Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/17/20
Area Forecast Discussion
National Weather Service Goodland KS
709 PM MST Thu Jan 16 2020
Issued at 706 PM MST Thu Jan 16 2020
Updated probability and coverage of precipitation mainly based on
radar reflectivities and reports of freezing rain mixed with snow
and sleet across the central portion of the CWA early this evening.
It looks like the HRRR had a good representation of the area of
precipitation during the first few hours, and have started out
with the HRRR for the rest of this evening with a blend to the
CONShort solution through the remainder of the night and through
the day on Friday.
.SHORT TERM...(This evening through Friday)
Issued at 259 PM MST Thu Jan 16 2020
The main concern in the near term forecast is the winter weather expected
to impact the region overnight and into Friday morning. An upper
ridge is currently situated over the Central High Plains with
southwest flow aloft over the Tri-State area. An upper level
trough is progressing eastward, having moved over the West Coast
earlier today. High pressure remains over Eastern Nebraska and
Kansas this afternoon.
A mid-level shortwave trough is expected to develop over Colorado this
evening, moving into the region early Friday morning. Moisture
being pulled in mainly from the southwest with some from the Gulf
of Mexico, combined with the advancing trough will provide give
the region a chance for precipitation through tomorrow morning.
Precipitation has developed along our southern border this afternoon.
Light snowfall is expected across the region, beginning from
South to North this afternoon and continuing into the evening
hours. Less than one inch of snow is expected, with the higher
amounts east of Highway 83. Snow amounts will be impacted by the
timing of the expected transition to a wintry mix later this
The forecast becomes a little more tricky with warmer air alfot expected
to intrude into the region. Thermal soundings continue to show a
profile indicative of more of a sleet and freezing drizzle event
than freezing rain, at least for the area. Have left a chance for
freezing rain in the forecast at this time, however, confidence is
low in this solution given drier air aloft. Confidence is
moderate that we will receive sleet with some drizzle on the back
side of this system as it tapers off Friday morning. Total ice
accumulations of under one tenth of an inch are expected with the
highest amounts east of Highway 83. Ice accumulations will be
dependent on the timing of the transition over from snow. While
accumulations are expected to be minimal for this event, light
icing may result in slick spots on roads and elevated surfaces.
Friday, the upper trough will move into the region with a
tightening gradient. Winds will be breezy through the day, picking
up in the evening. Eastern Colorado may have a chance of some
patchy blowing dust Friday afternoon due to gusty winds and dry
conditions. The timing of the exiting system will impact afternoon
high temperatures, particularly in the eastern part of the Tri-
State area. A warm front is expected to move into Eastern Colorado
on Friday, helping temperatures return to the 50s. Areas to the
east of the front are expected to remain cooler as cloud cover
lingers in the area.
.LONG TERM...(Friday night through Thursday)
Issued at 230 PM MST Thu Jan 16 2020
Friday night northwest winds will increase as the upper level trough
following today`s precipitation moves through. Isallobaric pressure
trends are the same as yesterday, 15-17 mb pressure rises per 6
hours during the night. Soundings continue to support strong winds
during this timeframe, with 40 KTS winds through most of the mixed
layer. A 60 MPH may occur, however the question is will these wind
speeds extend down deep enough into the mixed layer to reach the
ground. The shallow mixed layer persists through the night, but may
not be deep enough to reach these gusts. Therefore confidence is on
the low side of gusts this strong reaching the ground. Have higher
confidence of sustained winds close to 40 MPH occurring than gusts
of 60 MPH occurring. Gusts of 45-55 MPH are expected. The wind
speeds will gradually decline toward sunrise behind the trough.
Saturday morning the breezy winds will gradually decline, becoming
light by the afternoon.
For the rest of the forecast period, dry northwest upper level flow
will move across the Plains ahead of a short wave ridge early next
week. The ridge will bring in warmer temperatures.
The next chance for precipitation will be Thursday as an upper level
short wave trough breaks down the ridge and moves across the Plains.
