Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/22/17
Area Forecast Discussion
National Weather Service Wakefield VA
841 PM EDT Sun May 21 2017
.SYNOPSIS...
A frontal boundary over the Carolinas will lift north as a warm
front overnight into Monday Morning as an area of low pressure
tracks across the Mid Atlantic. This front will drop back into
the Carolinas Monday night, before lifting back north into the
region Tuesday and Tuesday night as a potent low pressure system
tracks along the boundary. Unsettled conditions continue into
the middle of the week as an upper level trough approaches from
the west.
&&
.NEAR TERM /THROUGH MONDAY/...
Latest surface analysis features 1028+mb high pressure over the
Srn New England coast, ridging down into the Mid-Atlantic
Coastal plain at 00z. To the south, IR/WV Sat imagery showing
developing Meso- low along the W NC/SC border, with the
associated warm front extending east across SE NC.
Showers and isolated T-Storms have moved a bit quicker than
forecast, closer to HRRR timing. Have therefore trended onset
timing of showers a bit quicker than previous. Aforementioned
Meso-low will lift NE across central/North Central Nc overnight,
with the associated front lifting N into central VA as a warm
front late tonight. Large scale ascent ramps up now through
midnight over the Piedmont, and have nudged up to likely wording
here after 03z. Moisture advection and lift increase overnight
with PoPs rising to high chc/likely along and NW of an AVC-RIC-
XSA line through 06z, with categorical for the extreme wrn
Piedmont, and retaining 20-40% POP farther E. Likely and
categorical PoPs overspread areas NW of the aforementioned line
after 06-12z late tonight/early Monday morning, before
progressing across central and Ern portions through midday
Monday.
Periods of moderate to briefly heavy rain are possible from the
Piedmont through the MD Ern Shore Monday morning through midday
Monday, due to the combination of decent forcing and pw values
of +1-2 st dev. QPF of 0.5-0.75" possible through Monday. The
primary forcing pushes offshore by later aftn, with some
lingering showers/tstms possible with PoPs diminishing to
20-40%. Instability is limited (500-1000 J/kg of 0-1km MLCAPE)
and 0-6km bulk shear is generally less than 25kt, so any threat
of severe tstms is very minimal. Lows tonight range from the 50s
NE to the 60s elsewhere, followed by highs Monday in the upper
70s to low 80s. Cloudy tonight through midday Monday with a few
breaks possible Monday aftn.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
The front drops back into the Carolinas Monday night with some
drying aloft as the shortwave aloft and surface low push
offshore. PoPs drop below 15% across the N with some partial
clearing possible, while mostly cloudy conditions continue S,
with a 20-30% chc of showers. Lows range from the upper 50s to
mid 60s.
The flow aloft remains SW Tuesday, with another wave lifting
newd across the Carolinas during the morning and the Mid-
Atlantic during the aftn and evening, with deep layer moisture
returning. Categorical PoPs overspread the entire area Tuesday.
21/12z NAM/GFS/GEFS/ECMWF continue to show some differences in
timing and location and strength of this wave of low pressure,
but the general theme is for a potent system with deep anomalous
moisture transport per strong H925-H700 southerly flow and pw
values climbing to ~1.75" collocated with the favorable RRQ of a
potent 120kt jet over the Northeast Conus. Have continued a
mention in the HWO for most of the CWA, and nudged into into the
NW counties to account for some uncertainty on the NW fringe,
with lower QPF expected SE. The current storm total QPF averages
1.5-2.5", but the 21/12z GEFS does show a mean of 2.5-3.5" for
much of the area, so higher amounts are possible. The current
high temperature forecast now shows generally low/mid 70s SE to
the upper 60s/around 70 F central and mid 60s far NW.
This shortwave/surface low push offshore Tuesday night, with
yet another wave approaching from the SW Wednesday as an upper
low approaches from the W. Unsettled conditions continue with
chc to likely PoPs continuing along with a chc of thunder
Wednesday aftn. Mostly cloudy to overcast with lows Tuesday
night in the upper 50s to mid 60s, followed by highs Wednesday
ranging through the 70s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The deep upper trough across the eastern U.S. will continue to
affect the Middle Atlantic into Thursday as there are some
indications that the trough may slow down and even become negatively
tilted as it moves off the east coast Thursday into Friday. This
should keep precipitable water values well above normal with an
upper jet axis nearby. As such, have raised PoPs to likely across
much of the area Wed night and maintained likely PoPs on Thursday
across the east before the upper trough axis moves east Thu night.
With weak high pressure building across the southeast and Middle
Atlantic for Friday and Friday night, will maintain a dry and
seasonable forecast with temperatures in the upper 70s/lower 80s.
The upper trough finally moves northeast by Saturday, leaving more
zonal flow across the region with building heights. The GFS and the
Canadian suggest a weak upper disturbance moving through the area in
W-NW flow later Saturday into Saturday Night, but the ECMWF keeps
this further north as it builds heights across the area faster than
the GFS/Canadian. With that being said, will Slight Chance of
showers/storms Saturday Afternoon for much of the area with the
exception of SE VA and NE NC. Better chances for showers and storms
Sunday with better agreement from the models of another upper
disturbance moving overhead.
In general, temperatures will stay seasonable for this time of year
with highs in the upper 70s and lower 80s with lows in the upper 50s
to mid 60s. No major warmth is expected through at least next
Sunday.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
A warm front laying north to south across West Virginia to
northern South Carolina will lift northeast overnight. A cold
front over the Ohio Valley will approach the area and move
through the TAF sites Monday night.
MVFR ceilings prevailed at PHF ORF and ECG and will spread to the
rest of the TAF sites overnight. IFR ceilings will be possible at
various times between 06 and 12z at RIC PHF and ECG but should only
last for a few hours. Kept IFR out of SBY and ORF for now. Showers
are expected to develop throughout the area Monday morning with
visibilities occasionally down to about 4 miles.
OUTLOOK...Precipitation will move out Monday evening as the cold
front passes through then redevelop Tuesday morning. A series of
weather systems will bring frequent periods of precipitation with
some heavy rainfall through Thursday. Degraded aviation conditions
will be likely at times. Dry weather returns for Friday.
&&
.MARINE...
Persistent northeast to east flow have allowed seas across the
coastal waters to remain around 5 feet all day. Expect this to
continue into this evening and perhaps even into the early
morning hours before subsiding as the winds diminish. As such,
will maintain the SCA for the coastal waters through 1 am Monday
morning.
The high shifts off the coast tonight with a weak frontal
boundary slowly moving east from the Ohio Valley before stalling
out over the area Monday. This will allow the winds to
gradually turn SE later tonight. Meanwhile, a weak low pressure
system develops along the front over the southern Appalachians
and moves toward the area Monday morning. This may allow S-SE
winds to increase once again Monday especially on the coastal
waters but should stay below small craft advisory criteria. As
the low passes NE, expect the winds to become northerly Monday
night before another stronger low pressure system moves across
the area Tuesday into Tuesday evening. This will bring increased
NE winds and potential waves of 4 to 6 ft along the coast. In
addition, the bay may see N-NE winds of 15-20 kt as well
especially late Tue into Tuesday night. The forecast is tricky
as there are some timing differences in the models. However, it
is safe to say at some point Tuesday into Tuesday night, winds
will become gusty as the low passes by. Quieter marine weather
expected for the end of the week as the flow becomes offshore
behind the low.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ650-652-
654-656-658.
&&
$$
SYNOPSIS...AJZ/MAM
NEAR TERM...AJZ/MAM
SHORT TERM...AJZ/LKB
LONG TERM...MRD
AVIATION...LSA/JEF
MARINE...MRD
Area Forecast Discussion
National Weather Service Burlington VT
716 PM EDT Sun May 21 2017
.SYNOPSIS...
Surface high pressure will translate east of New England this
evening allowing a warm front to push into the North Country
from the eastern Great Lakes region. We will see periods of
rain developing this evening across northern New York, and
during the overnight hours across central and northern Vermont.
Lighter rain showers and overcast skies will linger during the
day Monday, resulting in relatively cool temperatures. Rainfall
amounts between one-third and one-half inch are generally
expected across the North Country tonight into Monday morning.
Dry conditions return on Tuesday with a brief period of surface
high pressure.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
As of 715 PM EDT Sunday...Overall little change to previous
forecaster thinking for this update, but based on current radar
and hi-res model trends decided to increase PoPs to 100% for
tonight. Showers are finally beginning to reach the ground over
the Tug Hill area and will be shifting into the St. Lawrence
Valley within the hour, and eastward through the night with
everyone seeing measurable precipitation.
Previous Discussion...
Mosaic composite radar reflectivity indicates axis of
steady/moderate rainfall across sern Ontario swd across far wrn
NY/wrn PA and ern OH at 1830Z. There are some leading echoes
east of Lake Ontario into St. Lawrence County NY, which will
bring a few light sprinkles or isold -SHRA across nrn NY late
this afternoon/early this evening. However, bulk of steady
precipitation doesn`t reach nrn NY until after 00Z, with onset
of stronger 850-700mb WAA and isentropic ascent approaching from
the SW. Mesoscale models, including the HRRR /BTV-4km WRF and
NAM-Nest all show rainfall reaching the Champlain Valley by 03Z
or so, and far ern VT by 05-06Z. Anticipate a 5-6hr period of
rainfall, yielding amts generally between 0.33-0.50" thru early
Monday morning. Will also see increasing P-gradient overnight.
This will result in low-level channeling of winds in the
Champlain Valley, with gusts locally up to 30 mph in the BTV
area. A Lake Wind Advisory has been issued for Lake Champlain
beginning at midnight as south winds increase to 15-25kts during
the pre-dawn hrs. Overnight lows will generally be in the mid-
upr 40s tonight.
Best large-scale forcing slides to our east between 12-15Z
Monday, but NAM RH profiles indicate continued saturated
conditions in 950-850mb layer, and skies will generally remain
cloudy with low overcast in place. The low-level inversion
layer in place will keep sfc temps cool, despite 850mb thermal
ridge in place (+10C to +11C) across nrn NY. Sfc high temps
generally low- mid 50s east of the Greens, upr 50s in the
Champlain Valley, and upr 50s to lower 60s across nrn NY.
Maintained a chance of showers Monday afternoon. There is some
indication of a trailing sfc trough/convergence line moving ewd
across nrn NY into VT late in the afternoon, which may result in
an additional period of (brief) rain shower activity.
A weak sfc ridge builds newd into our region from western NY
Monday night. This results in lowering inversion layer and light
near-sfc winds. With moist soils, will see combination of
abundant low clouds and patchy fog areawide. Moist layer is
quite shallow, so not anticipating any precipitation. Lows
Monday night mainly 43-48F.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 339 PM EDT Sunday...The short term looks to be the quiet
intermission between the unsettled periods of the near and long
term. After the passage of a cold front and associated trough, a
weak ridge moves in, leaving Tuesday looking like a dry and fair
day across the region. Winds will remain west-southwesterly
behind the front so little change in the air mass leads to
warmer temperatures than just prior to frontal passage with
highs in the upper 60s and low 70s. Gradual increased cloud
cover moving in from the west Tuesday night ahead of the next
system will lead to low temperatures low 50s in the western
counties and 40s in the eastern half.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 339 PM EDT Sunday...The long term pics up again in
activity as multiple systems will impact the area through to
the weekend. A coastal low moves northeast into New England. The
GFS and ECMWF still disagree on the inland advection of the
precipitation with the GFS keeping it mostly offshore while the
ECMWF being more aggressive and extended the precip into
Southeast VT. For now have just kept chance PoPs east of the
Greens for Wednesday.
