Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/29/17
Area Forecast Discussion
National Weather Service Bismarck ND
932 PM CDT Sat Oct 28 2017
Issued at 932 PM CDT Sat Oct 28 2017
Temperatures slow to cool thanks to cloud cover and a steady
mixing wind. Adjusted hourly temperatures based on latest
observations, though overall I kept forecast mins roughly
Issued at 657 PM CDT Sat Oct 28 2017
ESRL HRRR and other high resolution guidance in very nice
agreement for tonight regarding the band of light rain forecast to
develop along a southward moving cold front. We opted to increase
POPs a bit based on this higher confidence. The aerial coverage of
POPs more or less the same as the inherited forecast portrayed.
Models have come in stronger with winds for Sunday. BUFKIT
indicates near to low end wind advisory gusts. No headlines issued
this evening, but we did increase the winds a tad and will throw a
mention in the HWO.
.SHORT TERM...(This evening through Sunday)
Issued at 233 PM CDT Sat Oct 28 2017
Tonight...A cold front will move through, bringing a chance of
rain and breezy northwest winds.
Most models depict some light rain forming along the front from
northwest to southeast stretching across North Dakota. Warm air
advection today has allowed temperatures to rise well above
freezing. These warmer temperatures will hold on through most of
the night and keep precipitation in the form of rain.
During the day Sunday cold air advection will be in full force.
The pressure gradient will steepen as a deep surface low passes
by to the north. Northwesterly winds gusting to around 40 mph are
possible during the afternoon. Most models top out with gusts at,
or just below 40 mph and keep the main area of pressure rises to
the southwest. Therefore, elected not to issue any wind headlines
for this forecast.
With colder temperatures filtering in Sunday afternoon and evening
some snow may develop around the Turtle Mountains as a secondary
cold front moves into the north.
.LONG TERM...(Sunday night through Saturday)
Issued at 233 PM CDT Sat Oct 28 2017
Overnight Sunday there is a chance of light snow as the secondary
cold front and an upper level wave rotates around the low in
Canada. Only minor moisture seems possible so little to know
accumulation is expected.
For the rest of the long term it appears rather chilly, with off
and on chances for rain/snow as northwest flow keeps dropping in
reinforcing shots of colder air.
The best chance for precipitation over the next week appears to be
Wednesday as the GFS and ECMWF models show a low moving across
southern Canada again.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 657 PM CDT Sat Oct 28 2017
Overnight a cold front will move from north to south across North
Dakota. With the FROPA, light rain and bkn-ovc mid level clouds
will push from north to south. Will go with a period of -RA in the
TAFs late this evening and overnight. In addition, MVFR CIGS are
expected for mainly southern terminals of KDIK-KBIS-KJMS after 08Z
through 14Z. Increasing northwest winds will follow the front,
gusting to 35 kts at all terminals by 17Z Sunday if not before.
Area Forecast Discussion
National Weather Service Louisville KY
1122 PM EDT Sat Oct 28 2017
Issued at 1121 PM EDT Sat Oct 28 2017
Video out of Lexington this evening shows some snow flurries flying.
The latest HRRR run actually does depict scattered flurries across
the region through the overnight hours. NAM soundings also show a
decently deep low level saturated layer up to -8 to -9C. Given this,
have added flurries in for the entire forecast area tonight. No
other major changes were made.
Issued at 935 PM EDT Sat Oct 28 2017
Temps very slow to fall this evening as the stratus deck remains
quite solid over the Ohio Valley. We`ll remain cloudy through the
night, and finally start clearing from west to east late Sunday
morning as the upper trof axis finally pushes across the Ohio
Valley. Min temps still on track to run just above freezing, with
cloud cover and light NW winds really limiting any frost formation.
No changes planned.
.Short Term...(This evening through Sunday night)
Issued at 220 PM EDT Sat Oct 28 2017
As of mid-afternoon, a surface analysis had low pressure near
Mackinac Island, Michigan while yesterday`s cold front was now along
the spine of the Appalachians. Visible satellite imagery showed a
blanket of stratus wrapping around the low from the Upper Midwest
through the lower Ohio Valley. Northwest winds prevailed, and
readings remained unseasonably cold in the upper 30s to lower 40s.
