Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/19/20
Area Forecast Discussion
National Weather Service Bismarck ND
948 PM CST Wed Nov 18 2020
.UPDATE...
Issued at 948 PM CST Wed Nov 18 2020
Observational and recent model trends were blended into the forecast
for this update. There is high confidence that the large stratus
shield over southern Canada will continue to expand southward
through the night, possibly reaching as far south as Interstate 94
Thursday morning. The RAP 925 mb RH field was relied upon for sky
cover updates, which seems to be a reasonable depiction of the
stratus so far. Still think that patchy fog is possible as well, but
should mainly be confined to higher terrain where the cloud ceiling
height will essentially be zero.
Recent guidance continues to trend a bit south and slightly drier
with the first wave of light rain overnight. Regional radar shows
the developing stages of this activity, but not much is reaching
the ground yet. Notably, the RAP is suggesting a slower saturation
of the column over central North Dakota. If these trends hold, the
threat of light freezing rain across central North Dakota prior to
12 UTC will be diminished.
The most noteworthy trend in recent guidance with regards to the
band of precipitation associated with the clipper on Thursday is
for a quicker cooling of temperatures aloft, resulting in higher
probabilities for snow and lower probabilities for freezing rain.
Nevertheless, freezing rain remains a concern and we continue to
carry ice accumulations as high as 0.05 inch. The corridor of
highest ice accumulations has shifted slightly to the south, now
mainly along and south of the Highway 2 corridor. North of Highway
2, ice accumulations were lowered and snow accumulations were
raised by narrow margins.
UPDATE Issued at 635 PM CST Wed Nov 18 2020
Precipitation chances and types were refined for this update.
Guidance initializing at and after 18 UTC has shifted the initial
overnight band of precipitation a bit to the south. Most of this
will fall as rain, though surface temperatures may fall below
freezing along the northern edge. This is handled well by the
earlier start time of the Winter Weather Advisory for Dunn,
Mercer, McLean, Sheridan, and Wells Counties.
The main band of precipitation associated with the clipper has
slowed down a bit in the latest guidance. There are still
precipitation type considerations involving both the presence of
frozen hydrometeors and maximum temperatures aloft. Soundings
suggest a higher level of uncertainty that there would not be
production of frozen hydrometeors compared to the contrary.
Therefore, we set a lower limit for the probability of the
presence of frozen hydrometeors to 50 percent. As for maximum
temperatures aloft, while research suggests partial melting of
hydrometeors when maximum temperatures aloft are between 0 and +3
C, we feel this tends to be observed more as a mix of freezing
rain and snow as opposed to sleet. Therefore, we trended the
precipitation types in this direction, though some sleet does
remain possible. This decision was also supported by very low
probabilities of measurable sleet in the 12 UTC HREF.
The adjustments listed above did not warrant a change of headlines
or messaging and had very little impact on snow and ice
accumulations.
A large area of low stratus and patchy fog currently over central
Saskatchewan is migrating south and eastward, and will likely
expand into northern and central North Dakota later tonight into
tomorrow morning. Patchy fog was added to the forecast based on
CAM visibility field trends.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 254 PM CST Wed Nov 18 2020
Weak ridging will begin to break down this evening and continue to
bring a warm southwest flow pattern through this evening. Embedded
in the flow could be an initial wave ahead of the much advertised
clipper. This wave could bring a swatch of scattered showers later
this evening and through the overnight hours. As this band lingers
it could transition rain over to freezing rain for many areas by
early Thursday morning. Meanwhile, a clipper system will move
across the state Thursday morning through the day Thursday. A
complete mix of wintry precipitation is still possible. Precip
still looks to start out as freezing Rain then transition to a
brief period of snow with some sleet in between. This wintry mix
could continue into the afternoon Thursday, although some rain may
also mix in and spread southward. Given timing of freezing rain
that may impact the morning commute, and some areas could see up
to 0.1 of an inch of ice, went ahead and issued a Winter Weather
Advisory for early Thursday morning through Thursday afternoon.
