Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/13/20
Area Forecast Discussion
National Weather Service Binghamton NY
942 PM EST Sun Jan 12 2020
.SYNOPSIS...
A weak system passes to our north on Monday and may bring a few
isolated showers into our region. Expect temperature to be
slightly above average through the middle of the week with
isolated showers Tuesday with another fast moving system.
Colder air arrives late in the week with snow showers possible
Thursday. A more significant system could impact the region next
weekend.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
The evening updates manly focused on the details of any
freezing drizzle discussed below.
Weak high pressure is building over the region and winds will
continue to decrease and become light/variable overnight.
Much colder temperatures tonight, as temperatures should radiate
out across the southern half of the area before more clouds push
in overnight. A weak short wave crosses to our north tomorrow.
Enough shallow moisture may be present for the formation of
drizzle or freezing drizzle tomorrow morning. A look at bufkit
soundings show only a very shallow layer of cold air
insufficient for snowflake formation. Road temperatures across
the Finger lakes and Ny thruway corridors have cooled enough to
where slick spots may be a concern with the morning rush hour.
However, considerable uncertainty remains if freezing drizzle
will occur and how widespread it is. As of late evening, the
HRRR is now indicating some patchy freezing drizzle across far
northern portions of the area while the 00Z NAM 1/12 is a little
more widespread. Given the continued uncertainty on coverage
will not issue an SPS at this time.
Surface ridging briefly builds back into the region tomorrow
night with dry and cool conditions through the overnight.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
2 PM update...
Tuesday into Tuesday evening a weak front moves east through the
region. The better dynamics are both north and south then east.
Low pressure tracks across southern Ontario into Quebec dragging
the front through. A stalled front in the mid Atlantic looks to
stay there now. Low pressure forms along it Tuesday evening to
possibly push some moisture north into NEPA and southern
Catskills. This develops too late to add anything to the weak
front. Precipitation type will be a mix of rain and snow.
Amounts will be very light. Less than a tenth of an inch of rain
and less than half an inch of snow. A mix to start changes to
rain showers as temperatures Tuesday rise to 40 to 45.
Temperatures fall back to the mid 30s allowing any remain
showers to change back to snow. This finishes pulling out of the
northeast late Tuesday night.
Wednesday weak high pressure with dry and mild weather. Cooler
with highs around 40 except AVP mid 40s. This is still above
average.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
2 pm update...
Little change. The first system Wednesday night into Thursday
looks like a mostly snow event with temperatures mostly in the
lower 30s during the event. Still much uncertainty as models
still do not agree. As below, Euro strongest with the most snow
as it tracks across upstate NY. Canadian now strengthens it
some but further south across the twin tiers. GFS still the
weakest. Some lake effect on the back side Thursday night before
high pressure Friday. Snow amounts only look to be a few inches.
Will have to watch the weekend storm. Better model consensus. A
good storm which could bring a several inches of snow to the
entire area late Friday night through Saturday.
previous discussion...
High pressure retreats eastward Wednesday night as another low
pressure system moves eastward from the Great Lakes. There is
quite a bit of uncertainty regarding the strength of this
system. The 00Z ECMWF seems to indicate a strengthening trend
as it approaches our area. Meanwhile the GFS and Canadian models
keep the system considerably weaker. Regardless of the strength
of the system, expecting some snow (with some rain mixed in
across valley locations) to move into the area late Wednesday
night and into Thursday. As temperatures warm up during the day
on Thursday to above freezing, the snow will likely mix with and
changeover to rain across many places, especially in the lower
elevations. Precipitation tapers off to rain and snow showers
Thursday afternoon and Thursday night as lake effect kicks in
(mainly Central New York). Overall, expecting this to be a minor
event as this time, especially if the weaker solutions end up
verifying. After morning lows on Thursday expected to be in the
mid 20s to mid 30s, highs will likely top out in the lower 30s
to lower 40s.
Any lingering lake effect snow showers will likely taper off
Thursday evening, as Canadian high pressure moves in north of
the area. Lows Thursday night will be on the chillier side, with
single digits expected across northern Oneida County and teens
to lower 20s expected elsewhere. This high pressure system will
keep conditions quiet for a brief time (through most of Friday),
before a much more potent low pressure system approaches the
area. Highs on Friday will likely be in the lower 20s to lower
30s.