This trough is looking more favorable for producing precipitation
than it did yesterday. However confidence is still on the low side
that this will actually occur.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 434 PM MST Thu Jan 16 2020
GLD will transition from MVFR to LIFR by 06Z as light mixed phase
precipitation moves northeastward into the area and both
visibility and ceilings decrease. Conditions will remain LIFR
through the night and will begin to improve Friday morning with
MVFR conditions by 17Z and VFR conditions by 19Z. Winds will
remain gusty through the night and will turn to the northwest and
increase after 22Z Friday late afternoon.
MCK will start out VFR but will become MVFR as light mixed phase
precipitation moves into the area by 05Z with a decrease mainly in
ceiling height. Visibilities and ceilings will continue to
decrease with conditions becoming IFR by 08Z. LIFR conditions are
possible between 14-20Z before improving to MVFR after 20Z and VFR
by 22Z as visibility improves and clouds begin moving out of the
area as the system moves out of the region.
KS...Winter Weather Advisory until 11 AM MST /noon CST/ Friday for
NE...Winter Weather Advisory until noon CST Friday for NEZ081.
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
940 PM CST Thu Jan 16 2020
Issued at 930 PM CST Thu Jan 16 2020
The current trends for overnight and through the day on Friday
look quite good and on target with the impending winter storm
system. The latest RAP, NAM, and several iterations of the HRRR
are still showing wintry precipitation spreading into central MO
between 12-13z in response to strong isentropic lift/WAA, with
the precipitation spreading quickly east through the morning
reaching the MS River between 15-17z. The precipitation should
initially be in the form of snow with diabatic cooling
contributions due to saturation of the initially dry low level
air, however after saturation the strong WAA and increasing
magnitude of elevated warm layer will result in a transition to
sleet and then freezing rain. Expect for northeast MO and west
central IL where the deeper cold air will remain entrenched a bit
longer, I don`t see anymore than a few hour period of snow before
the transition to sleet and then several hours later to freezing
rain. The magnitude of the elevated warm nose is quite stout by
mid-afternoon when surface temps are still at or below freezing
over most of the CWA, great enough that freezing rain efficiency
will be reduced due to warming hydrometer temps aloft. A tenth to
a quarter inch of an inch of ice from freezing rain, sleet
accumulations of a quarter to half inch, up to a couple inches of
snow still look reasonable as does the current winter weather advisory
area. The greatest accumulations of snow should be across
northeast MO into west central IL. Morning commutes/travel in
central MO will be messy and hazardous. Road conditions will
likely be quite poor/hazardous for late afternoon/evening
commutes/travel across much of the CWA. Temperatures will warm
above freezing across the entire CWA on Friday evening as surface
flow becomes more southerly and WAA continues.
.SHORT TERM... (Through Late Friday Night)
Issued at 336 PM CST Thu Jan 16 2020
Early this afternoon, an amplifying upper RIDGE was over the Plains
while a strong storm system was coming onshore in northern
California. The resultant flow aloft over our region was from the
northwest, but flow was already backing from the southwest over the
High Plains funneling several pieces of energy that had their
origins over the eastern Pacific into the southern Plains. This was
already causing clouds to increase over our region with
precipitation breaking out in much of Oklahoma, western Kansas,
Texas, and Arkansas. At the surface, a strong area of high pressure
representing a very cold airmass was centered over Iowa but had its
influence well south into our entire region, and despite sunshine,
has kept temperatures in the 20s for areas north of Interstate 70
and in the 30s for areas to the south.
