textproduct: Gray - Portland

WHAT HAS CHANGED

Minor update to the Aviation section for the 00Z TAFs.

KEY MESSAGES

1. Cool, dry air mass remains in place through Tuesday. There will be potential for both a hard freeze and elevated fire weather conditions.

2. A moderating pattern returns for mid to late week, along with a few chances for precip.

3. As temperatures warm, fire weather concerns increase between rounds of precip for Thursday and Friday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Temps in the 40s but very cold dewpoints are allowing much of the precip this afternoon to remain snow or at least a snow/rain mix. I have opted for allowing snow below 40 degree wet bulbs in the weather grids. Snow and rain showers will continue but steadily dissipate with the loss of daytime heating. Then ridge axis settles over the Northeast tonight. As it gets clear and calm temps will plummet in a dry air mass. A widespread hard freeze is expected tonight. Any early plant growth or sensitive vegetation should be protected. Not much heating is expected Tue, maybe a couple of degrees warmer than today. However, it will be very dry. Forecast soundings suggesting easily mixing thru 850 mb during the afternoon, which would tap single digit dewpoints aloft. I have blended those mixed down dewpoints with NBM guidance to produce a dewpoint forecast mainly in the upper single digits. The result is widespread minimum RH between 20 and 25 percent, especially away from the coast. The good news for fire weather concerns is that winds will be quite light. It will get breezy with any sea breeze that forms, but dewpoints will also come up substantially behind that front. Finally a weak warm front will approach the area Wed. Some light precip is possible with the front and the cool and dry air mass will once again support snow or snow mixing in. If enough precip can occur before sunrise, there may also be light accumulations in places, especially on grassy surfaces.

KEY MESSAGE 2 DESCRIPTION...

A moderating trend gets underway on Wednesday as a warmer airmass follows the passing cold front on westerly flow. The warming airmass won't be evident with temperatures on Wednesday, as highs will be similar to Tuesday's, but will be noted by increasing dew points. Scattered showers will be possible Wednesday afternoon as a trough passes through New England. By Thursday, the warmth will be more evident as broad high pressure builds into the Northeast. Temps look to be about 10 degrees warmer on Thursday, with southern New Hampshire pushing back to near 60 degrees. Some scattered showers will be possible across central Maine as a trough lingers to the east of Maine, with drier and brighter conditions to the west.

Friday looks to be the driest day as the ridge axis crosses through New England, with temps climbing a few degrees warmer. Going into the weekend, a large low pressure system tracks through the Northern Plains, while high pressure across Atlantic Canada works to suppress moisture from this system toward the south and west of New England. Uncertainty remains on whether or not precip from this system will reach into northern New England, but the best chance to see showers would be across southwest New Hampshire. Just how much cloud cover and showers reach New England will determine how warm highs will reach each day. Should sunshine prevail, highs could easily find their way into the 60s to low 70s this weekend, while rainier solutions would keep highs limited to the 50s. So this remains an item to watch over the next few days

KEY MESSAGE 3 DESCRIPTION...

As conditions warm and showers depart, fire weather concerns do increase for Thursday and Friday. Thursday the driest conditions are likely confined to southern and western New Hampshire with chances for showers lingering across Maine. Breezy northwest conditions are also likely on Thursday. Then on Friday, dry conditions are likely across all areas, but with less breezy conditions. Uncertainty then increases into the weekend as a system brings precip toward New England, but may not manage to reach most of the region.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Mainly VFR through the rest of tonight through Tuesday. Ceilings lower to MVFR Tuesday night west to east into Wednesday morning.

Outlook:

Wednesday: Any lingering MVFR improves to VFR conditions.

Thursday - Friday: VFR conditions expected.

Saturday and Sunday: VFR most likely, but some showers and MVFR possible across western terminals.

MARINE

Offshore winds thru tonight becoming onshore Tue thru Wed. Winds and seas both look to stay below SCA thresholds. Areas of low clouds and fog may develop towards Wed morning as a warm front lifts across the Gulf of Maine. Conditions continue to look to mostly remain below SCA from Wednesday through the weekend. Weak low pressure departs the waters on Wednesday, then broad high pressure gradually builds across the waters through late week and into the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.