Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/27/24
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
950 PM EST Thu Dec 26 2024
.SYNOPSIS...
Cool and dry weather is expected again today. Clouds increase
tonight through Friday, with occasional light rain developing
over the Virginia piedmont Friday afternoon and evening.
Temperatures warm back to above normal this weekend, as a more
unsettled weather pattern returns.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 945 PM EST Thursday...
Forecast in good shape. Much of the area remains clear except
the far south being impacted by high cloud. This has allowed
temps to drop into the low-mid 30s across much of the area. With
these clear skies persisting for much of the night, will keep
lows generally in the mid 20s in the Piedmont, 95 corridor and
MD Eastern Shore, and lower to mid 30s closer to the coast.
As of 320 PM EST Thursday...
Key Message:
- Seasonable tonight with lows mainly in the upper 20s to lower 30s.
Latest analysis shows ~1036 mb surface high pressure still in place
and centered from the Saint Lawrence Valley and interior New
England, ridging south into to the Mid-Atlantic and down the Eastern
Seaboard. Aloft, an upper ridge is moving across the Mid-Atlantic,
while a digging shortwave trough moves through the SW, setting up
the next system for the area.
High pressure will remain in place through Fri with a strong
inversion of cool CAD/wedged air. Mid-level cloudiness has thinned,
leaving high clouds across the area, clearing into the overnight.
Temps overnight will be very similar to last night, with lows in the
mid to upper 20s (SE VA/NE NC slightly warmer with lows in the mid
30s.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
As of 320 PM EST Thursday...
Key Message:
- Increasing cloud cover Fri with cloudy and cool conditions for
most of the area, moderate temperatures along SE coast.
- Spotty light rain and cooler conditions inland Friday night and
Saturday. Mainly cloudy, with warming trend continuing along the
coast.
- Multiple frontal systems will pass through the area bringing
chances of rain. The best chance of rain is from Sunday through
Sunday night, when precipitation amounts could exceed 0.50" across
much of the area.
The upper level ridge will weaken and slowly move offshore on Fri,
as the surface level high lingers around the NE coast allowing
CAD/wedge to develop along the eastern seaboard. Recent model
guidance is hinting to a stronger CAD event with the cool air
lingering around the Piedmont. It`s important to note that the
models do not have a good understanding on how the wedge performs
and tend to under perform. This being said, have leaned towards the
NAM guidance, rather than NBM, keeping high temps Fri in the mid 40s
for the majority of the region and Sat in the upper 40s in the
Piedmont to upper 60s in the SE VA/NE NC. As we saw with a similar,
albeit stronger, CAD airmass earlier in the month, it does not take
much overrunning moisture to result in persistent spotty showers and
cooler than otherwise expected temps. Overnight, lows Fri will be in
the upper 30s to mid 40s and lows Sat will be warmer, with lingering
wedged air towards the Piedmont with lows in the mid 40s to mid 50s
towards the coast.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 245 PM EST Thursday...
Key Messages:
- Milder temperatures are expected through at least Tuesday.
- A cold front will bring the chance for rain showers from
later Tuesday afternoon through Wednesday morning. Dry
weather and cooler temperatures return for Wednesday
afternoon through Thursday.
Milder temps are expected for Mon and Tue. Dry weather will
prevail for Mon aftn (behind an exiting front) into early Tue
aftn, before another cold front approaches and pushes across the
area and off the coast later Tue aftn through Wed morning. That
front will bring the chance for rain showers. Dry weather and
cooler temps will return for Wed aftn through Thu. Highs will be
in the upper 50s to mid 60s Mon and Tue, range through the 50s
Wed, and in the mid 40s to lower 50s Thu. Lows will be in the
upper 30s to mid 40s Mon night, range through the 40s Tue night,
and mainly in the lower to mid 30s Wed night.
This is my (Timothy Gingrich) last official discussion for the
NWS Wakefield, as I will be retiring as of Saturday, December
28th after 35 years as a forecaster in the NWS. Thank you to
all my colleagues and co-workers for their shared knowledge,
help, and friendship throughout my career. You all have made my
experience enjoyable and bearable in some tough times, both
professionally and personally. Thank you again.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
As of 650 PM EST Thursday...