A mostly quiet night is on tap tonight, as the strong storm system
will track from California into Utah, driving the upper RIDGE
through our region and allowing the initial pieces of energy further
towards our region from the southwest. In fact, the very upper
level disturbances that are in large part creating precipitation in
Texas and southern Oklahoma will be over Missouri by sunrise Friday
morning. The lift will be there. What they do not have to contend
with in Texas, however, is the cold dry air from the high pressure
currently entrenched over our region and will be slow to yield
ground as we head into Friday morning. This low level dry air is
the principal bone of contention between operational models, with
most advertising strength of lift that is in the neighborhood of
what is needed to overcome this low level dry air, with some above
it and some below it. Due to this disparity, Friday morning`s
possibilities look wide open, with widespread light precipitation
building in from west to east between 5am and noon, light patches to
areas of precipitation expanding from west to east, or precipitation
being very isolated. Trended PoPs upward during the morning but
held off on very high PoPs for most areas during the morning for
Precipitation looks to really begin in earnest by midday and
continue through Friday night as there is strong ensemble agreement
on the deep lift finally overcoming any barriers, with widespread
light to moderate to at times heavy precipitation occurring.
The cold and dry low level air will also serve to delay
precipitation transitions away from all snow just a bit, but once it
begins, should quickly progress through sleet to freezing rain,
especially during the afternoon hours with the low level jet having
its greatest effect on wet bulb temperatures aloft.
At this point, surface temperatures will dictate everything, but the
latest model trends have trended towards a slower warmup during the
day with the more substantial rise of temps occurring Friday night
as surface winds shift from E-SE to more S-SE. This means that
temperatures may not rise above freezing until early evening for
areas south of Interstate 70, and late evening (after 9-10pm) for
areas north of Interstate 70.
While snow (and sleet) accumulations continue to be advertised
similar from forecast package to forecast package, with the greatest
amounts of 2-3" in northeast MO and west-central IL and less than an
inch generally for areas near and south of I-70, ice accretion
potential has trended higher. Lots of QPF for ice accretion to tap
into, but the intensity of the precipitation at times could be its
biggest undoing with much of this expected to go into runoff. It is
this adjustment for the ice accretion forecast, that if the ice
accretion forecast ultimately misses its mark, it will be on the low
side of what happens and not because it was too high. That said,
the overnight shift will have one final look at this to adjust any
headlines before this event begins. A Warning for ice accretion may
be needed for areas, as it looks now, mainly to the north and west
of the STL Metro area. For now, Winter Weather Advisories have been
issued for the entire area from Friday morning until midnight Friday
night, when temperatures are expected to rise above freezing in all
Not be outdone, QPF on the order of a widespread inch with close to
two inches locally possible, with the heaviest expected during
Friday evening will combine with already elevated levels on creeks,
streams, and small rivers to result in a flood threat, especially
for widespread nuisance flooding. Have issued a Flood Watch for
much of the area Friday afternoon and night to account for this.
.LONG TERM... (Saturday through Next Thursday)
Issued at 336 PM CST Thu Jan 16 2020
Lingering precipitation can be expected Saturday morning, mainly
across west central and southwest Illinois into southeast MO. As
colder air filters in behind the surface low and trailing cold front
there may be a change over to snow across northeast MO and west
central IL just before the precipitation ends. Little if any snow
accumulation is expected. The chance of precipitation will end by
noon on Saturday as a surface ridge builds into our area from the
northern Plains. Strong and gusty winds can be expected due to the
tight surface pressure gradient between the deepening surface low
moving northeastward through the Great Lakes region and the surface
ridge building into the Plains. Much colder temperatures can also
be expected Saturday night with lows about 10 degrees below normal,
and wind chills dropping down to near 10 below zero across parts of
northeast MO and west central IL by early Sunday morning. Very cold
conditions will continue for the rest of the weekend into the next
work week with the coldest low temperatures forecast Sunday night. A
northwest flow shortwave will drop southeastward through our
forecast area late Sunday night and Monday morning. At this time it
appears that it will be too dry in the low levels of the atmosphere
for any snow associated with this feature. Will see a warming trend
beginning on Tuesday due to rising upper level heights, and as the
surface wind becomes southerly as the surface ridge shifts east of
the region. The operational GFS model brings precipitation back
into our area already by late Tuesday night, while the ECMWF model
is much slower not bringing any precipitation into our area til
Wednesday night. With model differences for now will only introduce
slight chance pops for mainly northeast and central MO Wednesday
afternoon and night, then gradually increase pops and spread them
east on Thursday. The ECMWF model has less QPF with a weaker upper
level and associated surface low over the southern Plains. The
operational GFS has a stronger upper level low and more QPF. At
this time it appears that there could be a wintry mix Wednesday
night, but the precipitation type should change to liquid rain by
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 544 PM CST Thu Jan 16 2020
VFR flight conditions are expected tonight with wintry
precipitation developing and spreading west to east across the
area on Friday morning. Flight conditions will deteriorate with
time as the precipitation becomes more continuous on Friday.