Thursday has a positively tilted upper trough associated surface
low over Ohio Valley with a closed off upper low. The low
progresses slowly to the northwest of the CWA before shifting
west over the northern counties. This leads to and extended
period of unsettled conditions and potential for precipitation
from midday Thursday and through midday Friday as low pushes out
to the coast. Lingering showers in the higher terrain remains
in the resulting northwest flow through to early Saturday
afternoon. The second half the weekend sees a high pressure
ridge begin to build back in leading to a brief return to fair
conditions.
High temperatures in the long term will range from the upper 60s to
upper 70s, while lows will be in the 40s to 50s.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday...Will see a gradual lowering of cloud
ceilings through the evening with increasing chances for rain
showers, especially during the overnight hrs. After midnight,
should see development of MVFR ceilings (2-3kft) at SLK/MSS,
along with HIR TRRN OBSCD areawide and vsby 4-5SM at times in
showers and BR. There is a chance of MVFR ceilings at the
remaining TAF locations, but anticipate predominantly 3-4kft
ceiling heights for RUT/BTV/PBG. Should see MVFR developing at
MPV by 14Z/Mon. Shower/rain activity diminishing in coverage but
another possible focus area coming across from west to east
late in the day. Otherwise, persistence with MVFR/VFR ceilings.
Winds generally less than 10kts through 06Z. Thereafter, should
see some gusts from the south approaching 20kts at BTV/PBG as
gradient flow strengthens toward daybreak.
Outlook...
Monday Night: VFR/IFR. Chance SHRA...FG.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. Chance SHRA.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Chance SHRA.
Thursday Night: VFR. Likely SHRA.
Friday: VFR/MVFR. Likely SHRA.
&&
.MARINE...
As of 231 PM EDT Sunday...A Lake Wind Advisory is in effect
starting at midnight (04Z Monday). Gradient flow increases out
of the south during the pre- dawn hours Monday, with sustained
winds over Lake Champlain reaching 15-25kts after midnight and
waves building to 2-4 feet. The highest waves are expected
across the northern portion of the broad lake south of Grand
Isle. South winds will remain generally in the 15-25kt range
during the daylight hours on Monday, before diminishing Monday
evening.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Banacos
NEAR TERM...Banacos/Lahiff
SHORT TERM...MV
LONG TERM...MV
AVIATION...Banacos/SLW
MARINE...Team BTV
Area Forecast Discussion
National Weather Service Flagstaff AZ
847 PM MST Sun May 21 2017
.SYNOPSIS...Expect mainly dry and warm conditons this week. Breezy
to windy conditions will return to the region Thursday and Friday.
&&
.UPDATE...No major updates were required to the ongoing forecast.
Details for the near term forecast are that a weak dry frontal
boundary moves through the area from north to south overnight
with brief northerly wind gusts up to 25 mph. It will be mostly
cloudy across the Kaibab Plateau and east to Kayenta through much
of the night with these clouds scattering out in the early
morning. Otherwise, scattered clouds and light winds for the next
24 hours across the northern Arizona region with a slight chance
of showers along the Mogollon Rim and White Mountains in the
afternoon and evening.
&&
.PREV DISCUSSION...A weak wave rotating eastward across Utah is
generating isolated showers over portions of northern Arizona,
primarily near the AZ/UT border. This activity should be light and
short-lived through the evening hours. The latest HRRR progs a dry
front to sweep across Navajo Nation between 5pm-11pm this evening.
The primary effect should be a brief increase in northerly winds to
around 25 mph. Winds should diminish after midnight.
Dry conditions will continue through midweek as Pacific ridging will
advance into the western US Monday-Tuesday. The ridge then flattens
over the southwestern US Wednesday in response to low pressure in
the Pacific NW. Wednesday should be the warmest day of the week with
temperatures 5-10 degrees above normal.
Relatively cooler, dry, and windy conditions will develop Thursday
and Friday in response to weak low pressure entering southern
California. By Friday, this low pressure system could produce a
slight chance of showers along the AZ/UT border with minimum impacts.
The trough axis should be through AZ Friday night with high pressure
forecast to build in over Arizona through the Memorial Day weekend.
&&
.AVIATION...For the 06Z package...Expect VFR conditions and light
winds, generally less than 10 kts, over the next 24 hours. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Isolated high-based showers are possible this
evening across the Kaibab Plateau, then will shift to the White
Mountains on Monday. Wetting rains are not expected. Otherwise,
expect light winds, mainly dry conditions and warm temperatures
through Tuesday.
Wednesday through Friday...Expect warm and dry conditions Wednesday.
Southwesterly winds will gradually increase Thursday and Friday with
relatively cooler conditions.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...McCollum/RR
AVIATION...McCollum/TM
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service Green Bay WI
1052 PM CDT Sun May 21 2017
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Monday
Issued at 237 PM CDT Sun May 21 2017
The latest rap analysis and satellite/radar imagery show low
pressure centered over the western Upper Peninsula and an occluded
front extending southeast into lower Michigan. Widespread showers
and a few storms exited earlier this morning, but additional light
showers/sprinkles are moving east across central and north-central
WI within the comma head of the system. Additional shortwave
activity is diving south over the eastern Dakotas, to the west of
the center of the upper low. As this shortwave moves into the area,
shower chances/trends are the main forecast concerns.
Tonight...Upper level low pressure will continue to spin across the
western Great Lakes, with one particular strong shortwave moving
across the state after midnight. Deeper moisture will continue to
wrap around the southern periphery of the low, causing skies to
remain broken to overcast over the region. Spotty showers will
mostly be confined to central and north-central WI during the
evening, but should become more widespread and push into eastern WI
after midnight with arrival of the shortwave. Low temps falling into
the low to mid 40s.
Monday...Mostly cloudy conditions with isolate to scattered showers
will be present at the start of the morning. As the shortwave
trough exits, showers should retreat to the northeast by mid to late
morning, while warming low level temps should lead to partial
clearing taking place over central and northeast WI through early
afternoon. But with increased solar insolation, clouds will build
again as convective temps are surpassed. This should lead to
scattered showers developing during the afternoon, perhaps initially
over north-central WI before spreading south and east. With ml
capes up to 500 j/kg over central and east-central, could also see a
few thunderstorms develop during mid to late afternoon. Highs
ranging from the mid 50s in the far north to upper 60s south.
.LONG TERM...Monday Night Through Sunday
Issued at 237 PM CDT Sun May 21 2017
Precipitation trends are the main forecast concern.
The combination of a slow moving cold front, deep upper trof
and surface wave developing along the boundary, will result in
periods of showers through midweek. Have boosted pops to likely
over our western CWA late Monday night, over most of the forecast
area on Tuesday, and over our southeast counties Tuesday night.
Thunder is also possible over central and east central WI Monday
evening, and over the Fox Valley and Lakeshore areas Tuesday
afternoon.
A brief period of dry weather is expected Wednesday night into
Thursday evening, as a narrow ridge of high pressure crosses the
region.
WAA will bring a small chance of showers back to the region late
Thursday night into Friday night, but most of the precipitation
should stay to our south, closer to a warm frontal boundary.
After a dry day on Saturday, models diverge for the rest of the
weekend, with the GFS exhibiting convective feedback with a deep
low pressure system moving through the forecast area Saturday
night into Sunday. The ECMWF seems more plausible, with an upper
trof and associated frontal system bringing a chance of showers
and thunderstorms.
Below normal temperatures during the midweek period will moderate,
and should get slightly above normal for Friday/Saturday/Sunday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1052 PM CDT Sun May 21 2017
Mainly MVFR cigs to prevail in the cool moist cyclonic flow
overnight into monday morning. A disturbance rotating around the
low pressure area over the northern Great Lakes Region overnight
will generate a period of IFR cigs with isolated mvfr vsbys due to
showers and fog. Conditions expected to improve to a lower end
VFR later Monday morning. There is a chance for more showers later
Monday as a weak front slides over the area.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......TDH
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1009 PM CDT Sun May 21 2017
.DISCUSSION...
Bit of a lull in the activity for the most part across Southeast
Texas at 9:30 PM. An analysis of the 00Z upper air surfaces showed
a shortwave ridge over the area from 850 mb to 500 mb; although,
the 200 mb and 300 mb surfaces both had good divergent winds
developing overhead. Best moisture was over South Texas at 850 mb
and the central part of the state at 700 mb. An 850 mb trough and
surface trough was helping to generate showers and thunderstorms
over mainly the offshore Gulf waters. These may drift onshore
later this evening.
The splitting jet structure over the western part of the state
will be moving eastward with the upper level shortwave trough.
Think this feature will help set off another round of showers and
thunderstorms. However, still some uncertainty as to location and
amounts. Shorter range models were pointing toward some higher
QPF amounts in the southwestern counties from just before sunrise
through at least the midday period. These include the Texas Tech
WRF, HRRR, and NAM12. Older and global models were pointing toward
further north of the I-10 corridor with lessor amounts. Flash
flood guidance values are still high enough to not warrant a
watch tonight. Will reassess later tonight for the Monday morning
timeframe as more models come in and to see how things develop as
the shortwave trough moves through areas west of the forecast
area.
So, not much to change for this update with only a few minor
tweaks.
40
&&
.PREV DISCUSSION... /ISSUED 650 PM CDT Sun May 21 2017/
AVIATION...
Showers currently across much of the TAF sites this evening
besides currently UTS and CXO, but thunderstorms will be moving
in later tonight. Based off model guidance and forecast soundings,
expecting locations IAH, HOU, and SGR to see mostly shower and
thunderstorm development between 07-11Z, and CLL CXO and UTS to
see more of the thunderstorm development a little later between
09-12Z. The coastal TAF sites are also subject to shower and
thunderstorm development during much of the night and through
late morning tomorrow. Wind gusts can be expected associated with
some thunderstorm development. Confidence is not fairly high in
terms of timing, because this will be a multi-round precipitation
event due to outflow and surface boundaries, as well as a
shortwave moving in from the west. Therefore, there could be some
occasional breaks between these rounds of showers and
thunderstorms.
Hathaway
PREV DISCUSSION... /ISSUED 411 PM CDT Sun May 21 2017/
DISCUSSION...
A line of thunderstorms continues to lift north across Southeast
Texas this afternoon as an outflow boundary from the Gulf of
Mexico has overtaken a nearly stationary frontal boundary that was
draped along the Upper Texas Coast. Farther west, showers and
thunderstorms continue to develop along the Rio Grande ahead a
shortwave trough moving across the Big Bend. Expect the
frontal/outflow boundary to stall somewhere near or north of
Interstate 10 this evening with loss of daytime heating, with
convection along the line gradually diminishing as a result. After
a brief break in rain during the early evening hours, expect the
shortwave and associated thunderstorm complex near the Red River
to continue to translate east tonight and reach the western
portions of the forecast area between 12-6 AM.
Environmental conditions will be very supportive of thunderstorms
capable of locally heavy rainfall, both with the activity ongoing
this afternoon and the next round of rain later tonight. Some of
these conditions that indicate showers and thunderstorms will be
efficient rainfall producers include warm, moist inflow (15-20
knot low level jet) overriding the stationary boundary in advance
of the approaching thunderstorm complex, saturated sounding
profiles up to 450-500 MB, and CAPE values generally below 2000
j/KG. However, wind profiles are not unidirectional (which does
not support training storms) and mean winds in the cloud bearing
layer (850-300 MB) exceed 20 knots out of the west, which
indicates storms will be moving.