VFR conditions prevail at the terminals early this evening.
In fact, much of the area is clear. However, there seems to be a
great deal of stratocumulus to the north of the area, and also
to the south. Latest NAM and HRRR guidance suggest that these
lower clouds may fill in or move into the area overnight. There
is somewhat low confidence of this occuring, especially given
the very low LAMP probabilities of MVFR conditions. Still, will
include some TEMPO MVFR conditions at the terminals tonight -
generally early at RIC and SBY and later on in the night at
ORF/ECG/PHF as guidance suggests a better surge of 925mb
moisture from the south. Will keep VFR conditions at all sites
on Friday, however late in the forecast period CIGS are expected
to lower in advance of the next frontal system. NE winds will
continue generally less than 10 kt.
Outlook: This weekend, as high pressure moves offshore, a warm
front will push north through the area bringing chances of rain
Sat with rain likely on Sunday, as a cold front moves through
the area. MVFR CIGs are possible by Friday night with potential
restrictions Sun into Sun night as well. Dry/VFR conditions
return Mon, as high pressure builds in from the W.
&&
.MARINE...
As of 315 PM EST Thursday...
Key Messages:
- Relatively benign conditions continue through Saturday.
- The next chance of SCA conditions arrives Sunday with increasing
southerly winds.
High pressure dominates the local weather pattern through Fri
with winds remaining generally steady through Fri before
diminishing to 5-10 kt and becoming SE Fri night behind a warm
front lifting N. S winds remain light Sat before increasing to
10-15 kt with gusts up to 20 kt Sat night. Winds continue to
increase to 15-25 kt with gusts up to 25-30 kt Sun into Sun
night ahead of an approaching low pressure system and associated
cold front. Confidence continues to increase in SCA conditions
during this timeframe. Widespread showers with embedded storms
move across the local waters Sun into Sun evening ahead of and
along the aforementioned cold front. Gusty winds are possible
with the line of showers along the cold front as 925mb winds
increase to 45-55+ kt. Winds become W behind the cold front Mon.
Will note that a brief period of gusty W winds is possible
behind the cold front as well depending on how strong the low
pressure and associated CAA becomes. High pressure builds in
early next week with an unsettled pattern developing around New
Year`s Day.
Waves and seas were generally 1-2 ft and 2-4 ft (2-3 ft N and 3-4 ft
across the NC coastal waters) respectively this afternoon.
Waves and seas build to 3-4 ft and 4-6 ft respectively by Sun
with seas potentially remaining elevated through Mon.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...MAM
NEAR TERM...KMC/MRD
SHORT TERM...KMC/MAM
LONG TERM...TMG
AVIATION...
MARINE...JDM/RMM
Area Forecast Discussion
National Weather Service Grand Forks ND
645 PM CST Thu Dec 26 2024
.KEY MESSAGES...
- Dense fog is expected across the region tonight into Friday
morning.
- Light wintry mix moves through the Devils Lake Basin into
eastern North Dakota late Friday morning into the afternoon.
- Broad area of rain moves through north central and west
central Minnesota Friday evening through Saturday, with a
brief wintry mix Saturday morning.
&&
.UPDATE...
Issued at 645 PM CST Thu Dec 26 2024
Dense fog is being reported over parts of the Sheyenne River
Valley (Valley City to Cooperstown) and this is matching the
CAMs and all blends that have been showing dense fog developing
and overspreading northeast ND into the Red River Valley.
Advection fog will tend to dominate where moisture advection
and pooling is occuring along/east of the valley, while
radiational fog may dominate where clearing has been in place,
with some terrain influences near the SD causing "gaps" in fog
coverage that are reflected in CAMs. Considering the trends that
support at least patchy to areas of dense fog I went ahead and
extended the Dense Fog Advisory to include my entire CWA.
Temperatures vary from the northwest to east with freezing fog
more likely in ND that in MN, but impacts are a bit more
uncertain. Depth of saturation is shown by NAM/RAP to increase
after midnight and this may be a supportive of drizzle/freezing
drizzle development though there isn`t an organized forcing
mechanism (other than weak WAA) and better forcing/precipitation
signals in CAMs aren`t until later in the day Friday. We`ll
monitor for any potential precipitation/icing impacts.
