Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/25/17
Area Forecast Discussion
National Weather Service La Crosse WI
620 PM CDT Tue Oct 24 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 248 PM CDT Tue Oct 24 2017
Afternoon satellite and surface observations show a stacked low
pressure system drifting eastward across the Northern Great Lakes.
This system has brought cloudy skies and strong northwest winds to
the local area today, with gusts approaching 40 mph. With the
surface pressure gradient weakening and winds no longer reaching
advisory criteria, Will canceled the wind advisory for the entire
area.
The main concern for tonight into Wednesday will be a vorticity/jet
streak streaming down from southeast Manitoba/southwest Ontario.
Associated low-level frontogenesis under the left exit region of the
300 mb jet streak should provide enough forcing to overcome a lower
layer of dry air and produce at least light precipitation east of
the Mississippi River from around 25.09Z to 25.15Z Wednesday. Model
soundings indicate below freezing thermal profiles with deep lift
and saturation through the DGZ and surface temperatures around 32F.
Therefore, snow is the expected precipitation type until diurnal
heating warms surface temperatures above freezing. Given the time of
year with regards to ground temperatures, do not anticipate much in
the way of snow accumulation, but recent runs of the RAP are hinting
at weak banding potential.
The rest Wednesday should remain dry under partly to mostly cloudy
skies. Northwest winds will be gusty west of the Mississippi River,
but not as strong as today. Temperatures will remain near to
slightly below normal.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 248 PM CDT Tue Oct 24 2017
This looks to be a somewhat active period with the potential for
some light precipitation for much of the period. The northwest
flow aloft has become established over the region and this does
not look like it will be breaking down in the near future. After a
bit of short wave ridging Wednesday, this will quickly break down
as the next short wave trough drops southeast out of the Canadian
Rockies Wednesday night. This system will evolve into a closed
upper level low over the Upper Mississippi River Valley Friday
that will move slowly northeast across the Great Lakes into early
next week. The first chance for precipitation will arrive Thursday
afternoon and night in the warm air advection ahead of the system.
The 24.12Z GFS suggests up to 4 ubar/s of up glide on the 290K
isentropic surface as the system comes. Initially, most of this
goes into cloud production trying to saturate the column, but it
looks by late Thursday afternoon, this should be overcome for at
least a chance of some light precipitation across the northern
sections of the area. These chances will continue to drop south
Thursday night but may become more confined to areas east of the
Mississippi River as the isentropic upglide slides more over that
area. This could leave southeast Minnesota and northeast Iowa dry
for much of Thursday night. As the upper level low closes off over
the region Friday, a deformation band of precipitation will start
to form on the northwest side of the surface low. Some differences
between the models on where the surface low will be located, but
for the most part, they all agree that most of the area will have
at least a chance of seeing some of the deformation precipitation,
with the highest chances across the northern parts of the area. As
the surface low then starts to move slowly northeast away from the
area Saturday, it looks like the deformation zone should gradually
swing east across the entire area and then start to diminish from
west to east Saturday night into Sunday. Temperatures will be cold
enough at times for the precipitation to fall as a rain/snow mix
or as just some light snow. With the expected light nature of the
precipitation and warm ground surface, would not anticipate much
if any accumulation to occur.
By early next week, another system looks like it will move
dropping southeast out of Canada toward the Upper Midwest and
Great Lakes. There are some differences between the 24.12Z ECMWF
and GFS on just how far south this system will get before turning
more to the east. For now, will just a some small chances for
precipitation across much of the area for Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 620 PM CDT Tue Oct 24 2017
Clear skies and breezy northwest winds this evening will be
short-lived as a band of VFR ceilings currently across ND/northern
MN dive southward overnight. Expect cloud bases in the 6000 to
8000 ft agl layer with winds decreasing a bit and shifting to the
west-southwest. Some light snow is possible tonight, but
expecting it to be mainly north and east of KLSE, so will keep
TAFs dry. Periods of VFR clouds will continue through the day on
Wednesday with modest northwest wind, gusting at times to around
20 kts at KRST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...MH
LONG TERM...04
AVIATION...Rogers
Area Forecast Discussion
National Weather Service Taunton MA
954 PM EDT Tue Oct 24 2017
.SYNOPSIS...
