Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/14/18
Area Forecast Discussion
National Weather Service State College PA
1044 PM EST Tue Feb 13 2018
High pressure will drift east and off the New England coast
tonight. An increasingly moist southerly flow will bring
unsettled conditions from mid week until a cold front passes
through Friday ushering drier conditions for the weekend.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Near term forecast problem remains centered on the potential
for some light icing overnight into early Wednesday morning.
The favorable right entrance region of an upper jet streak and
increasing warm advection/isentropic lift will bring a small
chance of some very light rain/drizzle/freezing drizzle. The
latest radar shows some light disorganized showers moving
through WRN PA. With surface temps hanging close to freezing,
we will issue an SPS to cover potential for icy pockets. If it
becomes apparent precip is actually hitting the ground as it
moves into the CWA, we may need a short lived advisory.
The HRRR shows a small area of very light precip streak across
the area from I-80 northward after midnight. The SPC HREF keeps
the area dry so the confidence in actually seeing precip is
Covered the low threat and spotty nature of any light icing in
the Hazardous Weather Outlook for now. If confidence increases
that some light precipitation will actually develop, we will
have to issue a short lived headline for slippery travel.
Min temps overnight will be in the 25-30 deg range. The wind
will be mainly east to southeast at 5-10 mph.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Better chances for rain arrive late in the day or early evening
Wed with upper level diffluence increasing and mid-lvl winds
into the 50s out of the West.
Max temps Wednesday will be about 10F warmer than Tuesday and it
will be mild enough for plain rain everywhere by then.
Rainfall amounts will stay rather light and generally several
hundredths to around 0.10 of an inch, as the forcing continues
to look disorganized.
Temps will be very mild with well above normal mins and maxes
Wed night and Thursday. So, despite the cloudiness on Thursday,
the temps should rise into the 50s and some 60s across the
south. 70F might not be all that far south of the Mason-Dixon
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Temperatures will be on the rise for the second half of the
week, along with the opportunity for rain. The springlike surge
of mild air should send temperatures 20+ degrees above average
Thursday and Thursday night. The mild weather will be erased
(briefly) as a cold front sends temperatures falling on Friday
before readings bottom near normals levels for mid February on
Saturday. High temperatures on Saturday will be 20 to 30 degrees
colder than Thursday (48-hour change).
As high pressure migrates off the Eastern Seaboard, broad
ascent in the warm air advection pattern will allow for clouds
and periods of light rain, drizzle and fog to develop Wednesday
night and Thursday. Model guidance continues to advertise the
potential for enhanced rainfall Thursday night into Friday in
response to strengthening southwesterly low level jet along a
tightening baroclinic zone/frontal boundary pushing southeast
from the Midwest/OH Valley. Ensemble PWAT values reach +3SD
above normal. The anomalous moisture combined with cold
ground/enhanced runoff could lead to heavy rainfall (1-2+
inches) and flooding potential. At this time, the greatest risk
area is focused from southern OH into northern WV and southwest
PA including the Laurel Highlands. The placement of the high
QPF axis is still uncertain and the Day 3 WPC excessive rain
risk area splits the difference between the southern GFS and
northern ECMWF precip axis.
An ECMWF/CMC/GEFS consensus brings the possibility of some
wintry weather back into the picture later Saturday into
Saturday night. Will need to see if this recent model trends
hold and the GFS comes on-board before increasing confidence
and sensible wx elements. But it is something to definitely
monitor in the coming days. Sunday looks dry for now with
precipitation returning into early next week. After a short
break, the mild trend should resume next week with above average
temperatures a good bet.
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
MVFR has spread through the western TAF sites as southwesterly
upper level flow couples with moist southerly flow at the
surface. Expect this flow to continue as the night continues.
Cigs and vsbys will continue to degrade as the night continues
and through the daybreak.
There is a low probability for some patchy little mixed
precipitation (mainly light freezing rain or freezing drizzle)
late. For now...left this out of the TAF fcsts... given how dry
the low levels are and anticipated spottiness with little
organized upper dynamics to generate appreciable swaths of
Wed-Thu...Low cigs/light rain possible, mainly N Mtns (KBFD).
