Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/11/18
Area Forecast Discussion
National Weather Service Boston/Norton MA
1008 PM EDT Tue Apr 10 2018
.SYNOPSIS...
Drying out tonight into Wednesday, though low clouds, cooler
onshore flow lingers. Low pressure lifting into northern New
England will result in milder weather Thursday and especially
by Friday. A strong backdoor cold front will cross the region
sometime on Saturday with large variation in temperatures across
the region dependent on the timing of the front. Unseasonably
chilly weather anticipated Saturday night and Sunday with
scattered showers before widespread rain likely impacts the
region sometime Sunday night into Monday.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1015 PM Update...
Trend in the forecast remains on track for this evening. Spotty
showers across eastern MA are beginning to dissipate. Still
cannot rule out a sprinkle/flurry but expect little impact.
Focus then turns to the potential for fog development especially
for the eastern coastline. High pressure overhead has resulted
in light winds and clearing skies. Temperatures are beginning
to fall/radiate out across the region. A few locations are
already reporting fog where temp/dewpoint spread is low. Will
have to keep an eye to see how dense this fog will get. HRRR
shows vsbys dropping below 1/2 SM. However the more reliable
NARRE-TL is not as aggressive. Regardless they both pinpoint
the eastern half of MA in low vsbys. Will have to monitor this
area over the next few hours.
Previous Discussion...
Dry the remainder of the night with clearing across the
interior. However...very tricky sky/temperature forecast on the
coastal plain. Lingering low level moisture and very light winds
may allow low clouds and fog patches to develop overnight on
the coastal plain. Greatest risk across the eastern MA coast
with light onshore winds...but overall confidence is low.
As for temperatures...readings should drop well down into the
20s across the interior where skies should become mostly clear
along with light winds. Along the coastal plain...overnight
lows will likely range from the upper 20s to the middle 30s and
exact readings will be dependent on the extent of cloud cover.
As previous forecaster mentioned...low risk of patchy black ice
developing along the coastal plain so will have to keep a close
eye on temperatures overnight.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Wednesday...
Lingering low-level inverted trof boundary, convergent focus with
onshore easterlies, low clouds hang over E/SE New England early,
eroding with daytime mixing W to E. However clear W, high pressure
shifting S/E, will see E flow race into the interior before becoming
S (roughly getting to Worcester MA). Low level moisture beneath a
lingering colder airmass, well mixed up to H7, mix down drier air,
faster W winds with layer top around 25 mph, resultant scattered to
broken cloud decks up around 4-5 kft. Highs, leaned close to WRF-
ARW, capturing onshore flow, cooler. A blend with mean-preferred
guidance, highs near 50 CT River Valley, while down to low low 40s
along E MA coast. Dry forecast. Followed closely with HREF trends.
Wednesday night...
Daytime heating concludes, expect low clouds to erode, however mid-
high cloud increasing associated with a weak, diffusing cold front.
Strong dry punch associated with building heights ahead of a warm
frontal boundary approach for Thursday, kept PoPs low, confined to
the Berkshires, but can`t rule out shower activity into the CT River
Valley. Otherwise flow turning W. Dry forecast mostly.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...
* Milder Thu and especially by Fri afternoon with springlike temps
* Timing of strong backdoor front makes high temps quite uncertain
Sat but a spread of 30 to 40 degrees possible across the region
* Unseasonably chilly Sat night/Sun with scattered showers and even a
low risk for a bit of light icing across interior northern MA
* Widespread rain sometime Sun night into Mon...but timing uncertain
Details...
Thursday...
Low pressure over the Great Lakes will be moving east into northern
New England Thu. This will allow milder air to work into the region
on southwest flow aloft. While we should see clouds increase in the
warm air advection pattern...expect enough mixing to push highs well
into the 50s to perhaps even a few lower 60s. While the best
dynamics/forcing should remain well to our north...enough will
probably exist for a brief band of scattered showers to cross the
region. Increasing southwest low level jet will result in gusty
winds developing late in the day and into part of the evening.
Thursday night and Friday...
While a cold front will cross the region Thu night it will pretty
much just be a windshift. Upper level ridging over the southeast
will result in westerly flow and mild temperatures Friday. While a
spot shower or two can not be ruled out...mainly dry weather is
anticipated. Given 850T of at least +6C to +8C and westerly
flow...high temperatures should reach well into the 60s to perhaps a
few lower 70s. It is possible the gradient becomes weak enough that
sea breezes result in localized cooler temperatures along the coast
during the afternoon.
Saturday...
