Rochester, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

065
FXUS61 KGYX 031457 AAA
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1057 AM EDT Sat May 3 2025

.SYNOPSIS...
A cold front will slowly move across the forecast area today,
bringing another round of showers and thunderstorms. Some of
these thunderstorms may be strong to severe, capable of
producing gusty winds and hail. The front stalls along the
coast this evening, continuing unsettled conditions into early
next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update...Minor changes to reflect latest observational trends.
Warm front lifting into the area is forcing some showers along
it as it moves northward. Otherwise it will mainly be rain
moving into the mountains before convection takes off this
afternoon south of the warm front.

Previous Discussion...
Fog in valleys and more widespread into central ME will retreat
to the coastal waters shortly after sunrise. Here, it may lurk
just offshore or on the islands/peninsulas through the evening.
All in all, daytime mixing should make short work of it inland
and along the land/sea interface.

The main focus today will be a cold front and associated mid-
upper trough providing forcing/lift for shower and thunderstorm
development this afternoon into early evening. After assessing
consistency and latest guidance trends, the SPC Marginal Risk
area was expanded, with the introduction of a narrow Slight Risk
area into southern NH. Gusty to damaging wind and hail will be
the primary threats today, but all hazards are possible given
available parameters today.

After valley fog dissipates this morning and scattered mid
clouds pass, rapid daytime heating is expected ahead of the
front. This brings surface temps quickly towards yesterday`s
highs in the upper 70s for southern NH. Due to less low stratus,
warm temps also spread into interior ME, albeit a few degrees
cooler. Destabilization takes place late morning, with more
robust convection initiation early this afternoon for parts of
central/southern NH, and then interior ME.

Today`s limiting factor will be buoyancy and mid level lapse
rates, but these arent at deal breaker values by any means.
Convection opportunity is fairly narrow both spatially and
temporally, bounded to the northwest by the impinging cold
front, and to the east along the coast by low level stability
from the marine layer.

SBCAPE values through late morning and mid afternoon have
varied, but shown good consistency in areal coverage for
southern NH, parts of central NH, and into SW ME and the Lakes
Region. This lays out the general area for thunder chances by
Sat afternoon. Greater values of CAPE have been more consistent
near the NH/MA border, encompassing mainly the Monadnock region
and Merrimack Valley. Low level lapse rates of 7-8 c/km mirror a
similar footprint, supportive of sustaining initial updrafts,
especially when paired with shear outlined below. As is typical
for the region, mid level lapse rates around 5-6 c/km are flat,
and not indicative of a more widespread severe event.

The environment will be well sheared in proximity to the slow
moving cold front. Beneath the mid level jet, 0-3km shear has
been consistent across NH and ME with values of 35 to 45 kt, and
this exists in deeper layers too. Additionally, 0-1km shear of
around 20 to 25 kts will also be available generally along the
ME coast and into southern NH.

This combination of CAPE and shear should be ample to develop
and sustain single cell and mini supercell structures, with some
CAMs hinting at evolution towards a linear storm mode nearing
the NH Seacoast and southern ME coast this evening. This could
occur as the front nears the coast after a window of more
discrete shower/storm development ahead of it. Low level
vorticity is also a value to watch today, with enough to sustain
mesocyclones and a non-zero risk of low level rotation for a
brief tornado if instability/moisture allows.

Additional threat will be heavy downpours within these cells,
with a risk of minor poor drainage flooding if they begin to
train or track over the same location. Where the front slowly
tracks and allows repetitive development, rainfall amounts may
eclipse 1 inch across interior ME and NH through the early
evening.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
The window for convection and thunder should be waning early to
mid evening as the front nears the coast. This will leave a few
isolated to scattered showers for the overnight period before
another advancing cold front converges on remaining moisture
inland for Sunday.

Showers or periods of rain continue Sunday, mainly inland
towards the foothills. Any additional destabilization through
the day Sunday could promote shower development closer to the
coast and southern NH. It will be cooler Sunday as the region
remains under cloud cover. Highs only reach the mid to upper
50s, with some 60s possible near the NH/MA border.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
1040 PM Update...No major changes with the latest NBM guidance.
There will be chances for showers most days next week as a cut-
off low slowly tracks across the Ohio Valley into the
Northeast. The highest chances for widespread soaking rainfall
will occur late Tuesday into Wednesday as the low makes its
closest pass to New England.