Those in this advisory will want to monitor conditions closely and
prepare for a potentially slick morning commute. As this clipper
moves through there is also the potential for some breezy winds.
Right now thresholds look to be below advisory criteria, although
gusts could get close. Temperatures on Thursday look to be cooler,
with 30s in the north and 40s to low 50s south.
.LONG TERM...(Thursday night through Wednesday)
Issued at 254 PM CST Wed Nov 18 2020
Precipitation looks to come to an end late Thursday afternoon or
early Thursday evening. The remainder of the long term period then
looks to dominated by westerly flow with perhaps a few weak
clippers at times. Early indications are these clipper systems at
the moment do not look to amount to much precipitation wise, with
very little to almost now chances currently in the forecast. The
only exception being in southern areas on Saturday where some
slight snow chances exist. Early indications are by mid next week
a cold front may move through the area. Uncertainty remains on if
this will produce any precip or be mainly dry with breezy and
cool conditions. Something to keep an eye on, especially for those
with any travel plans for the upcoming Thanksgiving holiday.
Temperatures during this period look to remain mild and generally
near to perhaps slightly above normal, with some cool periods in
the north.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 635 PM CST Wed Nov 18 2020
There are multiple aviation hazards possible this forecast period,
with the greatest likelihood of impacts across northwest and north
central North Dakota. All TAF sites start out with VFR ceilings
this evening. A chance of rain will move from southwest into
central North Dakota overnight, but is not expected to cause any
flight category restrictions at this time. A large low stratus
shield currently over central Saskatchewan is forecast to expand
into northern and central North Dakota tonight into Thursday
morning. Expect IFR to LIFR ceilings and MVFR to IFR visibility
restrictions with this deck of low clouds. There is greater
confidence in these lower flight categories at KXWA and KMOT than
KBIS and KJMS, with KDIK more likely to remain at VFR.
A north-to-south oriented band of mixed precipitation is forecast
to move from west to east across North Dakota Thursday morning and
afternoon. Southern North Dakota should mostly see rain, and
additional aviation impacts from this precipitation are unlikely
there. Meanwhile, a mix of freezing rain and snow is favored from
KXWA to KMOT.
Light winds through the night will become westerly on Thursday,
increasing to 15-25 kts across western North Dakota.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 AM CST /2 AM MST/ to 6 PM CST /5
PM MST/ Thursday for NDZ018-019-021>023.
Winter Weather Advisory from 6 AM CST /5 AM MST/ to 6 PM CST /5
PM MST/ Thursday for NDZ001>005-009>013-017.
&&
$$
UPDATE...Hollan
SHORT TERM...Anglin
LONG TERM...Anglin
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Dodge City KS
503 PM CST Wed Nov 18 2020
...Updated Aviation...
.SHORT TERM...(This evening through Thursday)
Issued at 1212 PM CST Wed Nov 18 2020
Morning water vapor satellite imagery and 17Z RAP analysis
indicates a weak upper level ridge is in place over the central
CONUS with a trough over the west coast states. Both features will
move east through the short term period and dampen with time as
the upper pattern becomes mostly zonal. At the surface, high
pressure over the Appalachian Mountains and low pressure over
south-central Canada has preserved the tight pressure gradient
over southwest KS making for another windy day with south winds
sustained in the 23-27 mph range and gusts of 40+ mph possible.
This combined with the very dry airmass in place has fostered near
critical fire weather conditions, and a red flag warning has been
issued for the southeastern counties where the winds are expected
to be strongest. Afternoon highs will be a bit warmer than
yesterday, ranging from the low 80s across all of western KS to
the mid 70s in central KS. Winds will finally relax this
evening/overnight from northwest to southeast as a weak cold front
sags into southwest KS. This will optimize radiational cooling in
the northwest zones allowing temperatures to drop into the low
40s by Thursday morning while areas to the southeast, where winds
are expected to be stronger, hold in the upper 40s to lower 50s.