Essentially, while the environment is supportive of this locally
heavy rainfall... the thunderstorm attributes which allow these
rain totals to pile up are not supportive for that to occur. This
would mean flash flooding would be more of an isolated as opposed
to widespread occurrence. In addition, even after today`s
rainfall, one hour flash flood guidance values still range from
2.5-4 inches of rain. This has led to the decision to hold off on
issuing a flash flood watch at this time. For now, advertising
widespread 1-3 inch rainfall amounts but cannot rule out locally
higher amounts leading to isolated flash flooding especially
along any residual boundaries left across the region. Anticipate
the heaviest rainfall totals to occur along the frontal/outflow
boundary as it will serve as a good low level focusing mechanism,
but concerned that there may be a secondary swath of maxima near
or to the north of the boundary where RAP and NAM guidance have
advertised some 850 MB speed/directional convergence.
Drier air and subsidence behind the Big Bend shortwave may result
in rain chances tapering off Monday afternoon and evening. Another
round of showers and thunderstorms will be possible as a shortwave
now over Utah on water vapor imagery dives into the region Monday
night, sending a cold front across the region on Tuesday. Another (but
much lighter) round of rain is possible as a third shortwave near
Saskatchewan rotates around the upper low over Minnesota and
drags the upper trough axis across the region. This will end rain
chances for a few days as dry northwest flow quickly transitions
to shortwave ridging by the end of the work week. Gradually
strengthening onshore flow and returning moisture may bring low
rain chances back to the region by the end of the weekend/
beginning of the next week.
Huffman
MARINE...
Light to occasionally moderate onshore winds are expected to
persist through Monday night. Periods of showers and thunder-
storms are possible through Tuesday night. Some of the storms
could become strong or severe. Winds and seas will be higher in
and near the storms. A cold front will move through the area on
Tuesday with winds shifting to the north behind the boundary.
Caution flags might be needed Tuesday night through Wednesday due
to increasing north winds and building seas. Onshore winds come
back on Wednesday night and strengthen through the end of the
week. 42
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 67 77 65 80 59 / 70 80 40 30 20
Houston (IAH) 72 77 67 83 62 / 70 90 60 40 20
Galveston (GLS) 77 80 73 82 69 / 70 80 70 40 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...40
Aviation/Marine...08
Area Forecast Discussion
National Weather Service Huntsville AL
821 PM CDT Sun May 21 2017
.NEAR TERM...(Tonight)
Issued at 820 PM CDT Sun May 21 2017
The slow moving cold front is now along a line from Murfreesboro SW
to around Corinth with scattered showers and thunderstorms along and
ahead of the front. Now that we have lost heating, you can see in
last 15-30 minutes of radar, most of the storms are showing a general
weakening trend with lower levels of lightning activity. A few
isolated strong storms are still possible along the front but these
likely won`t amount to much. Latest HRRR is close to this idea with
storms decreasing in coverage as they move into NE AL. Adjusted PoPs
downward over the next couple of hours to reflect the trends
mentioned above. The front should wash out and stall just to our
south tonight.
The drier air behind the front will slowly filter into the area.
Satellite data shows some clearing behind the front but high level
debris clouds from storms to our south and west will keep skies
mostly cloudy. Temps should be able to drop down into the upper 50s
to lower 60s as we approach sunrise Monday. The drier air should
prevent fog from forming tonight but with the 1-2 inches of rain the
past few days, there might still be enough moisture right at the
surface for fog to form in some low-lying areas.
.SHORT TERM...(Monday through Tuesday)
Issued at 300 PM CDT Sun May 21 2017
The break from the showers/storms will be short-lived on Monday,
however, as another system moves in quickly in its wake. Though a sfc
high will be anchored over the OH Valley, a disturbance in H5 flow
rounding the base of the upper low well N of the TN Valley will
develop another sfc low to our SW. This system will move to the NE
thanks to SW flow around the parent upper low, and this will
translate to showers/storms moving back into the area by Monday
afternoon. This will mainly be a rain-event, though a few rumbles of
thunder are possible through this time, with more coverage expected
over Srn/Ern portions of the area. Nrn/Wrn locations will see
rainfall, although it will be several tenths of an inch less.
The parent upper low over the Great Lakes will begin to wobble to
the SE, bringing a cold front toward the area on Tuesday. So, as one
cluster of showers/storms is moving N/E of the area, another round
along/ahead of the front will be advancing from the W. The GFS is
much drier with the `in-between` timeframe between these two systems,
and the ECMWF is considerably wetter. As such, given the uncertainty,
have only gone with a 30-PoP, with higher PoPs along/ahead of the
front for Tuesday aftn/evening.
.LONG TERM...(Tuesday night through Saturday)
Issued at 300 PM CDT Sun May 21 2017
The unsettled weather pattern will continue into the middle of the
week as an amplified trough swings across the Midwest and a cold
front moves through the TN Valley. A disturbance rounding the base of
the trough and a cold front will move through on Wednesday bringing
showers and some thunderstorms across the area. There is a decent
amount of deep layer shear but not a lot of CAPE with the front.
These values could change depending on how Gulf coastal development
pans out. With the front, breezy conditions and cloudy skies, daytime
temps will only warm up into the lower 70s with overnight lows
cooling down into the lower 50s. Rain will linger into Thursday
morning as the upper-level trough moves overhead. Otherwise, dry
conditions and decreasing clouds are expected thereafter as sfc high
pressure builds into the region. Southerly flow returns on Friday
helping temps warm back up into the 80s just in time for the weekend.
However, rain chances return for the weekend as the sfc high shifts
eastward and another frontal systems approaches.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 622 PM CDT Sun May 21 2017
Isolated showers and thunderstorms are forming along a cold front
that is moving through the MSL terminal as of 23Z. These storms will
continue to move slowly east and arrive into the HSV terminal
between 0000-0100Z. All activity will be east of both airports by
03-04Z this evening as the front moves south and east of the area.
Winds shift to the NW behind front with speeds remaining below 5kts.
VFR conditions are forecast through Monday afternoon.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...Stumpf
SHORT TERM...12
LONG TERM...JMS
AVIATION...Stumpf
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington NC
958 PM EDT Sun May 21 2017
.SYNOPSIS...
A weak front stalled near the coast will return northward late
tonight ahead of a stronger frontal system approaching from the
west. A series of storm systems moving across the Southeastern
United States will bring an increasing potential for showers and
thunderstorms this week. The best chances of rain should occur
from late Monday through Wednesday. Conditions may dry out
somewhat toward the end of the week.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 1000 PM Sunday...Our swath of bone-dry mid-level air is
obviously in place given what happened to the band of rain that
completely died upon reaching the Florence vicinity a couple
hours ago. Latest RAP forecast soundings show this dry air
persisting along the coast overnight, so I have removed PoPs
completely for coastal South Carolina and left only a narrow
zone of 20 PoPs for coastal North Carolina where a few very
shallow convective showers and sprinkles have managed to develop
beneath the warm/dry subsidence inversion aloft. In fact the
only "good" chance of rain overnight may develop around 1-2 AM
back in Darlington and Marlboro counties as the next band of
rainfall approaches from the west, although its eastward
progress will be again limited by the dry mid-level air
currently feeding onshore on a south-southeasterly 850 mb flow.
Discussion from 630 PM follows...
A close look at visible satellite imagery this evening shows
the old stalled front out over the ocean south of Cape Fear. The
boundary becomes harder to locate as it curves northwestward
and inland toward Whiteville and Elizabethtown. This boundary
should move little through the evening hours, but is expected to
begin moving northward later tonight as the overall
environmental flow veers more southerly in advance of a more
significant synoptic front advancing eastward through the
southern Appalachians.
Showers and thunderstorms in a north-south oriented band across
central North and South Carolina are collocated with a band of
good mid and upper level moisture and a weakening upper level
vorticity maximum. Linear motion extrapolation insists these
showers would race to the South Carolina coast between 9-10 PM,
however this appears unlikely due to a layer of intensely dry
air located above a subsidence inversion located between
3500-5000 feet AGL. Both the GFS and NAM show dewpoints as low
as 0-10 degrees F through a deep layer between 4000-10000 feet
AGL. Regardless of what`s going on to our west, this kind of dry
air is going to eat up any precip attempting to fall through
it and is the reason I have dramatically trimmed back PoPs
through the evening hours.
I didn`t entirely remove PoPs however, as below the inversion
layer lapse rates are steep and with small temp- dewpoint
depressions at the surface it`s not impossible some small
towering cumulus clouds could push onshore over the next 5 or 6
hours dropping a few hundredths of an inch of rain in spots.
Models show the dry air will eventually get nudged closer to the
coast, and offshore by sunrise Monday morning as the mean layer
flow veering more southerly.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM Sunday...Broad 5h troughing over much of the CONUS
during the period will maintain unsettled weather through Tue
night. Weak cold front stalls in the region Mon evening, ending
up parallel to the steering flow. Weak low developing along the
front over AL will track northeast along the front Mon night
into Tue. Deep southwest flow, directing the low northeast, will
help spread deep Gulf moisture over the region. Precipitable
water values are forecast to approach 2 inches Tue and the weak,
but developing low will help provide upward motion. Shortwaves
within the large scale 5h trough will further enhance upward
motion, timing dependent. Worth noting that the bulk of the
guidance is about 12 hours slower with the development of this
scenario compared to Sat, mainly due to the 5h trough being more
amplified. However, thinking has not changed much and all of
the guidance still has the low developing and tracking
northeast, across the western Carolinas. Best rainfall chances
and highest rainfall totals are expected across inland areas,
closer to the surface low, but just about the entire region
should receive rainfall from this event.
Surface low moves off the coast near the NC/VA border Tue evening,
but with the 5h trough axis remaining west of area the front will
continue lingering in the area. Larger differences between the
guidance are evident Tue night but most agree that at least a
portion of the Tue night period has a good chance of being wet.
Coverage will be a little less than during the day Tue but still
potential for showers and thunderstorms with both PVA ahead of any
shortwaves and lingering front having an abundance of deep moisture
to tap into. Also evidence of an increasing low level jet Tue night,
some disagreement on exactly how strong but range of solutions is 40-
50 kt which is sufficient to enhance dynamics. Clouds and low level
moisture/rain will keep highs near to slightly below climo but help
keep lows above to well above climo.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 300 PM Sunday...Relatively narrow warm sector spreads
into the area on Wednesday. The warm front early may bring some
light rain but the approach of the cold front yield the more
significant rise in POPs as well as the chance for higher
rainfall amounts. Wind fields not quite as strong as previously
forecast and instability should be limited by cloud cover so
severe weather threat seems minimal. The main energy associated
with the upper trough crosses Thursday but the deepest moisture
will be well offshore by then. Even so, the strength of the main
vorticity max should be able to wring out a few showers
especially if breaks of sunshine provide some instability. Deep
layer westerly flow will bring sunshine on Friday with much
lower humidity levels that will recover slightly into Saturday.
A healthy disturbance may come across in this zonal flow on
Sunday bringing some minor rain chances.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 00Z Monday...A weak stalled front near North Myrtle Beach
and Lumberton will begin to return northward late tonight.
Showers across central South Carolina will weaken later this
evening as they push eastward into very dry mid-level air across
the eastern Carolinas. What`s left of these showers should move
overhead and offshore late tonight into Monday morning.
Extended Outlook...Reduced flight categories will be possible
in periodic showers and thunderstorms Monday evening through
Wednesday. The strongest convective activity will occur
Wednesday.
&&
.MARINE...
NEAR TERM /THROUGH MONDAY/...