&&
.DISCUSSION...
Issued at 309 PM CST Thu Dec 26 2024
...Synopsis...
Upper level flow continues to be southwesterly through the near
term, with a gradual transition to northwesterly flow over the
weekend as a Hudson Bay low develops. Continued dense fog chances in
the morning thanks to low level saturation. A weak upper level wave
moves out through Canada into ND late Friday morning merging with a
larger synoptic system moving out of the southwesterly flow late
Friday into Saturday. Period of light wintry mix and rain moves
through central North Dakota into the Devils Lake Basin late Friday
morning. This shifts east into the valley and transitions over to
rain. The larger system brings more broad light rain to north
central and west central Minnesota late Friday into Saturday, with a
transition over to a light wintry mix Saturday morning. As the
northwesterly flow develops our temperatures start to decline. End
of the long term and beyond ensembles hint at temperatures dropping
into the single digits for highs.
...Dense Fog...
Current satellite has a broad area of stratus over Minnesota and
into the Red River Valley this afternoon. A brief mist has occurred
at times or a few flurries. Some of the stratus has eroded in the
Red River Valley, but recent guidance from HREF and HRRR have it
building back toward the west as we approach the evening hours. Low
level saturation continues to be amplified over the region, with dry
air aloft. Winds overnight drop to below 10kts and dense fog starts
to develop. HREF paints a picture of widespread dense fog developing
where saturation is highest (east of the Red River Valley) late
this evening and overnight. Atmospheric soundings support the HREF
guidance thus a Dense Fog Advisory was issued for areas east of the
Red River Valley overnight. Areas within the valley may see areas of
dense fog, while Devils Lake Basin sees patchy dense fog overnight.
Visibility reductions of a quarter of a mile or less are likely in
the advisory, with chances within the Red River Valley. Advisory
goes through 18z Friday.
...Light Wintry Mix Friday...
A weak upper level wave moves out of Canada into North Dakota Friday
morning bringing weak upper level synoptic forcing to central North
Dakota. This weak wave has enough moisture and forcing to bring the
chance of a light wintry mix to the central North Dakota and the
Devils Lake Basin by late Friday morning. Temperatures will be
around freezing, with a stout warm nose aloft. As temperatures near
the surface warm and air cools aloft the light wintry mix turns to a
rain/snow mix and later rain. Any light wintry mix that does occur
may bring the chance for minor impacts to travel due to slick
conditions.
The upper level wave merges with a larger synoptic system out of the
southwesterly flow Friday afternoon. Light rain moves into the Red
River Valley Friday afternoon and shifts into lakes country and
northern Minnesota late Friday.
...Rain chances late Friday into Saturday...
A large synoptic system moves out of the Texas Panhandle Friday into
Minnesota. A strong surge of moisture accompanies this system as it
shifts through Minnesota. Strong warm air advection moves into
northern Minnesota with light rain spreading across the state.
Guidance continues to push highest QPF further toward the east into
the arrowhead of Minnesota. As we wrap colder air around the system,
the light rain will transition over to a wintry mix with a chance
for light freezing rain for a brief period Saturday morning. This
may result in slick travel and minor impacts. Ice accumulations are
minor and look to be less than a hundredth of an inch. None the less
any accumulation of ice would pose a minor impact. We will continue
to monitor the latest as the system develops and moves into
Minnesota.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 532 PM CST Thu Dec 26 2024
Low stratus (IFR) is already in place over parts of eastern ND
and much of northwest MN, with clearing over northeast ND
towards KDVL. Stratus is expected to fill in and lower (LIFR)
through the late evening/overnight, while fog begins to develop
and overspread the region. Vis may vary quite a bit, with the
strongest signal for VLIFR visibilities in northwest MN and the
Devils Lake Basin currently, however all TAF sites have a chance
(30%) for 1/4sm early Friday morning. Visibilities should
improve during the daytime period Friday, however low stratus is
more likely to persist (IFR).