Guidance now suggests the weak cold front will push through our
area during the day Thursday instead of briefly stalling out.
Given the weak nature of the boundary, there will be little, if
any, associated impacts other than a wind shift from south to
north. Very weak/nebulous pressure gradient north of the boundary
will limit north winds to 10-15 mph, which will also limit the
amount of cold air that reaches southwest KS. Accordingly, highs
on Thursday are not expected to be much cooler, with highs ranging
from the lower 80s near the KS/OK border to the mid 70s near the
I-70 corridor.
.LONG TERM...(Thursday night through Wednesday)
Issued at 133 PM CST Wed Nov 18 2020
Upper level west-southwesterly flow will be in place over the
majority of the CONUS at the beginning of the long term period,
and remain established into the weekend. Surface winds Thursday
night will be light and variable, but will increase out of the
north overnight as a weak low pressure center develops in far
northeastern NM and temperatures drop into the upper 40s to upper
30s. Sustained north winds in the 15-20 mph range can be expected
during the day Friday as the weak low moves eastward just south of
KS, and this will combine with increasing clouds to hold high
temperatures in the upper 50s to lower 60s. Winds will weaken
quickly after sunset with the loss of boundary layer mixing and
the weak low dissipating in central OK.
Friday night, guidance is in good agreement regarding a subtle
upper level shortwave disturbance ejecting from the central
Rockies and providing sufficient lift to cause rain to develop
along a weak baroclinic zone draped across southwest KS. Rain is
expected to increase in coverage and intensity Saturday morning
through the evening as another shortwave impulse digs southeast,
and precipitation is expected to last through Sunday morning. High
temperatures on Saturday will struggle to breach 50 as overcast
skies and rain prevent significant daytime heating. Lows Sunday
morning will be near or below freezing as evaporative cooling and
increasing cold advection bring temperatures below freezing, and a
brief period of wintry mix or snow still cannot be ruled out.
Any lingering precipitation late Sunday morning will move out of
the area by early afternoon as surface high pressure builds into
the northern plains. Winds will increase into the 15-20 mph range
out of the north in response, which will reinforce the cold air
mass left behind by the earlier system. Therefore, highs on Sunday
will only reach the upper 40s to lower 50s. South winds will
resume over southwest KS on Monday as the surface high pressure
center moves east over the Midwest, however Monday will only be
slightly warmer. Monday night into Tuesday morning, guidance is
hinting at another potent trough ejection into the high plains,
however spatiotemporal inconsistencies between the ECMWF/GFS/CAN
have limited confidence, and trends will continue to be monitored.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 501 PM CST Wed Nov 18 2020
VFR conditions for all airport sites through the time period. Mid
and upper level clouds will pass through the region this evening
along with breezy surface winds of 18-25 kts with occasional
gusts. Winds around 2,000 ft will increase between 01Z-07Z to
40-50 kts for all airport sites before slowly decreasing after
07Z. Surface winds should start to diminish into Thursday morning
and in general be under 12 kts by Thursday afternoon.
&&
.FIRE WEATHER...
Issued at 1137 AM CST Wed Nov 18 2020
Strong south winds will continue through the afternoon today as
southwest KS resides between surface high pressure to our
southeast and low pressure to our northwest, therefore maintaining
a tight pressure gradient over our area. All guidance is in
agreement the strongest winds will impact the far southeastern
zones, gradually decreasing with northwestward extent.
