Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/21/17
Area Forecast Discussion
National Weather Service State College PA
1055 PM EST Mon Feb 20 2017
.SYNOPSIS...
An extended period of mild weather with well above normal
temperatures is expected through the end of the week. A weak
cool front will push through the state late Tuesday and Tuesday
night. A stronger cold front is expected for Friday into
Saturday.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Expect fair weather overnight with increasing cirrus, as upper
level ridge axis shifts eastward from the Grt Lks. At the
surface, a dying back door cold front is over the central
mountains at 03Z, with markedly lower dewpoints behind this
boundary across the eastern half of the state. Mostly clear
skies and drier air should result in the best radiational
cooling across the eastern counties, where min temps have been
adjusted downward slightly. Euro Ensemble MOS and latest HRRR
support this idea of slightly lower temps, with mins ranging
from 25-30F across the Middle Susq Valley/Poconos, to the mid
30s over the Laurel Highlands.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
A weakening front and the associated shearing upper shortwave
will bring increasing high clouds to the area Tuesday, likely
resulting in max temps several degrees cooler than those of
Monday. A few showers may work into the northwest mountains
toward evening, ahead of the weakening shortwave over the Grt
Lks. Otherwise, confidence is high for another dry day across
the remainder of central Pa.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Gradually milder temperatures will return for the extended
period as no genuine cold air push is in sight. High
temperatures in general will be 10 to 20 degrees above normal
with min temperatures mainly above freezing.
Upper ridge axis is forecast to be located east of the state
Tuesday night. The weak cold frontal boundary will produce a
brief period or two of showers for late Tuesday (Northwest) and
over the Central and Eastern parts of PA Tuesday night into the
mid morning hours of Wednesday.
Clouds associated with this weak frontal boundary will help to
suppress temps a bit (but they`ll still remain well above
average).
The flow turns back to the SW by Wednesday causing temps to
rebound.
The overall, large-scale pattern becomes more amplified late in
the week as a system over the central plains deepens and lifts
into the Great Lakes. Clouds will increase Thursday and Friday
with warm front lifting through, and bringing increasing rain
chances heading into the weekend.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Looking back to last night, no low clouds were noted at
BFD or JST. Some fog at JST.
For tonight into Tuesday, just some high clouds prior to 00Z
Wed, as high pressure with dry air remains over the region.
Some showers late Tuesday evening into early Wednesday, as
a weak cold front moves across the region.
Outlook...
Wed...A.M. sub-VFR possible NW 1/3; otherwise VFR/no Sig Wx.
Thu...Sub-VFR possible with chance rain showers.
Fri...Sub-VFR possible with rain showers likely Friday night.
LLWS probable.
Sat...strong cold to bring Sub-VFR and possible thunderstorms.
&&
.CLIMATE...
Summary of record highs from 2/18 and 2/19...
Harrisburg: Record high of 69 degrees on 2/19. Previous record
high was 66 degrees set back in 1997.
Williamsport: Record high of 69 degrees on 2/19. Previous
record high was 60 degrees set back in 1997
Altoona: Record highs of 64 degrees on 2/19 and 66 degrees on
2/18 (tie). Previous record highs were 61 in 1994 (2/19) and 66
in 1981 (2/18).
Bradford: Record high of 62 degrees on 2/18. Previous record
high was 56 degrees set back in 1994.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Lambert/Gartner
AVIATION...Martin
CLIMATE...
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
657 PM EST Mon Feb 20 2017
.AVIATION...
Thin coverage of high clouds will continue during the evening and
then begin to thicken overnight ahead of the next frontal system.
This will be accompanied by southeast surface wind holding in the 5
to 10 knot range which is expected to keep LLWS on the marginal side
tonight through Tuesday morning.
Low pressure parent to the cold front will be well north over Hudson
Bay during Tuesday and moving away from the Great Lakes. The
trailing cold front that is left behind continues to exhibit signs
of weakening in model data as it approaches SE Michigan. MBS has the
best chance of MVFR rain showers from about mid morning through
early afternoon although MVFR ceiling is expected to hang on through
the day over the rest of the area. The frontal wind shift will
likely dissipate and leave light southwest flow over the region by
Tuesday evening.