There is a chance for drizzle/light rain and even a few pockets
of light freezing drizzle during the TAF period, but best
chances will tend to be later Friday afternoon in MN and even
then chances are too low for TAF inclusion at this point.
Southerly winds should decrease this evening then prevail under
12kt during the TAF period as weak low pressure builds into the
region and the low level jet pushes east of our region.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Dense Fog Advisory until noon CST Friday for NDZ006>008-
014>016-024-026>030-038-039-049-052>054.
MN...Dense Fog Advisory until noon CST Friday for MNZ001>009-
013>017-022>024-027>032-040.
&&
$$
UPDATE...DJR
DISCUSSION...Spender
AVIATION...DJR
Area Forecast Discussion
National Weather Service North Platte NE
937 PM CST Thu Dec 26 2024
.KEY MESSAGES...
- Another round of dense fog is expected to develop across
southwest into north central Nebraska tonight into late Friday
morning with very low visibilities and the threat for some
slick spots.
- Above normal temperatures in the 40s and 50s and dry
conditions return for the end of the week into the weekend.
- A strong cold frontal passage on Monday will bring strong
winds (40+ mph) and a threat for rain and accumulating snow
primarily for areas along and north of Highway 2.
- Dry conditions with seasonal temperatures (30s to low-40s)
expected Tuesday through the end of next week.
&&
.SYNOPSIS...
Issued at 241 PM CST Thu Dec 26 2024
Recent GOES-16 WV imagery and RAP 500-mb analysis showed ridging
extending northward from Florida into Ontario and Quebec. Three
upper-level shortwaves were traversing along the ridge with the
first moving northeast into the Great Lakes and Ohio River Basin,
the second diving southeast out of New England, and the third one
moving northeast across the south Atlantic. A potent upper-level
shortwave trough was moving eastward across the southern Plains.
Weak upper-level ridging extended along the northern Rockies
with a negatively tilted trough noted off the coast of British
Columbia into the Pacific Northwest and Great Basin. At the
surface, a trough axis extending along the Rockies. Areas of
dense fog gradually burned off through late this morning across
much of southwest into central Nebraska with clear skies noted
over the Sandhills. However, mid to upper-level clouds are
approaching from the west in advance of the previously mentioned
northern stream trough. At 2 PM CT, temperatures ranged from 38
degrees at North Platte to 50 degrees at Gordon.
&&
.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 241 PM CST Thu Dec 26 2024
As the upper-level shortwave ejects eastward out of the Rockies into
the Plains, an associated surface low over southern Alberta and
Saskatchewan will force a weak Pacific cold front through western
and north central Nebraska overnight. Not to sound like a broken
record, but another round of dense fog is in store for eastern
portions of the forecast area tonight into Friday morning as weak
southerly flow sets up ahead of the front. HREF Visibility
Probabilities of less than 1/2 mile ranges from 40 to 70% for
portions of southwest into north central Nebraska. Adding in
overnight temperatures falling into the mid 20s to low 30s, cannot
rule out patchy freezing fog which may create some slick spots,
particularly on elevated surface. At this time, confidence in dense
fog (< 0.25 mile visibility) developing is increasing, especially
given how the last few nights have paned out, thus did issue a Dense
Fog Advisory with this forecast package. Folks traveling should use
caution as low visibility and some slick spots may result in
hazardous travel tonight into the Friday morning commute. Conditions
will improve late Friday morning as the fog gradually lifts and
skies clear from west to east resulting in a rather pleasant second
half of the day for Friday. Dry conditions and above normal
temperatures will continue be the story Friday through the weekend.
Highs will warm into the upper-40s to mid-50s across the area on
Friday with lows falling into the 20s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 241 PM CST Thu Dec 26 2024
The upper-level ridge will attempt to establish itself across the
western CONUS through the weekend with broad troughing across the
eastern US. This will result in a dry and seasonally warm weekend
across western and north central Nebraska where highs in the
upper-40s to mid-50s will be common. However, a weather pattern
shift is in store for the area as we head into Sunday evening.
