Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/16
Area Forecast Discussion
National Weather Service Des Moines IA
357 PM CDT Thu Sep 1 2016
.SHORT TERM.../Tonight/
Issued at 354 PM CDT Thu Sep 1 2016
Nothing of concern tonight outside of minor fog development toward
daybreak. Diurnal cumulus should dissipate shortly after sunset with
broad subsidence in place with Iowa between departing Mid MS
Valley/Great Lakes long wave trough and plains upper level ridge.
Confidence is not great on the fog potential with a wide range of
conditions depicted by guidance. Persistence and HRRR and ESRL
HRRR runs suggest little if anything while the 00z NCAR 3km
ensemble suggests widespread fog. Have played a middle ground with
a brief period of patchy fog in typical locations. Should be
another good radiational cooling night with around 10 degree
spread possible between cooler areas and Des Moines heat island.
.LONG TERM.../Friday through Thursday/
Issued at 354 PM CDT Thu Sep 1 2016
The primary concern in this period will be in the extended portion
of the forecast. Overall the pattern will change little with slowly
progressive, high amplitude flow keeping a western CONUS trough and
east coast ridge in place, which will be further slowed by Hermine.
The current portion of the H85/H7 ridge was over the northern Plains
late today and should reach the Great Lakes early Saturday. This
will keep a dry airmass with either cool or neutral temperature
advection in place to start the weekend.
During this time warmth and moisture will continue to stream
north and east through the lee side of the Rockies and High
Plains. Eventually this summer-like airmass will reach at least
northwest Iowa by late Sunday ushering in a return of thunderstorm
chances to these areas. Iowa may be back in the full blown
warm/moist sector Monday with little precip but PoPs will be on
the increase into the week. The western CONUS trough will finally
be progressive enough to drift a frontal boundary NW-SE through
the state from Monday Night into midweek. There is some
discrepancy in timing with the ECMWF faster, but it appears
likely there will be a period of thunderstorms with heavy rains an
increasing concern. The mean flow will be parallel to the front
with steady low level moisture transport into it. The NAEFS Climo
and GEFS M-Climate specific humidity and precipitable water
percentiles are both anomalously high if not pushing maxes at
times suggesting heavy rain will be quite possible. Our recent
break with pleasant dewpoints will not last long with dewpoints
back to 70F or more by early next week. There will be some severe
weather potential as MLCapes seem to get back into the 2-3K j/kg
range and some adequate deep shear values immediate to the front,
but for the most part heavy rains will be a greater threat due to
an overall lack of deep shear.
&&
.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1256 PM CDT Thu Sep 1 2016
Primary concern will be fog trends later tonight. For this
afternoon, expect nothing more than SCT/BKN VFR CU which should
dissipate into the evening. The question will then turn to fog
potential with low confidence and a wide range guidance solutions.
With persistence not suggesting much, have played it fairly
conservative for now only mentioning MVFR at KOTM. There is the
potential for more widespread MVFR or lower conditions however.
Confidence does increase back into VFR area wide shortly after
sunrise.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
SHORT TERM...Small
LONG TERM...Small
AVIATION...Small
Area Forecast Discussion
National Weather Service Spokane WA
1044 AM PDT Thu Sep 1 2016
.SYNOPSIS...
Cooler weather will arrive for the Labor Day Weekend. The arrival
of a cold front late tonight will bring eastern Washington and
north Idaho a good chance for rain showers. Scattered showers and
isolated thunderstorms are expected to linger into Friday
afternoon. There will be another opportunity for showers and
thunderstorms on Sunday and Monday.
&&
.DISCUSSION...
Updated the forecast to fine tune the timing of the moist cold
front. Clouds will continue to thicken and lower today. Locally
gusty winds have already materialized as the atmosphere continues
to moisten. Radar has picked up on light returns over the east
slopes of the Cascades, most likely the lowering cloud deck,
although the HRRR and NAM4km show some measureable rain spilling
over the crest by mid afternoon. A band of light rain will spread
across the region through the afternoon into the evening hours.