For DTW... Easterly flow lingering around the 100 degree direction
during the evening will veer toward the south overnight with speed
10 knots or less. The veering trend will at least help switch
runways back to southwest traffic operations by morning. VFR will
otherwise persist until the remains of the cold front arrive during
Tuesday afternoon.
//DTW THRESHOLD PROBABILITIES...
* None
&&
.PREV DISCUSSION...
Issued at 315 PM EST Mon Feb 20 2017
DISCUSSION...
Record setting upper level ridge (574 DAM at 500 MB per 12z DTX
sounding) in place over Southeast Michigan Today, but backed surface
flow out of the southeast holding temps in the 50s this afternoon.
Upper level ridge axis will continue to slide East, reaching the
East Coast Tomorrow. Rather narrow upper level trough over Central
North America, to break off into two pieces, as 500 mb cutoff low
develops over southern Mississippi River Valley, with northern
stream energy lifting through western Great Lakes Tonight into
Ontario Tomorrow. Narrowing moisture Axis and weakening nature of
the front draws into question the rain chances over southeast
Michigan, as bulk of upper level forcing and low level jet lifts
north of the CWA. Still, it appears there will be enough low level
convergence for some light showers (likely) to hold together on
Tuesday as the front moves across the area, as Local SREF weighted
probabilistic guidance suggest pops around 70 percent are justified
across most areas. However, 12Z HRRR gives one pause, as front comes
through mainly dry with lack of instability. Regardless, does look
like bulk of shower activity arrives after 12z, and will be trimming
pops for Tonight, and a bit for tomorrow. Clouds and showers working
through during peak heating will limit maxes, but still expecting
temps around 60 degrees.
Another surge of warm air on Wednesday with increasing southwest low
level flow as low tracks through Lake Superior. 850 mb temps progged
to rise back to around 10 C over southeast Michigan, with lower
teens at 925 mb level, supporting highs well into the 60s to
potentially 70 degrees at the high end. However, there is some
concern in the development of low clouds Tuesday night into
Wednesday morning behind tomorrow`s frontal passage, but suspect
models over doing the low level moisture just a bit, especially if
rain is very light tomorrow or does not materialize, and planning on
skewing the forecast on higher end of guidance, mid to upper 60s.
With the higher chance of low clouds in the south, along with the
surface flow potentially more southerly vs southwest, would subsequently
favor Flint Vicinity to be the warmest location during the day.
Well above normal temperatures will continue through the end of the
week before cooler air works in bringing temps back down closer to
seasonal for this time of year. The main issue in the extended is
the strong storm system that models are showing coming up from the
plains for Friday and into the beginning of the weekend. Chances
for precipitation are expected to increase by later in the day on
Thursday as the warm front approaches. Currently, the low is
advertised to move northeast over the central Great Lakes area
keeping Southeast Michigan in the warm sector. A chance for
thunderstorms will be possible as well as gusty winds as the cold
front slides across the area this weekend. Conditions then look to
dry out for a brief time to round out the weekend as high pressure
settles in to the south.
MARINE...
East-southeast winds will continue to increase this afternoon and
persist into Tuesday morning as strong high pressure retreats to the
eastern Great Lakes. A frontal boundary will approach the western
Great Lakes. Warm air above the cold lake surface will keep fairly
stable conditions. Nonetheless, the gradient will increase with a
long trajectory over the lakes. This suggest winds will become
rather gusty tonight. Gusts in the 25 to 30 knot range knots are
forecasted across much of Lake Huron tonight. A cold front will
slowly move across Lower Mi and Lake Huron on Tuesday. There will be
substantial weakening in the winds as the broad frontal boundary
moves into the region. Further weakening of the post frontal
gradient will support light and variable winds Tues night. Modest
southwest winds are then forecast to develop on Wednesday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 10 PM this evening to noon EST Tuesday
for LHZ441.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....BT
DISCUSSION...SF/SS
MARINE.......CB
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
941 PM CST Mon Feb 20 2017
.UPDATE...
