Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/13/17
Area Forecast Discussion
National Weather Service Bismarck ND
956 PM CDT Sun Mar 12 2017
.UPDATE...
Issued at 954 PM CDT Sun Mar 12 2017
Have removed more areas from the winter weather advisory. The
only remaining counties until 11 PM CDT are for Sioux, Emmons,
McIntosh, and Dickey, so along the South Dakota border from south
of Bismarck to south of Jamestown.
UPDATE Issued at 815 PM CDT Sun Mar 12 2017
Have updated to remove the northern areas from the winter weather
advisory as snow had diminished to flurries there. Will expect to
be able to remove another layer along and north of Interstate 94
soon.
Radar returns continue to weaken from the north as the storm pulls
away and high pressure ridges in from the northeast.
Winds were also decreasing nicely, under 20 mph.
&&
.SHORT TERM...(This evening through Monday)
Issued at 402 PM CDT Sun Mar 12 2017
Snow will end from northwest to southeast through the evening, and
winds will concurrently decrease, as well.
As of 20 UTC, preliminary, non-operational satellite imagery from
GOES-16 reveals two primary vorticity maxima associated with the
mid-level shortwave trough crossing the region. Each maxima has an
area of low-level drying in its wake as well as a rather distinct
circulation center per the moisture channel and visible bands. A
notable decrease in snowfall intensity occurred during the midday
hours from Williston toward Bismarck as synoptic-scale ascent with
the shortwave trough ebbed, but since them a broader area of light
snow has taken over with ASOS/AWOS visibilities generally in the
1 to 3 SM range in most areas. This is likely tied to deformation
on the north side of the vorticity maxima traversing SD at this
hour. Recent RAP iterations key on that deformation and simulate
an area of slightly enhanced Omega in the dendritic growth zone
which sinks southward across central ND through late afternoon.
This area of forcing is almost entirely driven via deformation
since mid-level cold air advection is ongoing, and frontogenesis
worthy of more intense banded snow is now focused over eastern SD
and southern MN.
Therefore, while we expect a broad area of light snow to continue
sinking southward and ending from northwest to southeast through
the evening, additional accumulations will range from an inch or
less in western ND to between 1 and 3 inches in the southern James
River valley, where snow will last longest. The 16 to 19 UTC RAP
and HRRR iterations are generally in line with our observation-
based conceptual model and were relied on for the forecast through
the early evening. In general, web camera images suggest impacts
to travel are more of an inconvenience than anything else, but we
have chosen to maintain the areal extent of the advisory as-is
with this forecast release given widespread sub-2SM visibilities
being reported at mid afternoon. We did, however, choose to end
the advisory several hours sooner than earlier advertised given
these trends. Thus, the winter weather advisory end time was set
back to 00 UTC (7 PM CDT) for areas along and northwest of a line
from Bismarck to Rugby, and at 04 UTC (11 PM CDT) along and to the
southeast of a line from Fort Yates to Harvey, including Jamestown
and Ellendale.
In the big picture, a 1040 mb surface ridge located across central
Manitoba this afternoon is forecast to sink southward tonight with
its western influence nosing into north central ND. This will set
the stage for significant cooling if clouds thin or clear enough
in the Rugby and Rolla areas, where we leaned on the cooler edge
of the guidance envelope since model-derived soundings do indeed
suggest enough column drying to support efficient radiational
cooling. Elsewhere, lingering cloud cover will tend to inhibit a
drastic temperature fall, but given fresh snow cover temperatures
will certainly fall to between zero and 5 below in most areas. As
heights aloft begin to slowly rise by Monday afternoon and warmer
air surges eastward across MT, light snow may break out ahead of a
mid-level warm frontal zone in western ND by afternoon. The 12
UTC global models generally agree on that scenario.
.LONG TERM...(Monday night through Sunday)
Issued at 402 PM CDT Sun Mar 12 2017
A warm-up is in store this week as 500 mb flow across the lower 48
becomes characterized by mean ridging in the west and a deep and
energetic trough in the eastern part of the country. The 12 UTC
GFS and ECMWF and their ensembles are in good agreement with this
scenario and suggest that the ridge will flex eastward with time
and deliver several surges of mild air of Pacific origins to the
northern plains from mid-week on. This pattern fits well with the
hemispheric flow, which had been associated with a blocking ridge
aloft north of Alaska the last 10 or so days. The slow breakdown
of that feature will yield a more progressive downstream flow into
the western and central parts of the nation, particularly by next
weekend. Forecast 850 mb temperatures of 10+ C in both the GFS and
ECMWF should readily yield highs in the 40s to lower 50s F across
western and parts of south central ND beginning Wednesday. Global
models do suggest that light warm-advection-induced precipitation
may accompany the mild air on about Wednesday, though confidence
in its occurrence is low. Moreover, guidance suggests a stronger
mid-level shortwave may cross the region with a cold front about
Thursday or Friday, which could yield more light precipitation and
gusty winds along with a brief interruption in the warm-up.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 815 PM CDT Sun Mar 12 2017
Low pressure was pulling away from the area and toward Iowa as
high pressure was ridging in from the northeast. Snow had
decreased to flurries north and will be decreasing to flurries
south by 04Z. Expect IFR ceilings and visibilities to improve with
MVFR ceilings holding on even after the snow stops falling.
