Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/31/21
Area Forecast Discussion...UPDATED
National Weather Service Miami FL
852 PM EDT Sun May 30 2021
.UPDATE 2...
Quick update to add patchy smoke over Golden Gates area along with
the metro areas of West Kendall for tonight where there been
couple of small firefires that broke out late this afternoon into
early this evening. Patchy to areas of smoke has also been added
for SW Palm Beach and NW Broward counties for tonight due to a
wildfire that is burning over this area too.
Rest of the forecast looks good at this time and no other changes
are planned.
&&
.PREV DISCUSSION... (Issued 742 PM EDT Sun May 30 2021)
AVIATION(00Z TAFS)...
Scattered showers and thunderstorms continue across the interior
sections this evening. Some shower activity will remain possible
over the east coast terminals during the overnight hours. Winds
will increase once again out of the southeast on Monday. Scattered
showers and thunderstorms will develop once again Monday afternoon
and into the evening hours. Short fused AMDs will be likely again
on Monday afternoon into Monday evening.
UPDATE...
Scattered showers and thunderstorms continue this evening mainly
across the interior and Lake Okeechobee region. These storms will
diminsh later this evening, however, additional shower and
thunderstorm development is possible during the overnight hours
mainly over the Atlantic waters as well as the east coast metro
areas. Southeasterly flow continues tomorrow and the east and west
coast sea breezes will develop and push inland later on Monday
morning and into Monday afternoon. A mid level trough will remain
in place as well which will help to contribute to another round of
shower and thunderstorm development during the afternoon and
evening hours. The greatest chances of showers and storms will be
across the interior sections where the sea breezes collide and
interact with each other. Some strong thunderstorms will be
possible once again on Monday afternoon and they could contain
heavy downpours, gusty winds, and hail. High temperatures on
Monday will range from the mid 80s across the east coast metro
areas to the lower 90s across the western interior.
&&
PREV DISCUSSION... (Issued 349 PM EDT Sun May 30 2021)
DISCUSSION...
Short Term (Today through Monday)...
An unsettled pattern is expected through the short term forecast
period across South Florida. The main synoptic feature over the
area is a mid-level trough. An area of low pressure over the
northeastern United States has an associated surface front that
has pushed into Central Florida but will not be able to clear
South Florida. The trough at the mid-levels has brought cooler
temperatures aloft with the special 18z MFL sounding now showing
-9.5 deg C at 500 mb while MDCRS data from aircraft landing or
taking off from RSW shows a 500 mb temp around -11 deg C. This
continues to support the concern for strong to severe storms this
afternoon which could tap into the available surface instability
with the peak of diurnal heating today, the lift offered by
surface boundaries and their collisions, and the cold air
advecting into the area aloft around the trough.
The Storm Prediction Center continues to keep South Florida within
the marginal risk of severe weather for today/tonight due to this.
The primary concerns are strong to damaging wind gusts, small to
near quarter dollar sized hail, and localized heavy rainfall
accumulations from repeated storms. Waterspouts and funnel clouds
cannot be ruled out with boundary collisions today either. The
general pattern for convection today will continue to be focused
around the surface boundaries, such as the sea breezes and outflow
boundaries, and then as the cells growth in stature and are able to
overcome the challenge from drier air aloft, the mean flow out of
the west will push the stronger cells eastward towards the coast.
The retreating sea breezes will aid this movement along with the
potential for some coastal convection reaching the Naples metro
later into the evening.
Overnight, the convective focus will once again shift over the local
waters but remnant boundaries interacting with the land breeze
trough offshore could keep convection going through most of the
night into the morning hours. A general synoptic easterly flow will
allow any convection that initiates along this coastal boundary that
is stout enough to survive westward movement off the boundary to
push ashore which could bring some late night and early morning
showers and rumbles of thunder. The risk of severe storms should be
minimized overnight but you cannot rule out some concerns with heavy
rainfall.
On Monday, the mid-level trough will come into better phase with the
lower level pattern to allow the cold air aloft to persist. A
slightly more easterly flow will allow the convective focus to shift
west as the Gulf sea breeze is slightly more arrested and the
Atlantic sea breeze is expected to move inland more than today.
