Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/24/20
Area Forecast Discussion
National Weather Service Boise ID
821 PM MDT Wed Sep 23 2020
Smoke increased again today from California wildfires but
conditions improved a bit this evening. Latest HRRR suggests
smoke will decrease further tonight even though the flow aloft
will remain southwesterly. HRRR then shows complete clearing of
the smoke behind the cold front due to pass through northern areas
before sunrise, southwest Idaho around midday, and south-central
idaho late Thursday. Front will also bring breezy winds,cooling,
and showers in northern areas, especially during the morning.
Current forecast looks good on this. The supporting upper trough
will keep us cool through Saturday but another warming trend will
follow next week as the upper ridge fully rebuilds over western
VFR except for local MVFR in smoke. A cold front will bring a
chance of rain showers north of a KBNO-KSNT line late tonight
through Thursday. Surface winds southeast to southwest 5-15 kt
with gusts to 20 kt, becoming west to northwest on Thursday.
Winds aloft near 10k feet MSL southwest 30-45 kt.
SHORT TERM...Tonight through Friday night...Next system
approaching the Pacific Northwest coast spreading clouds and smoke
across the forecast area this afternoon. As the front approaches
tonight, winds will increase along with reduced visibilities in
haze and smoke. The front should move across the area Thursday
morning bringing showers mainly to the higher elevations of Baker
County into the West Central Mountains of Idaho. Breezy conditions
are expected in the Western Snake River Plain by Thursday
afternoon as the front continuous east. This should clear out the
smoke into the weekend as cool westerly flow prevails. Another
round of showers for the West Central Mountains is possible Friday
night with a weak shortwave passage. Temperatures will be near
normal through the period.
LONG TERM...Saturday through Wednesday...A shortwave trough passing
by to our north on Saturday will bring a chance of showers mainly to
the northern half of the forecast area. Temperatures will run
several degrees below normal with breezy afternoon winds. As the
trough departs, dry conditions will return to the region on Sunday.
An upper level ridge will strengthen on Sunday over California, with
temperatures warming back to slightly above normal. The ridge will
then amplify early next week, extending as far north as northern
Canada by Tuesday and Wednesday. This will keep our area dry, warm,
and mostly clear with temperatures well above normal.
PREV SHORT TERM...JDS
PREV LONG TERM....ST
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
924 PM CDT Wed Sep 23 2020
.DISCUSSION...Low cloud deck lingers over the Victoria Crossroads
this evening. Only the NMM model has a decent depiction of current
cloud deck. May see some brief improvement late this evening but
NMM and some other models show the low clouds returning overnight
to the Victoria Crossroads and persisting through the morning.
Made some adjustments to cloud cover. And raised minimum temps
up a couple of decrease due to this cloud cover in VCT area.
Tidal anomalies continue to come down with tides running from 1
to 1.5 feet above expected. This will lead to minor coastal
flooding during the time of high tide overnight with tides
approaching 2.5 feet MSL at Bob Hall Pier. With trend of tidal
anomalies on the way down, expect the current expiration time for
Coastal Flood Advisory will suffice.
.PREV DISCUSSION... /Issued 640 PM CDT Wed Sep 23 2020/
DISCUSSION...See Aviation section for 18Z TAFs.
AVIATION...Low clouds associated with post-tropical cyclone
Beta will continue to affect the Victoria Crossroads with
MVFR ceilings this evening. Should see some improvement late
this evening to VFR but HRRR shows MVFR ceilings will move
back into the VCT area overnight and linger through the
morning hours Thursday. May even see some patchy fog/MVFR
vsbys around daybreak. The rest of south Texas will see VFR
conditions through the period.