For this evening and tonight, plan on mostly cloudy to overcast
skies with the moisture remaining trapped in the low-level
inversion. Moisture time-height analysis across the area shows
little erosion or drying of the moisture overnight and this
increased cloud cover combined with a steady wind should preclude
widespread freezing or sub-freezing temperatures. No freeze
headlines will be needed across southern Indiana and central
Kentucky, though patchy frost may form in the sheltered areas. Lows
will range from 33 to 37.
For tomorrow, plan on mostly cloudy to overcast skies in the morning
then some improvement west to east in the afternoon as the upper
level trough axis moves east of the area. With the increased cloud
cover, especially across the Bluegrass, lowered highs a few degrees.
Look for readings to top out in the middle 40s.
Sunday night`s lows will bottom out early in the night with calm
winds and mostly clear skies expected, then begin to steady out as a
light southerly wind develops along with some increasing high
clouds. Readings are forecast to drop into the 30-35 range, coldest
along/east of I-65. This might be near levels for a freeze or frost
headline in some places but in coordination with surrounding
offices, will hold off on issuing any this afternoon.
.Long Term...(Monday through Saturday)
Issued at 225 PM EDT Sat Oct 28 2017
Fast zonal flow will setup across the central US Monday and
Tuesday with quick moving shortwaves staying north of the area.
Dry conditions are expected with seasonably cool temperatures on
Monday while a front swings through the area. It should pass
through with just increased cloud cover in the afternoon. Plan on
highs in the mid/upper 50s Monday followed by low/mid 50s on
Tuesday. Lows will stay mainly in the mid 30s to around 40.
Southwest flow aloft is then expected to develop Wednesday through
next weekend with several disturbances moving through the flow. The
first system still looks to arrive on Wednesday and Wednesday
night. Confidence drops off Thursday onward as a frontal boundary
may stall out in the region, and be the focus for multiple waves
of rain. Overall, the end of the upcoming work week looks
unsettled and will carry at least high chances to low likely range
PoPs into next weekend.
.Aviation...(00Z TAF Issuance)
Issued at 655 PM EDT Sat Oct 28 2017
NW flow well established in the boundary-layer, but enough low-level
moisture remains trapped below an inversion at 850mb for a stratus
ceiling, which has built down into MVFR but remains above fuel-
alternate. Synoptic and some hi-res models try to lift this deck
into VFR overnight. However, GFS LAMP still has conditional MVFR,
and NARRE shows oscillating probabilities of low ceilings. Given the
full suite of information vs the tendency for stratus to build down
at night, will split the difference and maintain status quo well
into Sunday morning, with light NW winds. Boundary-layer warming and
deeper mixing should lift ceilings to VFR around midday Sunday, but
won`t scatter out until mid/late afternoon as the upper trof finally
pushes east of the area.
Area Forecast Discussion
National Weather Service Raleigh NC
1010 PM EDT Sat Oct 28 2017
A cold front will approach from the west tonight and cross central
NC early Sunday. High pressure will build into our region behind the
exiting front Sunday night and Monday.
.NEAR TERM /OVERNIGHT/...
As of 1010 PM Saturday...
Forecast will require little adjustments through the overnight. Near
term model guidance as well as recent additions of the HRRR still
suggest that the bulk of the shower activity associated with the
front will remain west of our Piedmont counties through late evening
then progress eastward after midnight, though coverage and intensity
will be weaker compared to current radar presentation. Portions of
the Triangle may not see appreciable rainfall until closer to
HRRR trends still depict a batch of showers and isolated t-storms
lifting nwd over our southeastern counties (Sampson, Wayne and
Wilson) late this evening into the overnight. This region of the
state will have the best potential to experience weak
destabilization at the surface as sely low level flow advect warm
moist air off the Atlantic. In addition, mid level lapse rates in
this area hovering between 6.5 and 7 deg C/km. Enough bulk shear is
present to aid in organization of some of the cells, and with storm
relative helicity projected to be between 100-200 m2/s2 after
midnight, the deeper cells will likely exhibit some rotation aloft.