As of 630 PM Sunday...An old stalled front located about 20
miles south of Cape Fear curves northwestward and comes onshore
somewhere in the North Myrtle Beach vicinity. This front has
become weaker with time and currently separates easterly winds
to the north from more southeasterly winds to the south. While
the front is expected to hardly budge through the evening hours,
the overall environmental wind should veer more southerly late
tonight as a stronger frontal system begins to move our way from
the southern Appalachians. Seas currently around 3 feet (2 feet
nearshore) should build by maybe an additional half foot
overnight as onshore wind trajectories continue.
SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM Sunday...High pressure remains well off the coast
but its influence continues to weaken. Southwest flow will be
maintained through the period but gradient will be pinched
between the high and a series of developing surface waves that
will track northeast along the front stalled just west of the
waters. Southwest flow increases from 10 to 15 kt Mon night to
15 to 20 kt Tue before dropping closer to 15 kt later Tue night.
Increase in winds is related to the passage of the surface
waves so an difference in timing or strength of these features
would have a direct impact on wind speeds. Seas around 3 ft Mon
evening build to 3 to 4 ft Mon night, peaking at 3 to 5 ft Tue
and Tue night.
LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 300 PM Sunday...Broad swath of southwesterly flow in
place on Wednesday between large Atlantic high and cold front
approaching from the west. Winds may not ramp up to advisory
levels but seas likely will. This boundary will turn the flow
from SW to W by Thursday as well as a small decrease in overall
wind speed allowing seas to abate below advisory thresholds. The
circulation and gradient associated with the front will finally
move east of the area by Friday as high pressure builds into
Florida and the Bahamas. Locally wind will remain westerly and
continue to abate. Seas will follow suit.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...TRA
NEAR TERM...TRA
SHORT TERM...III
LONG TERM...MBB
AVIATION...TRA
Area Forecast Discussion
National Weather Service Jackson MS
932 PM CDT Sun May 21 2017
...FLASH FLOOD WATCH EXTENDED FURTHER NORTH......
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
In the latest forecast update, the Flash Flood Watch has
been extended to a few more counties north of I-20. In the latest
18Z model run from the GFS and the 12Z ECMWF-HiRes, the boundary
for tomorrows system has shifted a bit further north and caused
the QPF maximum axis to alter as well. We went slightly higher on
the accumulative precipitation values, and are now projecting 2-4
inches with some isolated areas that might obtain higher values.
Otherwise, POPs have been cleaned up to reflect the current state
of the radar overlay. Some areas of patchy fog are expected in
the southeastern quarter of the CWA ahead of that boundary pushing
in before first light. The HRRR suggests right now that the
timing for more rain showers pushing into eastern Louisiana will
be as early as 4am. /12/
Prior discussion below:
up across central Mississippi late this afternoon as a line of
strong to severe storms has formed along a weak cold front that
will drift southeast through the remainder of the CWA this
evening. The main threat with the storms is damaging wind gusts to
60 mph but locally heavy rain will also accompany the strongest
storms. This activity should end well before midnight but the cold
front will stall just south of the CWA. A disturbance within the
southern branch of the jet stream will swing across Mexico and
southern Texas tonight then across the Gulf coast states Monday
and Monday night. The 110Kt jet streak will help develop a surface
low the will ride along the stalled frontal boundary and develop
another round of thunderstorms with heavy rainfall. The 12Z models
differed and were farther north with the heaviest rainfall axis.
Current consensus suggests 2-3 inches with locally higher amounts
may fall across our southern zones. In addition, a few storms
across our southeast may produce damaging wind gusts. A Flash
Flood Watch has been issued for our CWA generally along and south
of Interstate 20 Monday and Monday evening. The surface low is
expected to shift northeast of Mississippi after midnight and
lower rain chances however, the large upper level trough over the
central CONUS will still result in southwest winds aloft across
our CWA. A few additional showers and storms will remain possible
through the night. /22/
Tuesday through the weekend...As the upper trough lingers over
the region, another round of rain will be possible for the
southern sections of the CWA on Tuesday given an atmosphere
characterized by PW of 1.5-1.6 inches. At this point, models are
not indicating much QPF for this round of rain but this may end up
exacerbating any flooding issues that may have occurred from
previous days rains.
After this round of rain moves out, another round will move in
quickly on its heels as the actual front moves through the region.
This rain should move quickly through the CWA but the upper
trough/upper low will linger across the region on Wednesday before
moving out. This will promote at least some shower activity to
linger into the northern parts of the forecast area.
Upper ridging will take hold for the remainder of the week into the
early parts of the weekend. Another front may bring another chance
for rain heading into the latter portions of the weekend.
Temperatures will gradually warm back into the mid 80s under this
ridging with overnight lows in the 60s and some 70s possible. /28/
&&
.AVIATION...
00Z TAF discussion:
MCS winding down at the moment with leftover rain in its wake
affecting the eastern TAF sites with MVFR conditions thru 22/02Z.
MVFR ceilings will overspread the area after 22/06Z with showers
and thunderstorms increasing from the southwest by 22/12Z and
continuing through the day./26/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 65 74 60 78 / 51 94 62 50
Meridian 64 76 59 77 / 51 92 76 60
Vicksburg 64 73 59 78 / 24 95 50 47
Hattiesburg 67 80 64 77 / 90 95 80 80
Natchez 65 74 60 77 / 34 95 64 58
Greenville 61 73 60 77 / 7 39 37 32
Greenwood 61 74 58 76 / 12 43 40 39
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Flash Flood Watch from 7 AM CDT Monday through late Monday night
for MSZ043>066-072>074.
LA...Flash Flood Watch from 7 AM CDT Monday through late Monday night
for LAZ015-016-023>026.
AR...None.
&&
$$
12
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1115 PM EDT Sun May 21 2017
.UPDATE...
Issued at 1105 PM EDT SUN MAY 21 2017
A narrow band of showers and some thunderstorms along and just in
advance of a cold front continues to move east across the region.
This band may continue to decrease in coverage, but many locations
should pick up measurable precipitation as it moves east. Hourly
grids have been updated for current observations.
UPDATE Issued at 825 PM EDT SUN MAY 21 2017
Showers and a few thunderstorms along and in advance of a cold
front continue to move across parts of central and eastern KY.
Most of these, however, appear to generally be weakening as
sunset approaches. Wind gusts of 20 to 30 mph and possibly pea
size hail will be possible over the next hour or two with the
strongest cells. The rather narrow bands or areas of showers and
some thunderstorms should bring measurable rain to much of the
area tonight. Hourly pops have been adjusted accordingly in line
with recent radar trends and short term model trends. The showers
are still expected to end late this evening into the overnight
from west to east, ending by sunrise even in the far southeast.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 425 PM EDT SUN MAY 21 2017
19z sfc analysis shows a cold front approaching central Kentucky
with new convection developing along it and east into the
Cumberland Valley. Far eastern Kentucky is still seeing light
showers tracking north out of southwestern Virginia. Even on
satellite, the clouds are more cumuliform over the western parts
of the CWA with breaks opening up. These should help to send
temperatures up into the middle to upper 70s in those locations
allowing for more instability to full the development of
thunderstorms. Will continue the mention of heavy rain potential
in the HWO as the PWs remain high and we have a few spots of low
FFG due to the storms of the past couple of days. Currently,
temperatures vary from the low 70s in the northeast where the rain
has been steadiest to the mid 70s elsewhere while dewpoints are
generally in the mid to upper 60s. Winds have been mainly light
and out of the south, but with some breaks for sunshine in the
west they have picked up to between 10 to 15 mph from the
southwest.
The models are in better agreement aloft through the short term
portion of the forecast as they all similarly depict the
evolution of the nearby and rather large mid level trough. This
low lies to the north of Kentucky tonight with nearly zonal flow
across the state along with the passing of a relatively minor
short wave by 12z Monday. Further amplification of the nearby
pattern then takes place into Monday night as the western portion
of the trough deepens over the Upper Midwest and starts to dig
south with more energy setting up to pass through the southern
Ohio Valley late in the period. Given the models` consistency and
agreement have favored a blend with a lean toward the latest high
resolution CAMS for details through the night.
Sensible weather will feature another round of showers and storms
for the forecast area before an eastward moving cold front shuts
down activity toward midnight from west to east. High pressure
follows briefly allowing the area to dry out through Monday
evening before more moisture is lured up from the south and may
return showers to the area by dawn Tuesday. Temperatures will be
near normal through the period with highs in the mid 70s and lows
in the mid 50s to lower 60s - though do anticipate a ridge to
valley split developing in the lows for Tuesday morning - not so
much tonight with the moisture and late CAA.
Used the CONSShort and ShortBlend as the grids` starting point
with some adjustments to lows Monday night owing to a ridge to
valley split developing. As for PoPs, have tightened them up in
the near term for radar and HRRR trends while also knocking them
down into Monday night.
.LONG TERM...(Tuesday through Sunday)
Issued at 300 PM EDT SUN MAY 21 2017
The extended portion of the forecast begins on Tuesday with an
amplified upper level pattern in place featuring strong ridging in
the west with a longwave trough digging into the Midwest and into
the OH Valley. This transitions to a more active and progressive
pattern and less amplified through the coming week. The passing
open low in the east swings through and into the New England states
by Friday. The ridging mentioned in the west will slide east as well
providing a break in the weather for Friday and Saturday, the last 2
days in the extended. The GFS and Euro show some disagreement on
this solution but overall, there is agreement on at least Friday
being dry.
Closer to the surface, with broad closed low overhead and developing
cold front over the southeast. In southerly flow, this will bring
ample moisture northeast into the Appalachians and a good chance for
showers and thunderstorms across the area. The upper low and remnant
surface boundaries coupled with any leftover mesoscale boundaries
will make for convection to initiate each day from Tuesday through
Thursday. Maximum occurrence will be associated with the diurnal
trend with cells peaking just after max heating and dissipating
after sunset. The main threat will tend to remain heavy rain as
instability and shear at this this point appear to be supportive of
a strong storm or two at most. Thus will stick close to the Super
Blend and may adjust dry according to the new Euro and neighbor
consensus for Day 6 and 7.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 820 PM EDT SUN MAY 21 2017
Showers and a few thunderstorms along and in advance of a cold
front will affect the TAF sites mainly during the first 2 to 6
hours of the period. MVFR and even brief IFR vis or ceilings are
expected with the stronger showers and any thunderstorms with a
lowering in the ceilings areawide to MVFR along and for a couple
of hours behind the cold front. As drier air moves in, the MVFR
ceilings should scatter out from northwest to southwest during
the 7Z to 13Z period, with VFR then developing. Outside of any
thunderstorms, winds should average 10KT or less shifting from
the south to southwest winds to west northwest during the 5Z to
9Z timeframe.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...GREIF
LONG TERM...SHALLENBERGER
AVIATION...JP
Area Forecast Discussion
National Weather Service Miami FL
808 PM EDT Sun May 21 2017
.AVIATION...
Convection continues near APF which should diminish in the coming
hours. Overnight, lighter southeasterly flow is expected. Wind will
pick up tomorrow with a Gulf sea breeze expected at APF again with
the potential for convection.
&&
.UPDATE...
IR satellite imagery shows ongoing convection over western
portions of Hendry and Glades counties. These storms formed along
the sea breeze boundary between the Gulf from the southwest
direction and Atlantic from the southeast. Short term model
guidance prog this activity to diminish over the next few hours.
Updated the grids to lower PoPs in eastern portions of Glandes and
Hendry counties. Otherwise, besides loading in new short term
wind data, all other variables appeared on track.