There is quite a bit of model agreement (especially for it being
this far out) that a strong low pressure system will track
across the Great Lakes on Saturday, with a potential secondary
low developing off or along the southern New England coast.
Should this occur, colder air would likely wrap around into our
region, keeping most of the precipitation as snow. Should the
secondary low pressure develop too late or not at all, then this
would likely be yet another mixed precipitation event across
our area. Definitely something to watch as we get closer. Due to
the uncertainty in the track of the system, high temperatures
on Saturday are highly subject to change. Right now went with
NBM (National Blend of Models) for highs, leading to
temperatures in the 30s.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Lower end MVFR and fuel alternate CIGS continue to be present in
the cool westerly flow from near Hornell to Ithaca, Norwich,
Oneonta and points north. This is bringing restrictions to KSYR,
KRME and now KITH...and these lower end MVFR CIGS should
continue through at least 04 to 07z this evening. The clouds are
very slowly inching south, but guidance keeps this restrictive
CIGS away from KELM and KBGM (perhaps a few or sct lower level
clouds (2-3k ft agl) sneak in for a few hours late evening. At
the same time we have a bkn to ovc high level cloud deck
overspreading the area from SW to NE; and this will be around
all night areawide (12 to 25k ft agl). KAVP should remain VFR
until after daybreak Monday. Right now, guidance is indicating
the lower level clouds up north should dissipate after about
05-07z Monday...but wouldn`t be surprise if these hang on a
little longer. Therefore, do have a period of VFR areawide (from
about 07Z to 14z Monday) until additional MVFR CIGS develop
after 14-15z Monday areawide...and continue much of the day.
Could see a few breaks in the clouds with perhaps periodic VFR
conditions return to parts of the area after about 20z Monday
afternoon.
Another thing to watch is a low chance for some spotty drizzle
or freezing drizzle Monday morning; mainly for the NY terminals.
Not enough confidence on timing or location to include in the
tafs at this time. Will monitor closely.
Decreasing northwest winds mainly under 10 kts this evening,
turning easterly and under 5 kts overnight. Southeast winds
Monday morning turn southerly up to 10 kts during the day.
Outlook...
Monday night through Wednesday...Periodic restrictions possible
in low clouds, drizzle or light showers.
Thursday...Restrictions likely in central NY due to snow
showers. Gusty NW winds are also possible.
Friday...VFR much of the day with high pressure overhead.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...MPK
NEAR TERM...MPK/MWG
SHORT TERM...TAC
LONG TERM...BJG/TAC
AVIATION...MJM
Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CST Sun Jan 12 2020
.UPDATE...
Issued at 948 PM CST Sun Jan 12 2020
Added in some scattered flurries over my central and east with
radar showing weak returns moving east across the area. A few
surface obs also reported flurries. Also adjusted temperatures
where they have dropped where the sky is/was momentarily clear
across portions of the far southwest/far south central.
Temperatures there should go back up as clouds advance east into
those areas.
Otherwise the forecast remains on track for tonight.
UPDATE
Issued at 700 PM CST Sun Jan 12 2020
Southwesterly flow aloft remains across the region with a sfc
boundary across western ND, resulting in northwest winds to the
west of the boundary and south/southeasterly winds to the east.
Fined tuned winds based on latest guidance as the frontal
boundary slowly moves east this evening, then washes out
overnight.
Some light radar returns over my east, little if anything but some
snow flurries. Updated POPs this evening, mainly decreasing with
the current activity moving to our east in a couple of hours.
Fined tuned POPs for the overnight through Monday morning as an
embedded S/WV moves northeast across my southwest and central.
Other changes with this update were to increase fog using latest
CONSHORT/RAP guidance and extending in time through Monday
afternoon. Sky cover was also modified to better reflect latest
sat imagery and trends of low stratus creeping into my southeast
and low clouds advecting into my west.
&&
.SHORT TERM...(This evening through Monday)
Issued at 301 PM CST Sun Jan 12 2020
A series of mid level waves are propagating across the region this
afternoon. These waves, combined with isentropic ascent and the
inferred presence of conditional symmetric instability given EPV and
theta-e lapse rates near zero, have produced isolated to scattered
snow showers across northern and central North Dakota today. The
most concentrated activity currently lies along Highway 83 north of
Minot. Expect the snow showers to gradually wane heading into the
evening, with isolated snow showers remaining possible across the
north through the evening.
