Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/28/20
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
647 PM EST Thu Feb 27 2020
.SYNOPSIS...
Cooler weather will prevail across the region through Saturday
night as high pressure slowly builds toward the area from the
southwest. A warming trend begins on Sunday as the area of high
pressure moves offshore. Rain chances increase by the middle
part of next week as low pressure and an associated cold front
approach from the west.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 630 PM EST Thursday...
Latest analysis shows a nearly vertically stacked surface and
mid level low over southern Quebec, with broad troughing over
much of the eastern CONUS. In addition, there is another weak
low over northern New England. Upper ridging prevails over the
western CONUS. ~1030 mb high pressure resides over the western
Gulf. Cooler and much drier airmass over the region tonight.
Surface Dew points are in the teens across the area, and skies
are clear. Temps at this hour range from the upper 30s NW to mid
40s SE, and expect overnight lows to range from the mid 20s NW
to lower 30s near the coast. Winds will slowly diminish
overnight to 5-10 mph inland and 10-15 mph closer to the coast.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
As of 330 PM EST Thursday...
A weak upper shortwave is progged to approach the area on
Friday before moving to our southeast by early Saturday morning.
A secondary CAA surge will follow the passage of the shortwave
as winds turn from the SW to W-WNW. While low-level moisture
will be lacking, clouds (w/ bases aoa 5000 feet) will increase
from west to east on Friday. Seasonally cool Friday with
temperatures rising into the upper 40s NW/low 50s SE by mid
aftn. Still a low-moderate confidence forecast with respect to
pcpn chances. On average, the 12z/27 GFS/CMC have a few
hundredths of an inch of QPF (at best) across parts of the area
as isolated-scattered showers cross the area from W to E Fri
aftn through late Friday evening. The ECMWF has little to no QPF
across the area. Most of the CAMs follow the GFS/CMC with
respect to pcpn coverage. The HRRR is somewhat of an outlier,
as it is forecasting some weak (SBCAPE 200-300 J/kg) instability
to develop by aftn (as it has higher forecast dewpoints than
other models). Low-level lapse rates will likely be steep with
the trough axis nearby. If the HRRR solution verifies, the
showers that cross the area would be in a fairly solid line.
Would likely see some graupel mixing in if the showers are as
strong as the HRRR is forecasting (w/ temperatures quickly
falling into the upper 30s-low 40s as the showers move
through). For now, will go with a consensus forecast and carry
PoPs of 15-25%. Would have been more aggressive w/ PoPs if the
other CAMs more closely resembled the HRRR. The most likely
timing for pcpn is from 2-5 PM across from the VA Piedmont to
Dorchester County (MD), 4-8 PM for the central third of the
area, and 6 PM-11 PM for SE VA/NE NC.
Pcpn chances end by early Sat AM...with decreasing clouds during
the second half of the night. Lows Sat AM will be in the mid
20s to low 30s. Dry (and cooler) Saturday as high pressure
builds slowly builds in from the W and 850 mb temperatures fall
into the -8 to -12C range (while the upper trough slowly moves
offshore). There will still be some energetic NW flow with the
trough moving offshore, and this could result in SCT CU,
especially NE. Cool with highs in the low 40s NW to upper 40s
across coastal NE NC. The high becomes centered from NE Florida
to the Carolina Coastal Plain Saturday night. With the high
nearby (and mainly clear skies), lows will fall into the low-mid
20s in most areas (w/ upper 20s-around 30F in coastal SE
zones). WAA increases on Sunday as the high moves off the
Carolina coast. 850 mb temperatures likely rise to 0-4C by late
aftn-early evening (highest SW). Warmer w/ highs in the 50s
across VA/NC, with upper 40s on the Lower Ern Shore.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 330 PM EST Thursday...
Unsettled pattern next week as an upper level trough over the SW US
makes it`s way eastward early in the week. Ahead of this feature,
several disturbances will pass across the area. Slight rain chances
across the northwest late Monday with better chances for rain across
the entire area on Tuesday and Wednesday. A cold front will cross
the area early Thursday bringing an end to the rain. Drier
conditions expected for the end of the work week.