Note that ASOS at KISN is malfunctioning. Electronic technicians
will attempt repairs on Monday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM CDT /10 PM MDT/ this evening
for NDZ045-046-050-051.
&&
$$
UPDATE...JPM
SHORT TERM...CJS
LONG TERM...CJS
AVIATION...JPM
Area Forecast Discussion
National Weather Service Columbia SC
728 PM EDT Sun Mar 12 2017
.SYNOPSIS...
An area of low pressure developing off the coast will bring the
next chance of rain to the area Monday through Tuesday morning.
The remainder of the week will be dry with temperatures well
below normal. Possible frost and freeze concerns through Friday
morning.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Visible satellite imagery this evening shows clearing skies in
the northern portion of the area pushing southward. Most of the
snow that fell earlier today has melted although there is some
remaining near the NC border as noted on SCDOT road cameras.
Roadways also continue to dry and with warm ground temperatures
do not expect much water to be left to refreeze on roads
overnight. Expect clouds to continue to diminish from north to
south through tonight although clearing may not reach the
southern portion of the FA. Overnight lows will generally be around
30 along the NC border...the lower 30s in the central Midlands
and the mid 30s in the CSRA. A freeze warning is in effect from
the central Midlands northward.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
Monday will bring additional cold air southward into the region as
on low-level wedge flow. Along the coast, an area of low pressure
will be developing off the South Carolina coast in response to a
deepening upper level trough moving towards the southeastern states.
Models start the day off dry, then begin bringing some rainfall into
the CSRA through the morning, then spreading northward through the
afternoon. Temperatures above freezing through this event, so an all
rain forecast at this time. The surface low will continue to deepen
through the day Monday, and then will begin moving northward along
the Atlantic Coast Monday night through Tuesday morning in response
to the approaching upper level trough and support. Models keep
rainfall in the area for much of Monday night, then towards sunrise
on Tuesday, majority of the moisture will rapidly move off to the
northeast away from the area. Generally have likely pops for much
of the early portion of Monday night up through about Midnight, then
begin tapering precip down to chance pops, finally drying conditions
out by sunrise. Temperatures by Tuesday morning will be cold and in
the 30s, but should be bottoming out after the rain and moisture
have left the area. At this time it appears as if temperatures will
remain above freezing at all locations, so no freeze warning
expected at this time. Tuesday will see some warming, although
minor, compared to previous few days as some downsloping and
sunshine help to counter any cold advection. Readings in the 50s
expected. Tuesday Night will see dry conditions, but a return to
freezing temperatures. Just about the entire cwa will be at or below
freezing, with some areas possibly seeing a hard freeze. Anticipate
a freeze warning being needed for late Tuesday night.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Dry weather expected through Friday. The main issue through the end
of the week is going to be the very cold morning temperatures. After
starting off the day on Wednesday at or below freezing for many
areas, highs will be in the middle 40s to lower 50s with plenty of
wind through the day. Wednesday night into Thursday morning will be
a critical period in regards to temperatures. Models continue to
indicate a high chance of the entire cwa experiencing a hard freeze,
with a prolonged period of temperatures below freezing. Readings
are expected to bottom out in the lower to middle 20s. Unless
things change significantly between now and then, a freeze warning
will likely be needed for this period.
Temperatures will begin to rebound on Friday with temperatures
climbing back to around 60. A weather system is then expected to
move through on Friday night or Saturday with another chance of
rain. However, both overnight lows and afternoon temperatures should
remain mild through the weekend with lows in the 40s and highs in
the 60s.
&&
.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
MVFR to IFR restrictions expected for much of the TAF period.
Satellite showing clearing to the north of CAE moving south.
Based on satellite observation expect CAE and CUB to go VFR
during the early evening with scattered low clouds. The clearing
may spread into the OGB terminal. This is somewhat supported by
HRRR and Lamp. The low cloud restrictions are more likely to
remain at AGS/DNL through the overnight. Despite improving
conditions this evening...low clouds will spread inland from
the coast after 06z as shallow onshore flow/isentropic lift
develops. Guidance suggesting MVFR and possibly IFR at times
through the morning. Rain may develop by afternoon as weak low
pressure develops along the coast. This may lead to visibility
restrictions late in the taf period.