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 69 88 68 89 72 / 0 0 0 0 0
Victoria 65 83 63 87 66 / 0 0 0 0 0
Laredo 70 91 70 93 71 / 0 0 0 0 0
Alice 67 89 67 92 69 / 0 0 0 0 0
Rockport 71 85 70 88 75 / 0 0 0 0 0
Cotulla 67 90 67 93 68 / 0 0 0 0 0
Kingsville 67 89 67 92 70 / 0 0 0 0 0
Navy Corpus 72 84 73 88 76 / 0 0 0 0 0
TX...Coastal Flood Advisory until 7 AM CDT Thursday For the following
zones: Aransas Islands...Calhoun Islands...Coastal
Aransas...Coastal Calhoun...Coastal Kleberg...Coastal
Nueces...Coastal Refugio...Coastal San Patricio...Kleberg
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
702 PM CDT Wed Sep 23 2020
.DISCUSSION...(This evening through Wednesday)
Issued at 324 PM CDT Wed Sep 23 2020
The stratus from this morning dissipated relatively quickly,
which has allowed temperatures to reach the 80s across area this
afternoon. A surface trough is situated over west-central
Nebraska, along with some mid-level clouds. The HRRR even shows
the potential for some sprinkles for far northwestern portions of
the area, but the potential and impacts are too low to include in
this forecast package.
Winds shift to the north tonight into Thursday morning, but will
remain relatively light. Another area of stratus may develop on the
southeastern portions of the forecast area tomorrow morning
(roughly southeast of Osborne to York), but mostly clear skies are
expected for the rest of the day on Thursday. Temperatures should
be to be near to slightly warmer than today, with highs in the
upper 80s for most.
Friday is expected to be the warmest day of the week, especially for
southern portions of the area that remain south of an advancing cold
front. Most locations are expected to hit 90 degrees, and
portions of northern Kansas could even make a run into the upper
90s. This heat will also push RH values down to around 20 percent
for a good portion for the area, but decreasing winds near the
front should hopefully help us avoid a significant fire weather
After this dry frontal passage, we should see a fairly mild day on
Saturday with highs back in the 80s. Sunday will be a bit breezier
and cooler as a broad trough moves into the northern Plains and
we get a push of colder air at the low levels. Even still,
forecast highs are in the upper 70s, which is a few degrees above
our climatological normals.
Temperatures should rebound a bit on Monday before a second system
pushes in from the northwest Monday night into Tuesday. This will
result in a much cooler and breezy day on Tuesday. Highs are only
forecast to be in the mid 60s to low 70s. And, unfortunately it
still looks like any meaningful precipitation will remain well to
our northeast. Beyond that, it looks like we will remain in a dry,
but cooler pattern through the middle of next week, with a gradual
warming trend by late in the week.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 700 PM CDT Wed Sep 23 2020
Although confidence is high in VFR ceiling/visibility through at
least the vast majority of the period (and in fact have maintained
VFR throughout), this is one of those situations where it`s
difficult to "guarantee" outright-VFR as there appears to be a low
probability for low stratus and/or at least light fog Thursday AM
(see below for more on this). Wind-wise, no major issues
anticipated as sustained speeds should prevail near-to-below 10KT
throughout, although direction will transition from southerly this
evening, to northerly Thursday morning (behind a passing trough
axis), to generally light/easterly Thursday afternoon. While
precipitation chances are extremely low, a few models suggest a
passing sprinkle/brief shower cannot be completely ruled out
mainly 03-06Z, but the likelihood seems too low for formal TAF
inclusion. Read on for more on the low chance for sub-VFR
conditions Thursday AM.
Ceiling/visibility uncertainties Thursday AM:
While the majority of models/guidance focus the main area of
possible low ceilings/fog at least slightly south/east of
KGRI/KEAR, there are suggestions that this could be a close call,
and as a result just cannot completely rule out at a brief period
of sub-VFR ceiling and/or visibility mainly during the 09-14Z time
frame. As a "compromise" between the previous outright VFR TAFs
and the outside chance of sub-VFR actually materializing, have
opted to at least "hint" at the possibility with "6SM BR"
visibility and a SCT/FEW low cloud mention for the early-AM hours.
Area Forecast Discussion
National Weather Service Hanford CA
530 PM PDT Wed Sep 23 2020
.UPDATE...Updated for the air quality section.