Issued at 941 PM CST Mon Feb 20 2017
Still waiting to see when and where potential dense fog may
develop. Most hi-res and MOS guidance continues to support the
development of fog tonight as winds become light within an
environment of high low level moisture. This scenario makes sense,
although coverage and how dense remain questions. Also, mid-cloud
moving in from the west may limit fog potential. Give the mid-
cloud, went higher coverage east of the valley. Most areas will be
near or slightly below freezing, potentially adding to the impacts
(icy roads?). Lots of uncertainty still.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 311 PM CST Mon Feb 20 2017
Precip winding down and additional fog formation tonight will be
the main headaches for the period.
The main upper trough continues to lift quickly through the Plains
states, with the surface trough axis currently moving into our MN
counties. The central CWA has seen some break in the rain with dry
slotting but there is still some rain to the west with the mid
level deformation band. The RAP and to a lesser extent HRRR have a
decent handle on rain trends, taking the trailing edge of the
precip into MN in the next 2 to 3 hours with the rest of the rain
exiting the far eastern counties by 03Z. At this point think an
additional 1 to 2 tenths of an inch of rain are possible in spots
but not everywhere.
Clouds have already cleared out of western ND and the clearing
line will begin to move into the western counties in the next few
hours. The center of the surface ridge will pass by to our south
so winds will not go completely light, staying from the west and
then southwest later tonight. In addition, a weak shortwave
approaching through the near zonal flow will bring some additional
cloud cover later tonight to the northern counties. That shortwave
could bring some precip clipping our far northwest later tonight
but not expecting much of anything south of the international
border. With recent rain and melted snow, there will be plenty of
moisture and the west winds bring slight drying but not a lot.
The SREF probabilities of visibility less than a mile are very
high tonight, and many of the CAM models break out fog. Will keep
a fog mention in some areas going but will stay vague on density.
Followed along with the blend of guidance and have fog
redeveloping overnight and moving eastward, but will have to watch
visibilities closely.
As for temperatures, some drier dewpoints moving in will help
readings overnight fall into the mid 20s to mid 30s. Southwest
winds become westerly again tomorrow and fog should burn off by
mid morning. Cold air advection will hold off until Tuesday
evening, so the abnormally warm highs will continue for Tuesday.
Have highs ranging from the upper 30s north to upper 50s in the
far south, with some records again on the chopping block.
.LONG TERM...(Tuesday night through Monday)
Issued at 311 PM CST Mon Feb 20 2017
Temperatures begin to drop Tuesday night from northwest to southeast
as cold air moves in behind the cold front. The general pattern
aloft remains zonal Wednesday, keeping us from plummeting all the
way to seasonal normals until Friday and continuing to bring in
relatively moist air. Several upper level shortwave disturbances
move through Tuesday night through Wednesday night bring
precipitation chances to much of the area. At this time, a general
model consensus indicates scattered light snow showers along and
north of Highway 2 Tuesday night and into early Wednesday. As a dry
layer aloft gradually becomes saturated, precipitation will likely
begin as snow in the north and rain in the south. Colder air moving
in from the north will gradually transition precipitation to a
wintry mix and snow Wednesday afternoon from north to south.
However, the models differ significantly in the
locations/types/amounts of precipitation with temperatures around
the freezing mark in the central valley during the day. Some banding
is indicated by a few models along and south of Interstate 94, but
an overall temperature blend indicates that these heavier amounts
would fall as mainly as rain Wednesday afternoon, if they did occur.
The models do agree that precipitation chances will be out of
eastern North Dakota by Wednesday night and would be entirely out of
northwest Minnesota by Thursday morning.
On Thursday and Friday, the models have been coming into agreement
for the last few runs and generally indicate a Colorado Low system
bringing heavy snow across the Central Plains. Fortunately, this
system keeps us generally in dry northerly flow and is expected to
bring less than an inch of snow across the far southern Red River
Valley and adjacent portions of west central Minnesota. Temperatures
Thursday will still remain slightly above normal.