Previously...

Pattern Overview: A 500 mb low will be slowly meandering
eastward from the Ohio Valley through our area, departing mid-
week. This along with a series of fronts, keeps clouds and
showers in the forecast. There is some uncertainty toward the
end of the week as the Euro suite shows another 500 mb low
swinging in right behind the departing one, but the GFS shows
nicer weather returning.

Impacts and Key Messages:
* No significant weather impacts expected.
* The area will see beneficial rain as low pressure brings
  rounds of showers through the weekend and at least the first
  part next week.

Details: Sunday: A wave of low pressure rides along a stalled
frontal boundary draped across the area Sunday. The latest hi-
res model suite is still uncertain on just how far south the
boundary makes it before stalling, with the NAM Nest continuing
to be the outlier that isolates showers to the coast. The tail
end of the HRRR and the RRFS are in the camp of the boundary not
making it much past the mountains. Will go with a consensus
approach, keeping at least a chance of showers across the area,
with more likely probablilites south of the mountains. Global
models remain in good agreement that high pressure building into
the area overnight Sunday pushes the front along, but it may
not clear the coast until early Monday. These showers look light
with some embedded heavier showers, but generally areas could
see another 0.25-0.50 inches with Sundays shower activity.

Monday and Tuesday: As mentioned above, light showers may
linger across southern New Hampshire into Monday morning as high
pressure continues to push a frontal boundary out of the area.
Ultimately, this brief nose of high pressure looks to keep
Monday mostly dry, but our proximity to the meandering 500 mb
low likely keeps skies mostly cloudy across much of the area.
High temperatures may not make it out of the 50s with the
increased cloud cover, and as such low temperatures only bottom
out in the 40s. As high pressure slides eastward overnight
Monday and the first part of Tuesday, this will allow the
vertically stacked low pressure to begin moving toward our area.
There are some subtle differences in timing, but the trend has
seemed to hold steady with the more widespread showers holding
off till later on Tuesday. Skies remain cloudy through the day
so high and low temperatures remain very similar to Monday.

Wednesday-Friday: Low pressure moves overhead Wednesday, so
widespread showers look to continue into at least the first part
of the morning. How quickly showers exit is a point of
uncertainty in the model suites, but that is unsurprising at
this time range. Thursday and Friday are also a big question
mark as the Euro brings another upper level low into the area
right behind the one departing, and the GFS builds high pressure
in. For now the NBM probabilities seem reasonable with a chance
of showers through the day Thursday, then decreasing heading
into Friday.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Terminals in IFR/LIFR due to fog or low stratus
early this morning see improvement after sunrise. Fog likely
remains in vicinity of coastal terminals, over the coastal
waters. Rounds of SHRA and TS are expected this afternoon,
initiating in NH late this morning. These will mainly impact
LEB, CON, MHT, and PSM...eventually making it to the ME coast
for PWM and maybe RKD. These push off the coast this evening,
with more isolated SHRA overnight. There is a lot of
uncertainty on ceiling conditions this evening and overnight,
but generally expect MVFR to continue in most locations, with
some IFR in southern NH.

Long Term...Some improvement may be seen Monday, but widespread
MVFR ceilings are likely through Tuesday. Tuesday night is when
conditions go back downhill again with a mix of restrictions
likely as widespread showers return. Improvement is expected
again on Wedensday, but the timing is more uncertain. Generally
winds look light with gusts less than 15kts.

&&

.MARINE...
Short Term...Conditions remain below SCA today and tonight, but
impactful weather arrives in the form of strong thunderstorms
approaching the coast this evening. These may contain periods of
strong erratic winds and hail. Fog persists much of today,
potentially becoming more patching tonight as a cold front
stalls over the waters. This lingers on Sunday, with continued
showery/foggy conditions.

Long Term...Wind gusts and wave heights are below SCA criteria
in this forecast period as high pressure slides over the waters
on Monday. Winds are generally northeasterly through Monday with
a brief wind shift as a front moves over the waters on Sunday.
As high pressure moves over the waters Monday evening winds will
shift around more onshore through Wednesday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$

NEAR TERM...Legro
SHORT TERM...Cornwell
LONG TERM...Baron/Schroeter