Additionally, the airmass will continue to dry out as boundary
layer mixing and daytime heating reduce relative humidity into the
12-15% range near the CO/KS border, to the 20-25% range in central
KS. Despite poor juxtaposition of the strongest winds and lowest
relative humidity, conditions still appear sufficient for a red
flag warning across Stafford, Kiowa, Pratt, Clark, Comanche, and
Barber counties through 6 pm CST this evening. While this warning
only affects a handful of counties in our area, outdoor burning
of any kind is strongly discouraged across all of southwest KS.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 50 78 43 60 / 0 0 0 0
GCK 45 76 40 58 / 0 0 0 0
EHA 51 82 41 61 / 0 0 0 0
LBL 48 82 40 61 / 0 0 0 0
HYS 47 76 41 59 / 0 0 0 0
P28 51 78 48 63 / 0 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM CST this evening for KSZ066-080-081-
088>090.
&&
$$
SHORT TERM...Springer
LONG TERM...Springer
AVIATION...Tatro
FIRE WEATHER...Springer
Area Forecast Discussion
National Weather Service Lincoln IL
754 PM CST Wed Nov 18 2020
.SYNOPSIS...
Issued at 159 PM CST Wed Nov 18 2020
High pressure dominating the eastern U.S. will move off to the
east over the next few days enabling strong southwest winds to
bring above normal temperatures into Illinois for the end of the
week. A cold front should move through the area Friday and then
stall over southern Illinois giving portions of the region a rainy
weekend.
&&
.UPDATE...
Issued at 752 PM CST Wed Nov 18 2020
Breezy south winds continue late this evening across central
Illinois with a number of sites still gusting up to around 30 kt.
Strong south flow will continue overnight resulting in non-diurnal
temp trends. Temps will bottom out this evening, then hold steady
or rise slightly overnight. Wind Advisory continues for Thursday
remain on track.
&&
.SHORT TERM...(This evening through Thursday)
ISSUED AT 159 PM CST Wed Nov 18 2020
Increasing gradient over the Midwest enhance gusty winds through
the short-term. Models consistent in developing LLJ tonight and
much of Thursday with 925mb winds approaching 70 kts by sunrise.
Main question regards how much of that momentum will be able to
work down to the surface. NAM and several NMM members of the SREF
limit mixing tomorrow with a boundary layer inversion remaining in
place through the day. This solution is inconsistent with the dry
ground and strong warm advection. Will favor a warmer low-level
temp profile which should allow mixing from the LLJ. This is
captured best by HRRR which brings surface gusts approaching 50
mph by mid-morning to the central CWA. Will go with wind advisory
from 12z Thu to 00z Fri for all but the the extreme northwest
portion of the forecast area which is northwest of the main LLJ
jet axis
.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 159 PM CST Wed Nov 18 2020
Northern stream wave is progged to push a cold front through the
area late Friday. As the front gets hung up as the energy moves
off to the east, overrunning pcpn is expected to develop with a
prolonged period of good isentropic lift. The temporal trend in
forecast solutions for the best lift has been further south with
time as the front`s final position is dependent on the strength of
the initial shortwave which the trend has been a bit stronger than
older runs. This would place the axis of the heaviest precipitation
near I-70 though that position could sag a little further south
with rainfall possibly reaching 2 inches locally over the
weekend.
The next shortwave approaches the Midwest late Saturday and
enables a sfc wave to develop along the stationary front in the
ozarks region and pushes the front northward into the forecast
area. As the dynamics moves across the Great Lakes, the sfc low
moves across Illinois and then forces the front back across the
area in its wake as a reinforced cold front, finally ending
precip chances temporarily.
However, the pattern continues to be progressive with the next
shortwave moving into the Midwest on Tuesday and producing another
round of significant precipitation. The ECMWF and CMC are much
stronger with this wave than the deterministic GFS and may
support a potential for strong convection. Will have to monitor
the system closely over the next few runs.
