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Office: BIS

FXUS63 KBIS 200542
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1242 AM CDT Thu Sep 20 2018

.UPDATE...
Issued at 1230 AM CDT Thu Sep 20 2018

For the early morning update the main change was to update pop
grids to delay the onset of precipitation. Currently a couple
blips showing up over western ND with closest reflectivities from
Glasgow to Miles City. Utilized a blend of short term model
guidance with official grids through Thursday morning. Short term
models hold off precip even longer but looking at bufkit sounding
and latest medium range guidance, strong forcing should really
pick up 12-15 UTC over western ND. Made a few adjustments to sky
cover and resulting temperatures in the near term.

UPDATE Issued at 917 PM CDT Wed Sep 19 2018

The short-term forecast remains on track. Future updates may need
to slow down the arrival times of likely PoPs across southern ND,
but left as is for now.

Made a few minor adjustments to the Thursday afternoon into Friday
morning timeframe. The first concern is the potential for snow
mixing in with rain Thursday evening as both diabatic and
advective processes cool the boundary layer into the 30s. Think
that for any given location, by the time thermal profiles would
cool enough for snow to reach the surface, much of the
precipitation will have concluded. However, there does appear to
be some potential for dynamic cooling. Do have a bit of rain mixed
with snow mentioned in the forecast for parts of western North
Dakota, but do not expect this to be a widespread occurrence.

The second concern involves the potential for frost Thursday night
into Friday morning. It will greatly depend on how quickly clouds
dissipate and where the center of the surface high winds up.
Recent guidance suggests that cloud cover will hold on across much
of western and central ND until at least 06-09Z, which would
allow only a few hours at most for strong radiational cooling.
Raised low temperatures Thursday night by a degree or two and
trended somewhat away from widespread/areas of frost mention. Will
let the next shift evaluate 00Z guidance before making further
adjustments.

UPDATE Issued at 652 PM CDT Wed Sep 19 2018

No major changes for this update. Blended in current obs and
short-term forecast guidance.

Over the last hour, a weakening trend has been observed in the
showers streaming across northeast MT into far northwest ND.
These showers appear to be tied to weak mid-level frontogenesis,
which latest runs of the RAP indicate will continue to weaken this
evening.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 330 PM CDT Wed Sep 19 2018

Chances of showers and amounts of expected rainfall are the main
concern in this short term period...followed by possible frost
Thursday night into Friday morning.

Cool high pressure was center over the Saskatchewan/Montana/ND
border this afternoon, with a large and deepening low pressure
system over the central Plains - centered over eastern Colorado. At
upper levels, a West Coast trough continued to deepen, with
southwest flow aloft set up over the US Rockies and fairly zonal
flow aloft over the Northern Plains. Some light rain showers
continued over northeastern Montana into northwestern North Dakota,
associated with some upper level impulses moving east in the zonal
flow aloft.

Tonight:

The upper level West Coast trough continues to dig as it moves east
across the Rockies, with the leading edge of its stronger upper
level impulses reaching far southwestern North Dakota by around
midnight tonight, then continuing north and east. Meanwhile at the
surface, a warm front develops northeastward tonight from the
Colorado low as a low level jet develops over the southern Plains
into the central US Plains. The surface low and warm front move
northward, the low center reaching into central Nebraska and the
warm front reaching into southern Minnesota by daybreak Thursday
morning.

Thursday:

The base of the upper level trough lifts northeastward into the
Dakotas through the day. The surface low develops northeastward
along the warm front, crossing southern Minnesota into Lake
Superior. Thus North Dakota remains on the cooler side of the
system, with increasing easterly winds becoming northeasterly, and
finally northerly by Thursday evening. Plenty of upward motion with
this system over our area, with h500-300 Q vector divergence and
h700-500 lapse rates of 4-6 C/km and plenty of low level isentropic
lift.

Thursday night:

The upper level trough moves east across the Dakotas into Minnesota
by daybreak Friday morning, with a cold surface Canadian high
pressure system following the exiting system. Low temperatures are
forecast to drop into the 30s for much of western and central North
Dakota. Areas where precipitation is lingering as cold air moves in
may see a rain/snow mix develop briefly. Radiational cooling where
cloud cover clears with the post-frontal surface high will become an
issue for frost/freeze conditions Thursday night as well.