&&
.PREV DISCUSSION... /issued 344 PM EDT Sun May 21 2017/
DISCUSSION...
A large dome of upper level high pressure can be observed
on water vapor imagery over the mid Atlantic region. Although the
1018 mb surface high remains below this feature, surface pressure
gradients are slightly weaker than 24-hours ago. Thus, east southeast
flow has been lighter, generally around 10 to 15 mph across the
region. The Gulf coast sea breeze has developed along the
immediate Gulf coast, with some wind reporting sites already
indicating a shift to the southwest. Diurnal heating, combined
with sea breeze convergence should generate enough lift late this
afternoon to generate a few showers and thunderstorms over
portions of the western interior. The HRRR and WRF indicate this
activity to pulse up by mid afternoon, then dissipate after
sundown. The main threats from the showers/storms will be brief
heavy rain, and cloud to ground lightning. On the contrary, dry
conditions will prevail along the east coast metro region. A SAL
layer, as seen on this mornings MFL sounding, remains in the mid
levels, which typically prevents convection. Rather benign
conditions are expected tonight with partly cloudy skies, a light
easterly flow, and near normal minimum temperatures.
Monday through Thursday: On Monday, both the GFS and ECMWF begin to
slowly deepen a long wave trough of low pressure over the central
CONUS. This will further weaken the aforementioned surface high
near Bermuda. Thus, anticipating slightly weaker flow over South
Florida, once again allowing both the Atlantic and Gulf sea
breezes to develop. As moisture levels remain similar today, the
shower and storm activity will again be limited to the western
interior, with the east coast metro remaining dry under mostly
sunny skies. As the trough begins to dig on Tuesday, flow becomes
more south southeast. This should allow the Gulf sea breeze to
penetrate further east, shifting the chance for afternoon
convection near Lake Okeechobee across the northern interior.
Wednesday into Thursday, models are in good agreement, deepening
the trough further and pushing a defined front eastward towards
Florida. Out ahead of this front, flow will veer to the south
southwest, drawing in deeper moisture from the northern
Carribean. The GFS indicates an area of positive vorticity
advection swinging around the longwave trough, PW rising to
between 1.75"-2.00", 500 mb winds around 45 KT, and 500 mb falling
to -10 C. These factors may increase the risk of organized
thunderstorms, especially for portions of the northern CWA
Wednesday into Thursday, in which SPC has already indicated a 15%
percent chance of severe weather.
Friday through next weekend: Both the GFS and ECMWF show the
boundary fizzling out over South Florida. If this solution pans
out, residual moisture will maintain an elevated chance for
showers and thunderstorms for peninsula with light flow. However,
nearly a week out, confidence in the final solution remains low.
MARINE...
Surface high pressure over the western Atlantic will maintain
moderate east to southeast flow through tonight. A front will
begin to approach Florida this week, shifting winds south southeast
by Tuesday, then increase out of the south southwest Wednesday
and Thursday. Deep moisture out ahead of the approaching front
will bring an increased chance for showers and thunderstorms by
mid week. Wave heights through the period should remain below 3
feet.
AVIATION...
VFR conditions prevail along the east coast terminals with a brief
gusts 15 to 20 kts possible but returning to less than 15 kt for
late this afternoon. Short term models continue to keep most of
the shower and thunderstorm development interior and west coast.
Included tempo group with TSRA for portion of this afternoon over
APF terminal. Expect low vis as storms may move near or over the
terminal. Activity will diminish this evening with VFR conditions
prevailing through Monday for all terminals.
BEACH FORECAST...
Ten rescues from rip currents have already been reported today
along Miami Beach with ties to strong rip currents. Easterly
winds will begin to subside after this evening, slowly decreasing
the rip currents threat. Thus, the rip current statement will
likely be allowed to expire by tonight. However, easterly winds
will continue on Monday, continuing at least a moderate rip
current risk for the Atlantic beaches.
&&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 74 87 74 89 / 0 10 10 20
Fort Lauderdale 75 87 76 88 / 0 10 10 20
Miami 75 88 76 89 / 0 10 10 10
Naples 71 89 73 88 / 40 20 20 10
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 8 PM EDT this evening for FLZ168-172-
173.
AM...None.
GM...None.
&&
UPDATE...27/JT
DISCUSSION...27/JT
MARINE...27/JT
AVIATION...02/RAG
BEACH FORECAST...27/JT
Area Forecast Discussion
National Weather Service Marquette MI
641 PM EDT Sun May 21 2017
.SHORT TERM...(This evening through Monday)
Issued at 407 PM EDT SUN MAY 21 2017
WV imagery and RAP analysis indicated a mid/upper level trough over
the cntrl CONUS with a low center over nrn MN. At the surface, low
pressure was located over far nw WI with an occluded front draped
eastward through srn Upper Michigan. Although most of the pcpn had
ended early this afternoon in the wake of the stronger shortwave
lifting through Lake Superior another weaker shrtwv was bringing
another area of light rain or drizzle through the wrn cwa.
Tonight, models suggest that sct -shra will increase gradually from
west to east as a shortwave over wrn MN slides toward the area and
additional wrap-around moisture filters into the area. However, any
rainfall amounts will be light with QPF of only a few hundredths of
an inch.
Tuesday, expect the greatest pcpn coverage over the east half in the
morning as the shrtwv moves through the area. Even with some drying
in the afternoon, diurnal heating, max readings into the mid to
upper 50s, with the mid level trough over the area may still be
enough to support some inland sct/isold -shra development.
.LONG TERM...(Monday night through Sunday)
Issued at 314 PM EDT SUN MAY 21 2017
The main forecast highlights through the first half of the week will
be cloudy with temperatures running around 5-10 degrees below
normal, with chances for rain showers. Towards the middle of the
work week, cloud cover will begin to diminish and rainfall chances
will vacation the area with temperatures returning to near normal.
The medium range models are not in great agreement with how things
will unfold towards the end of the week and this weekend; however,
with upper-level ridging beginning to exit the region and shortwave
troughing beginning to encroach on the area, wouldn`t be surprised
if we see the return of some precipitation, perhaps with some
isolated thunder.
Monday night a weak cold front will push east across the area as a
weak surface low lifts east of the area over Ontario. As this front
pushes through, there doesn`t look like too much precipitation will
develop along the front as convergence and moisture are lacking,
along with the better upper-level lift well east of the area.
However, into Tuesday morning and through the overnight hours,
chances for precipitation will increase as a shortwave digs south
across the Upper Mississippi River Valley. Models are in good
agreement that height falls associated with this shortwave moving
across the tail of the cold front, which should be sufficient enough
for a weak low pressure system to develop across the Lower Great
Lakes region. The models are not in good agreement with the track of
this low, with the NAM being the furthest north and the ECMWF being
the furthest south. Therefore, confidence in coverage and
precipitation amounts is low at this time and have only opted to
mention chance PoPs for now.
Wednesday onshore/upslope flow may allow some light precipitation to
linger across the central and eastern portions of the area; but
precipitation should wane from west to east through the afternoon
and evening hours as upper-level subsidence increases. Cloud cover
will begin to decrease in coverage as well; however, with lingering
cooler air aloft and still a bit of wrap around moisture over the
area, don`t think skies will completely clear. On Thursday, as a 100-
120kt jet continues to lift meridional on the eastern side of the
upper-level trough to our south, it will begin to lift out of the
Ohio River Valley. This will allow the associated surface low to
lift across eastern Great Lakes with precipitation staying mainly
east of the area. As 850mb temperature begin to modify and
insolation increases on Thursday, expect temperatures to climb back
up into the 60s. A few locations across the south should see
temperatures climb back to near normal, especially where good
downslope winds develop.
Thursday night through Friday, high pressure will begin to build
across portions of the area as weak upper-level ridging begins to
develops across the Upper Great Lakes. 850mb temperatures will
continue to modify a bit by Friday and will likely allow
temperatures to warm a bit further. A few locations may climb into
the upper 60s and possibly even lower 70s. Locations along the
Wisconsin border and locations across south central portions of
Upper Michigan will likely see the best chance at seeing
temperatures climb into the 70s given downsloping effects and
vegetation characteristics. There are some hints of rain showers,
and perhaps a thunderstorm or two, developing across the west as a
subtle shortwave lifts across the area on Friday.
Next weekend, as warm air advection increases, it does look like the
warm temperatures will be around to stay through at least the first
half of the weekend. The GFS seems to be the outlier in regards to
how the next system will evolve with troughing ejecting out of the
northern Plains. Therefore tend to favor the Canadian and ECMWF
solutions keeping the track of low pressure north of the area,
pushing a weak surface trough through the area. This will bring back
chances for rain showers, and perhaps some thunderstorm activity as
MUCAPE values increase to around 500 J/kg. However, the best chance
for precipitation next week looks to be on Sunday as the main upper-
level waves moves overhead.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 641 PM EDT SUN MAY 21 2017
Westerly winds will result in upslope flow that will keep IWD and
CMX in LIFR/IFR conditions tonight. Drier air moving in Monday
morning will help bring conditions back to MVFR at both sites. With
sw downslope winds at SAW, this will keep MVFR conditions there
through most of the period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EDT SUN MAY 21 2017
Low pres moving across Lake Superior this evening will result in
diminishing winds and shift in wind direction from e-ne to w-sw late
tonight. Winds under 20 kts should then be the rule Mon into Wed as
a relatively flat pres gradient dominates the Upper Lakes.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...Ritzman
AVIATION...07
MARINE...JLB
Area Forecast Discussion
National Weather Service New York NY
1022 PM EDT Sun May 21 2017
.SYNOPSIS...
High pressure moves east of the area today. A series of low pressure
systems will impact the area through the week, resulting in
periods of unsettled weather.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Clouds continue to overspread the area this evening, although
plenty of dry air remains at low levels. This dry will likely
hold off any measurable rain until towards day break. Last
several runs of the HRRR have been indicating quick development
of rain with approaching shortwave after 06z, so will need to
monitor trends over the next few hours.
Overnight lows of 45-55 degs are fcst, slightly lower than
normal based on southeast winds off the cool Atlantic Ocean.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
Monday...Prepare for a widespread moderate rainfall ranging from
around 2/3-inch to 1 and 1/4-inches, mainly between 8 am and 8
pm. Minor urban flooding of low lying poor drainage areas is
possible.
The combination of increasing low lvl warm air advection and
convergence, an upper lvl short wave mvg NE toward the area and
a developing occluded front approaching will cause this rainfall
along with areas of fog. As southeast winds continue blowing off
the cool Atlantic Ocean, day time temperatures will range 60-65
degrees.
Monday Night...Light rain will gradually end as the low moves SE
of Long Island.
Tuesday...As the upper lvl low digs SE across the Western Great
Lakes, another short wave will rotate arnd the base of this low,
causing cyclogenesis in the SE that will move NE toward the
region, bringing our next chc of rain.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The developing upper trough over the central U.S. will continue
to amplify over the midwest and southern plains Tuesday night,
then move slowly east through the end of the work week. This
will result in unsettled weather through the period as a series
of lows and upper level vorts move through, bringing multiple
chances for rain to the region.
Models are in somewhat better agreement in the large scale trough
evolution, although differences continue in the timing and placement
of individual shortwaves and the associated sensible weather. Based
on the 12Z model suite, the general consensus is for a period of
rain Tuesday night into Wednesday, then again on Thursday, with a
chance of lingering showers in between.
The trough begins to lift to the northeast late in the week as a
ridge builds in for the weekend. This will allow for generally dry
conditions for a period Friday into Saturday. Models then diverge on
the placement of a shortwave undercutting the ridge, which could
bring a chance of rain back to the region on Sunday.