An upper-level trough across the Pacific Northwest will dive
southeast into the northern Plains, causing the ridge to
breakdown. As the trough approaches, cyclogenesis will begin to
organize across southwest Nebraska and northwest Kansas, driven
by mid-level height falls and upper-level divergence under the
left exit region of the 250mb jet streak. A strong surface cold
front will then sweeping through the area by Monday morning
bring a few weather concerns with it. The two things that
appear more certain at this time is the potential for strong
wind gusts exceeding 40 mph on Monday and temperatures falling
back to seasonal values in the 30s to low-40s through next week.
Strong pressure rises and cold air advection (CAA) behind the
front will result in widespread, strong northwest wind gusts of
35 to 45 mph to encompass western and north central Nebraska.
Gusts exceeding 45 mph remain on the table as NBM Probabilities
continue highlight the potential being over the western
Sandhills into southwest Nebraska. Increasing mid-level
frontogenetical forcing, CAA, and moisture across northern
Nebraska will present our only shot at rain/snow in the 7 day
forecast being Monday. The Extreme Forecast Index (EFI) for QPF
and Snow of 0.5 to 0.7 across the Nebraska/South Dakota border
indicates increasing confidence in anomalous rain/snow, however,
with no SoT (Shift of Tails) across this area, do not
anticipate a record snowfall event by any means. Guidance
continues to highlight areas along and north of Highway 2 being
where the main threat for a quick shot at accumulating snow
exists. This is supported by recent NBM Probabilities of 24
Hour (6 AM Mon to 6 AM Tue) Snowfall >1" highlighting near 50%
for the Highway 20 corridor, falling near 20% down to the
Highway 2 corridor. Given the probability of accumulating snow
and strong winds, blowing snow will be of concern, increasing
confidence on the potential for hazardous travel across northern
Nebraska on Monday. WPC`s probabilistic WSSI highlights the
potential for winter weather impacts for areas along and north
of Highway 2 with a 20 to 30% probability for minor impacts,
primarily driven by the potential of blowing snow. Those with
travel interests for this period should check future forecasts
as the details become more certain. As the system exits the
local area through Monday night, precipitation will gradually
come to an end with breezy winds, though not on the same
magnitude as during the day on Monday. The colder airmass will
remain over the central CONUS through the week with upper-level
ridging amplifying over the western US.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...Updated
Issued at 919 PM CST Thu Dec 26 2024
Latest short-term models note surface trough to move east into
western Nebraska through 06Z with areas to the east to see
higher boundary layer moisture. The surface troughs location
will result in KVTN`s terminal to flunctuate with IFR cigs
through 09Z. Otherwise VFR conditions across the Eastern
Panhandle east to Highway 97. Timesection shows low level
moisture prevailing through 09z with MVFR to IFR conditions to
hold on for most areas east of Highway 61. NDOT cameras show fog
in some locales just east of KLBF with greatest impacts from
dense fog to be seen between 06z and 10Z. After 15Z VFR across
most of the area except along and east of Highway 281.
The extensive stratus overnight will be generally east of a
line from IML to TIF and ANW. The low ceilings and visibility
will improve throughout beyond 15Z Friday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CST Friday for NEZ007>010-
025>029-036>038-059-070-071.
&&
$$
SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...Keck
Area Forecast Discussion
National Weather Service Marquette MI
936 PM EST Thu Dec 26 2024
.KEY MESSAGES...
- Very light freezing drizzle across portions of the interior
central UP this afternoon and evening could result in slick
roadways.
- Unseasonably mild temperatures Friday through Monday with
highs averaging 10-20 degrees above normal and lows around 20
degrees above normal.
- Moist air and rain over a melting snowpack will result in
patchy fog tonight to Sunday (75% chance). Some fog could be
dense (~20% chance).
&&
.UPDATE...