EXTENDED AVIATION OUTLOOK...Widespread MVFR or IFR conditions
expected through Monday night associated with low pressure off
the coast. Breezy conditions will likely occur Tuesday and
Wednesday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Freeze Warning until 10 AM EDT Monday for SCZ015-016-020>022-
026>029-031-038.
&&
$$
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1107 PM EDT Sun Mar 12 2017
.UPDATE...
Main point is that a winter weather advisory for light snow
accumulations has been issued for the southern 3 tiers of counties
from 6 AM EDT to 11 PM EDT Monday, excluding St Clair County.
Justification for the advisory is expectation to hit 4 inch snowfall
amounts in the Detroit Metro area.
There is really not much to add at the big picture for the northern
stream energy/warm advection that will impact southeastern Michigan
on Monday. Decaying system coasting in here locally, with sheared
out shortwave, virtually no favorable jet dynamics aloft, putrid
deep layer moisture, and much higher static stability than one would
like in the mid tropospheric frontal zone (between a high 9-20 kft
agl).
However, there are overachievers and with this particular system
there are a number of items that appear to line up favorably to hit
the 4 inch snowfall mark over a long duration.
1. Latest HRRR, RAP and some 4km hi-res WRF solutions are hinting at
a 1000-900mb convergence axis developing over and along the northern
shore of Lake Erie in easterly flow, funneling directly into areas
of the Detroit Metro area. In other words, lake enhancement.
Guidance suggests it could be along I 96 or 696 at light snow onset
through the morning commute before quickly transitioning southward
south of I 94, Downriver into portions of Washtenaw, Monroe, and
Lenawee counties between 14-17Z. Not comfortable to jump on any talk
of high snowfall rates now, but there are a couple solutions showing
in the in-house Probabilistic metrics, that suggests snowfall rates
in any lake enhancement could exceed one half inch per hour. Despite
cold surface lake water temperatures of about +1C, 1000-900mb theta
e lapse rates are neutral to negative within the band. More
importantly is the pre-existing mixed layer that exists in the 1000-
800mb layer. Models show the Lake Erie convergence axis providing
enough moisture to allow for a persistence of saturation in this
steep lapse rate pocket right through the afternoon. Top of this
mixed layer is shown to keep a connection with -15C. Therefore,
could very well see light snow fall off across much of southeastern
Michigan during the afternoon expect for those areas downwind of
Lake Erie. Confidence is too low to highlight a specific location or
a residence time of the band at any one location. However, there is
enough signal to provide support for an advisory with 4 inch snow
totals.
2. Near surface layer of theta e lapse rates is suggesting a
potential for late afternoon diurnal heating to contribute to lower
level ascent and light snow activity. Confidence in this is low.
3. Deep isothermal layer between 6 kft and 10 kft agl is
interesting. Expectations for weaker frontal forcing aloft to be
generating the seeder-feeder setup with hydrometeors at generally at
or above 600mb with snowflakes then falling down through this deep
isothermal layer. Favorable thermodynamics for snow is also supported
by supersaturation with respect to ice all day throughout much of
the entire column.
4. Not convinced on some of the MOS guidance that we can make a run
at surface temperatures of 30 degrees. Given mean 1000-850 mb temps of
-8 to -10C over semich and aforementioned deep isothermal layer
preference is to shade higher than climatology for liquid to snow
ratios. To generate the snowfall amounts used 16:1. Did not want to
get to go too much above that with overall lighter uvvs, however, if
the lake enhancement gets going these snow ratios would probably be
low.
&&
.PREV DISCUSSION...
Issued at 833 PM EDT Sun Mar 12 2017
AVIATION...
Quiet aviation weather in place over southeastern Michigan for the
majority of tonight as top-down saturation commences ahead of
approaching low pressure system. Latest probability trends are
suggesting that onset of light snow may wait until 11z. Once the
light snow begins, the area is looking at a long duration-low
snowfall rate grinder lasting from approximately 11Z-22Z.
Probability numbers match the qualitative eye-test (straight
midlevel warm advection, weak front structure aloft, virtually no
jet forcing aloft) in supporting very meager snowfall rates of a
less than .5 inch per hour rates during the aforementioned 11 hour
period. Flake size remains a wildcard and will probably support some
periods of IFR visbility restrictions. Given the setup, it is a low
confidence forecast at this juncture to include in the forecast.