On Friday through Monday, we will return to near normal temperatures
with highs in the lower 20s to middle 30s and lows in the single
digits to middle teens. The forecast for the weekend looks mostly
dry but cannot completely rule out some flurries over the weekend as
a shortwave disturbance or two pass overhead. Looking into early
next week, several models indicate a disturbance will bring
precipitation chances Monday into Monday night, but there is low
confidence in precipitation type, location, and amounts at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 648 PM CST Mon Feb 20 2017
As the main weather system moves out most locations can expect a
brief period of vfr conditions this evening. Devils Lake has
already developed dense fog, and anticipate most locations to
develop at least MVFR conditions tonight, with dense fog (LIFR)
possible. Still uncertain with duration of any possible LIFR
conditions.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...TG
SHORT TERM...JR
LONG TERM...BP
AVIATION...TG
Area Forecast Discussion
National Weather Service Lincoln IL
847 PM CST Mon Feb 20 2017
.UPDATE...
Issued at 840 PM CST Mon Feb 20 2017
Weak cold front over central Iowa was making slow progress east
this evening with a band of showers and isolated thunderstorms
along and to the east of the boundary. The leading edge of the
showers was pushing across far west central Illinois with a
track more to the north than east. Based on the current track
and speed, the showers should approach the I-55 corridor around
between 1 and 3 am. Models continue to suggest the slow moving
boundary to our west will weaken as it tracks across our area
Tuesday morning with the scattered showers moving out in the
early afternoon across the east. Another very mild night over
central Illinois thanks to the cloud cover and southerly breeze
with most areas remaining in the low to mid 50s, threatening
many record warm lows (see climate section below) across the
central, east central and southeast Illinois. The current
forecast has a good handle on the late evening and overnight
trends with respect to the precipitation timing from west to east,
as a result, no ZFP update will be needed at this time.
&&
.SHORT TERM...(This evening through Tuesday)
ISSUED AT 233 PM CST Mon Feb 20 2017
Earlier clouds/fog did not keep a damper on the unseasonably warm
weather, as partly sunny skies have pushed temperatures into the
upper 60s to mid 70s across the forecast area this afternoon. Gusty
southerly winds of 25-30 mph is helping out as well.
The large area of precipitation that was west of us continues to
lift north-northeast this afternoon, as the frontal boundary edges
eastward. A few echoes are scraping the Illinois/Iowa border, but
surface observations indicate these are largely not reaching the
ground. Water vapor imagery shows a nice moisture plume tracking
ahead of the deep trough in the Plains, and our rain chances will
mainly await this surge to moisten up the lower levels of the
atmosphere, currently suggested in forecast soundings to take place
mid-late evening. Latest high-res model guidance suggesting the rain
may only make it as far east as I-55 by midnight, but have included
some low chances east to I-57 late this evening, with the highest
PoP`s there after midnight. Thunder threat appears to still be
isolated and mainly west of I-55, although the RAP model has
MUCAPE`s up to around 100 J/kg as far east as Champaign and
Effingham after midnight. Temperatures will remain very balmy
overnight, only falling into the mid 50s, which could set some
record warm lows for the month.
While the upper trough starts to move into the western parts of the
state Tuesday morning, it will start to weaken as an upper low cuts
off over eastern Texas. The front will fall apart as a result, and
temperatures on Tuesday should still reach the upper 60s to lower
70s. The NAM/GFS suggest most of the lingering rain over the eastern
CWA would be early in the day, but some showers may linger into
afternoon as the trough passes.
.LONG TERM...(Tuesday night through Monday)
ISSUED AT 233 PM CST Mon Feb 20 2017
With the Mon night-Tue weather system east of the area, high
pressure ridge will slide across the CWA Tue night into Wed. This
will keep the area dry with continued southwest flow. This southwest
flow will keep the near record to record temps in the area through
the day Wed. Models look very similar with a weather system moving
through the flow across the northern US and into the Great Lakes
region Wed night. However, the trailing cold front associated with
this system will be dry as it moves through the region. It will be
the weather system developing in eastern CO and pushing out into the
plains that will ultimately bring the showers and thunderstorms to
the area for Thur through Fri.
This next system will develop a warm front that will extend into
central IL by Thursday afternoon. Showers are expected to begin
developing along this boundary over central IL Thur afternoon.
Amount of moisture return ahead of this system is in question right
now, so will just have a chance of showers along the boundary.