After a warm start to the weekend, 850 temps drop down to near
normal by Monday. There remains uncertainty for Tuesday and
Wednesday as the warm advection in the ECMWF is significant
stronger ahead of the highly dynamic wave mentioned above with
the GFS much more damped.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 522 PM CST Wed Nov 18 2020
A cold front will slowly approach the terminals over the next
36-48 hours with strong SW winds in place across central
Illinois ahead of the front through the period. Expect gusts in
excess of 20 kt to continue overnight, though may become sporadic
at times. Strong winds of 50-60 kt will develop aloft resulting
in LLWS overnight. These stronger winds will mix in part down to
the surface during the day Thursday with frequent gusts expected
to push into the high 30 to lower 40 kt range and a few sporadic
gusts near 50 kt possible. VFR conditions will prevail.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 6 AM to 6 PM CST Thursday for ILZ029>031-037-
038-041>057-061>063-066>068-071>073.
&&
$$
UPDATE...Deubelbeiss
SYNOPSIS...Barker
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Deubelbeiss
Area Forecast Discussion
National Weather Service Marquette MI
538 PM EST Wed Nov 18 2020
.SHORT TERM...(This evening through Thursday)
Issued at 344 PM EST WED NOV 18 2020
Broad mid-upper level ridging moving across the region as noted on
RAP analysis and water vapor imagery should ensure dry conditions
across the Upper Great Lakes for the next 24 hours. Ahead of a sfc
trough over the Dakotas, a 50-60 kt low-level jet max at around 850
mb will move over Upper Mi later this afternoon and evening.
Southerly winds already getting gusty across much of the U.P. this
afternoon as this low-level jet is beginning to nose into the area.
Although fcst soundings indicate mixing only to 1500 ft, this has
resulted in gusts generally in the 20-30 mph range with even some
gusts in the 35-40 mph at KSAW. Coinciding WAA with the approaching
jet max has also resulted in temps rising to around 40F to the lower
40s under partly to mostly cloudy skies. Winds are also already
picking up over over the Bay of Green Bay and northern Lake
Michigan, which will help kick up waves and drive minor lakeshore
flooding concerns. Lakeshore Flood Advisories will be continued for
Menominee through southern Schoolcraft counties. The only change was
to extend the advisory for southern Schoolcraft into 21Z Thu as a
longer period of south winds ahead of the approaching sfc trough
will sustain larger waves a bit longer there into Thu afternoon.
Tonight, as the LLJ and pres gradient continue pushing through the
region, the gusty southerly winds could extend into the evening
hours, before slowly diminishing after midnight. With the continued
cloud cover and the WAA regime over the region, overnight lows will
be mild and largely in the 30s across the region.
Thursday, under mid-level wsw flow, one shortwave will be tracking
toward James Bay with a second moving from the Dakotas into the
Upper Great Lakes. These waves will help propel a weak cold front
east into Upper MI during the late aftn/evening. Little in the way
of forcing and a lack of deep moisture suggest a dry fropa. Ahead of
the front, the NAM fcst soundings remain an outlier still suggesting
a stratus deck spreading across the area to hold temps down. Will
continue to ignore this solution. There will probably be quite a bit
of high cloudiness, at least thru the first half of the day. Used a
blend of MAV and NBM temp guidance for max temp guidance which
yields highs in the upper 40s/lower 50s across the board. Expect Thu
to be the warmest day of the week.
.LONG TERM...(Thursday night through Wednesday)
Issued at 420 PM EST WED NOV 18 2020
Weak H5 atmospheric ridge will propagate over the Great Lakes region
Thursday night into Friday morning. This will cause a gradual wind
shift from west to southwesterly by Friday morning at the 850 hPa
level in the atmosphere. Anticipate this to mix down to the surface
early in the morning keeping temperatures elevated. Additionally, a
quick moving H5 shortwave will be on the heels of this weak ridge
aloft by mid Friday morning. Height falls will occur rapidly causing
an uptick in surface wind speeds. 850mb winds courtesy of a LLJ will
approach 45-50 knots between 9-12Z Friday. This will continue to
occur for early Friday into the afternoon period. Winds speeds will
ramp up quickly, especially over the Lake Superior marine zones
where gale force gusts certainly look plausible by Friday afternoon.