Fri...Windy and turning much colder. AM rain, changing to
periods of light snow or snow showers mainly across the Western
Mtns. Cig reductions likely early, and continuing during the
afternoon across the NW mtns and Laurel Highlands.
Sat...No sig wx expected.
Sat night and Sunday...Chance of snow and lowering Cigs/Vsbys
to MVFR with areas of IFR.
NEAR TERM...La Corte
Area Forecast Discussion
National Weather Service Duluth MN
631 PM CST Tue Feb 13 2018
Issued at 628 PM CST Tue Feb 13 2018
Increased wind speeds and gusts along the north shore as Grand
Marais is gusting to 40 to 45 mph. Also, HRRR suggests just
offshore that these winds could be sustained through at least
UPDATE Issued at 532 PM CST Tue Feb 13 2018
Updated aviation section for 00Z TAFs.
.SHORT TERM...(This evening through Wednesday)
Issued at 255 PM CST Tue Feb 13 2018
Mostly sunny skies were observed this afternoon across much of the
Northland. The mid-level shortwave that brought light snow this
morning has moved off to the east, and mid-level zonal flow will
take its place. There is some expanding cloud cover over central
Minnesota where there is a lack of snow pack on the surface. This
cloud cover is anticipated to consolidate with a band of low- to mid-
level stratus currently located over north-central Minnesota per
GOES East satellite imagery later this afternoon and evening. This
cloud cover should linger over the Arrowhead region this evening
before shifting off to the east, leading to clearing skies to the
west, and a period of enhanced radiational cooling. Due to this, I
decreased the overnight low by a few degrees. Overnight lows will
range in the lower to middle teens.
For Wednesday, winds will remain from the southwest, so warm air
advection will continue. A thermal ridge will build into the
Northland, which will warm 850 mb temperatures to around +2 to +5
degrees C, so expect the warmest day across the Northland since
January 26, when Duluth reached a high of 45 degrees. It shouldn`t
be quite that warm, but highs are still forecast to reach into the
middle to upper 30s for much of the region. Surface low pressure is
expected to develop over Alberta/Saskatchewan Canada, and advance
east-southeastward to southwest Ontario Canada. This surface low
will bring our next chances of precipitation. There is only a small
chance for any precipitation over northern Koochiching county
Wednesday afternoon, with the better chances Wednesday evening and
.LONG TERM...(Wednesday night through Tuesday)
Issued at 255 PM CST Tue Feb 13 2018
The extended period will feature several shortwaves moving through
the region bringing opportunities for snow.
Westerly flow aloft will exist to start off the period. A cold front
will move south through the Northland Wednesday night and a surface
low will track across eastern Lake Superior into southern Ontario by
12Z Thursday. Light snow will occur with the front Wednesday night
into Thursday. Snow accumulation is expected to be light, less than
an inch for most areas. A couple of inches will be possible along
portions of the South Shore into Thursday evening, especially the
snowbelt of Ashland and Iron Counties as winds turn northerly and
temperatures cool. Highs Thursday will be much colder than
Wednesday, especially over northern Minnesota. Highs will range from
10 to 15 over the Borderland to the mid to upper twenties over
High pressure will move through the region late Thursday night into
Friday then another shortwave will arrive Friday night/Saturday
bringing another chance for light snow with light accumulation
expected. Highs Friday will be in the teens but warm into the lower
twenties to around 30 on Saturday. Yet another chance for snow will
occur Sunday into Sunday night and a few inches could occur.
Southern portions of the Northland are expected to warm into the
lower thirties Sunday with twenties elsewhere.
Quite a bit of uncertainty surrounds the Monday through Tuesday
period. A western trough is expected during that time but the
position of the trough and the track and strength of downstream
shortwaves differ between the various models. Some accumulating snow
could occur over portions of the Northland Monday/Tuesday but it`s
too early to say much more than that at this time.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 532 PM CST Tue Feb 13 2018
VFR, but strong low level winds continue to make LLWS a threat.