Daytime highs will be near normal through the majority of the
period, before rising to a few degrees above normal by the weekend.
Overnight lows will run around 5 degrees above normal through the
weekend.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
High pressure continues moving offshore tonight as a frontal
system approaches through Monday
Gradually weakening SE winds tonight, especially away from city
terminals. SE winds will increase again around day break and
continue through Monday, generally 8 to 13 kt.
VFR conditions continue until around day break. MVFR and rain
develop in the morning, with conditions lowering to IFR by late
morning and early afternoon. IFR should then continue into the
evening. There is uncertainty with the timing of lowering
conditions as well with the rain. Actual observation could be
off by 2 to 4 hours from forecast.
There is also a slight chance for thunder. Confidence on timing
and placement is too low to include in the TAFs at this time.
.OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...
.MONDAY NIGHT-TUESDAY...IFR early then gradually becoming VFR
Tuesday morning. VFR thereafter.
.WEDNESDAY-FRIDAY...MVFR or lower possible in showers. Slight
chance of thunderstorms Thursday evening.
&&
.MARINE...
Sub-advsy conds will remain across the waters through tonight as high
pressure gradually slides off the New England coast.
SE winds will increase to 15-20 kt as seas build to around 4 ft during
the day Monday across the Atlantic Ocean coastal waters. Areas of
fog are forecast to restrict VSBY to 1-3NM area wide through Monday
evening.
While winds will generally remain below SCA conditions, seas will
begin to increase on Wednesday as a series of lows move over the
area. SCA conditions are possible on the ocean waters Wednesday-
Friday before seas begin to subside on Saturday.
&&
.HYDROLOGY...
A widespread moderate rainfall ranging from around 2/3-inch to 1
and 1/4-inches, mainly between 8 am and pm. Minor urban flooding
of low lying poor drainage areas is possible.
Several opportunities exist for widespread rainfall during the mid-
to late-week time period. Around one inch of additional rainfall is
possible during this time period, although considerable uncertainty
exists in the details of these events.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...FEB/GC
NEAR TERM...FEB/GC
SHORT TERM...GC
LONG TERM...FEB
AVIATION...DS
MARINE...FEB/GC
HYDROLOGY...FEB/GC
Area Forecast Discussion
National Weather Service Mount Holly NJ
939 PM EDT Sun May 21 2017
.SYNOPSIS...
Low pressure tracks across southeastern Canada tonight through
Monday. An associated cold front will move through our area later
Monday, then stall just offshore through Tuesday. An area of low
pressure moves across our area Wednesday morning, followed by a cold
front late Wednesday night and Thursday morning. High pressure will
build in from the southwest late Friday into Saturday, then it
shifts offshore into Sunday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
800 pm update: Model agreement remains below desirable levels
this close to the event. The remaining discrepancies involve
three main forecast concerns: one in the near term and two in
the short term.
The near-term forecast issue is onset of precipitation. The
latest runs of the HRRR have sped up onset somewhat and are in
considerably better agreement with other convection-
allowing/mesoscale guidance (e.g., the WRF- ARW, RAP13, RGEM,
etc.). Nevertheless, the midlevel perturbation associated with
this initial batch of showery precipitation is somewhat on the
weak side, which may explain some of the remaining variability
among the model simulations. The 18Z NAM, e.g., remains on the
slower side with the perturbation, though it is notably stronger
with this first perturbation than most higher-resolution
guidance, at least in terms of precipitation- producing lift.
Given the remaining discrepancies in onset and rate of speed in
which the precipitation spreads eastward or northeastward,
reduced PoPs during the 03Z-06Z time frame but kept them similar
after 08Z, when most models agree that sufficient lift will be
present. However, one caveat to this is that there appears to be
two periods of steadier precipitation with this event. The
first is with the aforementioned perturbation tonight. The
second is with a cold front moving through the region tomorrow
and a frontal wave that moves rapidly northeastward through the
Mid-Atlantic. The insinuation here is that there may be a period
of relatively little or more scattered/showery precipitation in
between the two sources.
Previous discussion...
Rest of this afternoon...Clouds generally increase and thicken.
Max temps generally 1 to 4 degrees below normal except 5 to 10
below normal far s NJ and the DELMARVA. East southeast winds
continue gusting 15-20 mph.
Tonight...models have been differing timing of onset of rain
tonight. Am still unsure as we go to press, but since the HRRR
is still very very late tonight, have followed. no certainty of
.01 in ne pa so kept pops generally as previous but arrived at
those pops a little slower. Looks like with the PWAT advection
that the heavier showers may be occuring the Delmarva prior to
sunrise. 09z/21 SREF modeled PWAT increases to 1.7" by morning
Delmarva.
Thunder remains in the fcst but low confidence of occurrence on
the Delmarva and i could more easily easily see it not occur.
Forecast basis was a 50 50 blend of the 12z/ 21 GFS/NAM MOS.
LOWS normal to 5 degrees above.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
930 pm update: Amended QPF totals, to increase amounts slightly
from the urban corridor southeastward and decrease them from the
Fall Line northwestward. Past several HRRR runs have been
consistent in producing a swath of 1-2+ inch totals from
southern Delaware northeast through the coastal plain of NJ,
with sharply decreasing amounts northwest of the urban corridor.
With agreement from the 18Z NAM and a trend toward that
direction from the latest few RAP simulations, think the
adjustments were necessary. As mentioned previously,
local/mostly minor flooding issues may occur if convection is
present, which the HRRR strongly is suggesting at this point.
800 pm update: As mentioned in the near-term discussion, two
forecast concerns remain for the short-term period, largely
based on continuing model disagreement.
The first concern is QPF. A review of the 12Z and 18Z
simulations of the NAM and GFS, the latest higher-resolution
guidance, and comparison to 12Z non-NCEP models continues to
paint a rather unclear picture of how much precipitation falls
with this event. The 18Z NAM looks awfully dry northwest of the
NJ coastal plain. The latest simulations of the RAP are also
quite dry. However, the HRRR and to lesser degrees the 12Z
ECMWF, WRF-ARW, and WRF-NMM are more suggestive of heavier
precipitation in these areas. With the 18Z GFS somewhat on the
drier side northwest of I-95, as well as strong suggestion of a
sharp gradient between heavy precipitation and very low totals
in much of the higher-resolution guidance, I was inclined to
reduce QPF northwest of the urban corridor. I also narrowed the
axis of higher QPF a tad, based on stronger agreement regarding
locations of maximum QPF. However, confidence in magnitude of
QPF is very low. It is certainly possible my modifications
produce storm totals that are too low south/east of I-95. Expect
more fine-tuning through the overnight as the latest guidance
comes in. For now, totals are generally 0.25-0.75 inches
northwest of the urban corridor, 0.75-1.25 inches in the urban
corridor, and 1-1.5 inches southeast of I-295 (with locally
higher amounts almost certain to occur).
The second concern is presence of any elevated instability.
Latest model soundings continue to suggest meager parcel
buoyancy during the event, but it will not take much to generate
fairly deep lift, especially given the deep, moist profiles
expected. With PWs around 1.75 inches by Monday afternoon, any
convection will likely produce locally heavy rain rates. For
now, kept thunder confined to coastal NJ and Delmarva for
Monday, but this remains low confidence. If buoyancy appears to
be stronger than progged, fast rain rates are probable during
portions of the event, which would lead to somewhat greater
hydro concerns.
Main changes to the grids (besides to QPF) were lingering
higher PoPs longer in the daytime period, given somewhat slower
consensus of precipitation timing and increased chances of
instability showers subsequent to the main precipitation shield
moving through during the morning.
Previous discussion...
Monday...A wet morning-early afternoon is in store for the
region as a cold front approaches and moves into our area during
the afternoon. A little thunder maintained far south portion of
the forecast area but not probable and so a low confidence part
of the fcst.
Model consensus is for the heavier rain to occur southeast of
I95, near the path of any warm frontal wave of low pressure and
closer to the better instability. PWAT 1.5 to 1.75 inches so a
period or two of heavier showers and associated brief poor
drainage flooding possible. This rainfall should lower flood
guidance thresholds for mid week events. The DELMARVA and
southern NJ should be able to handle 2 inches of rain in 6 hours
Monday morning. Am expecting that nuisance poor drainage flood
statements that impact travel will need to be issued sometime
between 10z and 20z se of I-95.
The afternoon may see very little rain along and west of I-95
but showers could break out again late in the day if it warms
enough.
Fog should develop in the light and moistened boundary flow off
the ocean late in the day along the Atlantic coasts.
Forecast basis was a 50 50 blend of the 12z/21 GFS/NAM MOS.
These high temps may be several degrees too warm depending on on
the persistence of showers through the afternoon. If it quits
sooner, it would warm to our fcst values. For now the 330 Pm
fcst temps indicate about 5 to 8 degrees below normal, 10 below
near and north of I80 and only 2 below normal southern DE.
Uncertainty regarding temps and how persistent the afternoon
rain.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Summary...Times of wet weather, however warmer temperatures look to
occur especially later this week and next weekend.
Synoptic Setup...An amplifying upper-level trough is forecast to
gradually shift eastward from the Midwest and Plains Tuesday night
and Wednesday. This should move out of the East Friday as some
ridging arrives and establishes high pressure off the East Coast
during next weekend. At the surface, an area of potentially
disorganized low pressure looks to move through Tuesday night and
Wednesday. If short wave energy can consolidate more ahead of the
aforementioned trough, then surface low pressure would be able to
strengthen and organize. While the pattern for awhile looks
unsettled, there is less certainty with the details especially for
the Tuesday through Wednesday time frame. We used a model/continuity
blend for Monday night through Tuesday night, then blended in the
12z WPC Guidance thereafter. Some adjustments were then made
following additional collaboration with our neighboring offices.
For Monday night...An upper-level trough/closed low should be moving
well to our north and taking surface low pressure with it. An
associated cold front will slide across our area but it should then
stall just offshore. The associated warm advection and related
isentropic lift is forecast to be shifting north and east of our
area during the evening. This will result in any showers diminishing
and shifting offshore. A weak surface high then builds in overnight
and there might be just enough drying and subsidence for a time to
erode the lower cloud cover. If the clouds thin out enough, fog may
develop late especially across northern New Jersey and eastern
Pennsylvania as these locations will be more removed from a
developing northeast low-level wind. The highest PoPs were kept
during the evening hours.
For Tuesday and Wednesday...An upper-level trough is forecast to
migrate eastward from the Midwest and Mississippi Valley. This will
allow for some downstream riding, however the model guidance shows
several embedded short waves within the southwesterly flow aloft.
These should result in surface low development into Mid Atlantic
region, although the parent surface low is currently forecast to
track into the Great Lakes Wednesday night. The initial surface low
should develop on the stalled frontal boundary, however timing is
less certain as some guidance is faster with this feature. It
appears the main forcing may arrive Tuesday afternoon and night,
then some drying tries to work in during Wednesday. While there is
less certainty with the details, went ahead and made some
adjustments to the PoPs with the highest values mainly from about
I-95 on south and east later Tuesday into early Wednesday.