Easterly low level winds will try to sustain a feed of lower level
dry air. Easterly winds are forecasted Monday in the 10 to 20 knot
range.
For DTW... Onset timing of snow is projected for 10Z or 11Z starting
out MVFR and transitioning to periods of IFR. Slow grinder of an
event with snow accumulations of 3 to 4 inches by Monday evening.
//DTW THRESHOLD PROBABILITIES...
* Low for ceiling 5000 feet or less through 10Z, high after and
through Monday.
* High for a dry snow precipitation type.
PREV DISCUSSION...
Issued at 343 PM EDT Sun Mar 12 2017
DISCUSSION...
Remnant circulation of Pacific Northwest cyclone is streaming down
the front range of the Rockies in advance of a broad Canadian trough
axis. This energy will shear into Lower Michigan late tonight into
early Monday as a developing jet core forces further trough
amplification across the southern United States. This will set the
stage for a period of warm advection during the day Monday followed
by a glancing blow of deformation Monday night as the Canadian
trough phases with the deepening southern wave.
Echoes over the Upper Midwest this afternoon will continue to
translate east as isentropic ascent builds into the area after 06z.
Fairly dry progged soundings and low surface dewpoints obs suggest
at least a couple hours of virga before hydrometeors reach the
ground. Latest RAP/HRRR output paints a reasonable depiction of an
onset time between 10-12z.
Moisture quality is quite poor per NAM12 progs of 850-700mb layer
specific humidity of under 1.5 g/kg for the balance of the day.
Nonetheless, the resident cold thermal profile should be able to
make the most of the environment with predominant dendrite and plate
production. This is particularly the case given a DGZ dipping down
into the boundary layer during peak ascent early Monday. Thus,
relatively paltry QPF may still result in an inch or two in most
places. Some lake enhancement along the shorelines is not out of the
question, but overlake instability is modeled to be poor, so a
significant departure from the background moisture/forcing field is
not anticipated at this time.
The greatest potential for meaningful snowfall will be Metro Detroit
and points south where the northern reaches of the warm conveyor may
provide a burst of moderate or even locally heavy snow between 14-
18z Monday, when 2 to 3 inches will be possible. Evolution of the
large scale pattern toward east coast cyclogenesis will greatly
limit the potential duration as it forces the flow up the frontal
slope to rapidly back, bringing an end to any respectable snowfall
rates prior to 18z. The remainder of the event into Monday night
will simply be a low-intensity grinder yielding a few tenths every 6
hours or so. There is at least an outside chance that intensity
within the warm conveyor could approach 6 hour advisory criteria of
3 inches, most likely after the morning commute. Marginal confidence
and lower impact timing tipped scales in favor of withholding from a
headline.
Uncertainty increases Monday night into Wednesday owing to uncertain
character of phasing and evolution of the East Coast cyclone. Strong
consensus among the 12z suite on a lack of impactful snow in SE
Michigan during this time as the core of deformation centers over
Ohio. However, the 12z ECMWF allows low intensity deformation to
linger Monday night right into Wednesday, the result being continued
grinding of low-intensity snowfall rates. Chc pops in place for this
scenario, particularly since it appeared to be the only member of
the NWP in the company of the RAP with regard to handling upper
energy this afternoon. This period of the forecast will likely be
the subject of multiple refinements in the coming forecast cycles.
Temperatures gradually moderate toward climatological averages
through this week as a more progressive pattern takes hold across
the CONUS and heights rise in the wake of the departing east coast
storm.
MARINE...
Light and variable wind will increase from the east tonight as high
pressure exits into the New England states. The next low pressure
system will then move into the Ohio valley during Monday and boost
the easterly flow even more by Monday evening. The moderate easterly
flow is expected to build waves above 4 feet Monday night and likely
require a small craft advisory for the Bay and nearshore waters of
southern Lake Huron. The Ohio valley low is then projected to merge
with a nor`easter off the Atlantic coast Tuesday. This will turn the
wind to north over Lake Huron and increase speed to near gales
through Tuesday night. At this point, gust potential appears
marginal for a watch headline but this will be monitored in upcoming
forecast cycles. Cold northerly flow then continues through mid week
but mostly below 30 knots.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 6 AM to 11 PM EDT Monday for
MIZ068>070-075-076-082-083.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......CB
AVIATION.....CB
DISCUSSION...JVC
MARINE.......BT
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Houston/Galveston TX
913 PM CDT Sun Mar 12 2017
.UPDATE...
Cloudiness associated with the upper level system moving over and
east of the forecast area will continue over Southeast Texas
tonight. There may be enough breaks in the cloud cover to lead to
some slightly lower overnight temperatures than earlier forecast.