Accordingly, the resultant boundary collisions will occur closer to
the State Road 29 corridor on Monday compared to the center of the
peninsula which will bring the potential for stronger storms closer
to the Southwest Florida metro compared to today. The additional
moisture, the continued support aloft, and the potential for a small
amount of shear could allow for slightly better organization to the
convection on Monday compared to the expected multicell activity
today. Still some uncertainty with Monday`s forecast, but the
potential for another unsettled day of strong to potentially severe
storms cannot be ruled out.
Long Term (Monday night through Friday):
Model guidance keep a shortwave feature aloft lingering over the
peninsula through Tuesday, with an associated upper level trough
also digging down into Florida. These features will continue to
enhance instability, with steep lapse rates and cool-enough mid
levels temps to keep supporting an active weather pattern.
Expect widespread showers and scattered storms Tuesday and Wednesday
to develop, with highest POPs/Wx coverage in the afternoon hours.
Model PWATS remain well above normals as moisture advection persists
through much of the week under robust low level ESE flow. With the
added destabilizing forcing of the shortwave/upper trough combo, any
thunderstorm that develops could become strong or even severe, with
main threats being damaging winds, large hail, and localized
flooding.
By Thursday, models begin breaking down the shortwave feature and
show the western edge of the Atlantic ridge to nudge back into the
area. In response, low level winds veer a little and weaken. Thus,
afternoon sea breeze boundaries will again become the main focal
points for convection to originate. The weaker flow may result in
slower-moving thunderstorms, which will increase chances of having
longer heavy downpours over the same location.
Persisting cloud cover will likely translate in slightly cooler
temperatures during the long term with afternoon highs a few degrees
below normals through at least mid week. Then highs should warm back
up to around normals by the end of the work week.
MARINE...
A frontal boundary will stall just to the north of the area, while
increasing moisture brings better chances of showers and
thunderstorms through the rest of the week. Brief periods of rough
seas and gusty winds will accompany any thunderstorm that forms.
A few waterspouts are also possible.
BEACH FORECAST...
The ongoing light flow over the coastal waters will keep rip
current risk on the low side for all beaches. This may continue
tomorrow as well. However, the wind is forecast to increase out
of the east by mid week, enhancing the rip current risks for the
Atlantic beaches.
&&
.PRELIMINARY POINT TEMPS/POPS...
Miami 75 86 75 85 / 30 60 60 80
West Kendall 74 87 73 87 / 30 60 60 80
Opa-Locka 75 87 74 86 / 30 60 60 80
Homestead 74 86 74 85 / 30 60 60 70
Fort Lauderdale 76 84 75 85 / 30 60 60 80
N Ft Lauderdale 75 85 75 84 / 30 60 60 80
Pembroke Pines 75 86 74 85 / 30 60 60 80
West Palm Beach 75 86 73 85 / 30 60 60 70
Boca Raton 76 84 74 85 / 40 60 60 70
Naples 73 89 71 89 / 10 60 40 70
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&
$$
Update/Aviation...BNB/CWC
Tonight/Monday and Marine...RAG
Monday Night through Sunday...AR
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Area Forecast Discussion
National Weather Service Phoenix AZ
502 PM MST Sun May 30 2021
.UPDATE...
Updated 00Z aviation discussion.
&&
.SYNOPSIS...
Seasonable dry and warm conditions will persist under mostly
clear skies through Memorial Day. High temperatures will mostly
top out in a 99-102 degree range through the holiday with readings
likely a bit warmer for the middle of next week. A persistent
weak upper level low and a slight increase in moisture across
eastern Arizona may be enough for isolated showers and
thunderstorms over the higher terrain north and east of Phoenix
most days this week. An isolated shower or thunderstorm can not be
entirely ruled out for the Phoenix area later in the week, but
remains unlikely.
&&
.DISCUSSION...
A weak closed low will remains centered off the coast of northwest
Mexico this afternoon. The strength and position of this low will
oscillate somewhat, but will largely remain unchanged for the next
several days. In the short term, skies are clear with a very dry
airmass in place. ACARS soundings show precipitable water of just
0.37". Accordingly, skies are clear across the area. The position
of the low pressure center will generally allow for light
southerly flow through much of the lower atmosphere. Weak gulf
surges are likely for the next few nights, which will gradually
increase the water vapor content. As soon as Memorial Day
afternoon, showers will likely begin to develop over the Mogollon
Rim, but coverage will likely remain spotty. HREF guidance
supports this general idea, with little to no shower activity
making it into the CWA.
