Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/18/17
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
533 PM MDT Sun Sep 17 2017
00Z TAF CYCLE
Current round of showers and storms will persist into the evening
hours before diminishing. Terminals most likely to be impacted by
storms are KLVS, KSAF and KTCC and generally in that order.
Strong/erratic wind gusts to near 40kts will be the most likely
impact, with low probability of MVFR conditions. MVFR cigs may
develop at KTCC overnight, but forecast confidence too low to include
in TAF. Otherwise, storms will trend down significantly Monday
afternoon, with gusty southwest winds forecast.
.PREV DISCUSSION...347 PM MDT Sun Sep 17 2017...
A weak cold front has backed into northeastern New Mexico, and has
led to scattered storms developing over the eastern plains of the
state. Some of the storms have turned strong to severe, and are
expected to continue into the early evening. Most storms are expected
to diminish by midnight with some low clouds redeveloping over
northeastern New Mexico through Monday morning. Less moisture and
instability will be available for storms on Monday, limiting storms
with just a few stray cells possible in the southeastern third of the
state. Thereafter, a drying trend is expected Tuesday and Wednesday
with temperatures running near normal in western and central parts of
New Mexico and readings climbing slightly above average in the
eastern sections of the state. Precipitation chances will then begin
increasing Wednesday night into the remainder of the week as a deep
trough of low pressure closes in on the Land of Enchantment.
Active weather is in progress over New Mexico with a relative weak
long wave trough over the western U.S. and a couple of smaller scale
embedded short waves lifting east northeastward into AZ and the Four
Corners. This is providing large scale ascent that has assisted
shower/storm development since this morning. In addition, the cold
front invaded the northeastern quadrant of NM, providing a boost in
moisture and consequently fueling the area with steeper temperature
lapse rates, higher CAPE, and more significant bulk shear in the form
of veering wind profiles.
Storms have exploited these parameters with a crop of few severe
cells. Hail and gusty downburst winds will be the primary threat
through the early evening. The HRRR model, which has seemed to
outperform other synoptic models with convection lately, carries the
best axis of instability eastward in quick fashion and takes storms
into TX/OK before sunset. This seems reasonable, but the HRRR
redevelops additional storms over northeastern NM through the late
evening, likely forced by short wave energy aloft rolling off of the
Sangre de Cristos. This will need to be monitored through the evening
hours, but scattered coverage has been left in the POP forecast
Into Monday, the flow aloft becomes a bit less perturbed and weakens
some while retaining a westerly component. Moisture will decrease
some, as will temperature lapse rates/instability. This should limit
storm coverage significantly, however given the recent poor
performance with synoptic modeling of convection in NM, have opted to
leave some isolated storms in roughly the southeastern third of the
state. Temperatures will run near to slightly above average.
The drying trend persists into Tuesday and through the daytime
Wednesday with PWATs falling back too low to support storm
development. Temperature lapse rates will also lessen through this
stretch, inhibiting storms. Surface temperatures should remain near
to slightly above average on Tuesday, but should fall back a few
degrees into Wednesday.
Unsettled weather will then unfold Wednesday night into the remainder
of the week as a deep long wave trough carves itself over the western
U.S. drawing moisture into the NM plains from the south southeast and
generating dynamics into some central to western portions of the
...Critical fire weather conditions possible Tuesday...
Scattered storms have fired off over the central and northern mtns
and are quickly moving to the NE. The backdoor front slid down the
eastern plains reaching as far as Clovis and the east slopes of the
central mtn chain. Increased instability behind the front, CAPE
values 2000-2700 J/kg with 0-6km shear up to 40-50 kts has prompted
a slight risk of severe storms over the eastern plains through the
evening hours. Storms will be capable of producing gusts up to 60kts
and large hail. Garden variety isold to scattered storms will be
present west of the ctrl mtns, still capable of producing gusty
erratic winds up to 40kts.