Tweaked the temperature forecast for the first period.
40
&&
.PREV DISCUSSION... /ISSUED 641 PM CDT Sun Mar 12 2017/
AVIATION.../00Z TAF/
Overall aviation weather impacts look minimal with only concern
begin borderline MVFR/VFR ceilings. Visible satellite shows cloud
eroding from the east as drier air moves into SE Texas. The
problem will be timing if MVFR ceilings develop back over the
area. There will be some return flow at 925mb so could support
cloud cover overnight into Monday morning. Overall TAF continued
previous trends and went more optimistic with ceilings/visibility
than model guidance. HRRR seems to be preforming well to that end.
Models do have another front pushing through the area tomorrow
afternoon. This should help clear cloud cover and increase winds
from the NNW in the afternoon.
Overpeck
PREV DISCUSSION... /ISSUED 315 PM CDT Sun Mar 12 2017/
DISCUSSION...
Cloud cover has remained fairly persistent across Southeast Texas
this evening, but drier air has been able to work its way into
the extreme eastern counties and has cleared some of the low
clouds in place behind the front. Temperatures have been able to
warm into the lower 60s in this part of the region, with low to
mid 50s being observed elsewhere. Mostly cloudy to cloudy and cool
conditions will persist overnight, with most areas seeing lows in
the mid 40s to mid 50s. Will have to keep an eye on the eastern
counties in case cloud cover does not fill back in with nocturnal
cooling as low temperatures will likely be a few degrees cooler
than forecast.
A reinforcing cold front will move across the region during the
day on Monday, but temperatures will be able to rebound into the
upper 60s to low 70s as forecast soundings show the saturated
layer trapped beneath a persistent inversion becoming more
shallow... indicating drier air behind Monday`s front will be able
to help thin (or possibly scour) cloud cover across the region
and allow for more insolation to promote warmer temperatures.
Clearing skies will promote excellent conditions for radiational
cooling Monday night, with low temperatures falling into the 40s
Tuesday morning.
Dry northwest flow aloft will keep rain chances low and
temperatures near to just below seasonal normals through mid-week.
Strengthening onshore flow will allow for a few showers Thursday
and Friday, with temperatures warming into the mid to upper 70s by
Friday. Still some uncertainty with the advertisement of a
weekend cold front, with the GFS completely flipping the solution
it advertised 24 hours ago and now stalling the front north of the
region. The European now attempts to backdoor this front into the
region on Sunday, breaking out a few showers along it as it
slides into the region. Even if this weak front is able to make it
into the region by the end of the weekend, warm air advection
ahead of it looks to result in temperatures climbing to near 80
degrees by Saturday.
Huffman
MARINE...
High pressure building into the area will help to decrease winds
and seas tonight. A reinforcing front on Monday could briefly
increase the offshore winds and raise seas once again. Onshore
winds return to the area Tuesday night and Wednesday as high
pressure moves off to the east, and this flow will persist for the
remainder of the week with winds and/or seas reaching
caution/advisory levels at times. 42
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 47 70 45 70 51 / 10 10 0 0 10
Houston (IAH) 50 72 48 72 50 / 10 10 0 0 0
Galveston (GLS) 56 69 56 67 58 / 10 10 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Monday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM.
Small Craft Advisory until 1 AM CDT Monday for the following
zones: Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.
&&
$$
Discussion...40
Aviation/Marine...39
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
636 PM CDT Sun Mar 12 2017
.SYNOPSIS...
Issued at 325 PM CDT Sun Mar 12 2017
H5 analysis from this morning had a longwave trough of
low pressure over eastern Canada and New england with a trough
extending south into the central Atlantic. West of the trough
ridging extended up the west coast of the CONUS into northeastern
British Columbia and northwestern Alberta. Broad northwesterly flow
extended east of the ridge into the western Great Lakes. Embedded in
this flow, a nice shortwave was located over northwestern Wyoming
into central Montana. As of midday, this feature has tracked into
the western Dakotas and the Nebraska panhandle. At the surface, low
pressure was located northwest of Valentine Nebraska. A warm front
extended east of the low and roughly along highway 18 in southern
South Dakota while a cold front extended to the west southwest of
the low into the northern Nebraska panhandle. With the upper level
wave pushing into the western Dakotas, showers have developed from
southwestern South Dakota into the Nebraska panhandle. Most of the
precipitation has remained aloft with these showers, however, some
precipitation is hitting the ground over the Pine Ridge and
northwestern Sandhills per DOT cameras. Skies were mostly cloudy
across western and north central Nebraska and 2 PM CDT readings
ranged from 42 at O`Neill to 56 at Ogallala.
