textproduct: Baltimore/Washington

WHAT HAS CHANGED

No major changes were made to the previous forecast.

KEY MESSAGES

-1) Temperatures warm through the weekend with a cold front bringing showers and a chance for severe thunderstorms late Sunday.

-2) Quiet weather and cool temperatures through Wednesday before a cold front brings renewed rain chances late week.

DISCUSSION

KEY MESSAGE 1...Temperatures warm through the weekend with a cold front bringing showers and a chance for severe thunderstorms late Sunday.

Skies have cleared out across most of the forecast area this afternoon in the wake of a cold front that passed through this morning. Just a few fair weather cumulus clouds remain, mostly tied to terrain circulations that have formed over the mountains. Northerly flow behind the front has advected cooler, but still well above average temperatures into the area. Temperatures are nearing their highs for the day in the 60s to lower 70s (50s mountains).

Winds will shift to out of the east this evening, and then south later tonight. As low-level moisture starts to increase within southerly flow, there are some hints that low clouds and/or fog may try to form later tonight, especially to the east of the Blue Ridge. Temperatures will remain mild overnight, with lows in the mid 40s to mid 50s.

Any low clouds or fog should burn off quickly tomorrow morning. Much warmer air will advect into the area tomorrow in southwesterly flow aloft, with 850 hPa temperatures surging to around 14-17 C. Strong daytime heating will lead to deep mixing, enabling temperatures to near record values for late March. Most of the forecast area should climb into the 80s, with some locations potentially even making it into the mid-upper 80s.

A strong cold front will start to progress southward across PA during the afternoon hours tomorrow. Showers and storms are expected to develop along the front during the mid-late afternoon hours. Further south, model soundings show signs of capping with a remnant elevated mixed layer moving in aloft. This should help to prevent the development of storms ahead of the front, which will keep conditions dry through nearly all of the day in our forecast area. The storms over PA will likely drift southeastward toward northern Maryland around or shortly after dark. As low- levels stabilize with loss of daytime heating, the trend should be for these storms to gradually weaken as they move into our forecast area after dark.

The environment to our north tomorrow across PA looks very favorable for the development of severe thunderstorms, with a CAPE/shear parameter space capable of producing both supercells and bowing segments. If the timing/location of the front were to trend faster/further south, we could get storms in that type of environment prior to stabilization. And even if storms do move in after dark, they could still potentially produce severe hail, even if they're elevated. Tomorrow is certainly a day to watch for severe thunderstorms, but as it stands now, it may be a near miss for most of the area, with the capping serving as a potential saving grace.

As of now, SPC has northern Maryland and most of the eastern panhandle of West Virginia outlooked in a Slight Risk, and the rest of the area outlooked in a Marginal Risk. SPC also has far northwestern portions of the forecast in a sig hail outlook (indicating the potential for 2+" hailstones). That hints at the potential high ceiling for the severity of storms tomorrow, if they maintain their strength southward into our forecast area. As of now, the most likely timing for storms looks to be between 7 PM and Midnight, with remnant showers moving southward along with the cold front through the entire forecast area later during the overnight hours.

Winds will shift to out of the northwest behind the cold front on Monday. Conditions will dry out and temperatures will be much cooler (but near normal), with highs for most in the 50s and lower 60s (40s mountains). Winds will gust to around 25-35 mph out of the northwest.

KEY MESSAGE 2...Benign weather is likely during mid week before a cold front brings higher rain chances Thursday night into Friday.

High pressure will build overhead Tuesday before moving off to the east Tuesday night and Wednesday. Dry weather will prevail through this period beneath west-northwest flow aloft. Below normal temperatures on Tuesday will moderate Wednesday as low level flow turns southerly.

A warm advection pattern continues Wednesday night and Thursday. A subtle shortwave may cross around this time and aid in the chance for some light showers. However, dry low levels may limit how much rain can reach the ground. The best forcing will remain along the St. Lawrence Valley as a surface low crosses. It's possible this low may shove the frontal zone southward or stunt it from lifting northward. A slightly deeper trough will follow with another low tracking along the front around Friday. The front will sag southward as a cold front , but not too quickly as it will be somewhat parallel to the upper flow. Thus timing and amounts of any rain are uncertain although it does look to push south Saturday. The position of this potentially wavering frontal zone may have some impacts on temperatures Thursday and Friday, though they should be near or above normal.

By Saturday, high pressure of Canadian origin will be building in from the northwest, bringing a return to near to below normal temperatures.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

VFR conditions and light northerly winds are expected this afternoon. Winds will shift around to out of the east this evening and then south by later tonight. There are some signs that low clouds and/or fog may try to form late tonight at many of the terminals. For now, TAFs have been kept MVFR, but IFR CIGs are hinted at with a scattered group. Any low clouds or fog should quickly burn off tomorrow morning, leading to VFR conditions once again through much of the day tomorrow. Winds will gradually pick up out of the southwest, and could gust to around 20-30 knots during the late afternoon and evening hours.

A cold front will approach from the north tomorrow night. As that cold front drops southward tomorrow night, winds will become northerly behind the front, and chances for showers and a few thunderstorms will increase. Sub-VFR ceilings and visibilities may both be possible at times tomorrow night. Any precipitation should come to an end by daybreak on Monday, but winds will remain gusty (25-35 knots) out of the northwest during the day Monday.

Significant weather is unlikely Tuesday and Wednesday as high pressure builds across the area. Southerly winds may gust to around 20 kt on Thursday as a low pressure system passes well to the north. Locally rain chances will remain minimal.

MARINE

Sub-SCA level northerly winds are expected over the waters this afternoon. Winds switch around to the east this evening, and then south later tonight, but remain sub-SCA in nature. Winds gradually pick up out of the south to southwest through the day tomorrow, and could reach low-end SCA levels by the late afternoon/evening hours. However, warm air moving over much cooler waters could limit mixing and resultant wind speeds, especially over the wider waters.

A strong cold front will move over the waters tomorrow night, causing winds to shift to out of the north. Showers and a few thunderstorms may accompany the frontal passage tomorrow evening into tomorrow night, with the best chance for storms across northern portions of the Bay. SMWs may be needed tomorrow evening into early tomorrow night as storms move over the waters. Chances for precipitation will come to an end by daybreak Monday, but winds will remain gusty out of the northwest through the day. SCAs will likely be needed Sunday night through the day Monday.

High pressure will provide light winds Tuesday. Southwest winds may begin to increase Tuesday night into Wednesday as the high departs. However, advisory level winds may hold off until Wednesday night into Thursday as a low pressure system passes well north of the area.

LWX WATCHES/WARNINGS/ADVISORIES

DC...None. MD...None. VA...None. WV...None. MARINE...None.