Winds gradually weaken overnight. A little concerned that the
region could see advection fog Wednesday morning as warm air
continues to usher into the region, but think atmosphere may be
dry enough to stave off its formation and we may just see elevated
RHs more than anything.
.PRELIMINARY POINT TEMPS/POPS...
DLH 15 35 21 25 / 0 0 20 40
INL 13 38 11 13 / 0 20 60 40
BRD 13 37 20 24 / 0 0 20 30
HYR 15 40 22 31 / 0 0 10 20
ASX 18 40 24 28 / 0 0 20 40
Area Forecast Discussion
National Weather Service Jackson MS
1002 PM CST Tue Feb 13 2018
Updated for evening discussion.
The ArkLaMiss remains under the influence of southwesterly flow
aloft which continues to keep a moist airmass in place across the
area. Earlier elevated convection over south central Louisiana
has weakened as it moved further northeast into the CWA due to
less MUCAPE to further sustain more robust updrafts. Sufficient
MUCAPE will remain over the area tonight to help support a few
rumbles of thunder, especially with any deeper activity over the
Delta, but overall expect mainly showers along and northwest of
the Natchez Trace corridor where the moisture/ThetaE ridge will
reside. The other forecast concern tonight will be the potential
for dense fog along the Hwy 84 corridor and I-59 north to the
Golden Triangle. These areas won`t be as impacted by any precip
and light to calm winds combined with warm cross over temps and
cool soils will favor stratus build down fog. This fog is expected
to build in during the early evening hours and persist through the
mid morning. While areas of fog are likely, confidence in dense
fog is lower. Nonetheless, went ahead and added a limited area in
the HWO/graphics for patchy dense fog potential. /TW/
Prior discussion below:
Tonight through Wednesday:
Latest rap and satellite imagery showed southwest flow aloft with
high heights over the region thanks to a 593 dam ridge just east
of Florida. Partly cloudy skies were noted across the region at
mid afternoon. On the surface a warm frontal boundary was noted
off the Gulf Coast. Area radars were picking pickup some showers
over the ArkLaTex area extending toward our Northeast Louisiana
Parishes. Afternoon readings varied from the 40s to the lower 70s,
depending on sky conditions.
We will be looking at unsettled weather during the period with a
warming trend, esp for Wednesday, with above normal temperatures.
For tonight, as a weak disturbance approaches the region clouds
will increase from the west. Showers will develop across the
region overnight from west to east. The best rain coverage will be
in the north. There will be just enough elevated instability per
model soundings for some isolated embedded thunderstorms
overnight. Pwats will increase to around 1.5 inches. Expect to see
some patchy fog late tonight until mid morning Wednesday. During
the night dewpoints will rise through the 50s as a more moderate
airmass helps temps to slowly rise after midnight, which will
temperatures to slowly rise during the night. Lows for tonight
will range from the middle 40s northwest to the middle 50s south.
For Wednesday the elevated instability will wane as showers continue
through the day. Dewpoints will surge into the lower to middle 60s
as low level instability will be limited due to rain coverage. Rain
chances will gradually decrease from the south during the afternoon.
It will be a spring-like day with highs in the middle 60s northwest
to near 75 south. /17/
Wednesday night into early next week:
An unsettled pattern looks to remain through the period in the
vicinity of the Lower Mississippi Valley, but there are some
indications a majority of the Arklamiss region may remain outside
of the axis of the worst weather. That said, model agreement on
key features through the period is not at all great and lends to
more uncertainty than is typical for the mentioned time ranges.
The greatest uncertainty focuses on Friday through early Sunday.
During this time a shallow cold front will come in from the
northwest and stall, perhaps right in the middle of the forecast
area. Locations on the warm (east) side of the boundary could
continue to see abnormal warmth (highs 70-80 and lows in the
55-65), continuing the taste of spring that will slowly build over
our region now through Thursday. Of course on the cool side of
the boundary temps will be much lower, perhaps 20 degrees cooler,
with conditions tending to be more cloudy with a greater
prevalence of showers and/or drizzle. As you can see, if you want
to have a nice weekend you are hoping to be stuck on the warm
side of the boundary. Over the next few days we will build
confidence of frontal position this weekend.
