Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/21/25
Area Forecast Discussion
National Weather Service Bismarck ND
719 PM CDT Thu Mar 20 2025
.KEY MESSAGES...
- Southwest winds 20 to 30 mph and minimum relative humidity
values ranging from 17 to 25 percent will continue to result
in critical fire weather conditions this afternoon over much
of south central North Dakota into the James River Valley.
- 20 to 40 percent chance for light rain or snow over western
and central North Dakota tonight, departing Friday morning.
- Greater chances for rain or snow (50 to 70 percent) are
expected Saturday into Sunday, with the highest chances
Saturday night. Some snow accumulations are possible.
&&
.UPDATE...
Issued at 714 PM CDT Thu Mar 20 2025
RADAR shows showers that continue to move across eastern
Montana and are forecast to move into western and southwestern
North Dakota this evening. Winds remain elevated across the
state, but are forecast to decrease as mixing subsides. A cold
front continues to move down approaching the International
Border. Relative humidity continues to increase and decreasing
winds as a result critical fire weather conditions continue to
subside. Therefore, the Red Flag Warning was allowed to expire.
No updates are needed at this time as the forecast remains on
track.
&&
.DISCUSSION...
Issued at 248 PM CDT Thu Mar 20 2025
At the upper levels, a ridge axis is currently located near the
Montana/North Dakota border. This feature will continue to move
east through the day while deamplifying as the next shortwave
approaches. This pattern has led to a mostly sunny day with
only a few high clouds floating around. We have been warming
nicely with the ridging moving in as we are seeing widespread
temperatures in the 50s as of this writing. A few highs in
lower 60s are likely before the day is over across the southwest
or south central. On the other hand, dewpoints are only in the
mid teens to lower 20s, indicating a very dry airmass so
afternoon humidity values should bottom out into the 17 to 25
percent range across the southern half of the state. Southwest
winds have also increased this afternoon with several sites
currently seeing sustained values in the 20 to 30 mph range,
especially across the James River Valley. Here, we are likely to
see critical fire weather conditions continue for the next
several hours and the Red Flag Warning continues to be in good
shape. For areas just outside of the warning area and across
the rest of the south central and southwest, near critical fire
weather conditions will remain possible through the rest of the
afternoon. Conditions should improve this evening as we start to
cool down again.
A weak Clipper system approaches this evening and most of the
CAMs are suggesting some showery activity as it moves into the
west. RAP soundings suggest steep lapse rates and maybe some
weak MUCAPE on the order of 100 to 200 J/kg for a couple hours
early this evening across the southwest. Thus, a stray lightning
strike or two is not out of the question here. Low to medium
precipitation chances (20 to 40 percent) will then cross the
state overnight with some snow likely mixing in after midnight
and tapering off Friday morning. Little to no accumulation is
expected.
Western and central North Dakota transitions back into northwest
flow aloft on Friday with cooler temperatures. Highs are
forecast to range from the lower 20s in the vicinity of the
Turtle Mountains, to around 50 southwest. Ridging will once
again move in on Saturday which will promote another warmup.
Highs are forecast to range from the mid 30s northeast to the
low to mid 50s south central and southwest.
The next shortwave will then follow the ridge on Saturday
afternoon as a surface low deepens over eastern Montana. This
system will be a similar story to tonight regarding
precipitation type: starting as rain on Saturday, snow mixing in
by Saturday evening, and eventually changing to all snow
overnight and into Sunday morning. The difference is that this
Clipper is forecast to be a bit stronger, although it is
currently unclear just how much stronger. At the moment, cluster
analysis depicts two clear scenarios. One scenario would be a
weaker surface low and less precipitation and the other would be
a deeper low and more precipitation. As of now, the weaker
solution is favored by around 60 percent to 40 percent. The
stronger solution (or cluster) also seems to be GEFS heavy which
has been a bit of an outlier in the past several runs. Looking
at the NBM probabilities, there is a 40 to 60 percent chance of
an inch of snow or greater across much of the north and then
into the greater Devils Lake Basin and northern James River
Valley. Increasing that threshold to 2 inches, the same area
ranges from about 20 to 40 percent. If the stronger scenario
were to verify, these probabilities would likely increase quite
a bit with chances for some higher accumulations. That being
said, it is still too far out to speculate on exact amounts.
