Area forecast discussion
National Weather Service Gray ME
1218 am EDT Friday may 24 2013
Synopsis...
a cold front will slowly cross the region tonight will stall off
the coast on Friday. Low pressure will develop on the front south
of Cape Cod Friday night and slowly move north through the Gulf of
Maine through Sunday morning. Low pressure will continue north
through the Maritimes Sunday night. High pressure will build in
from the west Monday and will shift offshore on Tuesday. A warm
front will approach from the southwest on Wednesday.
&&
Near term /until 9 am this morning/...
1205 am...just a quick update to adjust probability of precipitation and temperatures a bit
overnight...and to focus on best ch of heavier downpours in the
06-13z time frame as 500 mb sh combines with middle-level jet and high
precipitable waters ...approaching 200% of normal com to together to produce a
surge of heavy rainfall...which will develop after midnight and likely
affect morning commute. 00z nam12 and latest hrrr focus the bulk
of the precipitation closer to the coast...where the ground can handle it
better. However...could cause some localized problems...ponding on
the roads and in urban areas.
Update...
have updated grids based on current conditions. Radar continues to
show areas of showers and isolated thunderstorms over the northern mountains where we
have issued an areal Flood Advisory. Over southern New Hampshire...the echoes continue to
weaken as they head north...despite a precipitable water level
axis of 1.6" over the region.
Latest hrrr run continues to show precipitation streaming in from the south
overnight...along and ahead of approaching cold front. Categorical
probability of precipitation will remain in the grids overnight with patchy/areas of fog.
Expect around an inch or so of rainfall over the coastal areas
which remains well below flash flood guidance.
Previous disc...
cold front approaching from the west will make for a wet and
breezy night across the region. Scattered showers and some
thunderstorms will gradually change to a widespread rain overnight
as the front slowly crosses the area. Expect thunderstorm activity
to be mainly confined to New Hampshire late this afternoon and
this evening as marine layer persists across most of Maine. Can't
rule out a rumble of thunder overnight but should be isolated and
have not included this in the forecast after this evening. Expect
overnight lows to be uniform across the region with most areas
dipping into the middle 50s to near 60.
&&
Short term /9 am this morning through 6 PM Saturday/...
front will stall just off the coast on Friday with rain continuing
through the day across the forecast area. Not expecting
temperatures to move much from overnight lows with most locations
only reaching the upper 50s to lower 60s. Rain continues Friday
night as low pressure tracks north along the front. Focus will
turn to area rivers in northern zones where storm totals could
will fall in the the 2 to 4 inch range by late on Sunday.
&&
Long term /Saturday night through Thursday/...
cutoff and surface low will drift slowly NE through the weekend
continuing prcp across the forecast area with the potential for heavy
rainfall. Models showing maximum quantitative precipitation forecast across the north/Montana zones to western New Hampshire
zones. GFS much higher on quantitative precipitation forecast...with other models preferred. Used
HPC quantitative precipitation forecast for a compromise. Cutoff and surface lows move NE of the area
Monday with improving weather...but still cool air and cyclonic flow
aloft along with fairly ample relative humidity could produce some clouds and
possible -shra even on Monday. For now will go with slight chance.
An upper level and surface ridge build in Tuesday finally bringing dry weather
with warming temperatures. An upper level short wave trough slides east through the
upper level ridge late Wednesday and Wednesday night...bringing isolated to
scattered rain showers to the region Wednesday night and Thursday.
Generally used blend of gfs40/NAM, met/mav & HPC quantitative precipitation forecast for days 4
and 5 then a blend of gfs40, gmos, mex/ece for the rest of the
long term forecast.
&&
Aviation /04z Friday through Tuesday/...
short term...IFR/LIFR ceilings/visibility tonight through Friday.
Long term /Saturday through Tuesday/...IFR/LIFR Saturday through much
of Sunday...improving to VFR with possible MVFR on Monday then VFR
Tuesday.
&&
Marine...
short term...Small Craft Advisory in effect through Friday tonight.
Long term /Saturday through Tuesday/...NE winds ahead of
approaching low and seas likely at Small Craft Advisory levels Saturday and may
need to extend the Small Craft Advisory through the day. Winds let up and back to the
northwest slowly Saturday night through Monday...likely dropping below Small Craft Advisory
levels by late Saturday night or early Sunday. Seas will be slower
to drop off. High pressure provides relatively calmer winds and seas
on Tuesday.
&&
Fire weather...
no problems noted.
&&
Gyx watches/warnings/advisories...
ME...none.
New Hampshire...none.
Marine...Small Craft Advisory until 8 am EDT Saturday for anz150>154.
&&
$$
Synopsis...
near term...cempa
short term...
long term...
aviation...
marine...
fire weather...
hydrology...