&&
.SHORT TERM...(This evening through Monday)
Issued at 325 PM CDT Sun Mar 12 2017
Tonight and Monday...The main forecast challenge in the
short term is determining the ending time of the pcpn threat this
evening, then temperatures on Monday. For tonight: The before
mentioned cold front will clear the forecast area by 00z tonight
with the h5 trough axis clearing the forecast area in the following
3 to 6 hours. The latest HRRR does indicate some limited post
frontal lift in the east through this evening and will hold onto at
least a mention of light pcpn in the east through midnight. Much
colder air, in association with a back door arctic front, will back
into the forecast area overnight with lows bottoming out in the
lower teens in the north to lower 20s in the south. For Monday, the
front will move only slightly east as a warm front, and will extend
from the far southwestern corner of the forecast area into the
southwestern panhandle. Highs Monday will vary widely across the
forecast area with mid 20s in the far northeast, to the mid 40s in
western Chase county and Deuel county.
.LONG TERM...(Monday night through Sunday)
Issued at 325 PM CDT Sun Mar 12 2017
Mid range...Monday night through Wednesday: In the mid range, the
main forecast issue will be the threat for light freezing
precipitation Tuesday night. For Monday night, an upper level jet
streak will approach northern Nebraska from the western Dakotas. Mid
level frontogenesis will increase from north central into south
central Nebraska Monday night. Lift along this mid level front will
be enhanced by the approaching jet streak, leading to an increased
threat for light snow Monday night from north central into eastern
portions of the forecast area. Forecast QPF`s are generally under a
tenth of an inch per the NAM and GFS solutions, so any accumulations
will be an inch or less. On Tuesday, the arctic cold front will push
east as a warm front and will make it as far east as a Valentine to
Broken Bow line. Like Monday, a large range in highs is expected
across western and north central Nebraska with highs around 30 in
the northeast to around 60 in the southwest. On Tuesday night, a mid
level warm front will push into central Nebraska with good lift
noted in the dendritic zone overnight. Looking at bufkit soundings,
there is a shallow, above freezing, layer just off the surface,
which would be favorable for light freezing precipitation. Normally
wouldn`t mention freezing pcpn in day 3, however the NAM and GFS
solutions are very similar in their solutions this morning. Also
the GFS solutions from yesterday were hinting at this freezing pcpn
threat as well. That being said, went ahead and introduced a mention
of light freezing precipitation in the central and east Tuesday
night into early Wednesday.
Wednesday night through Sunday: Ridging aloft will work into the
forecast area Wednesday night into Thursday. This will force the
stationary fronto boundary, forcing the frontal boundary into the
eastern CWA for Thursday. Highs Thursday will reach the mid 50s in
the northeast to the middle 70s in the southwest. Warm temperatures
Thursday will be followed by a cold front Thursday night and an
increased threat for light rain in northern and northeastern
portions of the forecast area Thursday evening. A temporary cool
down in highs is expected Friday as highs reach the 50s. Ridging
will begin to build back into the western CONUS Friday night into
Saturday. This ridge will transition east onto the plains by Sunday.
Highs Saturday will be in the 60s to lower 70s, followed by upper
60s to upper 70s for Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 636 PM CDT Sun Mar 12 2017
MVFR cigs are expected across Nrn Neb tonight through at least noon
Monday. VFR is expected overnight and Monday elsewhere.
The models show the cold air stratus across Nrn Neb shifting east
of KVTN by noon Monday. This bank of low clouds may last
throughout the day near KONL.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Memphis TN
915 PM CDT Sun Mar 12 2017
.DISCUSSION...Surface analysis this evening places an Alberta
Clipper cold front over portions of Nebraska and Kansas.
Meanwhile, high pressure is in place across the Mid-South with
temperatures as of 8 pm CDT in the 40s at most locations.
Regional WSR-88D radar trends the Middle Mississippi Valley
already showing some returns from Northeast Missouri back through
Southwest Missouri.
Latest HRRR and 00z WRF suggests a potential for precipitation to
arrive after 09Z across areas mainly west of the Mississippi
River. Model soundings indicate predominantly rain as the
precipitation type and perhaps some light sleet or snow initially
mixed in before switching to all rain Monday morning. In
addition, short term models indicate a potential for some
isolated to perhaps scattered rain showers for Monday afternoon
into Monday evening as 700-500 mb layer lapse rates steepen to 7-8
C/km in association with a mid-level trough. Will make some
adjustments to timing of precipitation overnight, add rain chances
in for Monday afternoon/evening, and to adjust any other elements
as needed to account for trends.
Update will be out shortly.
CJC
&&
.PREV DISCUSSION... /issued 627 PM CDT Sun Mar 12 2017/
UPDATE...
