Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
712 am EDT Thursday Jul 30 2015
a cold front will approach the area on this afternoon and move
across the region tonight with showers and thunderstorms. An
upper disturbance will cross northern Maine on Friday. Another
front will push through the state on Saturday and Saturday night
with more showers and possible thunderstorms.
Near term /through tonight/...
7 am update: got rid of fog away from the coast as sunshine is
helping to burn it off. The fog along the coast should lift and
burn off by 12z or so. Hrly temperatures were adjusted to the fit the
latest conditions. Tweaked the pop grids to back up timing by an
hour with the 1st set of light showers later this morning.
A warm and very humid day on tap. It looks like any severe
weather threat will be confined to far northern and western Maine.
Storm Prediction Center has kept the region in a marginal risk for a few storms to go
severe. The threat overall appears to have lessened from what was
first analyzed 24 hours ago.
A cold front is forecast to move into western Maine late this
afternoon. Instability is available west/heating early today. Cape
potential of 700-1000 joules roughly across the north and west
today. 0-6km shear around 30 kts from 18-02z west/a nice jet streak
at the 700-500mb layer. Upper difluence is noted and can be seen
on the 00z upper air residing over Ontario and western New York state this morning.
This feature is forecast to shift to the this afternoon. Dewpoints
of 65-70 this afternoon west/precipitable waters of 1.7+ inches and a deep south-southwest
flow will pose a heavy rain threat. So, thunderstorm potential is
expected. The question is how organized will it be. Strong lapse
rates in the middle levels are there but appear to outrun the main
precipitation shield by late afternoon. So, storms that get going this
afternoon over the western areas look like will become less
organized as they move east due to a south-southeast flow in the llvls will that
will allow stability to hold on longer keeping down the organized
convective threat. Other factors against organized severe
potential is the total totals stay below 50 and showalter index
remains above 0 into the evening. Therefore, decided to go
west/enhanced wording for strong wind gusts and heavy rainfall for
the west and far northern areas and general thunderstorm wording
elsewhere. The coastal areas could actually see little in the way
of convection west/the marine holding on.
For tonight, scattered thunderstorms are expected to move east west/showers
leftover as the front crosses the region. The NAM and WRF model
both show a 2nd burst of precipitation across northern areas after
midnight west/some decent middle level lapse rates. There appears to be
some elevated cape(450 joules) in this region. Decided to keep a
mention of thunderstorms through about 3 am. It will remain humid. Model
soundings show moisture getting trapped in the llvls after midnight.
A light south-southwest flow is shown west/some partial clearing possible, fog
potential is there. Added fog to the forecast overnight.
Short term /Friday through Saturday/...
a 500 mb low will remain across Hudson Bay in Canada through the
short term period. Weak disturbances will move east across
northern Maine through the upper level flow during the period.
This will result in chances for showers or thunderstorms from time
to time especially by Saturday afternoon. High temperatures both
days will be in the middle to upper 70s north and lower 80s down
east. It will be cooler along the coast.
Long term /Saturday night through Wednesday/...
the 500 mb will will move to the south and east through the long
term period. Unfortunately this will keep an unsettled weather
pattern across the region through the long term period with
chances for showers through the period. Temperatures through the
period will be close to normal for this time of year.
Aviation /12z Thursday through Monday/...
near term: VFR at this time west/MVFR and perhaps IFR for a brief period this
morning. The best potential for this will be from khul down
through kbgr and kbhb. Conditions are expected to improve to VFR
later this morning into the afternoon. Rain showers and thunderstorms and rain showers expected
later this afternoon into tonight. Thunderstorms and rain showers will be most prominent
north of kbgr and kbhb west/gusty winds of 35 knots in some of the
stronger cells. Stratus and fog expected overnight west/IFR after
Short term: mainly VFR although we could see MVFR or even brief
IFR flight restrictions in any heavier shower of thunderstorm
activity through the period.
near term: a south-southeast swell has been observed on the waters of 3-4 feet
west/a period of 10-11 seconds. Expecting the swell to continue into
tonight. Winds will remain light today but are forecast to
increase west/the approach of the cold front tonight. 10-15 kts
sustained from south-southwest away from the intra-coastal zone. Kept wave
heights of 2-4 feet. Fog will hamper navigation through the evening
west/visibility below 1 nm.
Short term: winds/seas will remain below Small Craft Advisory
levels through the period.