Cooler temperatures are expected today. /rfox.
&&
.AVIATION...
18Z TAFS: A band of light rain will sweep across the region
beginning over Central Washington late this afternoon spreading
into Eastern Washington this evening and then the Idaho Panhandle
overnight. Expect lowering CIGS although TAF sites should remain
VFR. Added -RA to all TAF sites followed by brief break during the
overnight hours. A moistening boundary layer over the Idaho
Panhandle could result in MVFR stratus late tonight...with a
slight chance for MVFR conditions at KCOE/KPUW. Added post
frontal showery conditions by 12z in most TAFs. /rfox.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 74 49 65 47 68 46 / 0 60 50 30 10 10
Coeur d`Alene 74 49 63 46 67 44 / 0 80 60 50 10 10
Pullman 74 47 64 43 67 42 / 0 80 40 20 10 10
Lewiston 80 55 72 52 75 50 / 0 80 40 10 10 10
Colville 73 52 62 43 70 42 / 10 60 60 40 20 20
Sandpoint 74 50 58 44 66 42 / 0 80 70 50 20 10
Kellogg 73 49 58 43 64 39 / 0 90 80 30 20 10
Moses Lake 76 49 73 45 74 46 / 0 40 20 20 10 10
Wenatchee 72 53 69 51 72 51 / 20 40 20 10 10 10
Omak 75 50 68 46 73 47 / 20 30 40 20 10 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
311 PM MDT THU SEP 1 2016
.SHORT TERM...(This evening through Friday)
Issued at 310 PM MDT Thu Sep 1 2016
...Storms stronger and more numerous on Friday...
Low clouds were slow to recede this afternoon over the Plains. KCOS
just now...as of 20Z...starting to clear out thanks to persistent
upslope and llvl moisture. Will likely see a return of low clouds
this evening and overnight...since low levels winds will maintain
an easterly component...but as the upper high weakens along with
weakening upslope...should not be as extensive or long-lasting
tomorrow as it was today.
A trough over the PacNW will slowly move eastward into the inter-
mountain region over the next couple of days. There will be
increasing southwest flow and moisture transport ahead of the
trough. This will keep storms mainly over the mountains and high
valleys today through this evening. Will maintain low POPs over the
I-25 corridor for this evening...but chances are pretty low and POPs
may have to be removed if trends continue. One exception might be
over the Pikes Peak Region...although the latest HRRR even keeps
this area dry tonight. Could see a slightly better chance of an
ISOLD storm over the southeastern Plains where there is a persistent
cu field this afternoon.
A short wave ejecting into the Central Rockies ahead of the trough
out west will set off widespread showers and storms Fri afternoon
and evening. With residual llvl moisture out east...could see s few
strong to svr storms Friday in the afternoon and eve...mainly east
of a line from KLIC to KLHX to KCAO. Should see CAPE of around 1500
j/kg and shear around 30 kts...parameters high enough for some
organized updrafts. Hail to the size of half dollars and wind gusts
to 60 mph will be the main threats. Elsewhere...the main threat from
storms tomorrow will continue to be the potential for locally heavy
rainfall and possible flooding over the burn scar areas.
Temperatures tomorrow should be a bit higher given an earlier burn-
off of clouds and greater westerly flow. Expect highs in the mid 80s
for the Plains and 70s for the high valleys. Rose
.LONG TERM...(Friday night through Thursday)
Issued at 310 PM MDT Thu Sep 1 2016
A weak disturbance wl be exiting the forecast area to the east early
Fri evening. In the evening there wl likely be some isold pcpn ovr
the mtn areas, with isold to sct showers/tstms ovr the sern plains.
By late night most if not all of the pcpn acrs the forecast area
should end, although some lingering showers could continue along the
CONTDVD. On Sat there wl be a trof along the west coast with
southwest flow aloft being ovr the forecast area. There wl still be
enough moisture ovr the forecast area for isold to sct pcpn ovr and
nr the mtns, but the sern plains may just see some isold storms.