A north-south line of widespread rain with embedded heavier showers
and isolated thunderstorms will gradually sweep E across S New
England through Wednesday night. With any heavy rain there is a
flash flood threat. Another round of showers expected Thursday as
a strong disturbance moves across the region. High pressure returns
Friday and Saturday with dry and seasonably mild conditions, then
more rain and wind is possible late Sunday into Monday as another
system approaches from the west.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
10 pm update...
South to north training of heavy rain along a slowly eastward
moving occluded front will present a flash flood threat through
the overnight hours. Strong low-level-jet deciphered from latest
vertical wind profilers ushering sub-tropical air N, squeezed
between an occluded front to a bombing low over the Great Lakes
region and a high pressure gyre across the NW Atlantic. SPC meso-
analysis highlighting precipitable waters up to 1.7 inches that
is maintained by strong moisture transport within the low-levels
and deep moist convergence along the front. High freezing level
heights, seeing the measure of lift along the front contributing
to efficient warm-rain processes as well as cloud tops reaching
25-30 kft agl. Conditionally unstable profile as discerned from
0z soundings enabling instability of around 250 J/kg in a region
of 0-1 km shear and helicity that promotes bowing segments and
storm-cell rotation, several threats continue in the way of
strong to damaging winds and flash flooding.
Following closely to latest high-res guidance, but believe that
both the HRRR and the RAP are moving things a bit too quickly.
The frontal boundary is squeezed between airmasses that are
slowly juxtaposition per WV satellite, holding their place more
or less or getting stretched out.
Growing concern that we are in for a long night of flash flooding
that will result in dangerous conditions with homes becoming
inundated, potential for water rescues. Very anomalous situation
that warrants to expect the unexpected.
Widespread 1-inch rainfall amounts with locally heavier outcomes
with any S to N training with anticipated rain amounts of 2 to 4
inches, some of that occurring in a short period of time far
exceeding flash flood guidance which is presently around 2 to 3
inches for the 1-hour and 3-hour timeframes.
Forecast wind gusts averaging around 25 to 35 mph, but within
the heavier rain cells anticipating gusts to exceed 40 mph
possibly up to 50 mph.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Wednesday...
As the front lines up parallel with the long wave upper flow
from S-N, the cold front continues its very slow trek across
eastern areas during the day Wednesday. There is the possibility
of the front stalling during the afternoon. This will keep
moisture feed working across eastern Mass and RI, while the
rains slowly lessen further W. Good instability continues early
Wed morning with LIs down to around -1 and TQ values in the
upper teens so kept mention of thunderstorms through about mid
morning Wed. However, will still see showers falling heavily at
times through the day, possibly with some locations seeing up to
1"/hour rainfall rates.
Drier air starts to work into western areas as PWATS fall
quickly behind the slow moving front. Also, the low level jet
also shifts E with the front, so while S-SW winds continue, they
will diminish by mid to late morning Wed. Across eastern areas,
gusty winds continue as well as threat for heavy rainfall at
times. There is the potential of another 1-2 inches of rain to
fall, possibly higher in localized heavy downpours.
Back edge of best moisture will slowly push off the coast late
Wed afternoon as higher PWAT air moves offshore, but scattered
showers will linger even into western areas through the day.
Temps will be turning cooler across the west with highs in the
lower-mid 60s, with readings ranging to the upper 60s across
eastern areas.
Wednesday night...
Big question during this timeframe is whether the front clears
the coast or lingers through the night which will keep the
potential for at least light rainfall across eastern areas. The
outer Cape and Nantucket may see another inch of rain early Wed
night. Also some question as to whether another weak low forms
along the front, again enhancing the potential of rain across
the east.
At this point, it looks like that the low may actually push the
front along, but will linger across E coastal areas by around
daybreak Thursday. Have carried likely to CAT POPs across
central and eastern areas and CHC POPs over the west.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...
* Numerous showers and a few T-storms possible Thu
* Mainly dry and seasonably mild Fri/Sat
* Return to stormy conditions late Sun/Mon with more rain and wind
Overview...
High amplitude +PNA/-EPO pattern across the CONUS during the
extended period with anomalous ridging across the northern Pacific
coast and north Atlantic. This allows high amplitude trough to
reload across the central CONUS late in the week into next weekend.
Prior to this, the start of the extended period will feature
numerous showers as neg tilt trough and closed low lifts NE across
New Eng during Thu. Ridging becomes re-established off the east
coast late in the week into the weekend ahead of amplifying upstream
trough resulting in dry and seasonably mild conditions, then a
return to stormy weather is likely sometime Sun/Mon timeframe as
high amplitude trough lifts NE across New Eng. Timing and details of
potential wind and rainfall still uncertain at this time range.
