Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/21/18
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1200 AM EDT Wed Mar 21 2018
.AVIATION...
Prevailing northeast flow will sustain dry low level conditions
through the TAF period. While a thickening canopy of high cloud
will lift into the region tonight, this will ensure skies remain
clear across the lowest 7-8k ft through Wednesday. The exception
remains near MBS, where a narrow strip of stratus continues to funnel
off Saginaw Bay. This will maintain the potential for periodic MVFR
conditions at this terminal. Firm northeast winds overnight turn
gusty again with diurnal support Wednesday.
For DTW...Winds hold from the north-northeast /010-030 direction/
tonight, gradually easing in both magnitude and gust frequency.
Gradual backing of winds to north and north-northwest throughout
Wednesday. Skies to remain clear across the lowest 5000 ft through
Wednesday.
/DTW THRESHOLD PROBABILITIES...
* None.
&&
.PREV DISCUSSION...
Issued at 309 PM EDT Tue Mar 20 2018
DISCUSSION...
Strong Canadian high pressure (1030+ MB) will remain anchored
along/near Ontario/Quebec border over the next several days.
12Z DTX indicated a very dry airmass in place over southeast
Michigan today, as 850 MB dew pt depression checked in at 32 C, with
a PW value of 0.14 inches.
Brisk northeast winds will continue through tonight (holding min
temperatures in the low/mid 20s), shifting to the North-Northeast
early tomorrow morning. Strengthening low-mid level circulation
tracking through southern Ohio will send 850-700 MB Theta-E gradient
over Lenawee/Monroe counties overnight. But with continued low level
feed of dry air, still looking at the snow shield holding near the
southern Michigan border. 12z Regional Gem would even argue for
light accumulations south of I-94 as 700 MB specific humidity rises
to 2.5 G/KG. Preference is more toward the slightly drier RAP
solution, but low chance pops for light snow late tonight still
seems warranted south of I-94, especially if that flow becomes a bit
more easterly off Lake Erie.
Upper level shortwave ridging to become established on Wednesday.
With northerly flow off cold waters of Lake Huron, looks like good
temp gradient setting up during the day, as 925 mb temps advertised
to range from -8 C over northern tip of the Thumb to -2 C along the
southern Michigan border, translating to highs in lower 30s to lower
40s.
Dry airmass and skies becoming clear Wednesday night will lead to a
favorable radiating night, sending temps into the lower 20s. Could
even see mins sneak into the teens in the normally colder locations
if winds fully decouple.
Thursday and beyond...
Confluent NW flow still forcing all meaningful precip south of the
area while ensuring mostly sunny skies with dominant high pressure
at the surface. The third week of spring will see temperatures
creeping ever-closer to average values as ridging builds over the
central CONUS for the remainder of the forecast period.
MARINE...
Large High pressure to the north and a low pressure system moving up
the Ohio Valley will continue a prolonged period of moderate
northeast wind which will continue this afternoon through Wednesday
before gradually diminishing Wednesday night. Occasional gusts to
30 kts are likely through Wednesday. The long northeast fetch over
open water will build high waves through the period and small craft
advisories remain in effect through Wednesday for all marine areas
except Lake St Clair which is through tonight. Advisories will
continue into Wednesday night for outer Saginaw Bay and Lake Huron
near shore. The wind will weaken and back north by Wednesday night
as the low exits the mid Atlantic coast and as the Ontario high
builds over the western Great Lakes. This will allow waves to
gradually diminish below advisory levels all areas by Thursday and
last through Friday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory until 10 AM EDT this morning for MIZ083.
Lake Huron...Small Craft Advisory until 2 AM EDT Thursday for LHZ421-441>443.
Small Craft Advisory until 4 PM EDT this afternoon for LHZ422.
Lake St Clair...Small Craft Advisory until 8 AM EDT this morning for LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory until 8 AM EDT this morning for LEZ444.
&&
$$
AVIATION.....BT
DISCUSSION...SF/JVC
MARINE.......DRC
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Wilmington NC
806 PM EDT Tue Mar 20 2018
.SYNOPSIS...