A jet max upwards of 100-110 knots will quickly propagate over the
region. This should enhance height falls ahead of the surface cold
front, behind it with MSLP pressure rises of 3-6mb per 6 hours
according to the GFS analysis. Further convincing signal of a gusty
northwest winds over land with stronger gusts over the waters.
Unfortunately, model soundings are not showing saturation in the
column more than the bottom 200mb between 800-1000mb. Decided to
keep slight chance of precipitation mentioned until late afternoon.
This will certainly allow for low clouds to develop and persist, but
QPF values should stay low to only a few hundredths overall for the
CWA. Clearing skies will lead to chilly overnight lows Friday into
Saturday morning as CAA and subsidence begins to occur with a 1035mb
surface high moving from Saskatchewan/Manitoba toward the Great
Lakes area.
Zonal flow from the departing shortwave should keep temperatures
slightly cooler Saturday with most inland areas being near the
freezing mark, with slightly warmer temperatures near the larger
lakes. Saturday into Sunday morning will stay quiet regarding
weather with dry conditions anticipated. Model guidance is hinting
at a shortwave trough moving over the area on Sunday afternoon into
Sunday night. This should present the area with light rainfall ahead
of a weak surface cold front, and snow showers after dark.
For the medium to long range forecast, the models continue to
disagree on the handling of the weather system for Tuesday into
Wednesday across the Great Lakes. The outlier at this point of
analysis is the ECMWF. It certainly advertises an event that would
bring accumulating snowfall worthy of possible winter headlines for
the Upper Peninsula if it occurred. Leaning toward the conservative
end for the forecast package as the remaining model guidance has the
energy split to the north and south of the region, with only light
amounts of precip possible for our area. We will continue to monitor
the extended forecast trends in the event that the weather guidance
comes into better agreement as we approach the holiday next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 537 PM EST WED NOV 18 2020
Conditions will improve this evening at the surface, but with a LLJ
still impacting the region, some LLWS will be possible at IWD.
Otherwise, VFR conditions are expected during most of this period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 344 PM EST WED NOV 18 2020
Stuck between high pressure to the southeast and a low moving into
Manitoba today, southerly winds have increased to 25-30 kts in the
west and to 30-40 kts east. Will maintain the running gale warning
over the east half of the lake for this low end gale event into this
evening. By Thursday morning, winds should return to around 20kts
across the lake. A weak cold front will swing through Thursday,
allowing for winds to become westerly. A secondary cold front is
progged to pass through the lake early Friday, with stronger west-
northwest winds to 25-30kts setting up across the lake. Might even
see gusts to 35 knots over the east hlaf of the lake. Light winds
near 20kts are expected to return Friday night and persist through
the weekend.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lakeshore Flood Advisory until 5 AM EST /4 AM CST/ Thursday for
MIZ012-013.
Lakeshore Flood Advisory until 4 PM EST Thursday for MIZ014.
Lake Superior...
Gale Warning until 1 AM EST Thursday for LSZ248>251-266-267.
Gale Warning until 9 PM EST this evening for LSZ265.
Lake Michigan...
Gale Warning until 5 AM EST Thursday for LMZ221-248-250.
&&
$$
SHORT TERM...Voss
LONG TERM...BW
AVIATION...07
MARINE...Voss
Area Forecast Discussion
National Weather Service Paducah KY
451 PM CST Wed Nov 18 2020
.UPDATE...
Issued at 448 PM CST Wed Nov 18 2020
Updated Aviation discussion for 00Z TAF Issuance.
&&
.SHORT TERM...(Tonight through Thursday night)
Issued at 239 PM CST Wed Nov 18 2020
Main concerns for the short term are near Advisory level winds and
potential Red Flag conditions on Thursday.