Regarding rainfall:

Expecting best chances of rain showers beginning in southwestern ND
after midnight tonight, spreading north and east across western and
southern North Dakota. Daytime Thursday appears to be the time of
highest precip chances and the time when the highest amounts of
rainfall will occur. By Thursday evening, the better precip amounts
lift northward across northern and eastern ND, before tapering off
from west to east after midnight. Storm totals tonight through
Thursday night appear to be in the 1/2 inch to 1 inch range for most
of western and central North Dakota. There may be some locales that
receive more than an inch, and some areas that receive less than 1/2
inch...but for the most part this should be a widespread rain event
with nearly all areas receiving some decent amounts of rainfall.

.LONG TERM...(Friday through Wednesday)
Issued at 330 PM CDT Wed Sep 19 2018

Cooler and dry conditions on Friday with high temperatures in the
50s.

Zonal flow aloft Saturday, with some upper level impulses moving
east across northern ND. This will bring small chances of rain
showers across the north with cooler conditions - highs Saturday in
the 50s north, while 60s and lower 70s are forecast for southern ND.

On Sunday another longwave trough digs across the northern Rockies
into the Northern Plains, bringing off and on chances of showers to
most of North Dakota Sunday through Wednesday. Highs mainly in the
50s to lower 60s this time period, with lows mainly 35 to 45.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1230 AM CDT Thu Sep 20 2018

VFR conditions to begin the 06Z TAF period. Expect widespread
MVFR-IFR ceilings and visibilities to develop at KDIK and KBIS
from 12-15 UTC, KISN and KJMS 15-18 UTC and KMOT 18-20 UTC. Once
low ceilings/vsbys begin in rain showers and fog, expect them to
linger through the 06Z forecast period. Northeast to east surface
flow will increase during the morning hours to around 15 knots
gusting up to 25 kts and shift north during the afternoon. North
to northwest winds will then gradually diminish from 00-06 UTC.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...TWH
SHORT TERM...JV
LONG TERM...JV
AVIATION...TWH

FXUS63 KBIS 200542
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1242 AM CDT Thu Sep 20 2018

.UPDATE...
Issued at 1230 AM CDT Thu Sep 20 2018

For the early morning update the main change was to update pop
grids to delay the onset of precipitation. Currently a couple
blips showing up over western ND with closest reflectivities from
Glasgow to Miles City. Utilized a blend of short term model
guidance with official grids through Thursday morning. Short term
models hold off precip even longer but looking at bufkit sounding
and latest medium range guidance, strong forcing should really
pick up 12-15 UTC over western ND. Made a few adjustments to sky
cover and resulting temperatures in the near term.

UPDATE Issued at 917 PM CDT Wed Sep 19 2018

The short-term forecast remains on track. Future updates may need
to slow down the arrival times of likely PoPs across southern ND,
but left as is for now.

Made a few minor adjustments to the Thursday afternoon into Friday
morning timeframe. The first concern is the potential for snow
mixing in with rain Thursday evening as both diabatic and
advective processes cool the boundary layer into the 30s. Think
that for any given location, by the time thermal profiles would
cool enough for snow to reach the surface, much of the
precipitation will have concluded. However, there does appear to
be some potential for dynamic cooling. Do have a bit of rain mixed
with snow mentioned in the forecast for parts of western North
Dakota, but do not expect this to be a widespread occurrence.

The second concern involves the potential for frost Thursday night
into Friday morning. It will greatly depend on how quickly clouds
dissipate and where the center of the surface high winds up.
Recent guidance suggests that cloud cover will hold on across much
of western and central ND until at least 06-09Z, which would
allow only a few hours at most for strong radiational cooling.
Raised low temperatures Thursday night by a degree or two and
trended somewhat away from widespread/areas of frost mention. Will
let the next shift evaluate 00Z guidance before making further
adjustments.

UPDATE Issued at 652 PM CDT Wed Sep 19 2018

No major changes for this update. Blended in current obs and
short-term forecast guidance.

Over the last hour, a weakening trend has been observed in the
showers streaming across northeast MT into far northwest ND.
These showers appear to be tied to weak mid-level frontogenesis,
which latest runs of the RAP indicate will continue to weaken this
evening.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 330 PM CDT Wed Sep 19 2018

Chances of showers and amounts of expected rainfall are the main
concern in this short term period...followed by possible frost
Thursday night into Friday morning.