A very low confidence forecast on Saturday and the outcome will be
highly dependent on a very strong backdoor cold front. This front
will be driven southwest by an anomalously strong/cold high pressure
system in eastern Canada. A 6 hour change in timing will make the
difference between afternoon temperatures breaking 80 or falling
through the 40s. If you took the current model forecast highs
verbatim...it would suggest afternoon temps falling through the 40s
across eastern MA, while their pushing or exceeding 80 in the lower
CT River Valley. That does not really mean much at this point and
sometimes shallow cold air can surge down faster than models
suggest. While a slower arrival is certainly possible
too...probably would error a bit on the faster side given pattern
recognition and the magnitude of shallow cool air guidance is
depicting. Way too early to say for sure...but a large possible
outcome in temperatures exists along with a rapid change behind the
front.
Saturday night and Sunday...
Despite upper level ridging aloft an anomalous cold airmass will
likely ooze into southern New England. While all guidance indicates
rather chilly temperatures with east to northeast flow along with
the risk of some scattered light over running precipitation...the
ECMWF depicts a much colder scenario than the GFS/GGEM. While it is
probably overdone to some extent...can not rule out the low risk for
a bit of light icing across interior northern MA.
Sunday night and Monday...
Low pressure lifting northeast into the Great Lakes will result in a
period of widespread rainfall sometime Sunday night into Monday.
Uncertain how quickly we mix out the shallow cold inversion at the
surface...so temps are uncertain. Regardless...will have to watch
for some heavy rainfall given a decent low level jet/strong forcing
depending on the track of the system.
Tuesday...
Bulk of the heavy rain threat will probably be over...but there
might be a few showers on Tuesday.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...
Tonight...High confidence except low confidence across eastern
New England. Mainly VFR across the interior tonight.
However...low confidence on cigs/vsbys on the coastal plain
where trapped boundary layer moisture may result in the
formation of low clouds and fog patches. IFR conditions may
develop overnight but still quite a bit of uncertainty.
Wednesday...Moderate to high confidence. Morning, low-end VFR /
MVFR, possibly IFR holding along the E MA coast, while VFR
interior, warming. Onshore flow enhancing as CIGs mix. Looking
at E flow pushing across S New England, W, as SCT-BKN low-end
VFR CIGs emerge. Winds while pushing E shift S towards late.
Wednesday night...Moderate to high confidence. S flow
persisting with increasing low- mid CIGs from W, becoming SCT.
Only -RA chances along Berkshires early on, otherwise forecast
quiet.
KBOS Terminal...Low confidence. Main uncertainty is if we see
low clouds and fog develop overnight into part of Wed am.
KBDL Terminal...Moderate to high confidence in TAF.
Outlook /Thursday through Sunday/...Moderate confidence.
Thursday: Mainly VFR, with areas MVFR possible. Windy with
local gusts to 30 kt along the coastal plain late in the day.
Chance SHRA.
Thursday Night: VFR. Windy with gusts to 35 kt possible early on
the coastal plain.
Friday through Friday Night: VFR.
Saturday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA.
Saturday Night: Mainly MVFR, with local IFR possible. Breezy.
Chance SHRA, chance FZRA.
Sunday: Mainly MVFR, with areas IFR possible. Breezy. Chance
SHRA, chance FZRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...
Quiet boating weather throughout. Weak convergence boundary
across interior New England to persist, an E onshore flow
subsequent through midday Wednesday before shifting S ahead of a
weak diffuse cold front sweeping across the waters Wednesday
night. Perhaps a gust up to 20 kts, strongest with S flow ahead
of the cold front towards Thursday morning. Waves remaining
below 5 feet.
Outlook /Thursday through Sunday/...Moderate Confidence.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Seas up to 5 ft. Chance of rain showers.
Thursday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 13 ft.
Friday through Friday Night: Winds less than 25 kt. Local rough
seas.
Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas.
Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft. Chance of rain
shower.
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of rough seas. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Frank/Sipprell
NEAR TERM...Frank/Dunten
SHORT TERM...Sipprell
LONG TERM...Frank
AVIATION...Frank/Sipprell
MARINE...Frank/Sipprell
Area Forecast Discussion
National Weather Service Melbourne FL
906 PM EDT Tue Apr 10 2018
.UPDATE...
Tonight...Pesky front looks like it is finally starting to shift
southward based on northerly flow now occurring down through New
Smyrna Beach and Deland. Weak low pressure to the northeast will
continue to provide impetus for the front to shift southward, though
not that fast. Interestingly, the models have been regenerating
precip overnight ahead of the axis of a shortwave trough. There is
some lingering convection over the southern loop current, which the
HRRR has recently started to lift northeast into the area. Not
convinced of this scenario, but the trough looks strong enough to
warrant chance PoPs overnight. We`re probably looking at areas of
light-moderate precip developing, so haven`t included thunder. Have
kept thunder mention in the Gulf Stream though.