Temperatures will be well above normal next week with high and low
temps running about 10-15 degrees above normal. Warmest day of the
week will be Wednesday, where temps will range from the upper 60s
N/NW to mid 70s SE.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 630 PM EST Thursday...
VFR through the period. Gusty west winds will become
southwesterly overnight and slacken somewhat to around 10 kts at
all locations except ORF where winds will remain a bit stronger
with gusts of 15-20 kts. A weak low moves across the Mid
Atlantic on Friday with a front crossing the area late in the
period. This will result in the winds becoming gusty again with
20-25 kt gusts expected during the afternoon and evening hours.
There is a slight chance of precip Friday afternoon, however
chances are too low at this point to mention in the TAFS.
VFR and dry conditions this weekend as high pressure builds into
the area.
&&
.MARINE...
As of 330 PM EST Thursday...
Post-frontal westerly flow is in place across the region this
afternoon with winds generally running 20-25 knots with gusts to 30
knots. Waves are 1-3 ft in the Ches Bay and seas are 3-6 ft
offshore.
High pressure builds in from the SW this evening with a relaxing
pressure gradient. SCA headlines remain in effect for all waters
through at least 06Z/1AM tonight. The Gale Warning remains in effect
until 06Z/1AM for the northern-most coastal zone but winds so far
this afternoon have only occasionally gusted above 35 knots and this
headline may be converted to SCA prior to expiration. Winds will
slowly decrease tonight and are forecast to be westerly at 10-15
knots by Friday morning. Waves decrease to 2-3 ft in the bay and
seas subside to 2-4 ft. Flow becomes southwesterly around 15 knots
tomorrow afternoon ahead of a weak wave crossing the mountains.
Winds become WNW 10-20 knots behind the weak wave/front for
Saturday. High pressure to the south will set up south of the local
area on Sunday, leading to west and southwest winds 10-15 knots.
High pressure migrates offshore early next week ahead of the next
system approaching from the west.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 7 AM EST Friday for ANZ635>637.
Small Craft Advisory until 1 PM EST Friday for ANZ630>632-634-
638-650-652-654-656-658.
Small Craft Advisory until 1 AM EST Friday for ANZ633.
&&
$$
SYNOPSIS...AJZ/ERI
NEAR TERM...CMF
SHORT TERM...AJZ/ERI
LONG TERM...CMF
AVIATION...CMF
MARINE...RHR
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
638 PM EST Thu Feb 27 2020
.AVIATION...
An area of deep low pressure has becoming increasingly organized
from northern portions of Lake Huron eastward through Quebec today.
This has positioned Southeast Michigan favorably to strong westerly
gradient flow. A much drier boundary layer than forecasted yesterday
(see RAP soundings today) and the strong gradient has been good for
widespread winds today in excess of 40 knots at times. The deep
mixed layer will persist tonight, but loss of daytime heating should
allow for shallow surface based stability that will cause winds to
settle down some this evening. Latest satellite trends support some
enhanced I 94 corridor convergence. Do not think this will result in
precipitation, but earlier thinking of persistent stratocumulus
along this corridor appears to be spot on. Will be monitoring that
this evening. For Friday, models show additional strengthening of
the upper level low pressure system in Canada. This will result in
another day of strong west to northwest winds.
For DTW...Strong 270 wind will persist early this evening before
gustiness wanes as near surface stability develops. Question for
tonight centers on clouds as latest satellite suggests some I 94
lake cloud. With flow becoming more laminar tonight will need to
watch for cigs within this banding dropping into MVFR. Confidence in
that is low attm.
DTW THRESHOLD PROBABILITIES...
* Moderate to high for ceiling 5000 ft or less tonight.
* High for reaching crosswind threshold at start of the period.
&&
.PREV DISCUSSION...
Issued at 352 PM EST Thu Feb 27 2020
DISCUSSION...