Despite the mentioned uncertainty regarding temperatures,
confidence is rather high that the potential for hazardous weather
from heavy rainfall and severe weather is low through the period.
There certainly may be some isolated/embedded storms around Friday
through the weekend, but instability and shear levels should not
be enough to worry of severe weather and the synoptic/mesoscale
focusing for concentrated heavy rain should not be in place. One
potential concern will be the possibility of troubling fog on
many nights as the atmosphere will be very moist and southerly
flow could promote a hybrid advection fog advancing north from the
Otherwise, after this weekend the focus will turn to our west as
a front aligning from north to south between the subtropical ridge
to our east and a long-wave trough to our west should be producing
a variety of bad weather. Model consensus suggests this front will
have a tough time moving into our region from the west, although
there is certainly non-zero potential this front could get into
parts of the Arklamiss Delta with rain and vigorous storms before
the middle of next week. We will watch the evolution of forecasts
closely over the next few days but at this point we do not have
enough evidence to include hazardous threats in the HWO/graphics.
00Z TAF discussion:
Aside from the chances for SHRA activity, the primary concerns
will be for redevelopment of stratus overnight, and potentially
dense fog in areas that have cleared out for the early morning
hours. While the fog should dissipate mid/late morning, it is
questionable how soon the stratus will lift late Wednesday morning
and afternoon. Have kept TAFs on the pessimistic side in line
with most guidance, but would not be surprised if mixing is
greater and conditions improve more quickly than currently
forecast resulting in MVFR restrictions at worst. /EC/
.PRELIMINARY POINT TEMPS/POPS...
Jackson 55 73 63 80 / 71 41 12 12
Meridian 53 71 63 80 / 31 37 16 13
Vicksburg 56 74 62 79 / 84 46 10 13
Hattiesburg 57 74 62 80 / 9 22 14 13
Natchez 60 74 63 78 / 78 36 12 13
Greenville 48 67 61 76 / 72 68 15 13
Greenwood 55 69 63 78 / 50 70 21 13
Area Forecast Discussion...UPDATED
National Weather Service Norman OK
858 PM CST Tue Feb 13 2018
Lowered overnight lows in many locations tonight. Also, made
minor adjustments to hourly elements tonight, mainly temperature
and sky cover.
Fog potential tonight into Wednesday morning is the main concern.
Latest satellite imagery and surface observations at 845 pm CST
depicted abundant low cloud cover east of an Archer City, Texas
to Watonga to Medford line. Some high level cloud cover was over
Oklahoma and north Texas as well.
Rest of tonight, low level moisture/surface dewpoints will
continue to increase across much of Oklahoma and western north
Texas. The increase in moisture will allow for the expansion of
the low level cloud shield westward and northwestward. This cloud
cover should lower closer to the ground as well. Thus, think some
patchy fog will occur across much of Oklahoma and western north
Texas later tonight into Wednesday morning. Do not think the fog
will get too dense (visibilities staying above 1/4 mile) due
increasing low level winds which will veer from the southeast to
the southwest through the night into Wednesday morning.
The highest potential for dense fog may be across parts of south
central and southeastern Oklahoma (southeast of a Ardmore to Ada
line) where low level moisture will be deepest, deep enough to
support some drizzle. Noticed the latest surface observation from
Durant depicted 3 miles of surface visibility, which should
continue to fall in the next several hours. Will not issue a
Dense Fog Advisory at this time due to low confidence of
widespread dense fog.
Temperatures tonight will not fall too much more in most
locations and may actually rise by sunrise in some locations.
Wednesday will be much warmer across the area compared to today.
Fire weather conditions will be near critical levels Wednesday
afternoon across northwestern Oklahoma, but due to abundant
mid/high level cloud cover which may limit vertical mixing and
keep 20 ft winds below 20 mph, will not issue a Fire Weather
Watch or Red Flag Warning at this time.
Products will be updated shortly.