A north-south oriented surface trough currently lies across western
North Dakota. Temperatures have risen well above forecast highs in
the far southwest, where winds have become westerly. This trough is
forecast to drift eastward this evening, reaching central North
Dakota overnight. The HRRR and RAP have been persistent in
developing fog along and east of the trough. For now, just added a
large area of patchy fog to the forecast, but coverage may need to
be increased with later updates.
Later tonight, a mid level shortwave is forecast to approach the
area from the southwest. Hi-res model consensus depicts an area of
light to potentially moderate snow developing over southwest North
Dakota late tonight, moving northeast into north central North
Dakota through Monday morning. Contributing factors to the potential
for more moderate snowfall rates include strong lift in the DGZ,
steep mid level lapse rates near 8 C/km and near zero EPV once again
suggesting the potential for slantwise convection. The most recent
model runs have trended slightly away from moderate snow rates, but
still cannot be ruled out given the environment.
Another more potent shortwave is forecast to eject off the Northern
Rockies Monday afternoon. Light snow associated with this shortwave
will likely be moving into western North Dakota by sunset. Far
northwest North Dakota may actually see light snow as early as noon
as it lies closer to a strong low to mid level baroclinic zone.
Temperatures will remain below normal on Monday, with highs
generally in the teens. Expect slightly colder highs in the
northwest, which is in closer proximity to an Arctic air mass trying
to nudge its way into the region from southern Alberta.
.LONG TERM...(Monday night through Sunday)
Issued at 301 PM CST Sun Jan 12 2020
Below normal temperatures and periodic chances for light snow are
the main concerns for the long term period. While periods of
significant cold/wind chills remain possible, mainly across the
northern half of the forecast area, a prolonged Arctic outbreak
appears increasingly unlikely. Most, if not all guidance has
continued a warming trend from previous runs, including the
deterministic GFS which remains a cold outlier.
A shortwave trough will move across the area Monday night. There
does not appear to be any banding potential, so expect an area of
just light snowfall with the wave`s passage. Accumulations around 1-
2 inches are possible, maybe approaching 3 inches in the northwest.
Behind the shortwave, Arctic high pressure will try to build into
the region for Tuesday, but mid level heights look to rebound
quickly, keeping the coldest air in Canada. While the deterministic
GFS continues to be a very cold outlier, most guidance does bring
850 mb temperatures near -20 C into northwest North Dakota in time
for peak cooling early Tuesday morning. Lows there may fall into the
mid teens below zero, with wind chills possibly as cold as -35.
A surface ridge axis is forecast to lie from northwest to southeast
across the area on Tuesday, with weak ridging aloft. It will be
colder, but think that steady to rising heights will allow
temperatures to rise above zero Tuesday afternoon, except perhaps
along and north of Highway 2.
Yet another shortwave is forecast to move across the area Tuesday
night into Wednesday. Only expecting a quick shot of light snow with
this system, and once again, banding potential looks low. Height
falls associated with the trough will allow colder air to filter in.
However, there is more uncertainty in Tuesday night`s low
temperatures due to expected cloud cover from the shortwave passage.
The deterministic GFS is once again colder and more progressive than
other models, which are known biases. Think that the slower
solutions of the ECMWF and NAM are more likely, and lows around -5
to -15 F will be more common Tuesday night/Wednesday morning, though
colder is possible if clouds clear more quickly. Wind chills as low
as -25 to -35 appear possible across the northern half of the state.
The pattern developing behind this shortwave looks similar to that
of Tuesday, with surface high pressure building across the Northern
Plains. The ECMWF is quicker in bringing rising heights back into
the region, but this still does not occur until Wednesday night.
Therefore, think that Wednesday will have the coldest highs this
week, which could be below zero for much of the area. Thankfully,
winds look to be rather light.
A warming trend should commence for the end of the work week. An
interesting scenario appears to be emerging for the end of the week
as models show an aggressive shortwave moving across the central
CONUS. The general idea is that the Northern Plains could see
accumulating snow from an inverted trough. Details remain highly
uncertain, though GEFS plumes at Bismarck are already clustering
around 0.1"-0.3" QPF, with no significant outliers.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 700 PM CST Sun Jan 12 2020
Main aviation concerns for the 00Z TAF period will be IFR/LIFR
cigs developing into southeast North Dakota, impacting KJMS 02-04Z
this evening, and expanding farther north and west, eventually
impacting KBIS after 11Z Monday morning. The low stratus will be
accompanied by areas of fog. Both linger through much of the 00Z
period for both of these two terminals. MVFR/IFR cigs along with
some light snow will develop across western into north central ND
(KXWA/KDIK/KMOT) this evening/Monday AM. KDIK will see IFR cigs
after 12Z Monday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...NH
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...NH
Area Forecast Discussion
National Weather Service Corpus Christi TX
544 PM CST Sun Jan 12 2020
.DISCUSSION...Updated aviation discussion for 00z TAF cycle.