Cool high pressure was center over the Saskatchewan/Montana/ND
border this afternoon, with a large and deepening low pressure
system over the central Plains - centered over eastern Colorado. At
upper levels, a West Coast trough continued to deepen, with
southwest flow aloft set up over the US Rockies and fairly zonal
flow aloft over the Northern Plains. Some light rain showers
continued over northeastern Montana into northwestern North Dakota,
associated with some upper level impulses moving east in the zonal
flow aloft.

Tonight:

The upper level West Coast trough continues to dig as it moves east
across the Rockies, with the leading edge of its stronger upper
level impulses reaching far southwestern North Dakota by around
midnight tonight, then continuing north and east. Meanwhile at the
surface, a warm front develops northeastward tonight from the
Colorado low as a low level jet develops over the southern Plains
into the central US Plains. The surface low and warm front move
northward, the low center reaching into central Nebraska and the
warm front reaching into southern Minnesota by daybreak Thursday
morning.

Thursday:

The base of the upper level trough lifts northeastward into the
Dakotas through the day. The surface low develops northeastward
along the warm front, crossing southern Minnesota into Lake
Superior. Thus North Dakota remains on the cooler side of the
system, with increasing easterly winds becoming northeasterly, and
finally northerly by Thursday evening. Plenty of upward motion with
this system over our area, with h500-300 Q vector divergence and
h700-500 lapse rates of 4-6 C/km and plenty of low level isentropic
lift.

Thursday night:

The upper level trough moves east across the Dakotas into Minnesota
by daybreak Friday morning, with a cold surface Canadian high
pressure system following the exiting system. Low temperatures are
forecast to drop into the 30s for much of western and central North
Dakota. Areas where precipitation is lingering as cold air moves in
may see a rain/snow mix develop briefly. Radiational cooling where
cloud cover clears with the post-frontal surface high will become an
issue for frost/freeze conditions Thursday night as well.

Regarding rainfall:

Expecting best chances of rain showers beginning in southwestern ND
after midnight tonight, spreading north and east across western and
southern North Dakota. Daytime Thursday appears to be the time of
highest precip chances and the time when the highest amounts of
rainfall will occur. By Thursday evening, the better precip amounts
lift northward across northern and eastern ND, before tapering off
from west to east after midnight. Storm totals tonight through
Thursday night appear to be in the 1/2 inch to 1 inch range for most
of western and central North Dakota. There may be some locales that
receive more than an inch, and some areas that receive less than 1/2
inch...but for the most part this should be a widespread rain event
with nearly all areas receiving some decent amounts of rainfall.

.LONG TERM...(Friday through Wednesday)
Issued at 330 PM CDT Wed Sep 19 2018

Cooler and dry conditions on Friday with high temperatures in the
50s.

Zonal flow aloft Saturday, with some upper level impulses moving
east across northern ND. This will bring small chances of rain
showers across the north with cooler conditions - highs Saturday in
the 50s north, while 60s and lower 70s are forecast for southern ND.

On Sunday another longwave trough digs across the northern Rockies
into the Northern Plains, bringing off and on chances of showers to
most of North Dakota Sunday through Wednesday. Highs mainly in the
50s to lower 60s this time period, with lows mainly 35 to 45.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1230 AM CDT Thu Sep 20 2018

VFR conditions to begin the 06Z TAF period. Expect widespread
MVFR-IFR ceilings and visibilities to develop at KDIK and KBIS
from 12-15 UTC, KISN and KJMS 15-18 UTC and KMOT 18-20 UTC. Once
low ceilings/vsbys begin in rain showers and fog, expect them to
linger through the 06Z forecast period. Northeast to east surface
flow will increase during the morning hours to around 15 knots
gusting up to 25 kts and shift north during the afternoon. North
to northwest winds will then gradually diminish from 00-06 UTC.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...TWH
SHORT TERM...JV
LONG TERM...JV
AVIATION...TWH