.PREV DISCUSSION... /issued 553 PM CST Tue Feb 13 2018/
MVFR stratus is widespread across central Oklahoma, but has eroded
(at least temporarily) across western Oklahoma and western north
Texas. The stratus should fill in again, lower, and spread
northwest this evening encompassing all the TAF sites except KGAG
and KWWR, although there is a chance that the stratus could
briefly brush these sites as well according to the HRRR model. It
appears that ceilings will be the main issue, although the HRRR
and RAP do show for potential across western Oklahoma (KHBR, KCSM
and perhaps KLAW) as moisture pushes back in to areas where skies
will have cleared temporarily this evening.
PREV DISCUSSION... /issued 320 PM CST Tue Feb 13 2018/
Stratus has been persistent across much of the area today in
warm/moist southerly low level flow regime. This will continue
through the night and upstream moisture will advect northward
resulting in low clouds and fog across much of the area. Model
soundings show deep enough low level saturation for drizzle across
roughly the southeast third of the area. This will mostly be a non-
measurable precipitation event, but a few locations in far south-
central/southeast Oklahoma could receive a couple hundredths of an
Low clouds should gradually clear tomorrow as low level flow veers
and strengthens. Temperatures will warm substantially as a result.
This pattern will favor increasing concern for wildfire spread (see
fire weather section below). The closed low off the California coast
will open/deamplify and shift east at least partially phasing with
northern stream wave. This consolidated trough will approach
Thursday with one more warm day before it forces a cold front
through. Windy conditions behind the front Thursday night into early
Friday can be expected. Large scale ascent may be enough for showers
to develop across mainly the eastern portion of the area Thursday
night, but coverage/amounts should be limited.
Positively tilted trough/shear axis Friday is expected to be
oriented east-northeast to west-southwest across the area during the
day Friday and could provide just enough mid level forcing for some
precipitation across the south. A better chance may occur Friday
night as another shortwave results in veering/strengthening
southwesterly low level flow and isentropic ascent. There is some
model disagreement, however. ECMWF is more amplified with a stronger
low level response along with more robust moisture advection and
QPF. If this trend continues, we may need to increase probabilities,
but recent systems have proved to be less productive at rainfall in
the short term than medium range.
We`ve trended warmer for the weekend as mid-level height rises have
trended more dramatic and southwesterly downsloped/adiabatically
warmed plume should advect over the area again. We may need to
increase temperatures even more if the trend continues. Although
details in geometry and amplitude of western trough are yet to be
resolved (still differences in deterministic guidance and a decent
spread in the ensembles), the general pattern should support
southerly low level moist advection beneath capping EML (a familiar
pattern) again which could bring stratus and drizzle to the
southeast Sunday night. As the trough approaches, assuming it
doesn`t deamplify and weaken like has been the trend the past few
weeks, warmth/moisture could contribute to enough instability for
thunderstorms Monday-Tuesday. We`ve kept probabilities lower than
we otherwise would in the pattern depicted in medium range
guidance in case we do trend toward a less favorable scenario
Dormant fuels with ERC-G values near the 90th percentile and
increasing southwesterly winds, warmer temperatures, and low RH
values (as low as 10-15 percent) will all combine to result in
near-critical to possibly critical fire weather conditions
tomorrow afternoon across northwest Oklahoma. There is some
uncertainty with how thick cirrus will be and how that may impact
temperatures, and more importantly fine fuel heating.
Nevertheless, the wind/RH combination will support rapid fire
spread. In case any fires are ongoing, RH recovery Wednesday night
is expected to be 50-60 percent.
Winds may not be quite as strong and RH values may not be as low
Thursday afternoon, although they will be sufficient for elevated
fire weather conditions at least.
The other concern for area fire managers will be the wind shift
Thursday night. Strong northerly winds are expected behind a cold
front that will progress through the area Thursday evening and
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 42 71 56 78 / 0 0 0 0
Hobart OK 40 73 52 80 / 0 0 0 0
Wichita Falls TX 42 74 56 82 / 0 0 0 0
Gage OK 38 79 53 74 / 0 0 0 0
Ponca City OK 42 71 57 76 / 0 0 0 10
Durant OK 40 66 58 74 / 20 20 10 10