&&
.AVIATION...Current VFR conditions will deteriorate overnight as
increasing moisture and a weak warm front cross the terminals and
create conditions conducive for fog formation. MVFR and
occasionally IFR cigs (and vsbys in some locations) will improve
somewhat during the day, but persistent weak isentropic lift
should be enough to maintain cigs through the day, although those
cigs may be VFR at some locations. Winds will remain light through
the period.
&&
.PREV DISCUSSION... /Issued 331 PM CST Sun Jan 12 2020/
SHORT TERM (Tonight through Monday Night)...
Things will change heading into tonight and Monday as a warm
front lifts north into the region. Dry conditions with partly
cloudy skies this afternoon will become muggy and mostly cloudy
tonight as moisture with the boundary increases PWATs to 1.2-1.5
inches. Although weak, flow within the 295-300K isentropic levels
will support light rain late tonight into Monday, moving in from
the gulf into the Coastal Bend and Coastal Plains during the
morning hours, shifting east toward the Victoria Crossroads in the
early afternoon. Little accumulation is expected with only a few
hundredths of an inch likely. Texas Tech 3km WRF and HRRR also
supports this. The increase in warm, moist air will also bring
back fog development. Patchy to areas of fog are expected to
develop inland overnight. As dewpoints increase further into the
afternoon and Monday night, will expect sea fog development over
the bays and nearshore waters, where SSTs remain in the lower 60s.
Overnight temperatures will also be warmer due to the increased
moisture, with lows in the mid-upper 50s, roughly a 10-20 degree
increase in some locations. Highs will be slightly tricky for
Monday, mainly due to the increased cloud coverage, but will
continue to keep temperatures to warm into the 70s, although it
will be more humid. Another mild and muggy night will be in store
for Monday night.
LONG TERM (Tuesday through Sunday)...
Tuesday opens with a very moist warm sector over all of the
region in the wake of Monday`s warm front. Although PWATs should
be 1/2 to 3/4 of an inch above normal, lift will be waning across
much of the forecast area as the primary zone of isentropic ascent
shoves north. Barring a few showers and some thunderstorms around
the Victoria Crossroads on Tuesday, most of South TX should be
dry. As winds aloft trend more anticyclonic by Wednesday, mid-
level drying will nudge PWATs lower (1/3 of an inch or so) which
should favor stable conditions region wide. Models begin keying on
a daytime LLJ on Thursday from the Brush Country west to the Rio
Grande which could open the door to stronger ascent, particularly
in the Hill Country where this jet intersects the lingering
frontal boundary. Opted to leave some PoPs in across our N-NW
zones on Thursday, but a better opportunity for some rain should
wait until late Friday night with the arrival of a cold front.
However, upper forcing and drier SW flow at 850 mb preceding the
front are not particularly favorable for rainfall, so will keep
PoPs lower than MOS and the blends until dry and much cooler
northerly winds arrive for the weekend. Otherwise, a stubborn
pattern of sea fog (mainly nearshore) looks on track for much of
the week as dewpoints in the upper 60s traverse water temps in the
lower 60s.
MARINE...
Weak to occasionally moderate easterly flow will continue tonight
into Monday. Winds will turn out of the southeast through Monday
afternoon as a weak warm front lifts north over the region. The
warm front will trigger light rain over the waters. Patchy to
areas of sea fog will also begin to develop over the near shore
waters and bays Monday into Monday night as warm moist air moves
over the cooler shelf waters.