Thursday...
Cold front will be moving offshore with any lingering showers
exiting the Cape/Islands in the morning. Otherwise, rather robust
negative tilt trough/closed low and assocd cold pool will lift
northward across New Eng. 500 mb temps cooling to -24C and
steepening mid level lapse rates combined with deep column moisture
and good synoptic forcing will result in numerous convective showers
redeveloping across the region and can`t rule out an isold t-storm
given the convective instability and marginal MUCAPES. In addition
to brief downpours, small hail will also be possible given the
low WBZ heights. Seasonable temps expected.
Friday and Saturday...
High pres returns with building ridge along the east coast will
result in sunshine and seasonably mild temps.
Sunday into Monday...
Next high amplitude trough to the west will become negatively tilted
as it lifts across New Eng Monday. The attending cold front will be
preceded by a strong low level jet which will transport anomalous
moisture north. Ensemble guidance showing PWAT plume +2SD and low
level jet +3SD which are impressive anomalies at this time range
suggesting potential for another round of heavy rainfall and strong
winds sometime late Sun into Mon, although confidence in timing and
details remain low. Mild temps expected in southerly flow regime.
Tuesday...
Looks mainly dry and seasonable behind departing system as high
pres builds over the mid atlc coast.
&&
.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/...Moderate confidence.
Tonight into Wednesday...
Trending MVFR with -RA/RA, IFR with RA/+RA with respect to both
CIGs and VSBYs. Also with RA/+RA a VCTS mention. Impacts through
Wednesday, across the W overnight into morning, across the E
morning through the day. Slow movement of outcomes and gradual
improvement E through the timeframe. Could see flooding at
terminals.
Gusty S winds around 25 to 35 kts, locally higher with RA/+RA
potentially exceeding 40 kts and a LLWS threat with 2 kft agl
winds around 50-55 kts overnight, pushing offshore Wednesday.
Wednesday night...
RA/+RA expected to be along the immediate coast if not mostly
offshore with -RA/RA outcomes elsewhere. Low-end VFR / MVFR to
the W while IFR towards the E. S winds less, no longer a threat
anywhere of gusty winds or LLWS.
KBOS Terminal...Moderate confidence in TAF.
Gradual trend downward towards the AM push, with impacts developing
after midnight (5z). Could be too early in moving outcomes offshore
Wednesday morning in terms of +RA, LLWS and gusty winds.
KBDL Terminal...Moderate confidence in TAF.
Worst conditions ongoing across the terminal. Flash flooding is
possible. Trending IFR with RA/+RA and a VCTS mention. Impacts
through 6z but that may be too early, potential to last a bit
longer. Closely monitoring.
Outlook /Thursday through Sunday/...
Thursday: High confidence. Mainly MVFR, with areas VFR
possible. SHRA likely, slight chance TSRA.
Thursday Night: High confidence. Mainly VFR, with local MVFR
possible in the evening. Windy with local gusts to 30 kt, mainly
SE New Eng. Chance evening SHRA, isolated TSRA.
Friday: High confidence. VFR. Breezy.
Friday Night through Saturday Night: High confidence. VFR.
Sunday: Moderate confidence. Mainly VFR, but MVFR possible in
showers Sunday night. Becoming breezy Sunday night.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...Moderate confidence.
Tonight...
Expect S winds gusting to 35-40 kt with seas up to 7-11 ft
across the open waters, highest across the southern outer waters
this evening. Visibility restrictions in developing fog.
Showers, heavy at times, with chance for thunderstorms which may
produce gusts over 40 kt. Winds start to diminish after midnight
across the waters S of Block Island.
Wednesday...
S winds continue to gust up to around 35 kt with seas up to
7-11 ft early. Winds will diminish during the day from W-E.
Showers will continue, heavy at times, along with patchy fog
producing visibility restrictions. Showers linger across the
eastern waters through the day as the front slows its east
progression.
Wednesday night...
Continued S winds at 15 kt or less, highest across the eastern
waters. Seas will remain at 6-9 ft on the open waters, so small
crafts will continue. Visibility restrictions in showers and
patchy fog.
Outlook /Thursday through Sunday/...Moderate confidence.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Rough seas up to 10 ft. Rain showers likely, isolated
thunderstorms.
Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 11 ft.
