Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/31/17
Area Forecast Discussion
National Weather Service Wakefield VA
1006 PM EDT Tue May 30 2017
.SYNOPSIS...
A series of upper disturbances will move across the area today
through tonight. A cold front approaches from the northwest
Wednesday and tracks across the Mid-Atlantic region on
Wednesday night. High pressure rebuilds over the area for the
latter half of the week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
No major changes necessary to the previous forecast. Did raise
PoPs a bit over the Northern Neck/Middle Peninsula for an area
of strong tstms this eveng, but mainly just up to a slight
chance of rain elsewhere.
Previous Discussion...
Latest wx analysis reveals weak low pressure over South Central
VA, with a quasi-stationary frontal boundary draped from the
VA/NC border back into SE TN/N GA/AL. Aloft, deep occluded
cyclone continues to spin over Central Ontario. Mid-afternoon
regional radar mosaic showing a narrow line of showers, mainly
along and north of the aforementioned boundary in the southeast
into W SC. To the north, numerous clusters of storms have fired
across W PA/NY State...along and ahead of the front. Visible
Sat imagery showing partial clearing/thinning clouds back in
the E VA Piedmont west of RIC.
Continue to lean on the CAMs for the balance of the aftn/night,
with the time-lagged HRRR and to a lesser extent the RAP showing
a good handle on actual radar coverage thus far. Showers and
storms will continue to fire to our north, along and ahead of
the cold front. Expect a few isolated showers/storms will
approach northern parts of our area by late this afternoon.
Given lower PW/Theta-e values farther north, expect areal
coverage will remain low, isolated to widely scattered at most.
However, orientation of MLCAPE of ~1500 j/kg (750-1000 j/kg
DCAPE) with 40-50 KT of Deep layer shear across the north would
portend to a convective environment supportive of multi-cell
clusters, with some supercell potential also present. SPC
continues Day 1 Slight Risk just north of our local area, with
all but the strongly-capped Lower Eastern Shore in a Marginal
Risk Area.
HWO mention is mainly along and north of RIC-Williamsburg line
for the afternoon and evening, with damaging winds and large
hail the primary hazards. Farther south, lower shear values and
lingering clouds through the day (PW ~1.75" across the SE) have
kept a lid on additional convective development thus far. That
said, do expect convective development once again late this
aftn and early evening across the Carolinas, sliding NE across
E NC into South Central/SE VA from mid-evening through the
early morning hours Wed. Given aforementioned stable marine
layer across the Eastern Shore, have again held out thunder
mention over the Eastern Shore, despite some modest elevated
instability by early evening.
Deep layer shear diminishes with time tonight, and therefore
expect that activity across the north wanes steadily with loss
of heating. As referenced above, shearing/dampening shortwave
approaching from the SW argue for lingering a 30-40 POP into the
overnight across the southeast. Sky cover will remain partly to
mostly cloudy with stratus/patchy fog once again late. Early
morning lows mainly in the 60s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
An upper level trough will sharpen over the Great Lakes
Wednesday pushing the surface cold front toward the local area
from the interior northeast. 12z suite of guidance is once again
a bit quicker with the frontal passage Wed, which yields a
solution which leans toward a more active period of convective
development Wednesday aftn and evening, owing to the combination
of increased low-level moisture and stronger SW (rather than W)
flow aloft. 30-40 POPs have been maintained in anticipation of
scattered showers and T-Storms developing and pushing across the
area Wed aftn/night. Otherwise, look for highs Wednesday in the
upper 70s/around 80 along the coast, low to mid 80s inland.
The mid-level trough axis will shunt surface cold front across
the area Wednesday night, with POPs dropping off early across
the piedmont, and after midnight mainly along and E of I-95 as
the front clears the coast late Wed night.
Post-frontal W-NW flow and surface high pressure building from
the west should combine to yield a cooler/drier forecast for
Thursday. After early morning lows in the upper 50s to mid 60s,
highs Thursday should rise in the low 80s inland, with mid to
upper 70s for the Lower Ern Shore and along area beaches.