Fast nearly-zonal flow will push the surface high eastward while
surface low pressure inches southeast through the Plains and
upper Midwest. This will create a very strong pressure gradient
through the short term period with the strongest winds expected on
Thursday. Used ConsShort for winds and wind gusts and will come
up just below the 40 mph gust criteria for a Wind Advisory over
southern Illinois where the strongest winds are expected. The main
limiting factor for winds Thursday will be a fairly shallow mixed
layer that will not likely reach 3kft. Would prefer to see mixing
through a deeper layer to go with something closer to the HRRR
wind gusts. Will issue a Special Weather Statement for southern
Illinois and southeast Missouri to highlight the expected breezy
conditions tomorrow.
The other issue for Thursday will be dry conditions, resulting in
relative humidity ranging from 25-35% over much of the region. The
model consensus is typically too moist that first day on the back
side of a surface high, so we ran with a 75/25 mix of the ConsMOS
and ARW WRF for dewpoints, which has worked fairly well in similar
situations in the recent past. With the dry air in place and full
sunshine expected, temperatures should outperform the consensus of
guidance and the NBM. Went close to the 90th percentile of
available guidance for highs on Thursday.
For tonight, winds will settle just a bit with sunset, but will
begin to increase by mid-evening and will likely be gusting over
much of the region by daybreak Thursday. This will lead to evening
lows with temperatures rising overnight. Stayed close to the
consensus for lows tonight. Winds should stay up Thursday night,
so leaned a bit toward the warmer side of guidance. Some locations
may not drop below 50.
.LONG TERM...(Friday through Wednesday)
Issued at 239 PM CST Wed Nov 18 2020
Near-zonal and fairly fast flow in the mid levels across the CONUS
will eventually give way to a more dynamic flow pattern during the
weekend. Into the weekend, high surface pressure centered over the
Appalachians will slowly diminish while a quasi-stationary surface
boundary sets up just to our north. The NBM suggested that the vast
majority of the PAH forecast area will remain dry on Sat as the
frontal boundary flirts with the northernmost tier of counties,
possibly providing some shower activity there during the day. This
was supported by deterministic model solutions.
A surface low/trof is progged by the medium range models to develop
along this front early Sun and move to the northeast as mid level
shortwave energy digs through the region. Being this is Day 5,
deterministic model solutions differ somewhat on the exact evolution
and timing of this wave of energy as it moves through, but rain
showers should be common for most of the region during the day Sun,
with somewhat lower PoPs for western KY for the afternoon and
evening. PoPs are expected to increase overall however, as the event
gets closer and model solutions merge. At this time, the QPF
forecast for this system ranges from about 1 1/3 inches northwest to
about 1/2 inch southeast. Temps may cool enough late Sun night for a
few snowflakes to occur on the trailing edge of pcpn in parts of
southeastern MO/southern IL, with no impacts anticipated.
Mon/Mon evening should be dry under a surface ridge axis and a broad
ridge aloft, followed by another system early next week. The medium
range models/ensemble means now suggest a fairly vigorous mid level
shortwave trof moving through the central CONUS late Tue/early Wed.
The National Blend suggested a ramp-up of PoPs almost all rain
starting early Tue and peaking late Tue night. There is a limited
chance of snowflakes in the air for a few hours early Tue for much
of the region (southern parts of KY/MO not so much). There could
even be a dusting of snow in the higher elevations of the MO Ozark
Foothills region (not likely, but possible). As model solutions
eventually stabilize, the QPF forecast may end up being roughly an
inch (of rain) with this system. The models currently show enough
lack of instability to preclude a thunder mention in the forecast at
this time.
Expect temps to peak on Sat (Sun for the southern Pennyrile region
of KY), and should be significantly above average for this time
year, then will drop back closer to seasonable averages early next
week.
&&
.AVIATION...
Issued at 448 PM CST Wed Nov 18 2020
The main flight impact in an otherwise VFR forecast is for south
winds to pick up tonight, and really increase with gustiness tmrw.