For Thursday and Friday...As an upper-level trough shifts eastward
from the Great Lakes and Ohio Valley Thursday, surface low pressure
is forecast to move from the eastern Great Lakes toward northern New
England. Its trailing cold front should cross our area mostly
Thursday morning, however there may be a weak surface low near the
triple point as it crosses our region. Some showers are expected
with this system Thursday and enough instability should be realized
to generate some thunderstorms and therefore a chance of thunder is
included for much of the area mainly Thursday afternoon/early
evening. As the trough begins to lift out Friday, a weak cold front
or surface trough moves through. This in combination with cyclonic
flow and some instability may generate some showers especially
across the western/northern zones. The PoPs were kept on the lower
side at this time. A westerly wind will increase Friday as low
pressure strengthens across New England. There does not appear to be
much cooling though in the wake of this system.
For Saturday and Sunday...Some guidance is slower in removing the
upper-level trough from the Northeast Saturday, however overall a
narrow ridge should arrive as the next trough moves across the
Plains and Midwest. The arrival of the ridge allows for surface high
pressure to build in from the southwest before shifting offshore
into Sunday. There may be a warm front lifting to our north Saturday
night into early Sunday, however the opportunity for convection with
it is less certain this far out especially given the main energy is
currently forecast to be over the Great Lakes to the Central Plains.
As of now, included a slight chance PoP for most areas Sunday and
Sunday night.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
For the 00Z TAFs...BKN CIGs around 5-7 kft early this evening
will gradually lower to MVFR and potentially IFR by daybreak as
showers move into the region. Heavier showers look to move
through the terminals from 12Z to 18Z, but chances for rain
exist before and after this time frame. IFR should settle in
during the daytime hours and remain for the rest of the TAF
period. Winds generally at or below 10 kts from the S or SE.
Small chance of thunder, but probabilities are too low for TAF
mention at present.
OUTLOOK...
Monday night...IFR/MVFR conditions should improve to VFR from west
to east in the evening. Showers end in the evening, then local fog
is possible. Light south to southwest winds, becoming light
north-northwest or light and variable.
Tuesday...VFR ceilings lower to MVFR or IFR as showers develop,
especially from about PHL south and east. Lower confidence on the
timing. Northeast or east winds mostly 10 knots or less.
Wednesday...Times of MVFR/IFR conditions along with some showers. A
few thunderstorms are possible late in the day or evening. East-
southeast winds 5-15 knots.
Thursday and Friday...Some showers and thunderstorms around Thursday
resulting in times of MVFR/IFR conditions, improving Thursday night
or Friday. South to southwest winds Thursday, becoming westerly and
potentially gusty on Friday.
&&
.MARINE...
930 pm update: Small craft advisory for the Delaware coastal
waters has been cancelled. Seas at buoy 44009 have remained
below 5 feet all evening, and winds are well below thresholds.
Though seas will be close to the 5-ft threshold for much of the
night, do not think there is much justification for keeping an
advisory at this time.
Other main change was to add a slight chance of thunderstorms to
all of the marine zones tomorrow. No change to the rip current
forecast from the discussion earlier this afternoon.
Previous discussion...
Probably extending the SCA hazard grids for the Atlc DE waters
through midnight and then it may need a further extension
thereafter. Its a marginal SCA. Elsewhere, isolated southeast
wind gusts to 25 kt late this afternoon should subside this
evening. Southeast wind tomorrow but wind and seas just below
SCA criteria.
OUTLOOK...
Monday night and Tuesday...Fog should occur for a time, especially
on the ocean zones, Monday night as dew points around 60 degrees
move over the cooler waters. This may dissipate later at night
though as a northeast wind and clouds increase. Winds may gust to
near 25 knots late Tuesday across the southern zones with seas
building to around 5 feet. There is lower confidence with the
details given timing differences with low pressure along a stalled
front.
Wednesday through Friday...The winds should be below Small Craft
Advisory criteria, however seas may reach or just exceed 5 feet at
times on the ocean zones.
Rip Currents:
Onshore wind and continuing easterly swell projects a moderate
risk for the formation of dangerous rip currents this
afternoon/evening.
Water temps this Sunday afternoon were variable along the
coast...upper 50s to mid 60s.
Tomorrow tentatively: Please review the 830 PM update for tomorrows
forecast. We`re looking at low risk with a slightly smaller
primary easterly swell and a little less onshore wind. Its close
to moderate in a few spots. The weather Monday should be pretty
shabby by midday as showers low clouds develop with fog later
in the afternoon on the beaches.
The safety message: during this pre Memorial Day week... if you`re
a weak swimmer, swim with a strong swimmer and a flotation device
nearby. Do not swim near piers and jetties where any rip currents
tend to be stronger. Respect the power of water, and do not
overestimate your swimming ability. Ocean surf swimming is quite
different than swimming in the pool or lake. When departing the
surf zone...be aware of incoming waves. Sometimes a much larger
than expected wave can knock down a surf zone swimmer/walker,
especially if your back is turned away from the ocean. The wave
knock down-face plant can cause disabling upper extremity
injury.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.
&&
$$
Synopsis...Gorse
Near Term...CMS/Drag
Short Term...CMS/Drag
Long Term...Gorse
Aviation...CMS/Drag/Gorse
Marine...CMS/Drag/Gorse
Area Forecast Discussion
National Weather Service Pueblo CO
257 PM MDT Sun May 21 2017
.SHORT TERM...(This evening through Monday)
Issued at 257 PM MDT Sun May 21 2017
At 2 pm, ongoing convection across far southeast Colorado in eastern
Las Animas and Baca Counties. Isolated showers across the mountains
and high valleys. Temperatures were in the 60s to lower 70s across
the plains and I-25 corridor, 50s and 60s high valleys and 40s and
50s mountains.
Tonight, ongoing convection will continue through the evening as
shortwave moves from eastern Utah into western Colorado by 06Z.
Moisture and weak instability will be limiting factors for any
thunder across much of the area, with the exception of far southeast
Colorado, where CAPE values are at or above 1000 J/KG and bulk shear
around 40 knots during the early evening. The SPC outlook for that
area in Las Animas and Baca Counties for strong and/or a couple
severe storms looks good. HRRR and NAM forecasts develop an MCS just
south and east of our area in the early evening. Shortwave trough
axis will still not clear the area before 12Z, so suspect weak
convection will continue through the overnight from the eastern
mountains to the Kansas border.
Monday, in the wake of the shortwave, upper flow will be from
northwest to southeast, and there will be some subsidence. The next
shortwave is not forecast to start influencing southern Colorado
sensible weather until the evening, so will very weak instability
and dewpoints in the 30s to lower 40s, expect only isolated showers
in the lower elevations with more coverage over the mountains. High
temperatures will be similar to Sunday`s in advance of the next
shortwave.
.LONG TERM...(Monday night through Sunday)
Issued at 257 PM MDT Sun May 21 2017
Monday night and Tuesday...Brisk north to northwest flow aloft will
continue across the region through Tues, providing for continued
shower and storm chances, as well as cooler air. A shortwave late
Mon eve will drop south into the forecast area, bring the needed
dynamics for persistent convection through the evening hours as
well as a reinforcing push of cooler air. Shower and storm
activity is forecast to wane through the aftn hrs. Temps will be
cooler on Tue, with max readings in the 50s to upper 60s.
Wednesday through Saturday...Long range models are starting to come
into agreement on what will occur through the remainder of the week
and into next weekend. An upper ridge crosses the region on Wed,
producing dry conditions and warming temps. The ridge moves east on
Thu as an upper low crosses Canada and the northern Rockies. This
will produce westerly flow aloft across the Rockies for Fri through
Sun. Isolated aftn mt convection returns on Thu, then isolated
activity is forecast for all areas for Fri through Sun, tied to a
couple of shortwaves that will drop south across the state and bring
cooler air for the weekend. Temps are expected to warm back into the
70s for Wed, then 70s to lower 80s for Thu and Fri, then back down
into the 60s and 70s for Sat and Sun. Moore
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 257 PM MDT Sun May 21 2017
Generally VFR at KALS, KCOS, and KPUB tonight and Monday, though
MVFR will be possible at KCOS after 05Z. Mountains will likely be
obscured at times due to showers through the night.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...TM
LONG TERM...MOORE
AVIATION...TM
Area Forecast Discussion
National Weather Service Blacksburg VA
1045 PM EDT Sun May 21 2017
.SYNOPSIS...
Abundant moisture will lift over a stalled front tonight, then
a cold front will cross through the region from the west of
Monday. Several periods of precipitation are expected through
the rest of the week.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 1037 PM EDT Sunday...
Have cancelled the flash flood watch as hourly rainfall has been
generally no more than one quarter to one third of an inch.
Should see the rain move slowly north and east ahead of a
mesolow over southwest NC that will slide toward the Virginia
piedmont by morning.
Pops were adjusted to account for radar and high-res trends
keeping higher threat along/east of the Blue Ridge, with less on
the west side of the I-77 corridor. Both the HRRR and RAP show
it drying out in the southwest/west after 08-09z.
Staying generally cloudy but seeing opportunity in this weather
regime for dense elevation based fog. Will have to monitor obs
overnight to see if a dense fog advisory or special wx statement
is needed. This will be more likely along the southern Blue
Ridge, northwest to the Alleghanys.
Previous discussion from early evening...
Increased PoPs to 100% for the mountains and foothills counties where
rain shield currently resides. A vast majority of the area is
only seeing light rain. The heaviest rain remains south of the
wedge boundary and closer to the low`s center. This rain shield
will move east over the piedmont by midnight, exiting in the
morning.
Dry slot already moving northeast across the Smoky Mountains
and should be entering the Mountain Empire later this evening.
Flood threat looking less likely but will keep the watch in
place as the low is taking more of a north-northeast track into
North Carolina this hour.
As of 345 PM EDT Sunday...
Flash Flood Watch in effect along the southern Blue Ridge this
afternoon and tonight.
Regional radar showed elongated axis of showers from western
Pennsylvania to South Carolina. Along the southern end of this
band of precipitation the air mass was unstable enough to
support scattered thunderstorms. Soundings showed the wedge of
colder stable air below 850 mb with the boundary at the surface
well west of Boone and well south into northern North Carolina.
Satellite and radar loops showed a compact vorticity maximum
tracking into extreme southwest North Carolina. Models showed
good consistency in the timing and location of this feature
through Monday, bringing it into southern Virginia after
midnight tonight and into Maryland Monday afternoon. As this
wave crosses the area southeast upslope winds will be enhanced
and that will result in a period of moderate to heavy rainfall.
The surface cold front approaching from the west will cross
southwest Virginia, northwest North Carolina and southeast West
Virginia Monday morning. At 850MB the front may not make much
progress southeast as the region will be between the large 500MB
low moving east through the Great Lakes and the upper ridge
moving east off the coast.
Used a non-diurnal trend for both tonight and Monday.
Temperatures may have a slight rise as the wedge erodes tonight
and with any clearing behind the front on Monday afternoon.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 330 PM EDT Sunday...
Southwesterly flow aloft ahead of a developing closed low moving out of
the midwest will keep us in a wet and unsettled pattern through midweek.
A cold front will be pushing off to our east early Monday night, but
any break in precipitation will be short lived as the front stalls out
just to our east and waves of energy slide northward along the front
and push a good chance of precipitation back into the region during the
predawn hours of Tuesday morning. With the wave expected to pass by to
our southeast, the best isentropic lift and deformation look to bring
the greatest precipitation totals to locations east of the Blue Ridge.
There is considerable spread in guidance QPF but there is an upward
trend and the latest runs indicate a good probability for amounts over
one inch, especially across Southside. This will be enough to cause
hydro problems with the possibility of river flooding so later model
runs will be watched closely to see if the upward trend continues.