Finally, Saturday night through Sunday should be fairly windy as
decent cold air advection and strong pressure rises are
forecast to move through the region.
After another cool down on Sunday (forecast highs from around
30 northeast to mid to upper 40s southwest), we will rebound
mainly into the 40s and 50s early to mid week. The progressive
and active flow will continue early to mid week with a couple more
weak waves moving through the northwest flow aloft. Only low
precipitation chances (around 20 percent) are expected here and
there as these waves move through the region.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 714 PM CDT Thu Mar 20 2025
VFR conditions continue across the region tonight. Winds continue
across the state, but are forecast to decrease around Sunset. Winds
will veer out of the north tonight as a cold front moves through the
region. Showers are possible tonight for KXWA and maybe KDIK where
showers could transitions to snow later by the early morning hours
as temperature decreases. MVFR conditions are possible later
tomorrow morning across the state as low clouds move down from
Canada.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Johnson
DISCUSSION...ZH
AVIATION...Johnson
Area Forecast Discussion
National Weather Service Boise ID
858 PM MDT Thu Mar 20 2025
.DISCUSSION...Overcast conditions will persist this evening,
with showers increasing later tonight, primarily across our
northern zones, as a weak upper-level trough moves through.
High-resolution models now indicate showers reaching the
Treasure Valley between 10 PM and 3 AM MDT. However,
precipitation amounts will remain minimal, with less than 0.02
inches expected. Snow accumulation will also be light, with 1 to
3 inches forecast in the northern mountains above 5000 feet
MSL.
Showers are expected to taper off by sunrise, followed by a
brief break before a stronger system arrives Friday afternoon
and evening, bringing widespread precipitation. The region will
remain on the warm side of the upper-level jet during this
event, causing snow levels to rise to between 4500 and 5000 feet
by Friday afternoon. This system is expected to bring moderate
to heavy precipitation to the northern mountains, with liquid-
equivalent amounts ranging from 0.30 to 0.60 inches. Snow
accumulation between 4500 and 5500 feet MSL is forecast to range
from 2 to 5 inches, while higher elevations above 5500 feet
could see 5 to 10 inches of new snowfall. A minor update has
been made for precipitation tonight, but otherwise, the forecast
remains on track.
&&
.AVIATION...VFR with periods MVFR lower valleys through Friday
from rain/snow showers and low ceilings. MVFR-IFR in mtn valleys
through Friday with snow and low ceilings obscuring mtns. Snow
levels 3-4kft MSL rising to 4-5kft MSL on Friday. Surface winds:
W to SW 5-15 kt. Winds aloft at 10kft MSL: Westerly to 20 kt.
KBOI...VFR. A 40-50% chance of MVFR in rain showers overnight,
generally between 21/05Z-10Z. Light surface winds. Showers
Friday afternoon could produce brief MVFR conditions (15-25%
chance).
Weekend Outlook...Periods of precipitation will bring mtn IFR
and local valley MVFR. Best chance for VFR in e-central Oregon
and w- central ID mtns is Saturday afternoon and night. SE
Oregon and Snake Plain are dry with VFR on Sunday with lingering
showers in the mtns to the north. Snow levels 3-5kft from N-S
on Saturday rising to 5- 7kft from N-S on Sunday. Gusty W-NW
surface winds and strong westerly winds aloft on Saturday will
weaken on Sunday.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday night...Next Pacific
trough will spread light rain and snow across the northern half
of our CWA tonight. Latest NamNest and HRRR hi-res models have
lowered pcpn for tonight and are now closer to other models.