Weak to moderate onshore flow will continue through the week with
patchy sea fog likely most days and nights. A cold front will move
through early Saturday ahead of strong offshore flow through
Saturday Night. A few showers and thunderstorms will be possible
along the front.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 59 73 66 79 66 / 30 40 10 10 0
Victoria 52 70 63 79 66 / 20 30 20 20 10
Laredo 56 75 63 82 68 / 0 10 10 0 0
Alice 56 75 65 83 66 / 20 20 10 10 0
Rockport 59 72 65 76 65 / 30 40 20 10 0
Cotulla 54 73 60 81 65 / 0 10 10 0 0
Kingsville 58 77 66 83 66 / 20 30 10 10 0
Navy Corpus 61 71 65 75 67 / 30 40 10 10 0
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
JV/71...AVIATION
Area Forecast Discussion
National Weather Service Dodge City KS
519 PM CST Sun Jan 12 2020
...Updated aviation section...
.SHORT TERM...(This evening through Monday)
Issued at 1257 PM CST Sun Jan 12 2020
One upper level trough will move east of western Kansas early
tonight as another upper level wave begins to approach the Central
Rockies from the west. As this next upper wave crosses the
Rockies and moves out into the West Central High Plains early
Monday a surface boundary deepening over eastern Colorado will
begin to move east into southwest Kansas. Behind this boundary
drier air will begin to spread into southwest Kansas and gusty
southwest to westerly winds will develop during the afternoon.
Winds gusting in excess of 40 mph will be possible for several
hours Monday afternoon based on the NAM and GFS BUFR soundings of
the mixed layer winds. Given these gusty winds developing and
relative humidity values falling back into 15 to 20 percent range
the potential exists easily for near critical fire weather
conditions. Will be using the the lowest forecast afternoon dew
points from the ARW and HRRR given the mixing potential late day
and given this plus a high of 63 degrees this would produce
minimum relative humidity values of 15 or 16 percent for only a
hour or two near the Oklahoma border from Liberal to Elkhart.
Based on these conditions expected Red Flag Warning Criteria will
not be reached but it will be close. Will keep the Fire Weather
Watch going for extreme southwest Kansas just in case the mixing
Monday afternoon is better and results in lower afternoon dew
points. Elevated fire weather conditions will be possible however
as far north and east as Scott City, Ness City, Greensburg and
possibly even Coldwater. In and near these areas outdoor burning
on Monday is discouraged.
.LONG TERM...(Monday night through Sunday)
Issued at 1257 PM CST Sun Jan 12 2020
On Monday night an upper level trough will move east into the Mid
Mississippi Valley and a weak cold front will briefly drop south
into southwest Kansas. This cold front will lift back north during
the day on Tuesday. The highs on Tuesday will be in the 50s
across southwest Kansas. May even see a few highs near 60 based
on the 850mb temperature trends from 00z Tuesday to 00z Wednesday.
Across north central Kansas 850mb temperature trends and the
latest forecast location of the warm front late day it looks like the
highs on Tuesday are only in the mid to upper 40s.
This frontal boundary will then drop back south into southwest
Kansas Tuesday night allowing for a little better shot of cooler
air returning on Thursday but given the westerly downslope flow
potential this shot of cooler air appears to be shallow and will
only knock temperatures back into the 40s.
Another, stronger, upper level trough will then cross western
Kansas Thursday night into early Friday and given the forecast
moisture return and lift ahead of this upper level trough this
will produce our next opportunity for precipitation, especially
across south central Kansas. Later shifts will need to monitor how
cold the shallow cold layer of air will be near Thursday night.
At this time given the forecast surface temperatures and warm
temperatures around the 850mb level the precipitation thursday
night may end up being more of a rain event with a chance for some
pockets of freezing rain/drizzle as surface temperatures fall
below 32.
A cold frontal passage early this weekend will usher another
round of cooler air into southwest Kansas but again the cool down
will be brief as warmer temperatures (50s) are expected to return
on Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 518 PM CST Sun Jan 12 2020
VFR conditions will prevail overnight with increased high level
cloudiness. Winds will generally be from the south becoming gusty
by tomorrow afternoon.
&&
.FIRE WEATHER...
Issued at 1257 PM CST Sun Jan 12 2020
Near-critical to critical fire weather conditions are forecast to
develop Monday afternoon. A Fire Weather Watch is in effect for
Stanton, Grant, Morton, Stevens and Seward counties.
