Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
341 FXUS61 KGYX 240000 AFDGYX Area Forecast Discussion National Weather Service Gray ME 700 PM EST Sat Nov 23 2024 .SYNOPSIS... Low pressure will slowly move NE through the Canadian Maritimes through Sunday night. High pressure briefly builds in for Monday. A quick hitting system crosses Tuesday bringing wintry precipitation across the north and mainly rain south of the foothills. Brief high pressure crosses southern New England late Wednesday into Thursday. The next low pressure system tracks from the Ohio Valley towards New England late Thursday into Friday. && .NEAR TERM /THROUGH SUNDAY/... 7:00pm Update... No notable changes with this update as the forecast remains on track. Upslope snow showers continue north of the mountains, while brief isolated sprinkles and flurries continue south of the mountains. Winds remain gusty, and will only ease slightly through the overnight hours. Previous... Moist easterly flow has largely been confined to the upper levels across the forecast area. Closer to the surface winds have turned northwesterly and downsloping is already occurring southeast of the White Mtns. Overcast is breaking up across NH...and that will slowly creep northeast into ME this evening. Rain will be most likely near Penobscot Bay...closer to the main forcing from the low pressure over Nova Scotia. Upslope showers will also be likely along the northwest facing slopes of the higher terrain. Otherwise I do not anticipate much more than a sprinkle or flurry downwind of the mtns thru the overnight. Winds remain breezy to occasionally gusty overnight so I have blended in raw 2 m temps to keep min temps up slightly. && .SHORT TERM /SUNDAY NIGHT/... The region will remain under the influence of Maritime low pressure Sun. Forecast winds at 925 mb are fairly similar to today...but perhaps we get a little deeper mixing Sun. The result will be more widespread and more consistent gusts up to 30 or 35 mph. The deeper mixing will also allow inversion to lift above the ridgeline and Froude numbers are forecast to approach at least 2. I expect some upslope precip to hold together downwind of the mtns. However I do not expect it to be very heavy...so I have mainly added sprinkles/flurries. The low levels are fairly dry so wet bulb temps will be pretty close to freezing. I suspect more flurry than sprinkle out of any upslope precip. CAA will continue on the backside of low pressure. A steadily falling temp is expected Sun night. Once again I blended raw 2 m temp guidance into the min temp forecast to prevent any radiative effect from showing up. && .LONG TERM /MONDAY THROUGH SATURDAY/... Overview: Confidence is increasing in the development of an upper level flow pattern that will deliver cold air into the central and eastern CONUS starting around the middle of next week. Recent runs of global ensembles have been showing strong ridging building from eastern Siberia across Alaska into western Canada associated with a -WPO and -EPO. Meanwhile, the NAO is projected to turn more negative the second half of the week favoring a storm track along the East Coast. Before the aforementioned pattern comes to fruition, northern New England will be poised to receive widespread precipitation from a short wave swinging across the region Tuesday. Colder air will move in behind this system with global models suggesting a more robust system tracking near the Northeast coast around Friday. This late week system will involve the phasing or non phasing of northern stream and southern stream energy leading to large variance and uncertainty in model solutions. Impacts: *Wintry precipitation in the foothills to points north could bring slick travel Tuesday. *Low pressure tracking near the Northeast late Thursday and Friday could bring wintry precipitation to the region. Large variance and uncertainty with this system will likely continue for several days, but there is potential for impacts to travel during a time of high travel volume. Details: Low pressure in the Canadian Maritimes lifts northeastward Monday morning with a short wave ridge moving into New England Monday evening. This will allow for fair weather with decreasing winds. Highs on Monday will range from the mid 30s north to upper 40s south. A short wave trough swinging through the Great Lakes Monday night will spawn a surface low that tracks towards the St Lawrence Valley Tuesday. Several models solutions within the 12Z suite suggest a secondary coastal low will spin up in the Gulf of Maine Tuesday. Overall, this looks to be a quick hitting system with QPF around 0.5 inches. On the other hand, precipitation types are tricky depending on how cold the area can get Monday night and the timing of precipitation onset Tuesday morning. Model soundings suggest that areas from the foothills northward could see a period of wintry mix Tuesday morning around the time of the morning commute with mainly rain along the coastal plain. Depending on the strength of the coastal low, temperatures will rise above freezing south of the mountains Tuesday morning with rain becoming the dominant precipitation type. This system exits Tuesday night with upslope snow showers continuing in the mountains into Wednesday morning. High pressure slides across southern New England late Wednesday and Thursday morning for mostly dry conditions. Global models and their ensembles suggest a robust area of low pressure will track from the Ohio Valley to the East Coast late Thursday and Friday. One of the sources of this system is currently offshore the Pacific NW and the other can be traced back to the Bearing Sea. The phasing or non phasing of these features has produced run to run and model to model variance in this system. Ensembles loosely cluster a track along the southern New England coastline that would favor widespread wintry precipitation across the area centered on Thursday night into Friday. It will likely take several days to iron out the evolution of this system, but it will be one worth watching giving the elevated travel around the holiday. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... Short Term...CIGs continue to improve for most areas as winds become northwesterly. There remain areas of MVFR CIGs...but these are largely expected to lift or scatter out this evening. The one exception will be northwest of the mtns into the Upper Valley...where upsloping winds will keep MVFR CIG possibly thru Sun. SHRA/SHSN are most likely around HIE thru the overnight...and local IFR is possible if ptype is mostly SN. Surface gusts around 25 kt are expected at all terminals thru Sun...except at HIE where cloud deck will limit mixing. Long Term...Mainly VFR Monday into Monday night. Cigs thicken and lower early Tuesday morning with a brief wintry mix possible from KLEB to KAUG and points northward before changing to rain with all rain across the south. This will likely result in MVFR to IFR Tuesday. Conditions improve Tuesday night into Wednesday with VFR likely into Thursday. && .MARINE... Short Term...Gusty winds continue over the coastal waters thru most of the evening Sun. Low end gale force gusts over most waters will continue into Sun. The exception will be Casco Bay where fetch is just not long enough and winds not strong enough to generate consistent gale force gusts. Winds begin to diminish later Sun...but SCA conditions linger over all waters into Mon morning. Long Term...NW winds likely continue SCA conditions Monday morning with winds and seas dropping below SCA thresholds Monday afternoon into Tuesday morning. Low pressure tracking west to east across New England into the Gulf of Maine will bring a return of SCA conditions Tuesday into Thursday morning. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning until 6 PM EST Sunday for ANZ150>152-154. Small Craft Advisory until 6 PM EST Sunday for ANZ153. && $$ NEAR TERM...Clair SHORT TERM...Legro LONG TERM...Schroeter