A mid level trough swinging up through southern MI began to force a
strong surface low slowly northward into Quebec. As a result the
pressure gradient has tightened up while laying out west to east
across the state. Been quite breezy today with steep low level lapse
rates up to around 5-6kft developing under an 850mb thermal trough
averaging 16C. The resultant convective component to lake effect
snow showers helping to mix down winds around 35 knots across
southern MI. A few gusts have even reached into the upper 30s
(knots) while DET and PTK remains the outliers breaking 40 knots (43
knots and 42 knots). Some hires this morning suggested these higher
end gusts were possible though the bulk of guidance stuck with the
mid/upper 30s as a high end. Regardless, this is causing some
blowing and drifting to snow that fell Wednesday, in addition to the
widespread lake effect snow showers that have been around all day
today.
In terms of snow showers, these showers have been light with no real
reduction in visibility noted, even with brief heavier bursts. A
heavier band is now taking shape over western lower but with flow
slightly more northwest over Lake MI, the band would most likely set
up south of I94 tonight. No strong signal for surface convergence
showing up so not expecting this band to get too out of control but
will need to watch it`s integrity this evening and tonight as it
works across the state.
Thermal trough will continue to reside over the region on Friday
with another mid level trough rotating through in the morning. Winds
will continue to be gusty though a bit weaker than today maxing out
around 25-30 knots. The main concern for Friday is the potential for
a Lake Huron convergent band to pivot southward over the Thumb as
flow becomes more northerly over the water in the wake of the
trough. Increased POPs and snow amounts slightly to start
acknowledging it more, but still hold some reservation as we so
commonly see these bands stay offshore.
Heights start increasing on Saturday as winds begin to back to
southwest but the tail end of the thermal trough will hold for one
more day. This will allow max temps to increase back to around 32
before the more notable warming trend which will occur Sunday
through mid week. High pressure will drift to our SE setting
southwesterly return flow while westerly flow begins in the mid
levels with 850mb temps reaching back into the positive single
digits. Trough digging over the west coast then stalls the pattern
over the Great Lakes allowing moderating temps through mid week with
50s possible on Monday. Active jet pattern sets up just to our south
which will direct several shortwaves up through the Ohio Valley.
Could be the makings of an active stretch of weather through the mid
week with period chances of showers. As of now with the warm air
likely in place, we`d be dealing with mostly rain til late Wednesday
when cooler air arrives adding potential for snow.
MARINE...
The morning update extended the Gale and Freezing Spray Warnings
through Friday morning. The afternoon update adds Inner Saginaw Bay
to the Gale Warning based on observations verifying at the upper end
of guidance estimates while also considering the peak wind intensity
lasts until around midnight. High end gales with snow squalls and
freezing spray remain solid across the open waters of Lake Huron
tonight, peaking around midnight and gradually diminishing through
Friday morning. The pattern remains driven by low pressure over
southern Quebec deepening to near 985 mb this evening which
gradually fills and moves eastward Friday morning. A few hours of
sustained 35 knot gales with frequent gusts near 45 knots are likely
tonight. These winds and associated high waves combine with
favorable water and air temperature combination for heavy freezing
spray to go along with bands of snow squalls. Farther south, Small
Craft Advisories remain in effect for Lake St Clair and the Michigan
waters of Lake Erie where 30 knot gusts will be common even after
sunset. Conditions settle below gales during Friday and then
continue a downward trend Friday night as high pressure moves across
the Midwest. The high moves over the central Great Lakes by Saturday
leading to more favorable marine conditions to finish the weekend.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory until 10 AM EST Friday for MIZ049-054.
Lake Huron...Heavy Freezing Spray Warning until 10 AM EST Friday for LHZ361>363-
462>464.
Gale Warning until 10 AM EST Friday for LHZ361>363-421-422-441>443-
462>464.
Lake St Clair...Small Craft Advisory until 10 AM EST Friday for LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EST Friday for LEZ444.
Low Water Advisory until midnight EST tonight for LEZ444.
&&
$$
AVIATION.....CB
DISCUSSION...DRK
MARINE.......BT
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
508 PM CST Thu Feb 27 2020
.SHORT TERM...(This Evening through Friday)
Issued at 238 PM CST Thu Feb 27 2020
Low stratus has largely voided the area as of mid afternoon,
although a plethora of mid and upper level clouds have kept skies
partly to mostly cloudy. Temperatures with minimal or no snowpack
have risen into the 30s while elsewhere 20s have been common.