KCOU: precipitation is expected to begin as snow between 13-14z
then changeover to a sleet/freezing rain mix mid-late morning and
to all freezing rain on Friday afternoon.
KUIN: precipitation will begin as snow around 16z and changeover
to a mix of freezing rain/sleet around mid-afternoon.
SPECIFICS FOR KSTL/KSUS/KCPS: the onset type of precipitation is
the biggest challenge and current thinking is light snow will
begining mid-late morning, changing over to sleet several hours
after beginning, and then to all freezing rain by mid-afternoon.
MO...Flood Watch from Friday afternoon through late Friday night for
Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-
Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Lincoln MO-
Madison MO-Moniteau MO-Montgomery MO-Osage MO-Pike MO-
Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis
City MO-Saint Louis MO-Sainte Genevieve MO-Warren MO-
Winter Weather Advisory from 6 AM Friday to midnight CST Friday
night for Crawford MO-Franklin MO-Gasconade MO-Iron MO-Knox
MO-Lewis MO-Lincoln MO-Marion MO-Monroe MO-Montgomery MO-
Pike MO-Ralls MO-Reynolds MO-Shelby MO-Warren MO-Washington
Winter Weather Advisory from 9 AM Friday to midnight CST Friday
night for Jefferson MO-Madison MO-Saint Charles MO-Saint
Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
Winter Weather Advisory from 3 AM Friday to midnight CST Friday
night for Audrain MO-Boone MO-Callaway MO-Cole MO-Moniteau
IL...Flood Watch from Friday afternoon through late Friday night for
Bond IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey
IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
Pike IL-Randolph IL-Saint Clair IL-Washington IL.
Winter Weather Advisory from 9 AM Friday to midnight CST Friday
night for Adams IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-
Fayette IL-Greene IL-Jersey IL-Macoupin IL-Madison IL-
Marion IL-Monroe IL-Montgomery IL-Pike IL-Randolph IL-Saint
Clair IL-Washington IL.
Area Forecast Discussion
National Weather Service Norman OK
945 PM CST Thu Jan 16 2020
Only minor adjustments made to the forecast this evening with
timing of precipitation type transition and some modification of
POPs, although still generally in the categorical range.
The wet bulb zero line may finally be shifting northwestward as
winds across central and southwest Oklahoma begin to veer towards
a more warm advective direction. Over the past couple of hours,
the wet bulb temperature at the Medicine Park and Seymour mesonets
have risen above 32 (although a spotter in Meers reported a
temperature of 29, so there is some variability in the vicinity of
the Wichitas). We probably could remove Baylor County from the
advisory, but will wait a little bit until we can take out a few
more counties at the same time. Although most of Wilbarger and
Grady Counties are now warm enough for rain, the mesonets at Odell
and Minco respectively are still cool enough to be of some
concern in the northern part of those counties, but it should not
be long before those counties could be cleared.
The initial area of precipitation is moving into central and south
central Oklahoma, but the next area has been developing and
expanding in the western part of the CWA and the eastern Texas
panhandle and low rolling plains. Some of this area west of our
Texas counties even looks more convective, and there has been at
least one cloud-to-ground lightning strike detected west of
Guthrie Texas. Although at this point this precipitation is not as
widespread as the first area, we still expect some expansion
through the night.
The forecast in general is still in good shape, but have made some
minor adjustments to the POPs and the precipitation transition.