.SYNOPSIS...Dry weather will continue through the week. Mainly
clear skies will prevail, except for some areas of smoke and haze,
especially across the Sierra Nevada and adjacent foothills.
Temperatures will cool some each day through Friday then
strengthening high pressure will bring warming temperatures for
the start of next week.
Satellite images show areas of smoke along the east side of the
valley towards the sierra, Tehachapis and high desert. Otherwise
sunny with temperatures running a bit cooler than 24 hours ago.
Will likely see a repeat of smoke downsloping through the sierra
river basins tonight as the night time temperature sets in. HRRR
smoke model also moves smoke south towards the Kern county
mountains and desert tonight. More of the smoke may push east
towards Nevada Thursday afternoon due to stronger onshore west
flow as a trough pushes east through the Pacific northwest tonight
and Thursday. Additional upper level energy will follow keeping
the jet stream over the PacNW through the end of the week. This
will maintain the cooling trend through Friday with a cool onshore
flow across central CA.
Models in good agreement for next week. A ridge over the Epac will
start to strengthen on Saturday and amplify northward covering
much of the western CONUS Sunday and through much of next week.
This will result a warming trend across our area from Saturday
through the middle of next week with temperatures rising to well
above normal levels again by Monday. Conditions will also be dry
as wind flow turns to offshore Sunday and into early next week.
.AVIATION...Areas of MVFR visibility and local IFR visibility due
to smoke will continue across the Sierra Nevada and adjacent
foothills for the next 24 hours. Elsewhere across the Central CA
Interior, local MVFR visibility due to smoke and haze will
continue for the next 24 hours.
.AIR QUALITY ISSUES...
Please see SFOAQAHNX for an Air Quality Alert
On Thursday September 24 2020... Unhealthy for sensitive groups in
Fresno County and Sequoia National Park and Forest.
Further information is available at Valleyair.org
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is high.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
603 PM CDT Wed Sep 23 2020
.UPDATE...For 00Z Aviation discussion below
.SHORT TERM...(This evening through Thursday night)
Issued at 301 PM CDT Wed Sep 23 2020
From a big picture perspective, an upper level shortwave trough will
move through the region over the next 24 hours. This will cause a
surface low to form across southern Minnesota, and an area of
precipitation to develop across the Upper Midwest north of the
surface low. However, the exact details of how this will unfold are
challenging, and where/when the precipitation will fall is still
An area of elevated showers and thunderstorms on the leading edge of
the H850/700 warm air advection were slowly moving across central
Minnesota. HiRes models are pretty vague in the depiction of this
precipitation, but generally does try to focus it across central
Minnesota and northern Wisconsin this evening and overnight. SPC has
continued its marginal risk for severe storms given the CAPE/Shear
parameters, as a few updrafts could produce some large hail.
Meanwhile, the aforementioned shortwave trough will slide southward
across Minnesota late tonight into Thursday morning, and this will
be the focus for showers and perhaps some thunderstorms through
early Thursday afternoon. The track of this wave does seem to be
trending more north-to-south as opposed to east-to-west, and the RAP
does maintain around 1000 J/kg of MUCAPE, so did hang on to the
chances for precipitation into the early afternoon east of I-35.
.LONG TERM...(Friday through Wednesday)
Issued at 301 PM CDT Wed Sep 23 2020
This will be a fairly active period with multiple systems moving
across the Upper Midwest. There will also be a noticeable cool down
from above average temperatures Friday to near average temperatures
this weekend to below average temperatures early next week.
Friday... This could be out last "summer like" day of the year with
warm air advection of greater than 20 degrees C temperatures
advecting in at 850 mb. This should help the surface warm into the
upper 70s to mid 80s. This won`t last long as a cold front will pass
through Minnesota and Wisconsin providing some chances for showers
and thunderstorms Friday afternoon into the overnight hours. With
the ample warm air advection aloft a stout cap is expected to make
strong to severe thunderstorms unlikely. Rain shower and
thunderstorm chances are greatest north of Interstate 94 where there
is a better low level moisture profile.