Issued at 936 PM EST Thu Dec 26 2024
Dense fog and drizzle continue to plague the UP tonight, with much
of the drizzle particularly across the central UP so far. There,
temperatures still flirting with the freezing point continue to lead
to patchy freezing drizzle. However, temperatures are already on the
rise, and should climb above freezing around midnight. At that
point, freezing drizzle should become less of a concern, though will
continue to carry the potential for light icing along the WI border
in Dickinson and Iron counties into the early morning hours. A
Special Weather Statement has been re-issued for the central UP to
cover the potential for patchy freezing drizzle and freezing fog to
06Z. Meanwhile, with plenty of spots reporting visibility below a
mile, and even below a quarter-mile, the Dense Fog Advisory remains
in effect.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 117 PM EST Thu Dec 26 2024
GOES Water Vapor and RAP analysis position Upper Michigan within
southwest flow aloft between ridging moving from the Lower Great
Lakes north into Quebec and overall troughing across the west half
of CONUS, with notable shortwaves well south into Texas/Oklahoma
and another one moving through the northern Rockies. With mostly
cloudy skies under this southwest flow persisting through the day,
temperatures have warmed into the upper 20s to low 30s.
Additionally, the increasing moisture has supported fog and mist
developing across portions of central Upper Michigan. Given that
road temperatures are near or below freezing in many interior
locations, suspect some slick spots have or will develop on
untreated surfaces, particularly across central Upper Michigan. A
Special Weather Statement has been issued for the risk of slick
roadways this afternoon and evening in these locations.
Upper Michigan will continue to be under the influence of increasing
moisture and slowly rising temperatures with this southerly flow
overnight. This will support more widespread fog developing,
particularly in central Upper Michigan where the upslope flow will
aid development. Additionally, the increasing moisture and weak
isentropic lift will also enable any drizzle in some locations
before temperatures warm above freezing. This will continue to
enable a risk for slick surfaces, mainly untreated or snow covered
surfaces into this evening in central Upper Michigan. Overnight,
deepening moisture will allow a transition to rain, mainly in
eastern Upper Michigan and likely, more widespread fog developing.
Overnight temperatures will gradually increase through the night,
with most locations being at or above freezing after midnight.
&&
.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 335 PM EST Thu Dec 26 2024
Friday morning, light rain and fog will be ongoing over the UP as
High Plains troughing sets up warm, moist southwesterly flow into
the region. The 12Z HREF shows chances of 0.5 mi vis or less
throughout the day Friday at around 50-90%. RAP13 Prob Ice Present
ramps up during the morning hours, suggesting a less drizzly and
more rainy precip mode, though forcing through the morning to early
afternoon is fairly weak as 850mb warm advection ends and 500mb
shortwaves passing through are weak.
By Friday evening, however, troughing will lift out of the mid
Mississippi River Valley, supporting a near 1000mb low pressure
passing directly over the UP by Saturday morning. Moisture will be
abundant, as NAEFS vapor transport plots show the 90th to 97.5th
percentile of climatology over the UP early Friday through late
Sunday, also showing a Gulf of Mexico connection as the culprit. The
LREF shows chances of accumulated rainfall of a half inch at around
70% by the end of the weekend over southern and western portions of
the UP with up to 40% chances of 3/4 inch for those same locations.
Temperatures near the freezing mark Saturday and early Sunday will
allow for a few snowflakes to mix in for the interior west, though
chances for measurable snow peak at only 33% in the LREF, with
chances of a glaze of ice at only around 15%. The continued
southerly surface to 850mb flow will cause continued warm advection
and highs to climb to near 40 over the weekend. One thing worth
watching will be the lows, as the record warm low temperatures for
this time of year are right around freezing, and the 50th percentile
lows in the NBM are also around the freezing mark. Low visibility
will continue to plague the post-Christmas weekend travel period,
with Euro ensemble visibility meteograms showing up to 70-90%
chances of reduced visibility Saturday, with up to 70% chances of
the visibility dropping below 1 mile across the UP, though the HREF
shows the best chances at dense fog limited to the central and
interior western UP, so uncertainty does increase for the Saturday
period regarding lingering fog. As the low departs and phases with a
clipper low over northern Ontario Sunday and then another low (CO
Low-type) passing well south of the UP Monday, only lingering 15%
chances of rainfall cling to the forecast to end 2024 as highs slide
back towards the freezing mark.