Office: FGF FXUS63 KFGF 200442 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1142 PM CDT Wed Sep 19 2018 .UPDATE... Issued at 1142 PM CDT Wed Sep 19 2018 Made a few further tweaks to POPs and cloud cover, but overall continued trend of increasing clouds tonight and precip moving in tomorrow morning. && .SHORT TERM...(This evening through Thursday) Issued at 302 PM CDT Wed Sep 19 2018 Very light showers were observed through much of the day, mainly south of Interstate 94. Elsewhere, persistent cloud cover continues to slowly dissipate with temperatures climbing into the upper 50s to middle 60s. This evening brings partly cloudy skies with low temperatures falling into upper 30s along the U.S. - Canada border with lower to middle 50s south of Interstate 94. Cloud cover increases through the night and into Thursday morning with widespread rain chances expected through the day and into the overnight hours. Rainfall totals across the region will range from around 0.50 inch to nearly 1.25 inches. .LONG TERM...(Thursday night through Wednesday) Issued at 302 PM CDT Wed Sep 19 2018 Active flow out of the southwest will continue to characterize the region's weather during the extended period. Moderate rain should be ongoing over eastern forecast area (with risk of some sub-severe thunder) as the period begins as strengthening sfc low heads toward MN arrowhead while shortwave traverses ND causing lesser amounts of rainfall over western parts of the forecast area. The potential is there for one half to one and a half inches of rain with the higher amounts favoring west central MN. High pressure at the surface will follow on Fri into Fri night providing drier air and a cool down by Fri night. Frost potential looks to be problematic as some cloudiness/pcpn could occur over areas most likely to drop below 40 degrees. Best chances for frost would likely be over NW MN Sun morning, but again, both ECMWF and GFS are advertising shower risks proximal to the Canadian border. Of more consequence could be the next system for Mon. There are some guidance differences but a blended solution brings sfc low/boundary along a similar path to that of tomorrow's complex, with a trough of more than adequate potency for support. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1142 PM CDT Wed Sep 19 2018 High and mid clouds will continue to overspread the area overnight, with all TAF sites remaining VFR. Rain will begin to move into the area mid morning, starting out as VCSH but becoming more widespread so have all sites with -RA prevailing by afternoon. Ceilings will drop to MVFR or IFR conditions by the end of the period, and some visibilities will be down into the 3-5SM range. Winds will increase out of the northeast tonight and tomorrow with gusts above 20 kts at times, eventually shifting to the north. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR SHORT TERM...Lynch LONG TERM...WJB AVIATION...JR FXUS63 KFGF 200442 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1142 PM CDT Wed Sep 19 2018 .UPDATE... Issued at 1142 PM CDT Wed Sep 19 2018 Made a few further tweaks to POPs and cloud cover, but overall continued trend of increasing clouds tonight and precip moving in tomorrow morning. && .SHORT TERM...(This evening through Thursday) Issued at 302 PM CDT Wed Sep 19 2018 Very light showers were observed through much of the day, mainly south of Interstate 94. Elsewhere, persistent cloud cover continues to slowly dissipate with temperatures climbing into the upper 50s to middle 60s. This evening brings partly cloudy skies with low temperatures falling into upper 30s along the U.S. - Canada border with lower to middle 50s south of Interstate 94. Cloud cover increases through the night and into Thursday morning with widespread rain chances expected through the day and into the overnight hours. Rainfall totals across the region will range from around 0.50 inch to nearly 1.25 inches. .LONG TERM...(Thursday night through Wednesday) Issued at 302 PM CDT Wed Sep 19 2018 Active flow out of the southwest will continue to characterize the region's weather during the extended period. Moderate rain should be ongoing over eastern forecast area (with risk of some sub-severe thunder) as the period begins as strengthening sfc low heads toward MN arrowhead while shortwave traverses ND causing lesser amounts of rainfall over western parts of the forecast area. The potential is there for one half to one and a half inches of rain with the higher amounts favoring west central MN. High pressure at the surface will follow on Fri into Fri night providing drier air and a cool down by Fri night. Frost potential looks to be problematic as some cloudiness/pcpn could occur over areas most likely to drop below 40 degrees. Best chances for frost would likely be over NW MN Sun morning, but again, both ECMWF and GFS are advertising shower risks proximal to the Canadian border. Of more consequence could be the next system for Mon. There are some guidance differences but a blended solution brings sfc low/boundary along a similar path to that of tomorrow's complex, with a trough of more than adequate potency for support. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1142 PM CDT Wed Sep 19 2018 High and mid clouds will continue to overspread the area overnight, with all TAF sites remaining VFR. Rain will begin to move into the area mid morning, starting out as VCSH but becoming more widespread so have all sites with -RA prevailing by afternoon. Ceilings will drop to MVFR or IFR conditions by the end of the period, and some visibilities will be down into the 3-5SM range. Winds will increase out of the northeast tonight and tomorrow with gusts above 20 kts at times, eventually shifting to the north. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR SHORT TERM...Lynch LONG TERM...WJB AVIATION...JR