Snow amounts overnight will be 1-3 inches in northern mountains
above 5000 feet MSL, and less than one inch elsewhere. Flurries
will continue in the mountains Friday morning while other areas
dry out. On Friday afternoon the next and stronger Pacific
trough will spread more rain and snow across eastern OR, then
into western ID Friday evening. Pcpn with that system will be
moderate to heavy in northern mountains with .30 to .60 inch
liquid equivalent, or 2 to 5 inches new snow between 4500 and
5500 feet MSL, and 5 to 10 inches above 5500 feet. These
amounts are not quite enough for a Winter Weather Advisory in
the populated mountain areas. Southern areas will have .15 to
30 inch pcpn, or 2-4 inches new snow above about 5700 feet MSL,
with rain below. Pcpn will taper to showers Saturday morning,
but Saturday afternoon will become windy, especially in south-
central ID. Latest guidance, however, is not quite as windy as
before and a Wind Advisory looks doubtful at this time.
LONG TERM...Sunday through Thursday...A ridge will start to
build along the western U.S. Sunday, nudging the storm track
toward the north and east. As a result, a drying trend can be
expected across the forecast area, with the exception of west-
central Idaho and northeast Oregon where precipitation chances
(30-50%) will continue. Snow levels will rise through the day
Sunday, reaching approximately 6000 feet MSL for these areas.
The ridge will amplify Monday through Wednesday, supporting a
warming and drying trend in which temperatures are forecast
to climb 10-20 degrees above normal. A notable increase in
river/stream/creek flows are expected as these temperatures
accelerate snowmelt from the lower and middle elevations.
Thereafter, a broad, cold trough will approach the PacNW late
Wednesday, influencing E Oregon and SW Idaho by Thursday. Model
ensembles differ on the moisture and track of this low, which
will determine the extent of cooling and precipitation that
will occur. Currently, there is a 20-40% chance of precipitation
for the area on Thursday, with temperatures and snow levels
expected to gradually lower as this trough approaches.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...JDS
AVIATION.....DG
SHORT TERM...LC
LONG TERM....SH
Area Forecast Discussion
National Weather Service Des Moines IA
600 PM CDT Thu Mar 20 2025
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Increasing winds into Friday and warmer, with rain showers and
thunder possible by afternoon to evening
- Gusty winds Sunday with additional chances for more widespread
rain
- On and off chances for additional precipitation in the early
to midweek timeframe
&&
.DISCUSSION...
Issued at 248 PM CDT Thu Mar 20 2025
Following the dynamic system that brought a blizzard over
northwestern Iowa with several inches of snow, and convection, even
severe weather further east into Illinois, much quieter conditions
have spread across Iowa today as a ridge descends into the central
plains, with surface high pressure overhead. With snowpack over the
northwest, temperatures compared to the rest of the state were at
least a few degrees cooler in the upper teens to low 20s compared to
mid to upper 20s elsewhere this morning. However, with plenty of
sunshine and winds shifting more southwesterly through this
afternoon, temperatures have increased into the 30s north and in the
low 40s south. Satellite imagery shows melting of the snowpack
across the northwest with the abundant sunshine and warmer
temperatures, which should continue through at least the evening.
Highs in the 40s are expected across the state, warmest south. A
strengthening LLJ this evening into Friday will transport
warmer air into the state, with highs Friday expected to reach
into the 50s, while temperatures across the northwest with the
remaining snow reach the upper 40s. Increased winds, specially
in the morning are expected as model soundings indicate and
increase in low level mixing with dry air present, resulting in
gusts generally around 25- 30 mph. These breezy winds with
warmer temperatures and lower RH values dropping into the 30s
across southern Iowa will elevate fire weather concerns.