Monday could see lingering moisture across the E with some morning
low clouds and fog possible over the NE plains. Drier westerly flow
will continue to mix down over the west, and begin to erode moisture
across the east later in the afternoon. MinRH`s over the NW plateau
will fall to the teens, however winds will be the limiting factor
for any critical fire weather. Tuesday will see the dryness expand
further east with stronger winds as an upper trough moves over the
northern Rockies. Several hours of critical fire weather are likely
across the west and eastern plains, the majority of zone 104 and
much of zones 105 and 108. The one limiting factor at the moment is
remaining decent soil moisture still being observed on the NASA
SPoRT imagery. With today`s expected additional rainfall across the
east, soil moisture should be even further improved. MixHgts will be
a bit lower across the NE where Haines 5 and fair ventrates will
Another weak backdoor bdry is still forecast to pass into far NE New
Mexico Wednesday, keeping MixHgts lower, with Haines 5, and pockets
of bad to fair Ventrates. With the pressure gradient lessening as
the aforementioned trough moves away, winds will be lighter, with
only a small improvement in MinRHs as MaxT`s fall closer to normal.
Southerly return flow will improve moisture across the east and
central areas Thursday as another strong trough moves into the
Pacific NW. This will help improve sfc moisture helping to spark
afternoon scattered convection Thursday and into the weekend with
storm coverage being limited more to eastern NM by the weekend. SW
breezy winds pick up ahead of the trough Thursday and Friday.
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1153 PM EDT Sun Sep 17 2017
Another round of showers and isolated thunderstorms is expected
along the cold front moving very slowly through SE Michigan during
the night. This activity will be mainly south and east of FNT down
through the DTW corridor and could last through mid morning as the
front stalls while low pressure ripples along it. Evening
observations over northern Michigan also show mounting coverage of
IFR/MVFR stratus behind the northerly wind shift. This part of the
boundary will bring the best chance of stratus spreading southward
over the region. A clearing trend will then develop during late
morning through afternoon as high pressure builds into the northern
Great Lakes into Monday evening.
For DTW... Timing and coverage of additional showers and isolated
thunderstorms, mainly in the FNT to PTK area, will be such that
short term updates will be the best approach for forecast refinement
at DTW. VFR will then hold until borderline VFR/MVFR develops during
the morning associated with the cold front and northerly wind shift.
Clouds then diminish mid to late afternoon.
//DTW THRESHOLD PROBABILITIES...
* Medium for ceiling 5000 ft or less toward sunrise through mid
* Low for thunderstorms during the morning.
Issued at 938 PM EDT Sun Sep 17 2017
Clusters of showers and thunderstorms lingering along the primary
cold front are holding on near reservoirs of weak surface based
instability near Saginaw Bay and south of the Indiana border. Expect
the weakening trend to continue through midnight while the next upper
wave approaches. The wave can be seen in satellite imagery moving in
from northern Illinois at press time and which is expected to
produce a surface reflection along the cold front during the night.
Backing mid level flow and a slight uptick in low level jet forcing
will combine with some lift due to frontogenesis and DCVA to produce
another round of showers and isolated thunderstorms toward sunrise.
The latest model guidance supports scattered coverage - chance POPs
generally along and east of a line from Port Austin to Howell through
about mid Monday morning. Without the boost from daytime heating,
any new thunderstorms will be on the ordinary side of the spectrum
which will limit hazards to a brief heavy downpour.
Issued at 301 PM EDT Sun Sep 17 2017
Warm mid September day across southeast Michigan, as temperatures
have pushed into the mid 80s. The 12z DTX sounding showed a
significant warm layer around 650 MB, which may be too much to
overcome to generate much in the way of showers and thunderstorms
this evening, especially with surface dew pts mostly in the lower
60s. 18Z SPC analysis does show SBCAPES of 1000-1500 J/KG over
western Lower Michigan, but quickly tapering off as one heads east.