Hazardous thunderstorms are possible this afternoon and tonight as a
storm system approaches the region. Colder air will spill into the
Carolinas Wednesday and especially Wednesday night, with frost and
freeze conditions for portions of the area early Thursday and early
Friday. High pressure will maintain cool daytime weather this
weekend, with rain spreading in from the west Saturday night and
Sunday.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 710 PM Tuesday...Cooler surface air has knocked
instability values for surface parcels down to zero with the
exception of the I-95 corridor where SBCAPE is still near 1000
J/kg and new storms have lit up near and just northeast of
Florence recently. As colder air aloft works in from the west, a
few new cells could still develop from Dillon and Lumberton to
Elizabethtown as the last of the elevated instability aloft over
the frontal surface is expended. Rain chances are still
anticipated to ramp down from south to north over the next few
hours. Freezing levels are plunging with the incoming cold air
aloft, and we`ve observed almost any echo over 60 dBZ is
correlated with small hail at the ground. Emergency Management
in Bladen County reported small hail in multiple locations from
Elizabethtown to White Lake within the past 30 minutes.
Discussion from 550 PM follows...
Severe thunderstorms earlier this afternoon dropped hail at
least one inch in diameter near Trio, SC, but have weakened. The
convective cap has since broken and more widespread
thunderstorms have since developed east of I-95 to the coast.
One strong storm dropped a little pea sized hail here at the NWS
office in Wilmington, and hail will remain a possibility for
the next few hours as steep mid-level lapse rates will promote
large parcel acceleration aloft.
Visible satellite and radar shows the surface cold front moving
southward through Hartsville, Marion, Whiteville, to just north
Wilmington. The HRRR is doing an excellent job currently and is
our model of choice for the next 6 hours with convective
development and movement. Convection will remain largely east of
I-95, shifting almost exclusively into SE North Carolina in the
next couple of hours, then ending by late this evening as
colder and more stable air wraps in behind developing low
pressure exiting the coast. Some light showers should redevelop
late tonight across the northern sections of the Pee Dee into SE
North Carolina associated with a strong shortwave wrapping
around deepening upper level low pressure to our north.
One more change made to the forecast concerns sea fog that has
developed over the past few hours and is reducing visibility at
the beaches according to multiple beach cams across the Cape
Fear area. High dewpoint boundary layer air chilled by its
passage across the cold nearshore waters is responsible. Once
the cold front moves through the fog should quickly dissipate.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 340 PM Tuesday...NNW to NW flow through most of the
column Wednesday night ushering in cooler and drier air. The
flow will still be rather vort-laden, but most of the maxima
will be sheared out and to our south. So while a few of these
impulses may bring batches of mid level cloud the area will
remain rain- free. Lows in the mid 30s will support some frost
especially where winds grow light enough and guidance is
trending colder away from the ocean and much of the area may
experience a light freeze, at least according to the colder MET
MOS. It bears pointing out at this time that there is a good 6
degree separation between these values and the warmer MAV
numbers. Cold air advection continues Thursday and Thursday
night albeit weakening especially late in the period. Thursday
night may be a better candidate for a light freeze especially
over northern zones and our normal chilly spots as surface-based
decoupling appears more likely.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 340 PM Tuesday...this forecast period continues to show a
cool down as an upper level trough will be remain along the
east coast. In the large scale trough a shortwave is seen
dropping southward on the west side. This will bring in a colder
shot of air and a back door cold front. The 12 UTC GFS and
ECMWF are not in good agreement with the GFS being much faster
than the ECMWF. So uncertainty is high on timing of this front.
Will favor the faster GFS and its ensemble and introduce a
chance of showers late Saturday into Sunday night as the frontal
boundary shifts southward.
Temperatures will be below normal for the period with a
frost/freeze possible Friday night. Otherwise lows in the 40s
and highs in the mid to upper 50s to lower 60s.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...Surface front was located just south of a KFLO-
KILM line, with low center southwest of KFLO. Numerous
weakening showers were along and north of this boundary, and
will continue through about 03Z. The front will sag further
south and make it to the vicinity of KMYR before the low moves
offshore and winds shift to the W and NW. Expect MVFR ceilings
overnight, with some potential for IFR. Westerly winds will
become gusty Wednesday morning and continue through the day as
low pressure deepens off the Mid-Atlantic coast.
Extended outlook...VFR. MVFR/IFR/Rain Sunday.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 710 PM Tuesday...Quick update to remove the tornado watch
headline from the forecast. Severe thunderstorm potential has
really diminished in the past 60-90 minutes, and the remaining
showers on radar should gradually diminishing from south to
north over the next few hours. Discussion from 550 PM follows...
Forecast has been updated for sea fog that has developed over
the past few hours as high dewpoint air south of a cold front
has been cooled by contact with the cold sea surface. This fog
should be with us south of Cape Fear for another few hours
before increasing northwesterly winds bring drier and colder air
southward, dissipating the fog.