As 2025 kicks off next week, ensemble 500mb plots show a preference
for a more northwesterly pattern aloft given longwave troughing over
the eastern CONUS, which supports more seasonable, cooler air
filtering over the Upper Great Lakes. With Lake Superior around 5 C
(and not much cooling expected with the warmer than normal
temperatures expected this week), the target for 850mb temperatures
to support lake effect snow will be around -8C. By the time it
becomes appropriate to put up new calendars, the LREF shows
850mb temperatures over 90% likely over the west half of Lake
Superior, spreading across the rest of the lake by January 2nd.
A return of lake effect snow would help bring the snowpack back
after the toll taken on the snowpack by this week`s warmth and
rain. While there`s still plenty of time for a change in the
wind direction, ensembles are coalescing around the 925mb wind
direction being NWerly, with only the Canadian ensemble giving
even close to even odds of a Nerly setup for LES bands with the
overwhelming majority of members of the Euro Ensemble and GEFS
showing NW dominating.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 623 PM EST Thu Dec 26 2024
Warm air alongside increasing moisture will set up a period of low
ceilings and visibilities. LIFR conditions are expected to prevail
at KSAW with airport minimums, or lower, being possible overnight
tonight. Drizzle becomes more likely later this evening, especially
at KSAW and KCMX, with a brief period of freezing drizzle possible
before surface temperatures warm above freezing closer to midnight
and onward. KCMX will see a little slower decent into these
restrictions, potentially staying IFR overnight and dipping into
LIFR Friday morning. A slight downsloping component at KIWD should
prevent IFR conditions from further deteriorating to LIFR tonight.
&&
.MARINE...
Issued at 335 PM EST Thu Dec 26 2024
Tonight through Friday, winds will be near or below 20 kt, generally
out of the south under an unseasonably mild airmass. Wind gusts then
increase to the 20-25 kt range (near 30 kt between Whitefish Point
and Caribou Island) for the weekend as a low pressure passes from
the Plains over Lake Superior. Model guidance suggests a 30-40%
chance of a brief gale Saturday over the eastern end of Lake
Superior. Winds then fall back to 20 kt or less into early 2025 with
surface low pressures tracking away from Lake Superior. Persistent
southwesterly to southeasterly flow will allow waves of 4-5 feet
over north-central Lake Superior tonight, with a brief period of
weaker waves Friday before waves ramp up to 6-9 feet by Saturday
morning along the US/Canada maritime border, falling below 4
feet by overnight into Sunday.
&&
.CLIMATE...
Issued at 345 AM EST Wed Dec 25 2024
Record warm highs and lows at WFO MQT in Negaunee Township (records
date back to 1959):
Date High Low
Dec. 27 42 (1994/2008) 32 (2008)
Dec. 28 42 (1979) 34 (2003)
Dec. 29 43 (1979) 31 (2022)
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Dense Fog Advisory until 7 AM EST /6 AM CST/ Friday for
MIZ004>006-010>013.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
UPDATE...LC
SHORT TERM...JTP
LONG TERM...GS
AVIATION...LC
MARINE...GS
CLIMATE...
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1013 PM EST Thu Dec 26 2024
...New UPDATE...
.UPDATE...
Issued at 1002 PM EST Thu Dec 26 2024
No huge changes for the late evening update here. Made some minor
adjustments to PoPs through the day Friday, mainly to incorporate
the latest NBM guidance and some 00z HRRR guidance. Some light
returns over Georgia this evening have been producing some trace
amounts of light rain. The HRRR and to some extent the latest NBM
indicate an initial wave of some widely scattered showers lifting
northward through the CWA around daybreak or thereabouts. This
doesn`t seem unreasonable given the pattern, so I incorporated
that into the forecast. That`s about it other than upping cloud
cover. The wind advisory still seems to be a good bet, so no
changes were made to winds and will just reissue the product
momentarily.
&&
.SHORT TERM...
(This evening through Friday Night)
Issued at 254 PM EST Thu Dec 26 2024
Key Messages:
1. Strong winds are expected in the Tennessee mountains and adjacent
foothills late tonight through Friday night.
2. Rain will move into the area later on Friday through Friday
evening with less coverage further east due to downsloping.