Thursday night and much of Friday appear to remain dry. Have
gone with a slight to low end chance POP for some pulse
convection SW sections (Tri-Cities toward the I-85 corridor) on
Friday aftn as with developing low-level return flow.
Otherwise, slightly warmer with highs in the mid 80s inland, in
the u70s to around 80 along the coast.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Latest models now somewhat slower and farther north with a frontal
boundary placement over the weekend. Data now suggests boundary
stalls to the N across northern Va with several impulses riding
along it. The parent low tracks northeast into New England
early next week with the trailing cold front crossing the region
Monday. Upper level energy progged to rotate around this system
into Tuesday. Despite the synoptic difference from yesterday,
result won`t change much from previous thinking. Upshot will be
for periods of showers/T-Storms through the period. Given the
timing uncertainty, will keep pops capped at chc for now. Slight
chc Tuesday.
Highs sat 80-85, upr 70s-lwr 80s Sun and Mon, mid to upr 70s Tue.
Lows in the mid-upr 60s except upr 50s to mid 60s Tue.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
KSBY is expected to remain locked into LIFR/IFR CIGS through
Wednesday morning given persistent onshore flow. Elsewhere, am
anticipating potential for MVFR to IFR conditions at KRIC around
sunrise. Have indicated this in the KRIC TAF. Elsewhere,
conditions expected to remain VFR overnight with light winds.
Conditions improve at KRIC/KSBY later Wednesday morning as winds
turn to the southwest ahead of a stronger cold front.
OUTLOOK...There will be a chance for thunderstorms late Wednesday
afternoon and evening. A cold front crosses the area Wednesday night
and a dry day is expected Thursday as high pressure settles over the
Mid Atlantic States. The high slips off the coast Friday and
scattered showers and thunderstorms are indicated for the weekend as
a slow moving cold front approaches from the northwest. Patchy fog
will be possible within a few hours of sunrise each morning.
&&
.MARINE...
No headlines expected overnight as SE winds become S-SW at 10
KT or less. Seas avg 3-4 ft.
The next cold front approaches the region Wed as south winds incrs
to 10-15 knots. The front pushes across the waters late Wed night.
Height rises and modest cold advection behind the front result in a
wind shift to the N then NE but expect speeds to remain just below
SCA levels. High pressure slides offshore Thursday night/Friday with
flow returning to the south. The next front crosses the waters
Saturday night.
&&
.TIDES/COASTAL FLOODING...
Onshore flow/swell and high astronomical tides have resulted in
elevated water levels along the Bay and tidal rivers. Based on
the latest data, decided to upgrade the Ches Bay side of the Lwr
MD eastern shore to a coastal flood advisory through 12Z. Levels
should reach minor flooding levels at Bishops Head for both this
evenings and early Wed morning high tide cycles. Otw, additional
statements will likely be needed for the middle Ches Bay as levels
there reach action stage for tonight`s high tide cycle.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 8 AM EDT Wednesday for MDZ021>023.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...MAM
NEAR TERM...MAS/MAM
SHORT TERM...AJZ/MAM
LONG TERM...MPR
AVIATION...LSA
MARINE...JDM/MPR
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Burlington VT
803 PM EDT Tue May 30 2017
.SYNOPSIS...
Large upper level low pressure across central Canada will pivot
slowly east through the end of the week, driving a series of weak
frontal systems across the area. As a result expect a near daily
threat of showers, including scattered thunderstorms on Wednesday, a
few of which may trend strong. Temperatures will remain near late
spring norms throughout the seven day forecast period.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 727 PM EDT Tuesday...Evening forecast remains in good
shape with widespread showers from the Adirondacks eastward
quickly exiting within the next few hours. Still monitoring a
line of convection west of the St. Lawrence Valley that may clip
Ogdensburg to Massena from 00-01Z but the loss of daytime
heating has kept these storms relatively in check with no severe
expected. Beyond midnight we should be looking at a quiet night
with mild lows in the 50s and perhaps some areas of patchy fog.
Previous Discussion...