It will be a little cooler Wednesday morning, but cloud cover will
keep lows close to or a little above normal, upper 50s north and
upper 60s far south.
&&
.AVIATION...Extensive low stratus is anticipated behind a frontal
boundary that is sliding down the peninsula. Observations and
guidance support IFR, which should persist until sunrise or a little
after. Tightening pressure gradient on Wed will promote clearing by
late morning except maybe in the far south (KFPR-KSUA). Expect
northerly winds to gust to 20-25 knots by late morning/early
afternoon.
&&
.MARINE...
Tonight-Wednesday...The latest guidance continues to show northerly
winds increasing behind frontal boundary that will settle into the
northern Bahamas by mid morning on Wednesday. Expect wind speeds
around 20 knots and occasionally gusty to 25 knots. Therefore,
will make no changes to the current Small Craft Advisory that goes
into effect after midnight.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 2 AM to 8 PM EDT Wednesday for Flagler
Beach to Volusia-Brevard County Line 0-20 nm.
Small Craft Advisory from 5 AM to 8 PM EDT Wednesday for Volusia-
Brevard County Line to Sebastian Inlet 0-20 nm.
Small Craft Advisory from 5 AM Wednesday to 5 AM EDT Thursday
for Sebastian Inlet to Jupiter Inlet 0-20 nm-Sebastian
Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard County Line
to Sebastian Inlet 20-60 nm.
Small Craft Advisory from 2 AM Wednesday to 5 AM EDT Thursday
for Flagler Beach to Volusia-Brevard County Line 20-60 nm.
&&
$$
RL/AJC
Area Forecast Discussion
National Weather Service Marquette MI
736 PM EDT Tue Apr 10 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 424 PM EDT TUE APR 10 2018
WV imagery and RAP analysis indicated a mid/upper level ridge from
the sw CONUS through the nrn Rockies and Alberta with a downstream
trough from west of Hudson Bay into the Great Lakes. A shrtwv and
associated sfc trough was moving into nw MN. 280k-285k isentropic
lift (850-700 mb) ahead of this feature supported some light snow
over ne MN and increasing clouds from nw WI into wrn Upper Michigan.
Otherwise, diurnal cu had developed over the west along with
increasing high clouds.
Tonight, radar trends and short range models suggest that the area
of light pcpn will continue to progress into wrn Upper Michigan and
through the east overnight. With only weak to moderate dynamics and
marginal moisutre available as the system moves into the dry
airmass, any snowfall amounts should remain at or below a half inch.
There may also be a brief period of patchy fzdz over the west half
before the pcpn ends as the deeper moisture departs. Thicker clouds
over the area will keep min temps in the mid to upper 20s.
Wednesday, mid level and sfc ridging building quickly into the area
will bring clearing skies and relatively light winds. Plenty of
sunshine and 850 mb temps around -6C will allow temps to climb
closer to seasonal averages with highs in the lower 40s north to the
mid and upper 40s south.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 307 PM EDT TUE APR 10 2018
Moderating west to northwest flow aloft will gradually be replaced
by strong upper level troughing for the upcoming weekend. Clipper
low pressure system drops through the Upper Great Lakes Wed night
into Thu morning. Swath of moderate to possible heavy precipitation
is expected on the nose of upper jet moving out of the northern
Plains. Decent agreeement that most of the heavier precipitation in
form of wet snow and possible freezing rain/sleet would be over
south central with light snow over north and east. Want to start
messaging this as the Thursday morning commute could be hazardous
especially over the south central (eg. Iron Mountain, Escanaba and
Menominee).
Friday into the weekend remains a low confidence, but potentially
high impact winter system. Looking at the recent models and
ensembles there seems to be at least fair agreement in two main
phases of the weekend system evolution. First, Fri and Fri Night
expect widespread west to east oriented swath of moderate to heavy
snow from northern Plains to the Upper Great Lakes. Some of the
deterministic models indicate total qpf over 1.5 inches within axis
of heaviest precipitation. Primary upper low and sfc low will
still be well upstream over the central Plains by 12z Sat so most
of the this initial snow will be driven by frontogenesis in the
right entrance region of upper level jet northern Ontario to
Quebec. As such, this intitial snow could easily be influenced by
large high pressure/dry air just north of the fgen area with
expected northeast winds feeding in dry air to the north of the
system. We have seen similar systems recently that resulted in a
sharp northern edge to heavier snow. This will be important thing
to watch with this system as well.