High temps on Sat wl generally be around to a little below average.
We should again see most or all pcpn end by late Sat night.
On Sun, the western trof wl move inland and into the Great Basin by
late in the day. This wl mean continued southwest flow aloft ovr
the forecast area, with some breezy south to southwest sfc winds.
Sun looks like a drier day with mainly just some isold
showers/tstms. Temps once again wl likely be around to a little
below average.
The upr trof ovr the Great Basin is expected to lift northeastward
on Mon, and move acrs the northern Rockies and into ND and south
central Canada. A trof remains ovr the wrn U.S. on Mon and it
generally looks mostly dry Mon afternoon acrs the forecast area. The
ECMWF shows some pcpn acrs the sern corner of CO in the evening
hours and then dry the rest of the night. The GFS shows pcpn Mon
evening from the swrn corner of CO, extending east-northeastward
acrs the srn CO mtns and the sern and central plains. For now wl
go with just some isold pcpn chances.
On Tue and Tue night, an upr ridge is expected to be centered ovr
the Gulf coast states, while an upr trof moves from the Great Basin
eastward acrs CO and the nrn plains states into Wed. The upr level
flow on Tue wl allow monsoon mstr to be drawn up into the area,
resulting in increased chances for pcpn, especially ovr the mtn
areas. Then on Wed that moisture tap gets cut off and it looks like
a drier day. Wed night and early Thu a new upper disturbance is
forecast to move acrs the state, which may bring some pcpn chances
Wed night, however Thu is looking fairly dry at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 310 PM MDT Thu Sep 1 2016
Main AVN concern will be return of low clouds this evening at KCOS
and KPUB. Should see MVFR conditions redevelop through early
Friday...possibly a brief IFR period at KCOS. But clouds should burn
off a little more quickly on Friday. Then, concern shifts to more
widespread showers and storms Fri afternoon and evening. Storms from
KLHX eastward will have the best potential to become severe...but
all storms tomorrow will carry the threat of some small hail along
with locally heavy rainfall. Rose
&&
.PUB Watches/Warnings/Advisories...
NONE.
&&
$$
SHORT TERM...ROSE
LONG TERM...28
AVIATION...ROSE
Area Forecast Discussion
National Weather Service Tucson AZ
925 AM MST THU SEP 1 2016
.SYNOPSIS...Enough moisture needed to support scattered showers and
thunderstorms will linger across the area again today. Drier
conditions will start to return by this weekend resulting in very
minimal thunderstorm activity. Daytime temperatures will remain
above normal.
&&
.DISCUSSION...On this first day of meterological fall, regional
radars were showing isolated light shower activity across western
Pima county moving WNW around 10 mph. Precipitable water values
across the area, from various sources, ranged widely from 1" to
1.80" with the highest values being west of Tucson. The 12z Tucson
sounding came in with 1.70" but likely has been slowly falling since
the 4 am launch based on GPS sensor. Water vapor imagery showed that
yesterdays inverted trof was still over the area with possible weak
circulation developing southwest of Nogales. Latest runs of UofA
WRFNAM and WRFGFS along with the HRRR all are hinting at areas W, N
& E of Tucson will see the best chances for storms today.
&&
.AVIATION...VALID THRU 02/12Z.
Isold -SHRA far wrn Pima county thru 01/19z. Another chance of -TSRA
across the area after 01/19z through about 02/03z with brief MVFR
conditions possible with stronger storms. Easterly surface winds
generally under 15 kts outside of strong and erratic thunderstorm
outflows. Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Isolated to Scattered showers and thunderstorms
across the area today. A drying trend will then occur from west-to-
east Friday into this weekend with decreasing shower and
thunderstorm chances. 20-foot winds today will be mainly from the
east at 10-15 mph with gusts of 20-25 mph. Thereafter, expect
southerly to southwesterly winds with some elevated gustiness
especially Saturday through Monday.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
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Area Forecast Discussion
National Weather Service Miami FL
524 PM EDT THU SEP 1 2016
.SYNOPSIS...