Showers and thunderstorms developing across the area should
clear the SC coastal waters by 8 PM, but may linger for another
few hours across the SE North Carolina/Cape Fear waters as
surface low pressure develops overhead. All convective activity
should be out of the area by midnight, but light showers may
redevelop later tonight, brought southward by cold winds
draining offshore from northern North Carolina and Virginia
where snow may actually be falling late tonight.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 340 PM Tuesday...As is usually the case in a strong cold
advection regime accompanied by strong dynamics aloft conditions
will be hostile over the marine environment early in the
period. Advisory-worthy winds will be bringing steep, short
period waves that will also satisfy the (6ft) criteria.
Relaxation of wind and seas will be quite gradual on Thursday as
cold advection continues but weakens as does the strength of
the upper impulses moving overhead. Current 5PM ending time of
the advisory appears on track enough this far out int time to
preclude any changes. Northwest flow lasts into Thursday night
with the abating trend ongoing.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 340 PM Monday...high pressure will ridge down the coast
with a surge of cooler air on Sunday. The high pressure will
extend down over the local waters Friday through Saturday before
a cold front approaches from the north. Northwest flow of 10 to
15 knots will continue through Friday before veering to the
south and west on Saturday and Sunday. Winds will increase on
Sunday with a backdoor front and seas are expected to increase
to 4 to 7 feet by Sunday late.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until 6 PM EDT Thursday for AMZ250-252-
254-256.
&&
$$
SYNOPSIS...DRH
NEAR TERM...TRA
SHORT TERM...MBB
LONG TERM...DRH
AVIATION...CRM
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
623 PM CDT Tue Mar 20 2018
.SYNOPSIS...
Issued at 340 PM CDT Tue Mar 20 2018
H5 analysis from this morning had a fairly low amplitude
pattern across the CONUS. However, numerous shortwaves were noted
across the lower 48 and have led to active weather, particularly
across the eastern half of the CONUS. Across the eastern CONUS,
shortwaves were noted over the upper Ohio valley as well as across
the lower Mississippi valley. Further west, a shortwave was located
over northeastern Kansas with another upstream shortwave noted over
Wyoming. Further north, a tandem of shortwaves were noted from
eastern Montana into eastern Saskatchewan. Further west, a strong
shortwave was noted from swrn Washington state south into swrn
Oregon. Current WV imagery, continues to note an area of low
pressure around 1000 miles west of the northern coast of California.
At the surface: Weak high pressure was located over northern
Nebraska. Skies were partly to mostly cloudy this afternoon as
steepening mid level lapse rates have led to the development of CU
and Alto CU across the forecast area with isolated showers.
Temperatures as of 3 PM CDT ranged from 36 at O`Neill to 54 at North
Platte.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 340 PM CDT Tue Mar 20 2018
Tonight and Wednesday: Skies will quickly clear by mid
evening as we loose surface heating and the current steep lapse
rates relax. Looking at the latest NAM12 and to a lesser degree, the
HRRR soln overnight, yields a threat for fog across the north and
northeastern forecast area overnight. This seems plausible given the
degree of snow melt in the north today and light winds which are
forecast overnight. Will keep the mention on the patchy side for now
as the statistical guidance is void of fog attm. For Wednesday, a
warm front will begin to push into swrn, then central Nebraska.
Temps will warm into the 50s tomorrow with lower 60s in swrn
Nebraska. Like this afternoon, mid level lapse rates increase,
becoming nearly dry adiabatic, in swrn Nebraska late Wednesday
afternoon. Cloud cover was increased in swrn Nebraska. For now, will
leave the forecast dry, but wouldn`t be surprised if a stray shower
or two develops in far swrn Nebraska Weds. afternoon.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 340 PM CDT Tue Mar 20 2018
Mid range...Wednesday night through Friday...Ridging aloft will
build into the central CONUS Wednesday night into Thursday night
before shifting east of the area on Friday. Highs will reach the
middle 50s to lower 70s both days. Mainly dry conditions are
expected, however, there will be a small chance for showers across
northern Nebraska Thursday night, as a weak disturbance lifts across
the Dakotas. Weak lift in association with this feature will track
along the SD/Nebr. border, thus the low pcpn chances.