The RAP and HRRR seem to have a decent handle on the evolution of
the low-level temperature/wet-bulb overnight, so have used that
as a general guide for the transition from FZRA to RA.
.PREV DISCUSSION... /issued 629 PM CST Thu Jan 16 2020/
00Z TAFs and a mesoscale update.
The wet bulb zero line (where the wet bulb temperature is at
freezing) currently extends from southeast of Stillwater through
the OKC metro through Lawton to near Frederick... Vernon and
Seymour. Updated the advisory earlier to include Tillman,
Wilbarger, Baylor and Noble Counties to the advisory with the wet-
bulb zero line where it was, and have just added Oklahoma County
as well (although freezing rain will likely only be an issue in
the northwest portion of the county). We have been seeing
pictures of getting reports of ice accumulations in Vernon, Knox
City, Elk City, Weatherford and various other locations in the
advisory area. In the short term, the wet bulb zero line may not
move very much given the current surface wind field, so freezing
rain will remain possible north of this line over the next few
hours. Enhanced radar echoes along the Red River in southwest
Oklahoma may bring locally heavier freezing rain amounts to areas
near Vernon, Frederick and Lawton early this evening.
Over time, surface winds will veer and start advecting higher
temperature/dewpoint/wet bulb temperatures northwest as expected
allowing precipitation to transition from freezing rain to rain as
the temperatures above freezing advect northwest.
Widespread precipitation is expected along with associated MVFR
and IFR ceilings, although there is some VFR conditions north
early this evening before lower ceilings move in. There will be
areas of freezing rain affecting KCSM, KWWR and KPNC, but
temperatures will slowly rise overnight and into tomorrow allowing
precipitation to transition to rain. Of course there will be some
variability in ceilings and visiblities through the forecast
period, but hive kept the TAFs relatively simple.
PREV DISCUSSION... /issued 302 PM CST Thu Jan 16 2020/
The immediate concern is freezing rain across portions of western
north Texas and southwest Oklahoma. Several reports of a glaze of
ice on elevated surface has been received. Temperatures are
marginal for portions of this area and so icing may be tempered
some by latent heat of fusion, especially given rates are fairly
high (i.e., Crowell and Truscott mesonet sites have received
0.68" and 0.77" of liquid respectively). Deeper within the cold
air, across southwest and west-central Oklahoma, this is likely
where icing will be the most significant. Temperatures are just
below freezing and given dry air 3-5 degrees of wetbulbing should
bring temperatures down into the mid-upper 20s. Upstream advection
should be cold or at least neutral for several more hours. One
limiting factor may be saturation of this dry layer on the front
end may cut into amounts some, and rates may be high enough to
cause some "runoff" such that a straight conversion of QPF to ice
would be an exaggeration. In fact, applying a blended model QPF to
the FRAM model was the basis for our ice amounts and results in
locally near 0.25" of icing, with a maxima in southwest and west-
central Oklahoma. This is where the most significant impacts may
be as far as elevated icing resulting in some power outages.
Significant/widespread impacts seem unlikely at this point but
we`re going to need to watch trends very closely. This is
especially the case for west-central and into southwest Oklahoma
where the juxtaposition of sufficiently cold temperatures and
relatively high QPF amounts overlap.
We feel fairly comfortable with limited to no impacts further east
around the OKC metro area. Temperatures have increased into the
upper 30s to lower 40s as minimal solar heating has occurred
(obviously not much given the clouds and time of year). Also a
factor in the warmer temperatures has been veering winds and
neutral to weak warm advection gradually beginning. This should
keep the areas immediately east of the Winter Weather Advisory
from seeing more than a brief period of freezing rain with impacts
unlikely. A light glaze could occur, however. Further north, we
expanded the Winter Advisory to Kay County because they remained
colder than expected and are near/just below freezing now, and
probably have peaked. As precipitation starts some wetbulbing may
occur to bring temperatures down and possibly lead to more than
just a glaze (up to 0.10") of ice there. Although temperatures
should begin to warm later as winds continue to veer.