Friday: Winds less than 25 kt. Areas of rough seas.
Friday Night: Winds less than 25 kt. Seas up to 5 ft.
Saturday through Saturday Night:Winds less than 25 kt.
Sunday: Low risk for Small Craft Advisory winds with local
gusts up to 30 kt by late Sunday. Seas locally approaching 5
ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flash Flood Watch through Wednesday morning for CTZ002>004.
Wind Advisory until 2 AM EDT Wednesday for CTZ002-003.
Wind Advisory until 5 AM EDT Wednesday for CTZ004.
MA...Wind Advisory until 8 AM EDT Wednesday for MAZ007-013>021.
Flash Flood Watch from 2 AM EDT Wednesday through Wednesday
afternoon for MAZ005>007-013>024-026.
Flash Flood Watch through Wednesday morning for MAZ002>004-
008>012.
Wind Advisory until 2 AM EDT Wednesday for MAZ002-003-008>011.
Wind Advisory until 5 AM EDT Wednesday for MAZ004>006-012-026.
Wind Advisory until 11 AM EDT Wednesday for MAZ022>024.
RI...Wind Advisory until 8 AM EDT Wednesday for RIZ001>008.
Flash Flood Watch from 2 AM EDT Wednesday through Wednesday
afternoon for RIZ001>008.
MARINE...Gale Warning until noon EDT Wednesday for ANZ231>234-250-254.
Gale Warning until 6 AM EDT Wednesday for ANZ230-251.
Gale Warning until 4 AM EDT Wednesday for ANZ236.
Gale Warning until 8 AM EDT Wednesday for ANZ235-237.
Gale Warning until 10 AM EDT Wednesday for ANZ255-256.
&&
$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC/Sipprell/EVT
SHORT TERM...EVT
LONG TERM...KJC
AVIATION...KJC/Sipprell/EVT
MARINE...KJC/Sipprell/EVT
Area Forecast Discussion
National Weather Service Caribou ME
1053 PM EDT Tue Oct 24 2017
.SYNOPSIS...
A warm and humid airmass being drawn in on southerly flow will
bring the potential for widespread rain Wednesday and again
Thursday. Locally heavy rainfall is expected at times Wednesday
and Thursday as low pressure developing just off the Southeast
states moves straight north across the region.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
1050 PM Update... Decided to slow down the main rain band based
on the latest radar trends showing leading edge of rain moving
into sw Maine attm. Some light showers were lifting up out ahead
of the main line. The latest RAP and HRRR were matching up well
and bring the heavy rainfall into sw areas w/in the next 2 to 3
hrs and then this area will lift to the ne moving into the
Central Highlands and Downeast overnight into the early
Wednesday morning. The flow coming in from the Gulf of Mexico
and the Atlantic will lead to periods of heavy rainfall by early
morning. Further n, the steady rain will hold off til around
7-8 AM. QPF was also adjusted collaborating w/GYX and the NERFC.
Temps were staying up in the 60s. A slight adjustment to the
overnight mins was done to raise the mins a degree or two. It
will feel somewhat tropical out there.
The other concern as stated earlier will be the potential for
convection. The latest lightning display show a line of tstms
from MA and CT down into the western Atlc. This activity was
lifting n. Flash Flood Warnings have been issued for portions of
CT and MA this evening. Some of the high res models including
the HRRR and RAP show elevated convection moving into Hancock
County and western Washington County. Deep moisture profile up
through 700MBS by daybreak and a llvl jet of 50 kts could lead
to torrential rainfall and some stronger wind gusts. Will be
briefing the midnight crew on this potential.
Previous Discussion...
Expect the front to make only slow progress east tonight, as
the upper flow around a deep upper trough to our west remains
parallel to the approaching frontal boundary. Deep layered
southerly flow through the atmospheric column will transport
abundant moisture northward late tonight into Wednesday. This
will result in the potential for periods of locally heavy
rainfall late tonight and into Wednesday. The heaviest rainfall
tonight through Wednesday will be across down east areas, where
2.0 inches or more of rainfall is possible through Wednesday.