Potential for showers will increase during for the evening hours as
the system strengthens some and moves northeast...causing the warm
front to slowly lift northward. Models differ on amount and
location of qpf during the evening and then overnight, but all agree
that an increase in precip will occur during the night. Highest pops
will shift to the north as well. Fri should bring an increase in
moisture and continued warm temps ahead of the associated cold
front. Models differ with timing of the cold front, with the ECMWF
pushing the front quickly through the area, while the NAM and
Canadian still have the front west of the area at 18z and then
through the center of the CWA by 00z. The low pressure area
associated with the system is also slower on the GFS and Canadian
than the ECMWF. Despite the differences in speed of the front, all
three models generate precip in the eastern half of the CWA Fri
afternoon. So, higher pops warranted along the front Fri afternoon.
In addition, with increased moisture, instability should be
maximized ahead of the front during the afternoon, which should lead
to thunderstorms being more likely. So, have increased pops for
thunder as well...to likely. The low pressure area will lift
northeast across the state Fri night with some lingering showers in
the east during the evening and then colder air coming in on the
back side. This colder air will come around in the wrap around
section of precip, so precip should go from rain to a mix of rain
and snow, to all snow Fri night. The chance of snow will continue
into Sat, but with temps warming into the upper 30s to the middle
40s across most of the area, the snow will change back to rain
during the day.
After a dry and cooler period Sat night more precip is possible
Sunday afternoon and Sunday night. New runs of the extended models
are differing with location and amount...if any...qpf in the area
during this time frame, so will just keep the consensus forecast
going for now. Then pops will increase as the next significant
weather system moves into the area for Monday. All models agree on
this, but differ on timing. So, consensus pops have likelies in the
area during the day Monday.
Temps the rest of the week will stay above normal with record highs
still possible Wed through Friday. Sat temps will drop back down to
around or just below normal during the day, with Sat night lows
below freezing across the area. Temps will begin to warm back up to
above normal beginning Sun and then continue into Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 510 PM CST Mon Feb 20 2017
A frontal system out to our west late this afternoon will slowly
make its way east along with the precipitation shield that is
associated with it. VFR conditions are expected early this evening
with a transition to MVFR cigs starting between 05z-09z time frame
with the possibility for a brief period of IFR cigs along and
behind the weakening cold front which is slated to push across the
TAF area Tuesday morning. Forecast soundings suggest a return to
VFR conditions from west to east after 17z with PIA and SPI the
first to see the improvement with CMI seeing the VFR conditions
by 21z. Surface winds will be southeast to south at 10 to 15 kts
this evening with a few gusts up to 20 kts thru 03z...with winds
diminishing to 10 kts or less after 03z. Look for winds to
gradually switch into the west after FROPA with PIA and SPI
seeing the wind shift in the 12-14z time frame.
&&
.CLIMATE...
Issued at 312 PM CST Sun Feb 19 2017
Record Highs / Record Warm Lows - Monday Feb 20th...
Peoria........ 68 / 46
Lincoln....... 70 / 46
Springfield... 74 / 46
Champaign..... 71 / 45
Bloomington... 67 / 45
Decatur....... 70 / 47
Danville...... 70 / 48
Galesburg..... 64 / 41
Charleston.... 73 / 48
Effingham..... 68 / 54
Record Highs / Record Warm Lows - Tuesday Feb 21st...
Peoria........ 69 / 46
Lincoln....... 69 / 45
Springfield... 69 / 48
Champaign..... 67 / 47
Bloomington... 69 / 46
Decatur....... 68 / 48
Danville...... 67 / 50
Galesburg..... 68 / 40
Charleston.... 71 / 52
Effingham..... 73 / 52
Record Highs / Record Warm Lows - Wednesday Feb 22nd...
Peoria........ 71 / 51
Lincoln....... 71 / 52
Springfield... 71 / 53
Champaign..... 69 / 49
Bloomington... 70 / 53
Decatur....... 72 / 51
Danville...... 71 / 54
Galesburg..... 61 / 45
Charleston.... 71 / 52
Effingham..... 74 / 55
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...Geelhart
LONG TERM...Auten
AVIATION...Smith
CLIMATE...WFO ILX
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1032 PM EST Mon Feb 20 2017
.UPDATE...