Bottom line, power impacts across west-central and southwest
Oklahoma are most likely, but still possible elsewhere including
northwest Oklahoma. Some travel impacts are also possible.
Adjustments based on trends in the observations may be needed and
we`ll be watching observations and seeking reports aggressively as
this event continues to unfold, and will make adjustments
Early tomorrow, temperatures should have warmed to above freezing
all but northwest Oklahoma and southerly winds and warm advection
continue. As the main trough driving all this moisture advection
and ascent continues to move east, widespread rain should shift
east as well. We have the highest probabilities during the first
half of the day and back edge of the rain pushing through much of
the area by evening.
Precipitation will continue exiting the forecast area Friday evening
ahead of the surface cold front and eastward moving upper level
trough. Precipitation is expected to be completely out of the area
by Saturday morning. A zonal upper air flow will dominate for the
remainder of the weekend while cooler air continues to filter into
the region, resulting in below average temperatures for Monday and
A warming trend will begin Tuesday as a strong upper level ridge
begins to form over the Rockies and shift east over our region. The
next chance of precipitation is expected to be in the middle of next
week with the arrival of a upper level trough and low pressure
cyclone that develops behind the ridge with lee-side cyclogenesis
off the Rockies. Towards the end of next week, a stronger upper-
level trough and the possibility of a closed low development is
hinted at within the long range models, however there is quite a bit
of divergence between the models on the development and path of this
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 34 49 40 47 / 100 100 30 0
Hobart OK 29 43 36 49 / 100 90 0 0
Wichita Falls TX 37 50 41 53 / 100 90 20 0
Gage OK 23 45 31 46 / 90 50 0 0
Ponca City OK 31 46 36 45 / 100 100 20 0
Durant OK 41 54 46 51 / 90 90 80 0
OK...Winter Weather Advisory until 6 AM CST Friday for OKZ004>019-
TX...Winter Weather Advisory until 6 AM CST Friday for TXZ083>085-087-
Area Forecast Discussion
National Weather Service Sacramento CA
239 PM PST Thu Jan 16 2020
A Winter Storm moves through the area into early Friday bringing
periods of rain, snow, and gusty winds to the area. Unsettled
weather continues over the weekend into next week.
A winter storm continues to impact interior NorCal this afternoon.
Radar around 1:30pm is depicting the main band of precipitation
along the surface front has now moved south of the Sacramento
area and is stretching from Salinas to Auburn. Gusty winds and heavy
snowfall with significant snow accumulation will continue in the
Southern Cascades and Northern Sierra through late afternoon,
majorly impacting mountain travel. Snow showers are also still
occurring in the Shasta County mountains with lighter snow
accumulation. Caltrans has implemented chain controls over most
mountain roads including I-5, I-80, and Highway 50.
The main line of precipitation will continue to move southeast
through the afternoon. Post-frontal bands of precipitation have
formed and are now moving into the forecast area, bringing
additional Valley rain. CAMs continue to indicate the possibility
of thunderstorms embedded within these post-frontal bands this
afternoon, especially in Shasta County where the HRRR has
consistently indicated the formation of a convergence zone.
Periods of heavy rainfall and small accumulating hail are the main
concern with these thunderstorms.
Rain showers are expected to move out of the Valley by tonight.
Mountain snow showers will continue overnight with an additional 2
to 10 inches of snow accumulation forecast after 5pm. Snowfall
should taper off by around 4am to 5am Friday over the Sierra.
Light rain and snow chances will continue through tomorrow
afternoon for Shasta County.
An upper trough moving through the PacNW Saturday will just barely
graze western NorCal. Models continue to indicate the front
weakening significantly as it moves onshore. Precipitation will
be limited to the Coastal Range, Shasta County mountains, and far
northern Sacramento Valley with limited accumulations expected.
Dry weather forecast Sunday under brief upper ridging.
Cold temperatures are forecast through Saturday, especially today.