Although some localized ponding of water is possible on
Wednesday, no significant issues are expected through the day
Wednesday. It will remain continued unseasonably mild tonight
and again Wednesday with highs on Wednesday reaching the mid to
upper 60s.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Most models have gone back to the idea of having additional
banding of hvy rnfl working back into the FA from the SE late
Wed ngt into Thu after the initial hvy rn banding crosses the
Rgn on Wed. The culprit for this is the potential of a 2nd
strong s/wv alf diving SSE from NW Can erly this eve bottoming
out ovr the SE states south of the Srn Aplchns by Wed eve. This
system then lifts NNE with a negative tilt, taking a sfc low
from just off the SE U.S. coast straight N into our Rgn by Thu
eve. This in effect, allows the deep PWAT stream to back into
the FA late Wed ngt into Thu as s/wv ridging increases briefly
ahead of the s/wv trof axis. Subsequently, we now mention hvy rn
potential into Thu. Hvy rn banding should then be be pushed E of
the FA Thu aftn as sig mid lvl ht falls with the immediate s/wv
trof pushes the deep trop atmos rvr stream E into the Can
Maritimes. Mid lvl dry slotting should keep rnfl amts lighter
Mid to late aftn Thu and Thu ngt across ern ptns of the FA with
more rnfl ovr Wrn areas as deformation banding with the upper
low just catches this area.
All and all total rnfl amts attm look to range from 2 inches ovr
the NW to 4+ inches ovr Downeast areas. Given model uncertainties
regarding where the best rnfl banding will set up late Wed ngt
and Thu, we will hold off on issuing flood watches attm, but
reserve the right to issue on later updates. For example, its
interesting to note that the NAM/SREF shows heaviest rnfl
further W on Thu, particularly ovr the Cntrl highland areas
which is somewhat backed up by the latest 12z ECMWF dtmnstc
model run which indicate a little more wrly track of the sfc
low thru our area. This would also give the Rgn a greater wind
potential durg the day Thu, which we do not show attm. So, to
say the least, fcst confidence is not hi attm regarding the rnfl
outcome with the Thu ptn of the event.
Regardless of the absolute outcome, any left ovr shwrs should
be exiting NE of the FA Fri morn, with partial clrg working SW
to NE across the Rgn ovr the remainder of the day. Temps will
cont abv normal even behind the cold front for Fri.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Fair conditions will prevail Fri ngt thru Sun with cooler, but
still abv seasonal norm temps. Hi cldnss will begin to increase
from W to E across the FA late Sat ngt into Sun ahead of the
next sig sfc low and s/wv trof complex from the Midwest. Cldnss
will thicken with the apch of this system Sun ngt with rn xpctd
beginning very late Sun ngt and contg thru Mon which may be
accompanied by strong Srly winds as the sfc low tracks W of our
Rgn thru NW New Eng and S Cntrl QB. We bumped max PoPs up to hi
likely based on the potential for sig total QPF with this
event, but given the speed of the system, much less than xpctd
with this current Wed/Thu event. Rn will taper to sct shwrs SW
to NE across the Rgn Mon ngt, leaving ptly to mcldy skies with
slightly abv normal temps.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: VFR conditions this evening will give way to MVFR
overnight in lowering ceilings, with IFR expected after midnight
in developing rain. The rain may be heavy at times toward day
break Wednesday. Gutsy south winds can be expected tonight. Low
level wind shear is also expected to be a concern late tonight
into Wednesday morning KBGR/KBHB vicinity. Expect continued IFR
most of the day Wednesday in rain and low ceilings.
SHORT TO LONG TERM: LIFR to IFR conditions will likely be
ongoing Wed ngt and Thu across all of the TAF sites as rn, hvy
attms, and ngt and morn tm patchy fog conts. Conditions improve
from SW to NE to MVFR Thu ngt as rn tapers to sct shwrs and then
to VFR from SW to NE across the sites on Fri. VFR conditions
will then cont Fri ngt into Sun.
&&
.MARINE...
NEAR TERM: A gale warning has been issued starting late tonight
through Wednesday afternoon, with gusts as high as 35 kt
expected. Visibility will be reduced in rain and patchy fog,
mainly late tonight through Wednesday.
SHORT TO LONG TERM: At least SCA winds with high wvs will be an
issue Wed ngt into Fri morn, with a short pd of gale force wind
gusts possible Thu aftn and/or eve. Winds and seas slowly
subside Fri aftn and Fri ngt to below SCA thresholds by Sat
morn....contg so thru Sun. Went with a blend of WW3 and NWPS
wv guidance for fcst wv hts for this update.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Gale Warning from 4 AM to 4 PM EDT Wednesday for ANZ050>052.
&&
$$
Near Term...Hewitt