On into Sat and Sun, more complications/uncertainties are present
with next phase of the slow moving winter weather system. There are
differences on how quick main upper low and sfc low will shift from
the central Plains to the western Great Lakes. Model differences are
quite striking with Sat/Sat night with recent runs of the GFS and
associated GFS ensembles pointing to another round of moderate to
heavy snow, while recent runs of the ECMWF indicate some areas of
Upper Michigan may not see *any* snow. In fact, 12z ECMWF keeps all
but far scntrl dry Sat and Sat night as it delays main system from
ejecting out of the Plains until later Sun into Mon. Even during
that time, the ECMWF is not as aggressive in bringing heavier
qpf/snow to as much of Upper Michigan as it had showed in previous
model runs. These sharp differences and poor model continuity make
it tough to have any confidence with details for the weekend. In
addition to the snow, system could also produce strong winds and
blowing/drifting snow, in addition to high waves/lakeshore
erosion.
Main points for everyone is to keep monitoring the weekend system as
we get close to the weekend. Also, don`t take eye off the Wed night
into Thu morning system as the wet snow and some freezing precip
could result in issues for the Thursday morning commute. Overall
it is going to turn certainly more active than its been recently.
Also there appears to be no real significant change from the
ongoing winter pattern, at least for the next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 719 PM EDT TUE APR 10 2018
Tonight, an approaching disturbance should bring MVFR cigs to all
sites beginning late evening at KIWD and KCMX and overnight at
KSAW. Although areas of light snow are likely, little or no vsby
reduction is expected. Conditions should then improve to VFR by
mid to late morning Wednesday. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 424 PM EDT TUE APR 10 2018
southwest winds are expected to strengthen across all of Lake
Superior into early Wednesday, but should remain in the 15 to 25
knot range. As a strong low pressure system slides through the area
Friday through the weekend, winds will increase across the area with
gales of 40 to 45 knots possible through Saturday night.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JLA
AVIATION...Voss
MARINE...JLB
Area Forecast Discussion
National Weather Service Spokane WA
854 PM PDT Tue Apr 10 2018
.SYNOPSIS...
Periods of rain and mountain snow are expected Wednesday through
next weekend...with unsettled and occasionally showery break
periods between the wetter systems.
&&
.DISCUSSION...
Evening update: Forecast has been updated to adjust POP`s this
evening based on radar trends, and to slow down the arrival of
incoming precipitation on Wednesday.
GOES-16 Water Vapor Satellite this evening shows a mid level wave
tracking across NE Washington. Earlier thunderstorms developed
south of Highway 2 and north of I-90 in the Columbia Basin before
tracking east this evening into the Davenport, Spokane, Deer
Park, and Diamond Lake areas. HRRR shows this area of showers
gradually fizzling out as it approaches the ID/MT border but still
should have enough left of it to give showers to Sandpoint, Clark
Fork, and maybe as far south as Coeur d`Alene. Meanwhile a
secondary band of showers from the Camas Prairie to southern
Shoshone county will continue to slowly move east tonight.
For Wednesday afternoon and evening, models have trended slower
with incoming precipitation, reaching the Cascades noon-2pm, the
basin 4-8pm, and not until the overnight hours for N Idaho.
Forecast has been updated to lower POP`s for nearly all of Eastern
WA/N Idaho Wednesday afternoon, as well as into the early evening
hours over N Idaho. Current timing may still be a little fast and
will let mid shift take a closer look at this. JW
&&
.AVIATION...
00Z TAFS: A band of showers has shifted into SE Washington and the
Idaho Panhandle late this afternoon with additional showers
developing from afternoon heating around KMWH. HRRR shows these
showers dissipating before reaching Spokane area TAF sites this
evening. There is a slight chance of thunderstorms with this
activity but with only marginal instability for thunderstorms did
not mention them for any of the TAF sites. These showers will
dissipate after sunset. The next weather system approaches Central
WA with increasing mid and high clouds on Wednesday with an
increase chance for light rain late in the TAF period at
KMWH/KEAT. CIGS are expected to remain VFR except KCOE which
should see MVFR conditions at times into Thursday morning. JW
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 38 54 37 50 32 50 / 60 10 90 20 10 40
Coeur d`Alene 38 52 37 47 31 48 / 40 10 90 40 20 40
Pullman 39 54 36 47 33 50 / 10 10 90 30 20 30
Lewiston 43 60 41 53 37 57 / 50 10 90 20 10 20
Colville 37 54 37 53 31 53 / 20 10 80 50 10 40
Sandpoint 35 50 36 45 31 47 / 60 10 90 70 20 50
Kellogg 34 49 34 42 30 45 / 20 10 100 80 30 30
Moses Lake 40 58 39 58 35 59 / 0 40 50 10 10 10
Wenatchee 40 52 37 55 37 57 / 10 50 40 10 10 20
Omak 38 55 38 56 34 56 / 0 30 70 10 10 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$