Unseasonably warm temperatures and dry conditions can be expected
across southwest Kansas on Monday. A surface boundary will cross
southwest Kansas early in the day and behind this boundary surface
dew points are expected to fall back into the teens. These
afternoon dew points when combined with temperatures climbing into
the 60s will result in relative humidity values as low as 15 to
18 percent for a few hours late day. Gusty southwest to west winds
that will also be developing on Monday will create favorable
conditions for near critical fire weather conditions for locations
west of a Ulysses to Meade line. There is also the potential that
the afternoon dew points may end up being a little lower which
would produce critical fire weather conditions for a few hours
late day. Given this potential Fire Weather Watch has been issued
for extreme southwest Kansas Monday afternoon. Elevated fire
weather conditions will be possible however as far north and east
as Scott City, Ness City, Greensburg and possibly even Coldwater.
In and near these areas outdoor burning on Monday is discouraged.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 23 57 22 52 / 0 0 0 0
GCK 21 55 20 52 / 0 0 0 0
EHA 25 61 23 61 / 0 0 0 0
LBL 22 62 21 58 / 0 0 0 0
HYS 20 50 20 47 / 0 0 0 0
P28 22 55 25 52 / 0 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch Monday afternoon for KSZ074-075-084>086.
&&
$$
SHORT TERM...Burgert
LONG TERM...Burgert
AVIATION...Springer
FIRE WEATHER...Burgert
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
956 PM CST Sun Jan 12 2020
.DISCUSSION...See updated information for land areas below.
&&
.UPDATE...Evening surface observations and analysis show a warm
front extending across the western and north central Gulf of
Mexico and then arcing into the northwest FL panhandle. Surface
winds are becoming light southeasterly and dewpoints are rising
into the mid to upper 60s to the south of the warm front, while
very light north to northeast winds and temperatures in the mid
50s to lower 60s are noted to the north of this boundary. Patchy
dense fog is beginning to develop near the northwest FL panhandle
coast around Destin and Eglin AFB as of 9 PM. High resolution
guidance, including the RAP/HRRR, along with SREF probabilities of
visibility < 1 mile are in good agreement that fog will continue
to advance inland and become more widespread in coverage across
locations especially along and southeast of I-65 overnight into
early Monday morning behind the lifting warm front, while lower
fog probabilities/coverage are noted in model trends over interior
southeast MS and southwest AL which should remain to the
northwest of this feature. Showers, along with a few thunderstorms
should continue to increase in coverage across the area overnight
within increasingly moist southwest flow aloft and ahead of the
warm front. We will keep POPs high overnight.
Given that dense fog looks increasingly unlikely over far
northwestern portions of our area, we opted to remove Wayne and
Choctaw counties from the Dense Fog Advisory, but otherwise will
continue the advisory across the rest of the forecast area.
Overnight lows look on track to range in the mid 50s to around 60
degrees roughly along and to the northwest of I-65, with lows in
the lower to mid 60s across the rest of southwest/south central AL
and the northwest FL panhandle. /21
&&
.PREV DISCUSSION... /issued 611 PM CST Sun Jan 12 2020/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...
00Z issuance...Ceilings will generally be starting off at MVFR
thresholds across the region early this evening, but will
eventually lower to IFR to LIFR thresholds after 03-06Z. A few
showers and even an isolated thunderstorm or two will impact
portions of the region this evening. Areas of fog will also
develop late tonight through Monday morning, some of which will
become dense with visibility becoming reduced to less than 1/2
mile at times. Numerous to widespread rain showers and a few
thunderstorms will develop along a warm front from interior
southeast MS through interior portions of southwest AL starting
mainly after 09Z and continuing into the day Monday. /21
PREV DISCUSSION... /issued 329 PM CST Sun Jan 12 2020/
NEAR TERM /Now Through Monday/...Upper air analysis shows a
mid-level ridge of high pressure oriented from the southwest
Atlantic to the southeast Gulf, while high level trof maintains
its hold over the western half of the CONUS. Within the mid to
high layer southwest flow aloft between these two pressure systems,
lies a quasi-stationary frontal boundary draped from the Mid-
Atlantic southwest to the central Gulf. A weak surface pressure
ridge positioned over the Lower MS River Valley has allowed for a
stable air-mass under a light east to northeast flow. Little to no
rain is shown on radar thus far, but this is expected to change.
The Gulf front begins to lift northwestward as a warm front to the
coast by this evening, bringing an enhancement to ascent and a
return to high rain chances over the central Gulf coast.