Therefore, special care will be needed to avoid fire starts and
spread. By Friday afternoon, a mid-level shortwave will descend
from the Dakotas into the state, which looks to bring a frontal
boundary across the state and the chance for rain. GFS and Euro
guidance have rather widespread rain arriving by mid to late
afternoon and departing by mid-evening. A closer look at CAM
guidance depicts a rather variable set of solutions, with the
RAP showing a more defined line of showers passing through from
late afternoon to evening, while the NAM and HRRR depict more
spotty coverage over the CWA, though the timing is generally
similar. QPF amount generally less than a tenth of an inch
expected where these showers occur, with PoPs extended a few
hours to account for the expected later end time. Some rumbles
of thunder are not out of the question as low end MUCAPE values
of a few hundred J/kg are depicted per sounding data.
Dry air overspreads the region with high pressure quickly pushing
southeast across Iowa Saturday. Southerly flow will increase
temperatures with values largely in the 50s, even near 60 south.
Looking further west into Saturday evening, a pair of low pressure
systems per model guidance move into the central plains; the first
being a deeper trough with a more tightly wrapped surface low over
Montana and the Dakotas, and a weaker wave over Kansas/Oklahoma
tracking eastward into the central CONUS. The southern
aforementioned system is expected to generate precipitation into MO
and southern Iowa Saturday evening into Sunday morning before
becoming phased with the deepening low pressure further north as it
passes through MN and into WI by Sunday afternoon, with increased
forcing to develop a large area of rain showers largely across
southern and eastern Iowa into Sunday. With the cool sector of
the low remaining north into Minnesota, any precipitation should
remain as rain, with total accumulations below a quarter inch.
The resultant tightened pressure gradient with this system looks
to bring gusty winds as well, with gusts up to 30-35+ mph.
Upper level northwest flow returns into Monday as a large ridge
moves across the western CONUS, leading to initial quiet conditions.
Model guidance however depicts that activity may pick up again as
shortwaves riding the larger scale flow track through Iowa, hinting
at additional but low end chances at this time for precipitation by
Tuesday and Wednesday. The GFS shows a rather low signal for this
activity with a few relatively weak systems, whereas the Euro slows
the ridge arrival as a more defined mid-level trough ahead of it
descends further south across the Upper Midwest, with stronger
forcing overhead leading to a more pronounced low pressure passing
through Tuesday into early Wednesday. Specific details will be known
in the coming days as more information becomes available.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 600 PM CDT Thu Mar 20 2025
While VFR conditions will prevail tonight into Friday morning,
low level wind shear will move in overnight from northwest to
southeast diminishing by mid-morning. Ceilings will lower across
central Iowa through the day Friday with MVFR ceilings and
light rain showers possible at FOD, MCW, and ALO in the
afternoon, which for now is shown as PROB30 groups. Surface
winds from the south or southwest will increase overnight with a
bit of a lull midday Friday with winds becoming from the
northwest and increasing late in the day/period.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Bury
AVIATION...Ansorge/Bury
Area Forecast Discussion
National Weather Service Huntsville AL
959 PM CDT Thu Mar 20 2025
...New NEAR TERM and SHORT TERM...
.NEAR TERM...
(Rest of tonight)
Issued at 1000 PM CDT Thu Mar 20 2025
Skies have cleared across much of northern Alabama and southern
middle Tennessee at this time. Some clouds linger in far northeastern
Alabama, but this should push east of the area before 10 PM CDT.
Winds have dropped off and become calm in most areas. Despite
cooler temperatures this afternoon, dewpoint depressions are
mainly between 10 and 15 degrees. With even drier air seen
upstream and expected to advect into the area the rest of the
night, not expecting fog to form. Temperatures still look to be on
track for a good widespread freeze across northern Alabama
tonight (27 to 32 degrees). Given calm winds so early in many
areas, wouldn`t be surprised if guidance isn`t going quite cold
enough. However, flow upstream turns move westerly towards
daybreak in guidance. This may advect some warmer air toward the
region which could counteract the radiational cooling a tad. A
Freeze Warning continues from 1 AM through 8 AM on Friday.