Updated to include the 00z aviation discussion.
PREV DISCUSSION... /issued 240 PM CDT Sun Mar 12 2017/
DISCUSSION...
Clocks and Calendars doing more than an hour switcheroo today.
Melting of the overnight snow has drawn warmth out the lower
atmosphere...keeping temperatures well below normal...with
readings mainly in the 40s. The air was dry and northeast winds
were a bit gusty providing for wind chills in the 30s.
For tonight through Tuesday...diving clipper system in the
Midwest will bring increased clouds...warmer air relatively
speaking and rain to the midsouth starting after midnight tonight.
Short term model soundings place a small window where rain may be
mixed with snow or sleet across northeast Arkansas and the
Bootheel of Missouri just before sunrise when temperatures were
hovering a degree or two above freezing. Feel only very minor
accumulations are possible on elevated surfaces...with most of
the solid precipitation melting as it hits the ground. So a winter
weather advisory is not currently anticipated. Better chances for
liquid precipitation will arrive in the 13/12z to 13/21z time
frame...with most locations picking up a quarter of an inch or so.
The cold front associated with the clipper will exit the Midsouth
tomorrow evening...but low level cloud cover will hang around
behind it through Tuesday...a typical winter scenario. This will
provide for temperatures to stay just above freezing tomorrow
night...and only climb into the 40s for highs. A light rain or
snow shower will be possible in the east from the moisture
wrapping around the intensifying East Coast storm. Clearing skies
Tuesday night will likely prompt the need for freeze headlines.
Wednesday through next weekend...cool through the period with
fingers crossed that some of region will see 60F degrees.
Wednesday will be cold and dry with a likely second freeze/frost
headline during the overnight. Clouds will increase Thursday with
rain chances ramping up during the night and through Friday. There
may be a few cracks of thunder also as a swath of elevated
instability slides overhead. This all being triggered by a surface
low tracking from Texas to the central Gulf Coast. A few lingering
showers are expected Saturday.
A northwest upper flow will keep the latter half of the weekend
dry as upper heights slowly build in from the west. The following
Monday may be the first day depicted by the GFS and ECMWF where
a strong enough south wind will raise temperatures above normal.
JAB
&&
.AVIATION...
/00z TAFs/
VFR conditions will prevail through much of the overnight period
with light east to northeast winds. The next shortwave trough will
result in an area of light rain after 10z in northeast AR, moving
across the remainder of the Mid-South through early afternoon.
Ceilings are expected to be predominantly MVFR during this time,
but IFR conditions may accompany this rain for a few hours, mainly
during the morning hours. A few snowflakes could mix in with the
rain in JBR, but it will remain operationally insignificant. Winds
will veer from the southwest, then eventually from the west, after
the band of rain moves east, but should generally remain under 10
kts. A few afternoon showers will be possible as well, but
coverage should remain limited.
Johnson
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Melbourne FL
1000 PM EDT Sun Mar 12 2017
.UPDATE...
...High Rain Chances Mon and Mon Night, then Drier and much Cooler
Mid-Late Week...
Tonight...A northerly wind surge (weak frontal boundary) had settled
into central sections but there is just a little air mass change
behind it. Low level winds will quickly veer overnight as surface
high pressure to our north pushes to the eastern seaboard. This
will cause the weak frontal boundary to stall and gradually wash
out, but the models show an inverted coastal trough forming again
late tonight, with east/southeast winds over the waters and light
north/northeast winds inland. This configuration usually keeps
significant showers confined to the Atlantic, so 30-50 percent POPs
along the coast might be too high.
However, the NAM doesn`t show much of an inverted trough and
generates a little more precip close to the coast. Additionally,
the GFS develops some isentropic lift late and the HRRR model has
been generating light rain towards sunrise in the north. With radar
continuing to show some convection, and outflow boundaries, over the
Atlantic late this evening, do not plan to lower POPs any.
Otherwise, considerable mid-high level cloudiness will continue to
stream across and scattered/broken low cloudiness should persist in
the north behind the weakening boundary. Little change in min
temps, around 60 to the lower 60s.
&&
.AVIATION...
Some MVFR ceilings have been occurring behind a weak frontal
boundary that settled into central Florida, mainly KTIX-KMCO-KISM
northward. This cloudiness may persist into late night and there is
also a slight chance for showers and light rain late in that area.
There will be considerable mid-high level cloudiness areawide into
Mon morning then modest daytime heating should cause convection to
develop in the afternoon. Overall greater forcing is indicated so
coverage should be higher than today and a chance for lightning
storms exists again.
&&
.MARINE...