Initially, the high resolution convective allowing models (CAMs)
shows a gradual increase in the environmental instability by late
afternoon and on into the evening along the southern zones as the
warm front approaches. 12.17Z HRRR MuCAPE values to 800-1200 J/KG
by evening over the southern zones is indicated with a gradual
northward expansion of environmental de-stabilization thru the
night. An increase in southerly 0-1 KM bulk shear to 25 to 30 kts
also supports convection mixed in within a developing larger
coverage of showers. At this time, appears the threat of severe
weather is low. An active high level southwest flow with passage
of series of mid-level impulses supports maintaining periods of
showers and embedded storms into the day Monday as surface
boundary continues to lift northward. A gradual northward shift in
the higher PoPs is advertised for Monday night. Some areas could
see rainfall totals adding up to between a half to perhaps between
1 and 2 inches encompassing the upcoming next three periods.
In addition to increased rain chances will be a return to fog.
Short range ensembles show probabilities of fog increasing
substantially from southeast to northwest. High resolution
and Localized Aviation MOS products (LAMP) guidance also show
dense fog, with visibilities lowering to a half mile or less
forming along area bays and sounds northward over the land zones
through the night. Considering signals in guidance and the favored
synoptic scale set-up we have in place, a dense fog advisory will
be issued on this package beginning at 13.03Z for portions of the
coastal waters including bays and sounds and including all land
zones as well. Visibility is forecast to improve enough by and
after 13.15Z Monday over land zones but remain low over bays and
sounds where the advisory will continue. In fact, marine fog is
expected to carry over into Monday night, while increasing in
coverage again over land.
A high risk of rip currents will remain through at least
tonight. /10
SHORT TERM /Monday night Through Wednesday night/...The surface
warm front should lift north of our forecast area by Tuesday
morning with a warm and humid airmass in place in its wake. Dense
fog is again likely to form over the near shore coastal waters as
well as local bays and Mississippi Sound, as near 70 dewpoint air
overspreads water temperatures in the mid/upper 50s. This setup
favors dense sea fog development. Dense fog advisories may again
be needed later Monday night into Tuesday, especially over the
marine/coastal areas.
Several weak upper level shortwaves will move through
southwesterly flow aloft which should support scattered showers
and isolated thunderstorms through mid week. Despite increased
thermodynamic instability, weak lapse rates and marginal shear
values should limit any severe weather threat. Overall the greater
focus for storms will be north of the area, therefore not
anticipating any excessive rainfall at this time.
As southerly low level flow quickly returns to the area, the
potential for dangerous rip currents may persist into Tuesday.
This threat will be monitored closely over the next couple of
days. /JLH
LONG TERM /Thursday Through Sunday/...Another northern stream
shortwave aloft will eject from the Central Plains across the
Tennessee/Ohio Valleys through Thursday. In response, a cold
front will gradually slip south Thursday afternoon into Thursday
night. There remains some model discrepancies with regard to how
strong the Gulf Coast ridge will be by this time. This will play a
role in how far south the front progresses and whether it will
make it into our forecast area. At this time, have increased pops
across northern sections of the CWA to account for the front being
in the vicinity. This front should stall and lift back north in
response to a stronger digging upper trough over the Plains
States. Temperatures and humidity levels should remain above
seasonal normals through the remainder of this week.
As the upper trough shifts east by next weekend, expect a stronger
cold front to advance across the area. Showers and thunderstorms
should accompany the frontal passage. Colder temperatures and
drier conditions should follow the frontal passage for the second
half of the weekend. /JLH
MARINE...Fog is forecast to re-develop overnight and become
locally dense over bays and sounds as a warm front approaches the
coast. There are indications that fog will linger into the day
Monday carrying over into Monday night through Tuesday morning.
Coverage of showers will increase and be greatest tonight and
Monday. The potential exists for a few storms to be mixed in as
well. A weak cold front makes passage Wednesday night. Onshore
flow increases and seas build Friday ahead of a stronger cold
front moving eastward out of the southern Plains. /10
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Dense Fog Advisory until 9 AM CST Monday for ALZ052>060-261>266.
High Rip Current Risk until 6 AM CST Monday for ALZ265-266.
FL...Dense Fog Advisory until 9 AM CST Monday for FLZ201>206.
High Rip Current Risk until 6 AM CST Monday for FLZ202-204-206.
MS...Dense Fog Advisory until 9 AM CST Monday for MSZ075-076-078-079.
GM...Dense Fog Advisory until 9 AM CST Tuesday for GMZ630>636-650-655.
&&
$$
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