Saturday and Sunday... Cooler air behind the cold front and surface
high pressure will lead to a cooler, but generally quiet day on
Saturday. Saturday evening into the overnight could produce some
precipitation as a surface low moves across Iowa. Sunday could be
rather windy due to the pressure gradient across the Upper Midwest
and lapse rates that will favor mixing the higher winds aloft
down to the surface.
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 603 PM CDT Wed Sep 23 2020
Scattered showers and isolated thunderstorms will impact mainly
northern/central MN this evening, then expand south and east
overnight. Attendant visibility restrictions should mostly stay in
the 5-6SM range, but MVFR-level clouds are expected for a 3-6
hour period on Thursday morning and early afternoon.
KMSP...Spotty showers will be found in the vicinity of the site
this evening. Although confidence is still low, have centered the
next batch of showers around the 11Z-16Z time frame, although
can`t rule out hit-or-miss activity prior to that.
/OUTLOOK FOR KMSP/
Fri...VFR. Wind S to SW 10-15G25 kts.
Sat...VFR. Wind W 5 kts.
Sun...VFR. Wind NW at 15G25 kts.
Area Forecast Discussion
National Weather Service Nashville TN
846 PM CDT Wed Sep 23 2020
FOR EVENING DISCUSSION.
Light rain continues to move into the area from the southwest this
evening. The 00z OHX sounding still showed dry air below 7 kft.
This dry layer will shrink as deeper moisture moves into the area
from the southwest as the night progresses. Moderate to heavy rain
looks like it will hold off until after 12z with the axis of
heaviest rain impacting the southern counties from late morning
into the afternoon. 18z model data including the NAM and HRRR
showed the axis of heaviest rain from northern AL into southern
Middle Tennessee including Wayne, Lawrence, and Giles counties.
Given this information, I went ahead and extended the flood watch
to include Wayne and Lawrence counties. The latest 00z extended
run of the HRRR has now shifted southward with the axis of
heaviest rain, so this is something to keep an eye on as the 00z
model runs come in. As far as the forecast for the rest of the
night, I adjusted hourly PoPs upward to mesh with radar trends
and high res model solutions. Temperatures look good and no adjustments
were made there.
00Z TAF DISCUSSION.
Remnants of Beta will affect all TAF locations through the next 24
hours. As the moisture continues to lift northward and eastward
CIGs and VISs will continue to drop. VFR will become MVFR by 07Z
for MQY/BNA and drop further after that. Between 09Z and 12Z all
sites will become IFR/LIFR and remain that way through the end of
the TAF period. Models are indicating that the heavy rain could
move further north than previously forecasted which means periods
of heavy rain are now expected for BNA/MQY/CSV. If this trend
continues CKV will also be able to experience periods of heavy
rainfall. A flood watch has been posted for locations south of
I-40 and east of I-65 for tomorrow (11Z-05Z). After 00Z Friday
the rain should move out of CKV/BNA/MQY. It will take a bit
longer for CSV.
Flood Watch from 6 AM CDT Thursday through Thursday evening for
Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
435 PM MST Wed Sep 23 2020
.UPDATE...Updated aviation Discussion.
Dry conditions can be expected across the forecast through at least
the middle part of next week. High temperatures will fluctuate
during that time but remain at least several degrees above normal.
The hottest days will likely be Monday and Tuesday of next week with
readings very close to to the records for those dates.
Latest visible satellite imagery is showing mostly clear skies over
most of our CWA. The only exception is over the higher terrain of
Southern Gila County, where some CU buildups due to lingering mid-
level moisture ahead of a very weak shortwave that is moving
southward over that region. Latest 88-D radar imagery is even
showing a few very light showers attempting to make their way
southward into Southern Gila County, with a bit more activity over
the White Mountains at this hour. The latest HRRR high-res model run
is indicating that these few showers should dissipate by this
evening as the aforementioned shortwave moves off to the south and
somewhat drier air moves in from the north. Current temperatures
across the lower deserts are now in the upper 90-near 100 range,
with sfc dewpoints in the low-mid 40`s.