Long term...Friday night through Tuesday...The threat for
precipitation will increase Friday night as a lead shortwave
tracks east of the central Rockies. Better moisture is across
central and eastern Kansas where the GFS pushes surface dew points
into the lower 60s, however, sfc dew points do reach the middle
40s Friday afternoon. With steep lapse rates present, cannot rule
out thunderstorms and have inserted them into the fcst for late
Friday afternoon/Friday evening. Another shot of precipitation
will track through the forecast area Saturday night followed by a
stronger system on Sunday. This system will be associated with an
arctic cold front so the mode of precipitation will change from
rain Saturday night, to snow on Sunday night with cooler readings
expected for Monday and Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 623 PM CDT Tue Mar 20 2018
VFR is generally expected across western and north central
Nebraska tonight and Wednesday.
The ongoing shower activity will dissipate around sunset.
Thereafter, weak high pressure and more stable air will build into
the region. Patchy fog is possible for a few hours Wednesday
morning affecting areas along and east of highway 183. Once this
lifts, around 15z, VFR will become widespread.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
953 PM CDT Tue Mar 20 2018
.UPDATE...For 06Z Aviation discussion below
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM CDT Tue Mar 20 2018
Two short wave were evident across the Northern Plains, and Upper
Midwest this afternoon in the latest water vapor imagery. Forcing
associated with these short waves, and ample moisture, led to
occasional light snow. However, wind energy was weak, leading to
weak convergence and very subtle lift. Therefore, any snow,
combined with stronger solar insolation, kept snowfall amounts
very light. Snowfall amounts after sunrise today were kept below
one inch, and mainly in areas along the Minnesota River Valley
where slightly stronger energy was noted with the short wave in
Iowa. The main change overnight was to add some light freezing
drizzle in western Minnesota due to weak lift and the lack of
cloud ice seeding. A stronger wave was evident across northern
Montana this afternoon which may allow for a more concentrated
area of light freezing drizzle or light snow Wednesday morning in
central Minnesota. The latest HRRR has some weak returns noted in
central Minnesota after 12z Wednesday. However, even if some light
precipitation develops, it shouldn`t have much of an impact due
the very light duration/amounts expected.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 325 PM CDT Tue Mar 20 2018
The main concern for the upcoming weekend storm is whether the
current model trends have the right idea of moving the main storm
system further to the south, and cutting off any significant
precipitation over Minnesota, and western Wisconsin.
Over the past 24 hours, models have trended drier and cooler for
this upcoming weekend storm. Confidence has increased that most of
the precipitation Friday night, and into early Saturday morning
will be in the form of snow. A mixture of rain or snow is possible
Friday, but with a drier east/southeast flow initially, the
precipitation could be delayed. Plus, the higher March sun angle
will also play a role of precipitation type Friday afternoon once
precipitation starts in western Minnesota. Eventually the
combination of strong isentropic lift along a strengthening
thermal boundary will lead to widespread precipitation across
western Minnesota by Friday afternoon, it will slowly move
east/southeast, but the persistent drier easterly flow will limit
the forward progression to the east. This may be one of those
weather systems that have a very sharp precipitation gradient from
west to east. Overall, there remains high confidence that
precipitation will form and overspread Minnesota Friday
afternoon/evening. There is lower confidence on how far
east/northeast the precipitation develops. Therefore, west central
Wisconsin could be in the zone where only a light dusting of snow
occurs, vs a much heavier wet snow develops in central and east
central Minnesota.
This system is also fairly fast which leads to less likely of
flooding problems. However, the mean flow becomes more southwest
next week, and this is a very unsettled pattern for the Upper
Midwest. It is also a warmer pattern which is more prone to liquid
precipitation vs. frozen this time of year. Either way, a much
wetter pattern is likely next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 954 PM CDT Tue Mar 20 2018
MVFR conditions will prevail into Wednesday at most MN sites,
with IFR ceilings possible at times overnight at western sites
(KAXN and KRWF). Improvement will be slow on Wednesday, with MN
sites likely to experience MVFR ceilings through much of the day.
Light and variable to southeast winds gradually become southerly
on Wednesday, but speeds will be light overall(generally around
5 knots).
KMSP...
KMSP will be on the edge of MVFR ceilings, but expect the
potential to increase during the overnight hours. Would expect
them to stay above 1800 feet however.
/OUTLOOK FOR KMSP/
THU...VFR. Wind ENE 5 kts.
FRI...VFR early becoming MFVR with -RA/-SN. Wind ESE 10G15
kts.
SAT...MVFR with Chc -RA/-SN. Wind ESE 10G15 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...JLT
LONG TERM...JLT
AVIATION...LS
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