This Evening/Tonight
Currently this afternoon, a shortwave and area of low pressure is
moving through the Southern Plains with high pressure well to our
northeast. This evening into tonight, this system will continue
progressing northeastward towards Arkansas. During this time, the
MSLP gradient will strengthen across the area with 850mb winds
reaching near 50 kts to our west. These conditions are supportive of
mountain wave enhanced winds over the mountains and foothills with a
Wind Advisory having been issued. This will be the beginning stage
of this wind event with the continued breeze keeping temperatures
notably mild.
Friday and Friday Night
During the day on Friday, the system`s track will become more
northerly with 50+ kt 850mb winds setting up along western portions
of the area. During this time, the direction of 850mb winds will be
slightly more southerly to southwesterly, but the magnitude will
definitely be sufficient for the high-end nature of the Wind
Advisory. All things considered, it is definitely possible that
places like Cove Mountain could exceed 60mph, but the current data
still keeps most places in the high-end advisory range. Height falls
from the initial shortwave, followed by another shortwave, will
gradually increase rain chances across the region. However, the
strong downsloping will definitely limit this potential further
east. Some elevated instability in the south Friday evening into
Friday night supports potential of isolated thunder. However, most
places will just see showers with the best coverage further west.
&&
.LONG TERM...
(Saturday through next Thursday)
Issued at 254 PM EST Thu Dec 26 2024
Key Messages:
1. Warmer than normal temperatures will persist into the weekend.
2. Storms with heavy rains and gusty winds possible Saturday night
through Sunday morning.
3. Colder weather rings in the New Year.
Discussion: At the beginning of this period on Saturday morning,
we will be between waves in this busy pattern, still with an upper
flow from the southwest and a southerly low level flow. This
changes somewhat on Sunday with the passage of a shortwave trough
and cold front that will pass through the area. But then another
cold front quickly moves into the area and will push through on
Tuesday and start to cool things back to more seasonal normal
temperatures as we head into 2025.
Severe Storm and Flooding Threats...On Saturday, Saturday night, and
into Sunday there is instability for possible storms in the region.
For things to come together for strong storms, this looks most
favorable Saturday night lingering into Sunday morning as another
low level jet forms ahead of the cold front and as storms from the
west or southwest approach the area. The reason for lesser chances
during the day on Saturday is that the focus looks to be west or
southwest of our area, then lesser chances on Sunday afternoon as
the focus shifts into the Carolinas.
The flooding threats also parallel the time windows above, with the
heaviest rains generally Saturday night into Sunday morning, and
these rains probably heavier overall than the rains in the Short-
term part of the forecast. The overall flooding threats will be
limited by the on-going drought in the region with the heaviest
rains fortunately falling in the driest areas.
Ahead of the Sunday front, windy conditions through the mountains
are possible Saturday through Sunday, and southerly winds up the
valley will be increasing on Saturday and into Saturday night.
After the cold front passes Sunday, the airmass loses a lot of
moisture and the strong storm and flooding threat near the frontal
passage on Tuesday look much lower. After the front on Tuesday,
more seasonally typical temperatures (if not colder than normal)
will return to the area to ring in the New Year on Wednesday.
&&
.AVIATION...
(00Z TAFS)
Issued at 645 PM EST Thu Dec 26 2024
Rain associated with the next system will begin to push in from
the southwest by mid morning tomorrow, gradually filling in
across east TN by the late afternoon hours. Flight categories
will lower overnight for KCHA as a result. But KTYS will likely
have enough downslope flow to keep CIGS in VFR territory through
midday, with KTRI not decreasing until late tomorrow afternoon.
Some gusty SE winds are expected at KCHA by shortly after
daybreak.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 59 46 54 50 / 0 10 90 90
Knoxville McGhee Tyson Airport, TN 58 41 60 51 / 0 0 70 90
Oak Ridge, TN 58 41 55 50 / 0 0 80 90
Tri Cities Airport, TN 56 36 57 49 / 0 0 50 80
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 7 AM EST Saturday for Blount Smoky Mountains-
Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-
Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi.
VA...NONE.
&&
$$
SHORT TERM...CD
LONG TERM....GM
AVIATION...CD