This will be in response to an approaching/developing Low
pressure system in the High Plains/Midwest, and anchoring High
pressure here/to our east across the Mid Atlantic/Southeast,
creating a strengthening pressure gradient. The gusts and winds
should subside some toward sunset tmrw, ie the close of the
planning phase of the forecast.
&&
.FIRE WEATHER...
Issued at 239 PM CST Wed Nov 18 2020
The driest conditions (20-25%) are expected over west Kentucky
Thursday afternoon, but most of the region will be at or below
35%. South winds will be raging over southeast Missouri and
southern Illinois, but may only be near 15 mph over the LBL and
the Ft Campbell area. After collaborating with area fire
management officials and neighboring offices, we have decided to
issue a Fire Weather Watch for all of west Kentucky and southwest
Indiana. The expectation is that the Watch will be upgraded on the
midnight shift.
Fuels are plenty dry enough over the Shawnee to support a potential
warning there as well, if confidence in sub 25% relative humidity
increases on the midnight shift. It is certainly possible given
the magnitude of the winds expected over southeast Missouri and
southern Illinois that a Red Flag Warning could be issued for the
entire region, even with relative humidity just above 25%. For now
will settle for mentioning elevated fire danger in the Special
Weather Statement and HWO for southeast Missouri and southern
Illinois.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...Fire Weather Watch from Thursday morning through Thursday
afternoon for INZ081-082-085>088.
KY...Fire Weather Watch from Thursday morning through Thursday
afternoon for KYZ001>022.
&&
$$
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
705 PM EST Wed Nov 18 2020
.UPDATE...
Latest RAP model has mid/upper ridging over the eastern US through
Thu. At the surface high pressure in the central Appalachians this
evening eases eastward...reaching the Mid-Atlantic coast Thu. These
features remain in control with a stable and dry northeasterly flow
that becomes east-northeasterly during Thu.
Forecasts remain on track...mostly clear overnight then few to
scattered lower clouds Thu. Lows in the 50s to lower 60s by
erly morning with highs in the 70s for the afternoon.
&&
.AVIATION...
19/00Z TAFs. VFR with SKC to FEW-SCT SC. Gusty NE winds diminish AFT
02-03Z then become ENE and gusty at 15Z.
&&
.MARINE...
Robust high pressure easing eastward across the Mid-Atlantic will
keep a tight gradient across the waters overnight and into early Thu
morning. This results in northeast winds around 20-25 knots and
gusty with a small craft advisory in effect. Both Tampa Bay and
Charlotte Harbor may see winds drop off after midnight but still
gusty and in the 15-20 knot range so will leave the small craft
advisory in place there. Winds diminish Thu but remain near exercise
caution speed for the next couple of days.
&&
.Preliminary Point Temps/PoPs...
TPA 60 78 64 81 / 0 0 0 0
FMY 61 78 63 81 / 0 0 0 0
GIF 60 77 63 80 / 0 0 0 0
SRQ 61 79 65 82 / 0 0 0 0
BKV 55 76 60 80 / 0 0 0 0
SPG 63 76 66 78 / 0 0 0 0
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...Small Craft Advisory until 10 AM EST Thursday for Charlotte
Harbor and Pine Island Sound-Coastal waters from Bonita
Beach to Englewood FL out 20 NM-Coastal waters from
Englewood to Tarpon Springs FL out 20 NM-Coastal waters
from Tarpon Springs to Suwannee River FL out 20 NM-Tampa
Bay waters-Waters from Bonita Beach to Englewood FL out 20
to 60 NM-Waters from Englewood to Tarpon Springs FL out 20
to 60 NM-Waters from Tarpon Springs to Suwannee River FL
out 20 to 60 NM.
&&
$$
UPDATE/AVIATION/MARINE...09/Rude
UPPER AIR...04/Sobien
DECISION SUPPORT...04/Sobien