt. Waves flat.
Fri night..SE winds around 5 kt. Waves flat.
Sat..S winds around 5 kt. Waves flat.
Sat night..SE winds 5 to 10 kt. Waves 1 ft or less. A chance of rain.
Sun..S winds 20 to 25 kt...becoming nw 15 to 20 kt after midnight. Waves 2 ft. Rain likely in the morning. Showers.
Mon..W winds 15 to 20 kt. Waves 1 to 2 ft.

ANZ500 740 Am Est Thu Dec 7 2023
Synopsis for the tidal potomac and md portion of the chesapeake bay..
high pressure will build over the region through Friday, then move offshore this weekend. A strong frontal system will likely impact the region on Sunday. Small craft advisories may be needed starting Saturday night, and are likely Sunday and Sunday night. Gales are possible Sunday into Sunday night, as well.

FXUS61 KCTP 071155 AFDCTP

Area Forecast Discussion National Weather Service State College PA 655 AM EST Thu Dec 7 2023

SYNOPSIS
A fast-moving shortwave will dive across Northeast PA early today, then upper level ridging will build into the region late this week. Low pressure will track west of the state this weekend, with a trailing cold front traversing the region on Sunday.

NEAR TERM /THROUGH TONIGHT/
MRMS RALA shows a band of light snow from Southeast Ontario into Central PA at 11Z associated with warm advection ahead of a fast-moving shortwave diving across the Eastern Grt Lks. All recent guidance indicates the band of strongest mid level fgen forcing will run from Mckean/Potter County southeast to Schuylkill County, where model qpf supports around an inch of snow accumulation this morning, with little if any accumulation south of a line from KFIG to KTHV.

RAP cross section analysis indicates a decent instability signature across the east-central part of the forecast area later this morning, with a layer of negative EPV located just above the frontogenesis around 650mb. Thus, embedded bands of moderate snow for the morning rush hour are possible in this area during the mid morning hours. Although confidence is high that amounts will remain well below advisory criteria, timing around the morning commute may produce impacts given traffic volumes at that time of day.

The latest HRRR, which is doing a good job initializing where snow is falling now, indicates the light snow should taper off from west to east between 12Z-16Z. Some spotty very light snow/flurries may persist into the afternoon hours over the mountains north of KIPT, where an upsloping southwest flow and model-depicted sfc-700mb RH values near 90pct support light orographic precip.

Elsewhere, model RH fields support partial clearing in the afternoon, especially over the southwest part of the forecast area. GEFS 2m temp anomalies indicate highs will be several degrees above average across the southwest counties, while more persistent cloud cover holds readings down over the N Mtns. Max temps should range from the mid 30s over the N Mtns, to the mid 40s in the southern valleys.

SHORT TERM /FRIDAY THROUGH SATURDAY/
All guidance indicates upper level ridging will build into the region tonight into Friday, supporting fair and warmer weather.
A surface warm front pushing into Western PA may result in nearly steady temps across the Laurel Highlands tonight, while boundary layer decoupling further east results in lows in the upper 20s to low 30s across most of Central PA.

Southerly flow, warming aloft and a return of sunshine should result in a marked warmup Friday. GEFS 2m temps are +10-15F above climo, translating to highs in the upper 40s over the northeast part of the forecast area and the mid 50s in the southern valleys.

A similar west to east breakdown in min temps is expected Friday night with an active southerly breeze holding temps in the 35-40F range over the Allegheny Plateau, while surface ridging along the east coast results in decoupling and min temps in the low 30s over the eastern counties. Have also added patchy fog to the Sat AM forecast over the southeast half of the forecast area based on latest SREF and NAMNest guidance.

The slow moving warm front looks to be hung up along the Appalachians Saturday. Thus, the warmest temps with highs in the mid 50s are expected over the western counties, while cold air damming east of the front keeps readings a bit cooler in Eastern PA. Upper level ridging along the east coast should keep it dry for most, if not all, of Central PA. However, can't rule out a shower sneaking into the W Mtns toward dusk ahead of an upstream cold front.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
Wednesday evening update... Although some subtle differences exist with the speed and amplitude of the upper trough and associated moisture plume progged to impact the Commonwealth late this weekend into Monday, overall, large-scale agreement is good.

The big story this period will be an anomalous surge of warmth and moisture tracking up through at least eastern PA from late Saturday night into Monday. Heavy rain and strong wind threats remain, given the overall strength of this system. In the end, forward system motion will play a big part in how much rain falls. Also, luckily, snowfall is minimal this early in the season and long-term dryness over parts of the area are still prevalent. Those factors will help us, but we'll still monitor closely with 90+ precipitable water percentiles progged and a deep meridional fetch.

The degree of cold air infusion on the back side of this system and how much heavier precipitation remains behind the surface cold front are also open ended questions. Overall, recent model trends may have sped this system up a bit by early Monday, perhaps reducing the wintry threat. However, it's still way too early to make a call on this one.

All pertinent hazards (heavy rain/flooding, wintry precipitation, and strong winds) will be maintained in the Hazardous Weather Outlook at this juncture.

Behind the above noted system towards the middle of next week, the large-scale pattern should feature western North American upper ridging and broad troughing over eastern Canada, the upper Midwest, and the northeastern CONUS. This favors seasonably chilly temperatures and perhaps some lake enhanced/orographic snow showers, depending on the orientation of the low-level flow.

AVIATION /12Z THURSDAY THROUGH MONDAY/
Snow ongoing at 12Z as a wave of low pressure aloft moves across the region. BFD and IPT are already into IFR, but only a very brief foray below 1SM thus far at any terminal. Decent snow band with visbys <1/2SM per road cams/sensors is splitting IPT and UNV (right over KLHV, home to Piper Aviation/Museum). This band should continue to slide SE while additional bands may (30% chc)
develop near IPT. The worst of the visby within the current mesoscale snow band should slide S of IPT. The back edge of the precip returns on radar is already coming on-shore at ERI & BUF. This indicates the back edge of the forcing and limited moisture. Expect this snow to be over as fast as it started.
AOO, MDT and LNS will have a very low risk (10%) for IFR. P-type will be a mix at MDT, and it should start within the hour, working down from well aloft. De- icing could still be necessary there this morning, as it is everywhere else.

Strong winds just aloft will result in LLWS for all but MDT and LNS during the daylight hours. JST will likely see the winds at FL020 up around 45KT during the aftn in the strong warm advection layer & LLJet feeding the wave.

As the precip ends, many places will bounce back to MVFR and then VFR. BFD will stay down in MVFR (cig) or even IFR (later today) as cyclonic flow lasts until Friday AM. Wind direction favors good improvement elsewhere. MVFR cigs will be most likely to linger at UNV and IPT for the aftn as a weak trough forms in the lee of the Alleghenies. VFR follows for the overnight.

Outlook...

Fri...Mainly VFR. BFD may hold onto a MVFR cloud deck in the AM.

Sat...MVFR BFD and VFR elsewhere daytime. Showers NW night.

Sun...CFROPA. Widespread reductions in rain/snow. Windy.

Mon...Rain/snow showers poss N/W. Breezy west wind.

CTP WATCHES/WARNINGS/ADVISORIES
None.

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Port Deposit
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Thu -- 01:34 AM EST     Moonrise
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