&&
.SHORT TERM...
(Friday through Sunday)
Issued at 1000 PM CDT Thu Mar 20 2025
Zonal flow returns to the Southeast tomorrow and continues into
the weekend. A gradual warming trend begins as a result starting
during the day tomorrow with afternoon highs returning to near
normal in the lower 60s. Guidance and area soundings show a very
deep layer of dry air above the surface as the surface high passes
to our south during this period. Ensemble base guidance does not seem
to be picking up on the mixing potential of this drier air to the
surface during the late morning/afternoon hours. RAP13 and to a
lesser extent the HRRR seems to be picking up on this. Stayed
closer to the RAP13 given the depth and very dry nature of the
atmospheric column aloft. This could drop dewpoints into the mid
to upper teens in the afternoon, particularly in NE AL. For fire
weather concerns and due to expected spot forecasts, updated the
forecast to account for this. Luckily, KBDI values are still less
than 300 and winds will be fairly light, though may pick to around
10 mph with some higher gusts between 5 and 7 PM. The main fire
weather concern though is that afternoon relative humidity values
will drop into the 15 to 20 percent range in many areas, especially
east of the I-65 corridor.
Highs will continue to climb into the low 70s on Saturday, and
the mid 70s on Sunday. An upper level low is forecast to develop
across the Pacific Northwest on Saturday and then drop southeastward
into the Upper Plains Saturday night. As the low ejects across
the Midwest on Sunday, a cold front to its south will stretch
across the Ohio River Valley down into the Tennessee Valley. The
front should impact the local forecast area starting late Sunday
afternoon and continuing through the evening into the overnight
hours. There is some severe weather potential with and possibly
ahead of the cold front passage. As a result, the SPC has placed
the entire Tennessee Valley into the Slight Risk (level 2 out of
5) for the Sunday into Sunday night period. For our area, this
activity will impact northern Alabama into southern middle
Tennessee mainly late Sunday afternoon into Sunday night. Looking
at forecast soundings, vertical wind shear is good and there is
ample instability (more so in southern middle TN southwest into NW
Alabama). There also is fairly widespread and strong helicity
ahead of this system. Damaging winds and large hail look like they
would be the main threats at this time. However, given some
surface based instability shown by models during the late
afternoon into the early evening period, a tornado or two cannot
be ruled out. If more instability occurs then damaging winds,
large hail, and tornado threat could increase. Right now, confidence
in severe weather occurring in the afternoon hours is lower
overall due to a a strong cap seen in guidance around 700 mb. This
also makes the severe threat a bit more conditional if the cap is
not eroded by the early evening hours.
&&
.LONG TERM...
(Monday through Wednesday)
Issued at 1000 PM CDT Wed Mar 21 2025
Rain and thunder should come to an end from west to east by
sunrise Monday morning, and sfc high pressure will begin to sink
into the TN River valley during the afternoon. With this system
being less amplified than the previous one, cold air advection
will not be as strong behind this front and highs will climb into
the low to mid 60s with mostly clear skies. A dry forecast is
expected through Wednesday with mostly sunny/clear skies
persisting and daily highs in the mid 60s/lower 70s and lows in
the 40s primarily.
&&
.AVIATION...
(00Z TAFS)
Issued at 634 PM CDT Thu Mar 20 2025
NW winds around 10 mph gusting to around 16 knots will likely
continue with VFR CIGS through 01Z at KMSL and 03Z at KHSV. Then
expect CIGS to scatter and dissipate with winds becoming light and
variable with clear skies by 7Z at KMSL and 9Z at KHSV. Luckily,
very dry air will keep fog from forming late tonight despite good
radiational cooling conditions in place towards daybreak on
Friday.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Freeze Warning from 1 AM to 8 AM CDT Friday for ALZ001>010-016.
TN...None.
&&
$$
NEAR TERM...KTW
SHORT TERM....GH
LONG TERM....25
AVIATION...KTW