Focus through the rest of the afternoon into the overnight hours
will revolve around flurry and light snow chances. Have already seen
an area of such activity work through northern SD just now entering
our Hwy 14 corridor with upstream visibilities in the 1 1/2 to 5
mile range indicating a brief heavier burst of snow where sub-cloud
layer dry air can be overcome. This initial precipitation on the
edge of the better Theta-e advection is also fairly convective in
nature and thus fairly brief for any one single point. A bit of a
warm nose from the James River west depicted in the soundings could
also result in a wintry mix through the evening and early overnight
hours.
Of perhaps slightly higher concern is a bit stronger wave currently
evident on WV imagery diving south through Saskatchewan. This more
robust vort lobe dives through the central Dakotas through the
second half of the overnight, with various high res models keying in
on a bit of enhancement in QPF values (although last couple runs of
the HRRR have been much less exciting). Deep layer
saturation/moisture is still somewhat fleeting, but the presence of
some instability could help overcome this shortfall. Have increased
POPs fairly substantially for an area from near the James River to
very near the I-29 corridor with WPC and various model blends also
following suit with a notable increase in QPF. With all of this
said, still feel most locations stay at snowfall amounts of minimal
impact value (less than half an inch) but would not be surprised if
we end up seeing a narrow stripe of higher totals.
Once any remaining snow exits shortly after daybreak Friday, the
remainder of the day will begin our return to quiet weather and
warming trend in temperatures. Cloud cover and the lack of any
robust warm advection will keep temperatures only just a shade
higher than today`s values. Light winds and added boundary layer
moisture from snowmelt will lead to the introduction of some fog
chances Friday night into Saturday morning.
.LONG TERM...(Friday Night through Thursday)
Issued at 238 PM CST Thu Feb 27 2020
Saturday continues to looks very nice across the region with 925 mb
temps running from the +4-8 C north of I-90 to +8-12 C south. This
should drive temperatures into the 50s to perhaps near 60 along the
MO River for areas that are void of snow cover and 40s elsewhere.
Have pushed temperatures in favorable snowpack areas toward the 75th
percentile of guidance.
Sunday is a bit more uncertain when it comes to temperatures as 925
and 850 mb temperatures cool as a front slides through. We should
still see fairly mixed profiles, but with out the climatologically
abnormal air to draw down, will probably see readings cool over
Saturday`s values. At this time, high temperatures near 40 to mid
50s appear common.
Conditions through the first half of next week look to remain on the
quiet side as a deep trough sets up over the western CONUS with our
region on the fringes of a southwest flow regime. This flow turns
more zonal and eventually northwesterly as ridging builds to the
west. At this time, doesn`t look to be any significant
precipitation, although weaker disturbances will keep occasional
small chances in the extended forecast. Temperatures should run a
bit above normal or generally mid 30s to near 50.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 504 PM CST Thu Feb 27 2020
Brief periods of flurries and light snow will occur overnight
with mvfr/ifr ceilings at times. A heavier snow shower could
briefly reduce visibility. Winds will light and variable in the
evening, then pick up a bit out of the northwest for the remainder
of the TAF period.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...Kalin
LONG TERM...Kalin
AVIATION...JM
Area Forecast Discussion
National Weather Service Grand Rapids MI
910 PM EST Thu Feb 27 2020
LATEST UPDATE...
Mesoscale Discussion
.MESOSCALE DISCUSSION...