The front is attempting to generate activity at the present time,
but mainly over northern Lower Michigan, closer to upper level
support, and approaching northern Indiana where better instability
resides. Planning on continuing with scattered/chance pops. On the
flip side, there does look to be an upper level PV filament
streaking out of northern Missouri, which tracks through the State
tonight, which could be enough to support an uptick in activity
despite the loss of surface/daytime heating, as a repositioning/
modest increase in the low level jet occurs overhead. 17z HRRR also
suggesting an increase in activity late tonight. Regardless, main
moisture axis exiting southeast Michigan around 12z, leading to a dry
day on Monday as 850-700 mb Theta-E min/surface ridging become
established, with PW values dropping under 1 inch.
Another surge of moisture to arrive late Monday night/Tuesday
Morning, as upper level energy comes out of the Four Corners region
this afternoon, and an upper wave/trough seen tracking along or
close to the southern Michigan border on Tuesday, per 12z
Canadian/NAM. Still, looks to be getting just marginally unstable
north of the Michigan border, with surface ridging holding on,
suggesting just low chance pops warranted at the moment. A good deal
of clouds and light early flow in low levels expected to hold maxes
in the 70s both Monday and Tuesday.
Main story in the extended timeframe is the expansive ridging over
the eastern CONUS bringing a continuation to the above normal
temperatures into next weekend. A large trough will be situated
over western portions of the CONUS where it will stay through the
forecast period. As ridging and surface high pressure remain over
the Great Lakes region, southerly winds will bring temperatures into
the 80s for all of this week.
A series of fronts are forecast to cross through the Great Lakes
region this evening and through the overnight period. The first
front will be the focus for some scattered showers and thunderstorms
during the afternoon and evening time frame for the open waters of
Lake Huron. Post frontal winds will be shifting to a more westerly
direction around 5-15 kts. The secondary front will come during the
overnight hours in a more northerly direction and remain around 15
kts. The long fetch of northerly winds overnight could lead to some
higher waves along the shoreline of the Thumb on Monday morning. At
this moment conditions should remain under criteria for a small
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service Grand Forks ND
925 PM CDT Sun Sep 17 2017
Issued at 924 PM CDT Sun Sep 17 2017
Increased cloud cover a bit with advancing mid/high clouds
otherwise forecast ok.
UPDATE Issued at 626 PM CDT Sun Sep 17 2017
No changes necessary.
.SHORT TERM...(This evening through Monday)
Issued at 240 PM CDT Sun Sep 17 2017
Shower chances in the southern CWA late tonight/early tomorrow
will be the main forecast issue for the period.
The upper low over southern Canada continues to move slowly off to
the northeast. Clouds have been slowly clearing out with some
lingering stratocu over northwestern MN and the Devils Lake Basin.
The clearing trend should continue into this evening as the low
pressure system pulls further away from the area and diurnal cu
dissipates. Temps should fall off quickly after sunset this
evening, but then slow down as a surface trough developing to our
west shifts winds back to the south and clouds come in with the
next shortwave trough. Most spots should stay in the 40s although
a few locations in the far northeastern counties with latest onset
of clouds and south winds could drop into the upper 30s.
The shortwave currently over WY will move into the upper midwest
late tonight and tomorrow. At this point, it seems that the track
of the system will keep the best precip chances to the south and
east of us. However, the RAP continues to drop some precip in our
southern counties as that shortwave comes through. Model soundings
have most of the moisture around 700 mb or above, so not super
impressed with precip chances but will keep a slight shower
mention going. The shortwave will move quickly off to the east
Monday and skies should start to clear out, during the morning in
the ND counties but not until afternoon further east. With
the south fetch to the winds and at least some sunshine tomorrow,
highs will be near the 70 mark across the west but slightly cooler
in the eastern counties.