The cold front has dropped highs today into the 40s across the
Valley and 20s to 30s for the mountains, and highs are expected to
warm a few degrees every day. Below normal overnight lows are
forecast through the weekend with widespread 30s in the Valley and
teens to 20s in the mountains. HEC
.EXTENDED DISCUSSION (Monday THROUGH Thursday)...
Upper ridging exits early next week with another winter system
moving in. Timing is not certain at this point, but for now have
chances of precipitation spreading in over the area as early as
Monday afternoon, which is Martin Luther King`s Birthday. As the
system moves in, chances for precip will increase overnight and
into Tuesday. Ensemble averages suggest an early estimate of
around a foot of snow could be possible over 6500 feet in the
northern Sierra. This could cause travel difficulties during the
return period at the end of the holiday weekend, so monitor the
forecast closely if you have plans of mountain travel early next
week. Additional unsettled weather is possible through mid week.
Continue to expect changes to the timing of these systems. EK/KR
A storm system brought moderate to heavy rain to the Valley TAF
sites today, with the bulk of the rain over the northern San
Joaquin Valley at the moment. As the system exits the region,
showers develop behind it which will lead to additional periods of
MVFR or IFR conditions. Overnight, showers are expected to taper
off in the Valley while snow showers linger over the mountains.
Should clearing happen early enough, there could be patches of
fog. Best likelihood for this seems to be KMOD and KSCK.
Winter Storm Warning until 6 AM PST Friday for Burney Basin /
Eastern Shasta County-Clear Lake/Southern Lake County-Motherlode-
Mountains Southwestern Shasta County to Northern Lake County-
Northeast Foothills/Sacramento Valley-Shasta Lake Area /
Northern Shasta County-West Slope Northern Sierra Nevada-Western
Plumas County/Lassen Park.
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
732 PM EST Thu Jan 16 2020
Latest surface analysis has a frontal boundary along the GA/FL
border with strong high pressure...centered in the upper Mid-
West...building in behind it. the RAP model moves the front
southward across the area later tonight through Fri with limited
moisture and slightly cooler and drier air in it`s wake. Lower
level northwesterly flow this evening shifts rather quickly to
northeasterly then easterly during Fri and becomes gusty at times.
The drier air will preclude the foggy conditions of the pass
couple of mornings. However some brief low cloudiness can be
expected along and just ahead of the front. The front is weak and
has little upper level support so the forecast will be rain
free...except in the far southern counties Fri morning where some
deeper moisture will linger.
17/00Z. Generally VFR as clouds slowly increase although brief
MVFR CIGS will accompany a frontal boundary traversing south
overnight and in the morning. NW winds this evening gradually
veer to easterly and becomes gusty AFT 14-16Z.
A front moving into the northern waters tonight with drier air
and increasing winds will erode the sea fog up there. Anticipate
the dense sea fog advisory being allowed to expire at midnight.
The winds will reach advisory criteria on all the outer waters and
caution criteria on some of the near shore waters. Winds will
briefly slacken Sat then pick back up as strong high pressure
drives another cold front through the area Sun.
.Preliminary Point Temps/PoPs...
TPA 65 77 62 79 / 0 0 0 0
FMY 65 78 62 79 / 0 20 0 0
GIF 65 76 61 78 / 0 0 0 0
SRQ 65 79 62 80 / 0 0 0 0
BKV 62 77 57 79 / 10 0 0 0
SPG 65 78 62 79 / 0 0 0 0
Gulf waters...Small Craft Advisory from 4 AM Friday to 10 AM EST Saturday for
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
Dense Fog Advisory until midnight EST tonight for Coastal waters
from Tarpon Springs to Suwannee River FL out 20 NM.