Tonight-Mon...A wedge of stronger N/NE winds worked down the coast
this afternoon/evening. Winds are forecast to veer around to the
east over the coastal waters overnight with the pressure gradient
easing a bit. Will continue an exercise caution statement in the
north overnight. On Mon, a low pressure center approaching from the
Gulf of Mexico will veer winds around to southerly and they may
increase late in the day to 15-20 knots. Scattered to numerous
showers and isolated storms should push offshore during the
afternoon and evening.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Forecasts...Lascody
Impact Wx...Volkmer
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
723 PM CDT Sun Mar 12 2017
.SHORT TERM...(This evening through Monday)
Issued at 315 CDT Sun Mar 12 2017
The short term concern remains heavy snow potential to the south
and west of the metro into the evening...and how far east real
accumulation will occur. Also...headline resolution remains.
Snow...heavy at times is working across about the southern third
of the state at this time. Expect this to continue to work
east/southeast during the early evening...affecting mainly south
central MN into the evening. The nam was indicating fairly decent
-EPV potential across the region...into the southwest metro. SREF
and deterministic models paint a rather large dendritic growth
zone working over the region...with the best vertical motion
directed along the Minnesota River Valley into this evening.
Snowfall rates will likely range around 1 inch an hour in the
heavier snow area. Still looks like a potential for up to 11
inches in a portion of south central MN before it begins to taper
off. Total QPF around 0.60 inch likely into south central MN.
Lesser totals are expected to the northeast...as it still is
working into the very dry low level airmass...with some below zero
dewpoints remaining over west central Wisconsin at 20z. It should
gradually saturate the rest of the afternoon.
Overall...current headline configuration is looking good at this
time. Will retain as is for the interim. Will most likely cancel
headlines early into central MN...especially 06z-12z...when upper
trough exits to the southeast and somewhat drier air works in.
Some gusty wind potential into tonight and we continued to mention
patchy blowing snow west central into south central MN through
12z Mon. Some wind gusts 20-25kts possible as surface low exits to
the south later tonight.
The snow comes to an end over the far southeast early Monday with
clouds remaining...mainly to the southeast. We could see some
sunshine develop to the northwest during the afternoon as high
pressure builds southeast.
.LONG TERM...(Monday night through Sunday)
Issued at 330 PM CDT Sun Mar 12 2017
Models are fairly consistent in the overall long wave pattern
through the end of the week. Only concerns are timing on the next
weather system that will move into the Upper Midwest late Thursday
and into Friday. The EC is much flatter on the upper ridge by the
end of the week, which leads to a faster shortwave on Friday, but
much stronger than the GFS/GEM. This stronger shortwave also
translates into a stronger surface reflection vs. the GFS/GEM on
Friday. The thermal profile suggest that a mixture of rain/snow will
become snow on the back side once this shortwave moves through.
Otherwise, the only other concern is temperatures, especially
considering the snowfall today and how it will play on highs/lows
this week. Models seem to indicate a cooler reference where the
highest totals are expected. Didn`t deviate too much from this
scenario, which will likely be altered this week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 723 PM CDT Sun Mar 12 2017
Snow will continue through much of the night, though the worst of
the snow (1/2sm or less vis) as moved southeast of the MPX
terminals. Followed the HRRR to time snow through the area and
main change was to delay the snows departures a little. MVFR cigs
are expected to persist through the rest of the night, though
upstream obs do not really support the widespread IFR cigs the
LAMP has, so continued to be more optimistic than it. Lower
confidence on CIG improvements, though we may see lower
clouds/moisture get scoured out a bit faster than currently
indicated.
KMSP...One more band of 1/2sm at times type snow has developed
over the Twin Cities and will slowly slide thru over the first
hour of the taf. Once it`s gone, we should see vis 1sm or greater
until the snow departs.
/OUTLOOK FOR KMSP/
Tue...VFR. Wind NE 5 kts.
Wed...VFR. Wind becoming S 5-10 kts.
Thu...VFR. Wind S 6-12 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 1 PM CDT Monday for WIZ023>026-028.
MN...Winter Storm Warning until 1 PM CDT Monday for MNZ076-077-
083>085-092-093.
Winter Weather Advisory until 7 AM CDT Monday for MNZ041-047>049-
051-058-059-066.
Winter Weather Advisory until 10 AM CDT Monday for MNZ060>063-
068>070.
Winter Storm Warning until 7 AM CDT Monday for MNZ054>057-064-
065-067-073>075-082-091.
Winter Weather Advisory until 1 PM CDT Monday for MNZ078.
&&
$$
SHORT TERM...DWE
LONG TERM...JLT
AVIATION...MPG