Very warm and dry conditions continue to be the theme of the
forecast as a ridge of high pressure builds over the Desert
Southwest the next several days. A very minor shortwave will brush
by on Friday, temporarily hindering the ridge, before atmospheric
heights rise rapidly Sunday/Monday as depicted by global ensemble
guidance. By Monday afternoon, ensemble guidance generally shows the
ridge setting up slightly to our northwest with maximum H5 heights
of 594-595 dm centered near the southern portion of the Great Basin.
There is some uncertainty as to how far outward those heights will
extend, but guidance provides confidence that our forecast area will
see H5 heights somewhere between 590-594 dm, which places near the
99th percentile of climatology.
The latest forecast package for high temps is derived primarily from
the NBM, splitting the difference between the slight cooler GEFS
ensemble mean and the warmer EPS mean. In the end, we are still
looking at highs of 105-107 for the Phoenix area Sun-Wed, while Yuma
and El Centro will bake near 110. Monday and Tuesday seem to be the
hottest days within that stretch, and adding a degree or two to the
forecast is not out of the question if the ridge slightly
outperforms current trends and/or if the ridge centers slightly
closer to Arizona.
The NWS Experimental HeatRisk tool shows widespread Moderate Risk with
large chunks of High Risk categories beginning Sunday which could
lead to a late season issuance of an Excessive Heat Watch and/or
Warning within the next day or two. Phoenix is well past the latest
110 day on record (Sep 19th) but 110s have occurred as late as October
1st and 2nd for El Centro and Yuma, respectively. With the onset of
shorter fall days and less daytime heating, one would think (hope)
Phoenix would be hard pressed to see that temperature mark this late.
.AVIATION...Updated at 2335Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns for the TAF sites over the next 24 hours.
Except for a few late afternoon high based cumulus, skies should be
generally clear in the Phoenix area. Surface gradients are very
weak, supporting typical diurnal wind tendencies. There should be a
few westerly gusts into the teens thru about 02s, then winds
gradually diminish and become somewhat light/variable after 06z.
Winds then settle into an easterly regime by 10z with speeds mostly
8kt or less thru late morning Thursday before returning again to the
west. There may be a few gusts in the afternoon but confidence is
lower and no gusts will be mentioned in the TAFs at this time for
Southeast California/Southwest Arizona including KIPL and KBLH:
Strong high pressure aloft will keep skies generally clear across
the western deserts over the next 24 hours. Winds should be rather
light tonight, favoring the west at KIPL but being more variable at
KBLH. Winds increase a bit Thursday afternoon becoming more
southerly especially at KBLH where speeds should reach 10kt or so by
18z Thursday afternoon. Winds may be a bit more southeast at KIPL
and generally less than 10kt.
Saturday through Wednesday:
No change in the current forecast...Dry conditions will remain in
place with temperatures well above normal. The warmest days will be
Monday through Wednesday of next week with highs very close to the
records for those dates. Min RH values will generally be 10-15% for
most places (including higher terrain) through the weekend before
dipping to single digit values early next week (10%-12% higher
terrain). Max RH values will be 25%-35% for most lower deserts
through the weekend (35%-50% for portions of Imperial County,
southern Yuma County, and higher terrain of Gila County). Max RH
declines some early next week - most noticeably for the
aforementioned areas that had locally higher values during the
weekend. Winds will generally be light and follow familiar diurnal
Record high temperatures:
Date Phoenix Yuma El Centro
----- ----------- -------- -----------
9/27 107 in 2009 111 in 1963 111 in 2009
9/28 108 in 1992 108 in 1994 109 in 2009
9/29 107 in 2003 110 in 1980 110 in 1969
9/30 107 in 2010 109 in 2012 108 in 2015
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.