By Tuesday, an upper level high will begin to build over the
PNW, with northeasterly steering flow in the mid to upper levels
developing. This, along with the trend for increasing PWAT
(ensemble mean of around 0.60-0.80"), should allow for a slight
increase in convective coverage and the potential for a few
showers to make it into the higher terrain just outside of the
Phoenix area.
As we head into the second half of the week (Wednesday onwards) the
atmospheric pattern depicted by the WPC Cluster tool, as well as
the different global ensembles, continue to show bits of the
afomentioned trough`s energy lingering behind and redeveloping
into a cut-off low over Baja California. Meanwhile, the
previously mentioned high amplitude Pacific ridge is expected to
stretch into the Great Basin, giving the overall pattern some
semblance of a Rex Block. With this, guidance keeps the cut-off
low near Baja for an extended period. This should be enough to
continue to produce some showers and thunderstorms across the
higher terrain north and east of Phoenix.
For now, only a few ensemble members show even trace totals in the
lower deserts, those that do have this occurring between about
Wednesday and Saturday. NBM probabilities for 0.10" of rain are
less than 10% for almost everywhere in Arizona every day which
suggests that even the places that do see showers/storms should
not expect much rain either. However, there are looming weather
concerns such as dry lightning strikes that could ignite new
wildfires and gusty outflow winds from even distant storms.
Despite the proximity of the cut-off low all week, the aforementioned
eastern Pacific ridge will lead to a slight increase in atmospheric
thickness resulting in a slight warming trend Monday-Wednesday. The
greatest warming will occur along the Colorado River and southeastern
CA where highs will reach 103-108 degrees while lower desert areas
of south-central AZ will top out between 101-105 degrees. The
warming trend will not be limited to daytime highs either as
overnight lows warm by 5 degrees or so. Areas of Phoenix could
even struggle to cool much below 80 degrees some nights. By next
weekend, temps are expected to cool slightly and settle around
seasonal normal values.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Aside from westerly wind gusts this evening and again on Monday
afternoon and evening, impacts should be minimal through the TAF
period. Intermittent 15-20 knot westerly gusts will occur over the
next few hours before becoming more frequent later this evening
as a weak Gulf surge moves into the region. Winds should subside
after 06Z and become easterly late in the overnight hours before
veering back to southwesterly by 17-18Z. Another round of 15-20
knot wind gusts is expected by 21Z, with isolated convective
activity remaining well north and east of the Phoenix terminals.
Visibility impacts from smoke associated with the Courthouse fire
west of KBXK are generally not expected through the TAF period.
Southeast California/Southwest Arizona including KIPL and KBLH:
Aside from wind gusts up to 20-25 knots in the Colorado River
Valley including KBLH tomorrow afternoon, impacts should be
minimal through the TAF period. Winds will gradually veer from
southeast to southwest at 5-10 knots this evening before a Gulf
surge returns winds back to more southerly or southeasterly
headings around 06-08Z. Winds will generally remain below 10 knots
until tomorrow afternoon in the Colorado River Valley as
southerlies gust up to 20-25 knots. Skies will also remain mostly
clear through the TAF period with only a few passing high clouds.
&&
.FIRE WEATHER...
Wednesday through Sunday:
Expect max temps to remain slightly above normal through the
entire period. A gradual increase in moisture is likely to bring
some isolated thunderstorms across the AZ high terrain, with lower
desert storms not entirely out of the question, though much less
likely. However, wetting rains are not anticipated, so these
isolated storms may pose a dry lightning threat. Min RH values
will remain quite low, mostly staying between 7-12% each day.
Daily max RHs will mostly range from 20-40% with higher readings
across the western deserts. Winds will remain light to moderate
through the bulk of the period, but with typical afternoon
breeziness most days.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Hodges/AD
AVIATION...Hopper
FIRE WEATHER...Hodges/Kuhlman