Issued at 1032 PM EST MON FEB 20 2017
Temperatures are now into the mid 40s in the colder eastern
valleys. This is in line with updated forecast from earlier. This
will put our final lows somewhere down into the mid 30s tonight
for those valley locations. Elsewhere to the west, winds may stay
a bit more mixed tonight, keeping temperatures from completely
falling off, like in the east. Thus, a bit milder overnight for
most areas in the west. No changes warranted at this time.
UPDATE Issued at 705 PM EST MON FEB 20 2017
Temperatures have already started their steep descend into the
low to mid 50s this evening in the eastern valleys. With the
degree of dry air mixed down tonight, should not take much for
temperatures in the deeper valleys to again reach into the 30s
tonight. With his said, have lowered the eastern valleys well
below current forecast values in the 40s. We will likely see at
least some mid 30s by tomorrow morning. Given the colder
temperatures forecast, also beefed up the fog a bit, again mainly
for valley locations. Fog shouldn`t be as bad or as widespread as
last night, so no plans to highlight the fog in the HWO. Just some
thin cirrus drifting over the area overnight and this shouldn`t
have much impact on the overall expected weather.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 430 PM EST MON FEB 20 2017
21z sfc analysis shows high pressure shifting off to the
northeast with deep low pressure taking shape over the Norther
Plains. The pressure gradient between these is tightening up to
the west. Here in eastern Kentucky, the winds are starting to
respond to the passage of the high by turning to the southeast
and south - but still rather light. Ample sunshine through high
clouds helped to propel temperatures into the upper 60s and lower
70s. Dewpoints decreased a bit during the middle part of the day
with a range from the upper 30s to mid 40s for most places.
The models are in good agreement aloft through the short term
portion of the forecast. They all depict a strong ridge moving
from Kentucky east to the Southeast Coast tonight while a full
latitude trough splits apart with its southern extent closing off
over the western Gulf Coast. To the north of this developing low,
the northern portion will cross into the Great Lakes while some
energy runs out ahead of its trough axis and passes over Kentucky
into Tuesday morning. The main axis - though weakening aloft -
will make it into the state later in the day and slowly pass that
night along with some small height falls - more substantial in
the ECMWF. Given the general model agreement will favor a blended
solution for the larger scale while leaning toward the HRRR in the
near term along with the ECMWF for weather details from Tuesday
through Tuesday night.
Sensible weather will feature a rather warm evening with a
moderate ridge to valley temperature split developing under
variable amounts of high clouds and an inversion. Good drying and
mostly sunny skies today should limit the fog formation tonight to
just the valleys ahead of thicker clouds moving in towards dawn.
For Tuesday showers will push in from the southwest by mid
afternoon with plenty of clouds and mild conditions continuing.
The best rain chances will be later that night as a sfc low
passes by to the south coupled with the weak energy aloft. This
will make for another warm night with some places probably seeing
soaking rains - depending on the interaction of the departing 300
mb jet north of the state and any divergence aloft that it
generates over our area. For the most part the blended model
solution looked decent, though the NAM seems to cut off the
western extent of pcpn shield quicker than the ECMWF and GFS on
Tuesday night but this seems to fast so have not backed off on
the blended solution here.
Again used the CONSShort and ShortBlend as the starting point for
the grids through the short term portion of the forecast. Did
make adjustments to temperatures tonight to account for a decent
ridge to valley difference but readings should be similar Tuesday
night with the rain. As for PoPs, did adjust them for late Tuesday
into the night - translating the higher PoPs across the CWA more
cleanly.
.LONG TERM...(Wednesday through Monday)
Issued at 330 PM EST MON FEB 20 2017
The extended forecast period begins on Monday with a deep closed
upper low tracking northeast through the spine of the Appalachians.