.LONG TERM...(Monday night through Sunday)
Issued at 240 PM CDT Sun Sep 17 2017
A mild and breezy Monday evening is expected with overnight lows in
the low 50s and southeasterly winds under mostly clear skies. A cold
front is anticipated to move through central and eastern North
Dakota Tuesday afternoon and into Tuesday evening, reaching
northwestern Minnesota overnight Tuesday. Thunderstorms are expected
with the passage of this cold front including the chance for severe
thunderstorms Tuesday afternoon and early Tuesday evening. However,
questions remain about the northward extent of CAPE and favorable
shear supportive of severe storms. Wednesday and Thursday should
both be quiet days with partly cloudy skies, high temperatures in
the upper 60s on Wednesday and mid 70s on Thursday. Rain chances
will return to the forecast late Thursday night into the day on
Friday. Friday highs should reach the low 70s with Saturday seeing
highs in the mid to upper 60s across the region.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 626 PM CDT Sun Sep 17 2017
VFR through the period. Will see an increase in mid level clouds
later tonight with some light showers or sprinkles over the far
south however likely to remain south of FAR.
Area Forecast Discussion
National Weather Service Northern Indiana
729 PM EDT Sun Sep 17 2017
Issued at 350 PM EDT Sun Sep 17 2017
There is a chance of showers and a few thunderstorms tonight as a
cold front slowly approaches the area. Chances of rain will
diminish late tonight into Monday morning as this frontal boundary
stalls across central Indiana. An upper level disturbance will
approach the Great Lakes and Ohio Valley Monday night into Tuesday
providing another chance of showers and isolated thunderstorms.
Low temperatures tonight will range from the upper 50s northwest
to the lower to mid 60s southeast. High temperatures on Monday
will range from the mid and upper 70s across the north, to the
lower 80s south.
.SHORT TERM...(This Evening through Monday)
Issued at 350 PM EDT Sun Sep 17 2017
Chances of showers and storms tonight and Monday will continue to be
the primary short term forecast concern. Isolated showers have
developed this afternoon in association with pre-frontal trough
type feature from west central Indiana into northeast Indiana.
Greater coverage of scattered showers and isolated thunderstorms
also noted over past hour or two across northeast Illinois,
roughly from Lansing to east of Bloomington in proximity of
advancing cool front. Expecting these two general areas to
continue to be focus for additional showers and thunderstorms this
afternoon with greatest coverage expected to focus across western
portions of the forecast area with approach of better pooled
moisture axis/cold front. Surface based instability in the
1000-1500 J/kg should be sufficient for at least isolated thunder
through the evening hours. Effective shear values will remain
generally below 20 knots through the evening supporting more of a
pulsey nature to any stronger cores capable of producing brief
heavier rain showers and perhaps some wind gusts to 30 mph across
the west through early evening. Did maintain slight chance of
showers across the far northwest for a time behind the front late
this evening/early overnight with some indications over earlier
HRRR runs this afternoon of some development associated with
approach of low level trough/weak convergence axis.
A lull in precip chances is expected to develop late tonight into
Monday morning as frontal boundary drops just south of the area
and stalls out. Current indications suggest a south to north
moisture gradient should set up in association with this stalling
frontal boundary. Difficult to discern a clear forcing mechanism
for precip chances with low level boundary, and will maintain just
low chance PoPs through the day, focused mainly across southern
portions of the area. Highs will be cooler on Monday ranging from
the upper 70s north to the lower 80s south.
.LONG TERM...(Monday Night through Sunday)
Issued at 350 PM EDT Sun Sep 17 2017
It still appears though the best chance of showers/storms this
period will be Monday night into Tuesday as isentropic lift/WAA
ramp up in vicinity of stalled boundary as next upper level short
wave approaches from the Rockies. Local area will remain at nose
of modest low level jet through Wednesday, but mid level height
rises in wake of Tuesday system lends to much lower confidence in
precip chances Tuesday and beyond. Guidance remains in general
agreement of significant amplification of eastern CONUS ridge and
continued much above normal temperatures for the Thursday through
next weekend period. While cannot completely discount weak
perturbations in southwest flow tracking across the western Great
Lakes for late this period, tried to maintain a mainly dry
forecast for much of the Days 5-7 period given ridge amplification
and considerable uncertainty in short wave track.