Hurricane Hermine, now centered a couple hundred miles
west northwest of Tampa, will continue to strengthen as it moves
northeast. However, the system will be too far north of our
region to have much of an impact. Isolated showers may develop
tonight, otherwise a relatively dry forecast over the next
24-hours. For this weekend into mid next week, a typical summer
weather pattern will return to South Florida with south to
southeast flow and scattered afternoon/evening convection, mainly
affecting the interior and Gulf Coast.
&&
.DISCUSSION...
This afternoon, water vapor imagery showed a defined cyclonic
circulation from Hurricane Hermine over the Gulf with upper level
moisture streaming across South Florida. The center of the storm
could be seen spinning around 200 miles west northwest of Tampa.
Tonight, NHC forecasts Hermine to move onshore near the Floridas
Big Bend region. The system is then forecast to track northeast
over the next several days, possibly affecting Georgia and the
Carolinas. For our region, however, impacts from Hermine will be
limited.
The 18Z KMFL sounding showed a significant amount of moisture with
2.19 inches of PW, but a capping inversion around 850 mb and lack of
a trigger may keep the convection at bay. The sounding showed
unidirectional south/south southwest flow, 15-35 KT, from the
surface up through the mid levels. Gusty south surface winds over
the mainland should diminish slightly as the night progresses and
the atmosphere decouples. Short term models, including the HRRR and
Hi-Res WRF, show precip dwindling this evening. However, a slight
chance across the CWA seemed reasonable with south flow and a high
moisture remaining in place. Any shower or storm that does develop
overnight will be capable of brief heavy rain and gusty
south/southwest winds. On Friday, upper level subsidence over the
region will decrease storm chances once again over South Florida.
Thus, expecting only isolated convection, similar to today.
A High Risk of rip currents remains in effect for Gulf Coast beaches
tonight, with a Moderate Risk in effect for Atlantic beaches. Water
levels are still running above normal along the Gulf coast, but flow
remains more SSE. Will have to continue to monitor for the potential
of minor coastal flooding of susceptible locations in coastal
Collier County.
For this weekend into mid next week, a ridge of high pressure
building over the Atlantic will bring a return to a more seasonal
weather pattern. Expect mainly afternoon and evening convection in
interior and Gulf Coast regions with near normal temperatures.
&&
.AVIATION...
Widely scattered showers moving from south to north
across the region this afternoon, mainly over the interior. KAPF
and KPBI mostly likely to see shra this afternoon, and have
included VCTS for potential at these two sites, however limited.
Other sites may see brief SHRA, though most activity looks to be
west of TAF sites. Brief MVFR conditions possible at all sites,
even outside of convection. Gusty south winds will continue with
gusts to 25 kts possible through sunset. Lower coverage
overnight, with gusty south winds starting again after 02/14Z.
&&
.MARINE...
This evening into tonight, south winds will be around 15-20 knots
local nearshore Gulf waters, and 15-25 knots with gusts up to 30
knots possible for the local offshore Gulf waters. Winds will
begin to subside late Friday and continuing into the weekend. Seas
will generally be 2-4 feet over the local Atlantic waters, and 4-7
feet over the local Gulf waters, with occasional seas exceeding 7
feet for the offshore Gulf waters. Rough seas and brief gusty
winds will also be possible in and around thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 81 92 80 92 / 20 20 10 30
Fort Lauderdale 80 91 80 91 / 20 20 10 20
Miami 79 91 80 92 / 20 20 10 20
Naples 80 88 79 91 / 40 30 20 30
&&
.MFL Watches/Warnings/Advisories...
FL...High Rip Current Risk through Friday morning for FLZ069.
AM...None.
GM...Small Craft Advisory until 8 AM EDT Friday for GMZ676.
&&
$$
SHORT TERM...27/JT
LONG TERM....27/JT
AVIATION...88/ALM