As this feature tracks northeast, blocking over the New England and
Canadian Maritime region will hinder the exit of the back edge
precip moving through eastern Kentucky. This slow exit followed with
the approach of the colder air in behind on Monday night into
Tuesday may lead to a brief mix of rain and snow on top of Black
Mountain. In addition to this, models have been coming into more
agreement of a prolonged heavy rainfall event coming to an end
Monday evening into Monday night across eastern Kentucky. Some
lingering minor flood problems may be possible, if not just some
rivers running full. Both the Euro and GFS seem to have come to an
agreement on this with the Euro being slightly wetter. Will keep
this mention in the HWO.
Heading into the midweek time frame, a brief period of ridging moves
into the OH valley with a period of drying as southwest flow
increases ahead of the next incoming cold front. High temps on
Wednesday will climb into the upper 50s to low 60s with SW 10 to 20
knot winds bringing in an unseasonably warm airmass. In fact,
models are suggesting an overall drying trend to the approaching
front with the bulk of the moisture to the north over the Midwest
and into Ohio. Little if any precip is expected with this feature.
Passage of the front on Wednesday night will bring in a colder
airmass to the region by Thursday with a possible prolonged upslope
event taking shape for Thursday and Friday. At this point the
pattern brings in a longwave trough across the eastern CONUS into
the weekend. The northwest flow then brings a series of disturbances
in an upslope scenario. At this point, while the models hint at
temps being warm enough for rainfall during the day and snow showers
overnight, an upslope event with the correct wind component would
mean some convection and snowfall at warmer temps. For now, went
with a general snowfall at 34 degrees and below due to the
uncertainties in the models but this may need reevaluated. The
general trend is cooler towards the end of the extended but models
have backed off from the depth of the cold air. Due to this, will
leave any mention of snow out of the HWO as none is expected to be
impactful at this point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 705 PM EST MON FEB 20 2017
VFR conditions will continue through 00z Tuesday evening. Cloud
bases will start to come down through the day tomorrow, but any
lower MVFR cigs should hold off until after 00z. Some light rain
could move into the area late in the period, but confidence is low
on the arrival time of this precipitation.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...KAS
SHORT TERM...GREIF
LONG TERM...SHALLENBERGER
AVIATION...KAS
Area Forecast Discussion
National Weather Service Marquette MI
725 PM EST Mon Feb 20 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 356 PM EST MON FEB 20 2017
Strong upper trough is pressing across northern Plains with sfc low
lifting over southern Manitoba. Strong moisture advection with pwats
over 1 inch (a whopping 300-400+ percent of normal) surging in ahead
of the sfc trough is resulting in widespread showers and a few
clusters of tsra lifting toward Upper Michigan from the central
Mississippi river valley. RAP and HRRR matching reality well and
show showers moving over western cwa through late this aftn then
spreading to central cwa this evening and into far east cwa by late
evening. Have seen isold lightning strikes every now and then with
showers over eastern IA into western WI where RAP and NAM showed
elevated MUCAPE up to 100j/kg and based on the forecast instability
this evening could see isold tsra potential this evening as showers
slide across. Given the unusually high moisture lifting in and
the elevated instability could see heavy downpours as the rain
moves through.
As shortwave lifts across Upper Great lakes and sfc trough crosses
the region, showers should shift steadily west to east across Upper
Michigan. High res guidance including the NAM, HRRR, RAP and NSSLWRF
indicate that there will be brief break with initial showers and
then there may be another push of showers move through on the sfc
trough axis. Given steeper h85-h5 lapse rates near 7c/km moving in
with surge of mid level drying think best chance of tsra could
actually occur 05z-07z Tue over west, 08z-11z Tue over cntrl and
over east cwa 11-13z Tue. Effective shear up to 50 kts with wbzero
heights lowering to 7k and 50 dbz height for 1 inch hail of lower
than 20kft suggests that if storms can form overnight, there would
be risk of hail.
On into Tue. Once showers and possible isold tsra exit eastern cwa
early in the day should see column dry out quickly from west to
east. Breezy on the Keweenaw and those stronger winds are sign of
better mixing depth that will spread over rest of cwa. As main
trough exits east, low-level winds will start out west then shift to
the southwest ahead of another weaker low pressure system sliding
over northern MN. Overall mixing to 900-875mb supports highs well
into the 50s over much of cwa expect where winds are onshore. May
even see readings top out in the low 60s for interior west and
central. For now, increased temps to near 60F to come more into line
with better perfoming guidance with recent warm spell. Any showers
with the northern MN wave should stay west of cwa through late in
the aftn.