.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 725 PM EDT Sun Sep 17 2017
Scattered line of showers with a few tsra now mainly east of KSBN
and approaching KFWA. A few shra still possible at KSBN this
evening but chances of a restriction are small. KFWA still has a
chance of a VCTS for a few hours but even these chances are low
given recent radar trends. Outflow boundary pushing east and still
some chances for development so left vcts at KFWA for a few hours.
Some fog potential tonight but will depend on clouds and amount of
clearing. Stayed with MVFR for now at KFWA given uncertainty.
Light winds at KSBN could certainly support some development there
with clearing as well but will hold off introduction of any
restrictions given cloud cover concerns.
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East Central Florida Forecast Discussion
National Weather Service Melbourne FL
900 PM EDT Sun Sep 17 2017
...Large swells from Jose will produce dangerous boating and beach
conditions early this week...
Ltst soundings along with the Air Force 915 MHZ profiler network
indicate the mid afternoon surge of Nly winds ascd with a passing
sfc trough around 20 kt. Sub BL flow will show decoupling now
through the next few hours, as has already occurred at the somewhat
inland location of DAB airport. Beachfront sites should register
winds of 10 to 15 mph overnight. PWAT near 1.30 inches indicate
effects of mid level drying.
from prev disc...
Winds above the surface will increase and veer to NNE/NE tonight
bringing low-topped ISOLD-SCT shower activity across the coastal
waters and possibly along the immediate east coast late. Ltst HRRR
guid onboard with current satellite/radar indicated showers brushing
the coast during the early Monday hours.
Lows will drop into the L70s for the interior and M70s along the
A high risk for rip currents and high surf will keep a presence at
east central Florida beaches overnight with beach erosion possible
near the next high tide from 6-8 AM.
Monday...Lower than normal rain chances continue as drier air mass
remains over central Florida. Low-level moisture will moderate
somewhat as winds veer to a more north-northeasterly onshore
component. Believe MOS PoPs are still too high especially for the
Treasure Coast area. Carrying only slight chance of showers mainly
for coastal areas for any onshore moving showers from the Atlantic.
Highs in the upper 80s to around 90 and lows in the low to mid 70s.
.AVIATION...Mostly VFR. Northerly wind component, occasionally gusty
along the coast through early Monday will become lighter and back to
the northwest. Isold SHRA`s moving onshore from the ATLC may affect
cstl terminals aft 06Z tonight through Mon morning.
.MARINE...Seas became fully arisen early today and continue in
the 8-10 ft range over the open waters away from the immediate coast
with seas 6-8 ft near shore. Northerly winds of 15-20 kts over the
open Atlc will slowly decrease to around 15 kts overnight. An
advisory for seas remains in effect for all marine legs due to the
overall hazardous conditions. Expect an increase in marine shower
activity through the night with showers approaching the east coast
.HYDROLOGY...River levels along the Saint Johns are forecast to
continue a slow rise or remain stationary near Cocoa, Geneva,
Sanford, Deland and Astor early this week as runoff into the basin
moves slowly downstream. River levels in minor to moderate flood
stage are occurring at these locations.
The Saint Johns River above Lake Harney near Geneva is forecast to
remain in major flood stage into Monday.
FL...High Surf Advisory until 10 AM EDT Monday for Coastal Volusia
County-Indian River-Martin-Northern Brevard County-Southern
Brevard County-St. Lucie.
AM...Small Craft Advisory for hazardous seas until 11 PM EDT Monday
for Flagler Beach to Volusia-Brevard County Line 0-20 nm-
Sebastian Inlet to Jupiter Inlet 0-20 nm-Volusia-Brevard
County Line to Sebastian Inlet 0-20 nm.
Small Craft Advisory for hazardous seas until 11 AM EDT Tuesday
for Flagler Beach to Volusia-Brevard County Line 20-60 nm-
Sebastian Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard
County Line to Sebastian Inlet 20-60 nm.