Weak instability at the surface will likely prevent storms from
The upper level system affecting the southern FL peninsula appears
likely to disrupt the moisture transport into our region late
tonight into Sunday, leading to smaller precip amounts total. This
will likely be realized over the Triangle area where rainfall
amounts may total a quarter of an inch or less.
Min temps will likely be achieved at or shortly after daybreak as
the sfc front will be crossing the Piedmont at that time. Min temps
will vary from the low-mid 50s far west to the lower 60s east.
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 300 PM Saturday...
The front will initiate drying and cold air advection as early as
sunrise in the western Piedmont, with the chances for showers
tapering off post-fropa. The front will reach the I95 corridor in
the early afternoon and should be east of the area by sunset. Highs
will be hampered by earlier onset of cold air advection in the west,
and temperatures will top out in the mid 50s...while the far east
may reach 70 before the front makes it through. It will be breezy
behind the front, with northwest winds gusting 20 to as much as 30
mph behind the front for a few hours. The wind will relax late
tomorrow night, and a couple of hours of radiational cooling will
allow mins to fall to the low and mid 30s for Monday morning.
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 240 PM Saturday...
The upper level low pressure system will continue moving away from
the Mid-Atlantic, getting absorbed into a secondary low moving east
through Canada on Monday. The remnant weak upper level trough over
the Carolinas will relax on Monday. At the surface, high pressure
will build over and move through the region Monday and Tuesday while
a cold front lingers west of the Appalachians. The mid/upper level
flow over the region will become more westerly, then southwesterly
through the middle of the week as another upper level trough
gradually amplifies over the central U.S. As of the latest medium-
range model runs, the surface cold front should not make it into
Central NC by the end of the period, likely stalling over the mtns
and becoming more west-east oriented well north of the area. There
is still some uncertainty regarding the eventual progression of the
front late in the weekend. There is a slight chance for some
rainfall over Central NC ahead of the cold front, as the cold front
approaches the mtns and southeasterly return flow off the Atlantic
increases. However, the parent low is so far to the northeast (over
Eastern Canada) and the shear axis weakens considerably as it moves
into the mtns that the chance for any significant rainfall with this
system appears minimal at this time. Expect moderating temperatures;
from highs in the upper 50s/low 60s and lows in the upper 30s/low
40s Monday and Monday night, to highs in the mid 70s and lows in the
low/mid 50s Friday and Friday night.
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 800 PM Saturday...
The latest data analysis indicated a weak low pressure along the
front over the SW Piedmont near KCLT. This low is forecast by the
latest Hi-Res models to move northward toward KINT/KMWK in the
next 3-4 hours. The cold front is slated to move into the western
Piedmont, then stall for a few hours as another low develops to the
south. This low pressure will then move into VA around 12-13z/Sunday
propelling the cold front east across central NC during the
morning. A broad area of showers with IFR CIGS/VSBYS will accompany
the front as it moves slowly to the east overnight into Sunday
morning. A separate area of showers with possible isolated
thunderstorms is expected from near KFAY to KRDU eastward late
tonight. Some thunder may need to be added to the TAF sites in these
areas later, depending on development. Otherwise, VFR CIGS in the
east will become IFR tonight and linger Sunday morning with IFR to
MVFR CIGS with scattered to numerous showers.
As the winds become more westerly and increase in speed to 15-25kt
on Sunday, VFR conditions will return from southwest to northeast
between 15z-21z. Finally, VFR conditions with no CIGS will arrive
with much drier air late Sunday through Sunday night. Winds will
remain 15-25 kt with gusts to 30 kt until 06z/Mon when the winds
will begin to subside to 10 kt.
VFR conditions can then be expected Sunday night through the middle
of the week.