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 350 PM CST Thu Jan 16 2020
Overcast skies this afternoon with east to northeast winds near 10
mph has lead to enough insulation to keep temps cooler than
originally forecast with highs in the 20s today. The expected storm
system is coming onshore per water vapor imagery while low to mid
level moisture continues to stream northward over the southern
plains this afternoon. As the surface high to the north exits east,
winds veer to the southeast and increase late this evening as low
level theta-e advection rapidly spreads northward, developing a
swath of precip. 12Z sampled profiler data coupled with forecast
soundings suggest a slower onset of precipitation due to the ample
dry air aloft that needs to be overcome initially. Latest runs from
the HRRR and RAP are consistent with a band of freezing precip
entering the central and north central counties after 06Z, reaching
portions of east central and far northeast counties after 09Z
tonight. Latest sounding data is overall exhibiting lesser
probabilities for snow and higher chances for sleet to begin with,
especially in east central Kansas overnight. 12Z model guidance is
also a tad faster with the low level warm advection around 850 mb
towards sunrise Friday morning, leading to sleet transitioning to a
mix of freezing rain and sleet near or shortly after sunrise from
south to north. The 12Z ECMWF for this forecast package was the
outlier for the warm nose and sfc temps while the NAM, HREF, and GFS
were similar in that sfc temps were slower to rise above freezing
through mid afternoon. This increases concerns for additional ice
accumulation being possible through the afternoon and the reasoning
for extending the Winter Weather Advisory across far eastern areas
of Kansas. Current thinking is that the stronger warm nose and
isothermal depth of the warm layer throughout the morning and early
afternoon where maximum forcing is realized will lead to ice
accumulation in upwards of a quarter of an inch, especially along
and southeast of Interstate 335. Up to two tenths of ice are
possible elsewhere with around 1 to 2 inches of snow and sleet.
Mitigating factors for the higher ice accumulations would be that
the warm nose is not as strong, the cold layer depth below the warm
nose is higher resulting in enough residence time for rain to
refreeze as sleet, surface temps are a degree or two warmer, or
heavier rainfall rates leads to precip runoff and less ice forming.
Still cannot rule out isolated higher ice amounts, but overall due
to the uncertainties with this dynamic system, have decided to keep
the advisory in place with adjustments in start and end times.
Confidence remains high in freezing precip to occur across the
entire area with impacts likely. Winds during the morning and
afternoon may also exacerbate impacts with any ice accumulations as
they are sustained from 15 to 20 mph with gusts up to 30 mph while
precip is falling. Fortunately, sfc temps will reach above freezing
in the afternoon with lingering light rain falling through sunset.
.LONG TERM...(Friday night through Thursday)
Issued at 350 PM CST Thu Jan 16 2020
As the sfc low and attendant upper low matures Friday night, wind
gusts once again increase early Saturday morning in upwards of 20 to
30 mph with gusts up to 40 mph as the cold front swings through. A
wind advisory may be needed for this time period, especially over
north central Kansas. Temps will initially warm to the lower 40s
early Friday evening before dropping back to the 20s on Saturday
morning. All guidance continues to indicate a weak deformation band
of precip developing behind the boundary late Saturday, bringing a
light mix of snow and freezing rain over far northeast Kansas.
Little to no additional accumulations are anticipated.
The remaining extended period is dry and well below normal through
Monday evening with highs in the 20s and overnight lows in the teens
and single digits area wide. Southerly flow returns Tuesday as a
weak upper trough passes through the region by Wednesday.
Differences remain with the timing of the cold front, however
current indications are that our area would be on the warmer side
and would see mostly rain on Wednesday with highs in the 40s.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 540 PM CST Thu Jan 16 2020
Light snow will develop across the terminals after 7Z and then
transition to sleet and freezing rain after 11Z. After 11Z
ceilings will drop below 1000 feet and visibilities will fall
below 3SM in the sleet which will transition to freezing rain. The
freezing rain should end during the early afternoon hours. The IFR
ceilings will continue through the remainder of the afternoon
hours, though visibilities will improve to 5 miles or greater
after 21Z. There may be some moderate low-level wind shear of 20
to 30 KTS late Tonight and through the day Friday.
Winter Weather Advisory from 3 AM to 2 PM CST Friday for
Winter Weather Advisory from midnight tonight to noon CST Friday