Issued at 911 PM EST Thu Feb 27 2020
We have a narrow, persistent snow band, from near Grand Haven to
Grandville to Middleville. Looking at the nighttime microphysics
image, the band is on the south edge of the cloud shield coming
from Western Lake Superior across WI then central and northern
Lake Michigan. That band fits the area of maximum lift in the DGZ,
which has been nearly stationary over northern Allegan County
since 6 pm. It is forecast to continue there through 10 pm, after
which it starts to weaken. The band is also on the north edge of
the temperature gradient at 925 mb (this is seen on the RAP, HRRR
and NAM12). When the colder air over northern Wisconsin makes it
into central Lake Michigan is when that DGZ lift max weakens. So
the snow band will persist more or less till around midnight then
it should dissipate. Snowfall under the band from our Snow
Accumulation algorithm is 1 to 2 inches. However we have no ground
truth for this. It would seem maybe another inch would be
possible. I have around 2 inches in our snow total grid for this.
&&
.SYNOPSIS...
Issued at 259 PM EST Thu Feb 27 2020
-Snow showers tonight with local impacts
-Warming trend for the weekend into early next week
-Another storm system for the middle of next week
&&
.DISCUSSION...(This evening through next Thursday)
Issued at 259 PM EST Thu Feb 27 2020
-Snow showers tonight with local impacts
Bands of lake effect snow showers will continue to shift southward
through the CWA late this afternoon and into the evening. Inversion
heights generally stay under 6k feet but the moist layer is
within the DGZ. With little directional shear in the moist layer
forecasted coupled with somewhat of a diminishing trend to the
surface wind late this afternoon this may support a few bands of
snow which could feature locally low visibilities. Most locations
should see less than a half inch of snow but a few spots...where
any bands persist for more than an hour could pick up an inch or
more. Lake and Osceola counties may see more snow than most as the
moisture is progged to be the deepest there.
With the low level flow remaining cyclonic and the thermal trough
pivoting through the area on Friday...snow showers should persist.
Overall the surface flow is shown to be somewhat divergent which
could limit the snow shower coverage and potential impacts.
-Warming trend for the weekend and possibly into early next week
The low level winds back from west to southwest on Saturday. Strong
warm air advection develops with warming temperatures noted at 850
and 925 mb. During the day on Sunday guidance shows the 925 mb
temps reaching about 5 deg C...which should be warm enough for
surface temperatures to make a run at 50 degrees. A cold front is
shown by the models to approach the area from the northwest either
Sunday night or Monday morning. It is forecasted to slow down and
gradually fall apart as it moves in...which is a new trend.
Thus...some uncertainty exists on the timing and how much we end
up cooling down. Based on the latest trends with the structure of
this front...we will keep the temperatures above normal for this
time of the year through Tuesday.
-Another storm system possible for the middle of next week
On Wednesday a mid level trough is shown by the models to be near
or just west of the MS valley. The GFS is faster and more
progressive with this feature. This model supports little or no
synoptic precipitation...but some lake effect in the colder air
behind it. The High Res Euro is slower than the GFS and supports a
period of synoptic precipitation then a colder airmass moving in
behind it. The UKMET support precipitation on Wednesday with the
passage of a low. We will maintain some pops for this potential
system. At this time it looks too warm to be an impactful snow
event...but will will feature some snow mixing in with time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 632 PM EST Thu Feb 27 2020
I am thinking the snow showers will do what lake effect snow
showers typically do, which is contract toward the lake shore once
the sun sets. However, there is a weak cold front/shortwave that
comes through the area around midnight. Ahead of that the
inversion heights increase, so I am thinking the stronger snow
showers will be between now and say 06z.
After 06z through 06z Saturday the DGZ is in the clouds but
inversion heights are lower after 06z, mostly below 5000 ft so
that will limit the intensity of the snow showers. I put VCSH to
cover that, but realize any of these airports may have brief IFR
conditions in snow showers into Friday evening. It will also be
breezy into Friday evening, with gusts to 25 knots at times.
The bottom line is our TAF sites will mostly be VFR expect
briefly lower in snow showers from time to time (mostly early this
evening and during the day time Friday).
&&
.MARINE...
Issued at 259 PM EST Thu Feb 27 2020
Northwest winds will remain gusty for the next couple of periods
as the slow moving low winds up off to the east. Cold air
advection will continue to support high waves...which will be
hazardous for any small craft that head out.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 7 AM EST Saturday for LMZ844>849.
&&
$$
MESOSCALE...WDM
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
MARINE...MJS