Thus far with the warm up rivers have not responded much likely due
to gradual melt as nighttime lows have dipped near or blo freezing.
Rivers should respond tonight into Tuesday though more significantly
as mins tonight will remain above freezing and with rainfall and
melting snow tonight and since readings spike into the 50s on Tue.
Overall the rivers should see their greatest rises in the next few
days. At this time, significant hydro issues are not expected due to
lower river and stream levels, overall lower than normal amounts of
water equiavalent in the snowpack and generally quick moving
rainfall tonight with total qpf staying mainly less than 0.75 inch
in most areas. Still some unknowns though including extent of ice on
rivers. At the least with the rain and melting snow tonight could
see ponding of water in low-lying/poor drainage areas, especially if
there is any ice/snow plugging up storm drains. Will mention this
potential in HWO.
.LONG TERM...(Tuesday night through Monday)
Issued at 246 PM EST MON FEB 20 2017
Beginning Tue night...A weak shortwave moving through the area and
the presence of a frontal boundary could produce some
sprinkles/drizzle over mainly the northern tier of the forecast
area. Otherwise, expect dry conditions.
Most of the models continue to trend stronger with a shortwave
moving through the area late Wed into Wed night. The 12z NAM and
ECMWF favor a sfc low track over the western CWA which makes
sense given the trend toward a stronger solution. The 12z GFS
meanwhile remains weaker and farther se bringing the swath of best
pcpn through Iron and Marquette counties.
If the western solution of the NAM/ECMWF does work out, not much
precip will fall across the CWA and it will be mostly confined to
the far west and the Keweenaw. Most of the pcpn would be rain or
a mix or rain/snow and possible fzra. Will have to watch this time
frame as there remains plenty of uncertainty.
Attention then turns to Fri into Sat as models continue to bring a
strong low pressure system SE of the CWA. While there continues to
be uncertainty on track/timing of the sfc low, there is a general
consensus that the low will track through central Lower Mi late Fri
into early Sat. Model disagreement may increase over the next few
runs as is normal in this scenario until the shortwave associated
with the system moves onshore late Wed. Given the current track of
the GFS, ECMWF and GEMnh, all or most of the CWA will see snow, with
moderate to possibly heavy snow over the north-central U.P. where
upslope and lake enhancement from h85 temps between -10 and -15c
will increase synoptic amounts. Blowing snow would also be an issue,
especially near Lake Superior. Will need to keep an eye on model
trends with this system over the next few days.
The weekend will see h85 temps continue to fall with LES likely in
the NW-WNW snow belts.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 724 PM EST MON FEB 20 2017
Conditions will continue to deteriorate this evening with widespread
moderate rain ahead of a low pressure trough. Expect conditions to
fall to IFR at all terminals, even to LIFR at KSAW and KIWD later
tonight. Even with winds becoming gusty, persistent low- level
inversion will allow for LLWS into the late evening as strong low-
level jet ahead of approaching trough translates across the area.
After trough passes tonight, there is uncertainty in how quickly
low clouds will clear out. With upslope westerly winds, will plan
for low clouds to hang on through the night but with some
improvement to MVFR late. By mid morning on Tue, VFR conditions
will dominate with gusty westerly winds, especially at the more
exposed KCMX location.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST MON FEB 20 2017
Tighening pres gradient btwn high pres ridge shifting toward the E
Coast and an approaching low pres trof will result in SE gales of 35-
40kt thru much of tonight across the e half of Lake Superior. Gales
will end with the passage of the trof late tonight. Winds should
then stay mostly 25kt or less Tue thru Thu. Stronger winds, perhaps
gales, are expected later Fri into Sat as a low pres system tracks
ne thru the Great Lakes region. After a hiatus from winter type
conditions, should also the potential for freezing spray return
later Fri into Sat.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Warning until 1 AM EST Tuesday for LSZ264>267.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLA
LONG TERM...Voss
AVIATION...JLB
MARINE...JLA