The wave will move off to our northeast Tuesday night with some high
pressure wedging developing behind, but Wednesday looks to be wet once
again as another wavy front moves in from the southwest. Deep moisture
transport and strengthening low level flow will once again bring
widespread precipitation with potentially another good amount of
rainfall. If the expected antecedent wet conditions materialize as
currently indicated by guidance, the hydro threat will remain elevated
Just lingering showers overnight Wednesday night as we get into the dry
slot of the large stacked low spinning over the Great Lakes.
Given expected clouds, precipitation, and being on the cool side of the
boundaries, temperatures will be trending well below normal through
Wednesday.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 330 PM EDT Sunday...
On Thursday, short wave energy and the cold pool associated with the
upper low moving through the region will generate showers and
thunderstorms with moderately steep mid/upper lapse rates aiding
convective instability. Relatively low freezing levels and increasing
low level flow make graupel/small hail and gusty winds possible with
any showers/storms especially west of the Blue Ridge, but severe storms
are not likely.
The upper pattern will then be progressive into the weekend as the
upper low moves off to the northeast Friday allowing for a brief period
of ridging, followed by a transition to a zonal regime by Sunday. This
will give us a mostly dry Friday after any lingering upslope showers
west of the Blue Ridge dissipate, but another frontal system will push
in from the north and stall over the region on Saturday and bring an
increasing chance of showers/storms to the forecast for the weekend.
Temperatures will be trending from below normal on Thursday to at or
slightly above normal levels for the weekend with lower 80s east of the
Ridge and mid/upper 70s to the west.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
As of 720 PM EDT Sunday...
Stalled front over the southern Appalachians will result in
abundant cloud cover into Monday morning. A compact short wave
along the North Carolina/South Carolina border will track
northeast tonight. This will enhance southeast winds and
upslope along the Blue Ridge and into the eastern foothills.
For now, a vast majority of the area is only seeing light rain,
even in the upslope regions. The heaviest rain remains south of
the wedge boundary and closer to the wave`s center. This rain
shield will move east over the piedmont by midnight, exiting in
the morning.
Dry slot already moving northeast across the Smoky Mountains
and should be entering the Mountain Empire later this evening.
Even if rain should exit early, MVFR-IFR ceilings and/or
visibilities likely stay until west winds pick up Monday, behind
a cold front.
Extended Aviation Discussion...
Expecting several periods of precipitation with sub-VFR
conditions Monday night through Friday. Any breaks between
rainfall events with better flying conditions will likely be
less than 12 hours.
&&
.HYDROLOGY...
As of 1034 PM EDT Sunday...
Not expecting any flooding tonight, as high rainfall rates and
deep convection is not expected.
Will still need to watch Monday night into midweek as more
rainfall is expected, which could lead to small stream and river
flooding, with models favoring areas along/east of the Blue
Ridge.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AMS/PM/WP
NEAR TERM...AMS/RCS/WP
SHORT TERM...MBS
LONG TERM...MBS
AVIATION...AMS/RCS
HYDROLOGY...WP
Area Forecast Discussion
National Weather Service Tallahassee FL
812 PM EDT Sun May 21 2017
.NEAR TERM [Through Tonight]...
No significant updates were made since the current forecast
generally looks to be on track. Chances of showers and
thunderstorms across western areas were slightly adjusted upward
to 30-40 percent as a gradually weakening MCS could reach the FL
Panhandle and possibly SE Alabama later tonight or overnight.
Otherwise, just made minor updates to reflect current trends.
&&
.PREV DISCUSSION [715 PM EDT]...
.SHORT TERM [Monday Through Tuesday Night]...
A closed low over the Upper Mississippi Valley will amplify
through the entire Mississippi, Ohio, and Tennessee Valleys as an
area of +PV advects around the backside of the low through Tuesday
night. At the same time, a series of southern stream waves will
advect across the southern tier of the CONUS, helping to
strengthen the northern stream trough as it amplifies. At the
surface, a cold front will just have entered the Southeast on
Monday morning and is forecast to make very little forward
progress through Tuesday due to the temporary zonal flow regime
locally.
On Monday, the front will still be far enough west of us that it
wont have a direct impact on the afternoon convective coverage.
Instead, storms will likely be initiated on outflow from any
morning storms that develop in the Gulf, or along the seabreeze
circulation. Also on Monday, a southern stream wave will pass
through the northwestern part of the Southeast and result in
surface cyclogenesis across southern MS, central AL, and northern
GA. While the bulk of these storms should stay north and west of
us, it is possible that outflow generated from these storms could
result in convection locally through the evening. Regardless, by
Monday night the front should be close enough that scattered
showers and thunderstorms will continue through the night.
Tuesday will likely be our next best chance at widespread heavy
rainfall. Another southern stream wave will pass through the
Southeast, combined with strong low-level convergent flow,
boundary parallel steering flow, and unseasonably high PWATs
around 2". At this time, the core of heaviest rainfall is expected
to spread across areas west of a line from Tifton through
Tallahassee. This area of rain should gradually weaken and spread
eastward through Tuesday night as the next cold front (associated
with the northern stream trough) approaches the region. Through
Tuesday the threat for widespread severe weather remains low.
Isolated storms would be capable of producing strong to severe
wind gusts however.
.LONG TERM [Wednesday Through Sunday]...
Depending on how the evolution of the heavy rain event on Tuesday
plays out, Wednesday could get interesting. Coincident with
frontal passage, models suggest rather steep lapse rates, 40-50kts
of deep layer shear, and plenty of instability. Wind profiles
would suggest the potential for damaging straight line winds in
what would probably be a squall line rather than tornadic storms.
Large hail could also be possible. Once the front clears the
region Wednesday night, dry conditions are expected heading into
the weekend. Highs on Thursday look to be in the lower 80s, with
morning lows on Friday in the upper 50s.
.AVIATION [Through 00Z Tuesday]...
Scattered, small SHRA were developing around KTLH, KECP, and KDHN
this evening, and this may persist through about 04Z. The HRRR,
which appeared to be handling the MCS in MS and LA reasonably
well this evening, brings the remnants of this weakening
convection into KDHN and KECP around 12Z. At this time the HRRR
forecasts this perturbation to generate new SHRA/TSRA as it
encounters a very moist PBL with moderate instability, which seems
reasonable given synoptically favorable environment. This new cluster
of SHRA/TSRA will then move through KTLH and KABY mid to late
morning, and KVLD Monday afternoon. Brief periods of gusty winds
and IFR Vis are likely with some of these storms.
.MARINE...
Winds and seas will remain relatively calm through Monday, then
gradually increase to Cautionary levels through Tuesday, and to
Advisory levels by Wednesday. Winds and seas will begin to subside
by Thursday. Showers and thunderstorms should also be expected
through Wednesday night.
.FIRE WEATHER...
No fire weather concerns are anticipated for the next few days with
periods of showers and thunderstorms and high RH values.
.HYDROLOGY...
Radar a gauge data show that roughly 2-3" of rain (with isolated
higher amounts) have fallen over the past 24 hours west of a line
from Port St. Joe through Albany. West of this line, generally an
inch or less has fallen. Through Wednesday night, another 3-4" are
expected in the same hardest hit area, with 2-3" expected
elsewhere. The bulk of this QPF will fall on Tuesday through
Tuesday night. Isolated higher amounts of 1-2" above the average
amounts will also be possible. Ensemble guidance using the extreme
low-end of this envelope suggests that the Choctawhatchee and
Shoal should rise to Action stage. Expect the possibility for
Minor flood stage along these rivers. At this time, widespread
flooding, or flash flooding is not expected though a few issues
may arise should the isolated higher amounts occur over urban
areas.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 69 86 71 80 69 / 30 50 30 80 60
Panama City 73 80 75 78 73 / 40 40 50 80 60
Dothan 70 84 70 77 67 / 30 70 70 80 60
Albany 70 87 70 78 67 / 30 70 70 80 60
Valdosta 69 87 71 81 69 / 30 50 40 80 60
Cross City 70 88 72 84 72 / 20 30 20 30 70
Apalachicola 73 83 74 81 73 / 40 30 30 80 70
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...Lahr
SHORT TERM...Harrigan
LONG TERM...Harrigan
AVIATION...Fournier
MARINE...Harrigan
FIRE WEATHER...Lahr
HYDROLOGY...Harrigan
Area Forecast Discussion
National Weather Service Tulsa OK
851 PM CDT Sun May 21 2017
...UPDATE...
.DISCUSSION...
Mid and high cloud have overspread the entire area and should
persist through much of the night. Low shower chances still look
good after midnight in far southeast Oklahoma, but otherwise, the
majority of the area should remain dry until tomorrow. Updates,
featuring an increase in cloud cover, are already out.
&&
.PREV DISCUSSION... /Issued 615 PM CDT Sun May 21 2017/
..UPDATE...
AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
VFR conditions should prevail through the period. There is a
chance of tempo MVFR visibilities in light fog toward daybreak at
BVO/FYV. The greatest TSRA potential should be after the valid TAF
period, but there is a small enough potential after 21Z at the E
OK terminals to include PROB30 groups.
PREV DISCUSSION... /Issued 325 PM CDT Sun May 21 2017/
DISCUSSION...
A very nice late May afternoon is ongoing, with surface high
pressure sitting over the region. Looking aloft, westerly flow
prevails to the south of deep troughing over central NOAM. A small
PV anomaly currently rounding the base of the larger scale upper
trough over UT, and another larger PV max diving south out of
Canada will bring changes to our sensible weather over the next 48
hours.
Low level warm advection begins tonight as 925-850 flow turns
around to the south above a cool surface layer. The latest runs of
the HRRR show some shower activity approaching the Red River
toward 12Z and can`t completely rule out a shower near Hugo so a
20 percent PoP was added to the forecast. Will expand that north
some going into Monday morning and insert slight chance thunder
with a small increase in elevated instability. Focus then turns to
the west and north for the afternoon and nighttime PoPs. Lift from
the UT PV max will aid storm development in a couple different
areas, over the central High Plains and along the surface front
over Kansas, with the activity expected to move E/SE with time.
Some of this activity could clip portions of eastern OK and/or
western AR during the late afternoon and evening hours. As was
stated yesterday, the best moisture/instability will be confined
well to the south along the stalled front over central/southern
TX, so this should keep severe weather potential pretty low.
Thunderstorm potential will be focused over in far eastern OK and
western AR on Tuesday ahead of the front as it sweeps thru.
The Canadian PV max will dive down into the mid-Mississippi valley
by the middle of the week. With the cold air aloft, there could be
a few showers over NW AR Wednesday afternoon. Below average temps
can be expected Wednesday and Wednesday night behind the front.
A fairly quick transition from NW to W to SW flow aloft will occur
by the end of the work week as mid-CONUS upper trough lifts out
and another trough digs down into the Pac NW. As a result, a quick
transition from cool and dry to warm and humid is expected. The
best chance for elevated convection with the returning front will
be north of us, as warm mid-level temps overspread our area and
will act to keep things capped. Eventually, convection organizing
along a boundary over Kansas will work its way down into our area
by the holiday weekend.
Lacy
&&
.PRELIMINARY POINT TEMPS/POPS...
TUL 54 76 57 71 / 0 20 40 30
FSM 55 78 58 73 / 0 10 30 40
MLC 53 75 57 72 / 0 20 40 40
BVO 50 74 54 70 / 10 30 40 20
FYV 49 74 53 68 / 0 10 30 40
BYV 50 74 54 68 / 0 10 30 40
MKO 52 76 57 71 / 0 10 40 40
MIO 51 75 55 69 / 0 10 40 30
F10 53 74 57 71 / 0 20 40 30
HHW 57 74 58 73 / 20 30 40 30
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...22