An active early evening still expected across the area as a
distinct shortwave trough swings through the St. Lawrence
Valley, driving numerous showers and a few thunderstorms, a few
of which may be strong. A marine- modified airmass has
penetrated quite far west this afternoon, covering all of VT and
into the Adirondack Mountains where low level flow remains
backed to south/southeasterly. A narrow instability axis
extending from central New York north-northeast into the SLV and
far western Dacks has developed to the immediate west of the
marine airmass and it is in this small area where the potential
for any stronger storms will exist through late afternoon/early
evening. Please note Severe Thunderstorm Watch #299 remains
intact to our immediate south and west through 00Z. CAM output
has largely handled today`s activity quite well, especially the
HRRR and have leaned heavily in it`s direction in regard to
pops/weather through midnight. All and all it`s output seems
reasonable showing scattered/numerous showers/storms to
gradually weaken and morph into a larger area of rainfall across
our area through the evening hours, some of which could be
heavy at times along and south of a KSLK-KBTV-KISL line (please
see hydro discussion below). After midnight conditions should
largely trend dry leaving partly to mostly cloudy skies and
seasonable temperatures in the 50s for the overnight hours.
Could see some patchy fog in a few spots, but synoptic setup and
stronger flow aloft precludes widespread coverage.
Another potentially active day then develops on Wednesday as deeper
southwesterly flow develops across the area and kicks the stable
marine airmass out. Modest instability combined with ample shear
aloft should lead to the development of scattered to numerous
showers and storms, especially from the Adirondacks east where best
forcing and low level convergence will exist. For now have
introduced non-severe small hail/gusty winds wording, omitting any
reference of severe per marginal SPC SWODY2 output. Temperatures
expected to be about 10 degrees warmer than today per 925 mb thermal
profiles, mainly upper 60s to lower 70s.
By Wednesday night showers/storms exit east by midnight leaving
mainly partly cloudy skies overnight. Low temperatures blend of
available guidance - mainly from 45 to 55.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 316 PM EDT Tuesday...Ground Hog Day...the movie...all over
again. The steering and driving of our weather continues to be
the deep trof with shortwaves rotating around the closed low and
timing/position of shortwaves determining the shower threat.
Thursday appears to be the day in which the southern extent of the
closed low and shortwave pivots across the area. Although deep
layered moisture is lacking...persistence, climatology and
model data still brings a threat of showers but largely northern
and higher terrain and in the morning thus the timing could be
diminishing morning showers then more Thu ngt for a relatively
drier day.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 316 PM EDT Tuesday...Models are fairly consistent through
Saturday...as upper low lifts ENE but with another shortwave
(there`s always another one) sweeping across the area on Friday
night. Thereafter it appears we stay in much broader cyclonic
flow with differences between ECMWF/GFS of potentially ANOTHER
strong shortwave and closed low rounding the base for Monday.
I`m looking for a time that I can leave out POPS but frankly trying
to time a long enough period is a guestimate at best. Showers return
by Friday morning and become more numerous during the day with
possibly enough instability for a few embedded thunderstorms Fri
aftn with showers to linger into Sat morning, then drying
possibly til Sun aftn until the next shortwave and surface
reflection moves into area Sunday night-Mon and still unsettled
Tue.
Cool, cyclonic flow means temperatures will remain largely AOB
seasonable levels through the period.
In the end...no real changes from previous forecasts for this time
period.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday....Showers and isolated thunderstorms
continue this evening. MSS most likely site to see some thunder
or VCTS. Otherwise, showers expected to exit the area around
06Z. Lots of low level moisture will keep mix of VFR and MVFR
conditions throughout the overnight. Expect MPV and SLK to see
IFR conditions late this evening through early Wednesday
morning.
Winds will continue out of the south at 5-15kts, becoming gusty
out of the south to southwest during the day Wednesday.
VFR conditions return late Wednesday morning with breaks in
clouds before more afternoon showers and thunderstorms develop.
Outlook...
Wednesday Night: VFR. Slight Chance SHRA...Slight Chance TSRA.
Thursday: VFR. Breezy. Slight Chance SHRA.
Thursday Night: VFR. Chance SHRA.
Friday: VFR. Chance SHRA.
Friday Night: VFR. Likely SHRA.
Saturday: VFR/MVFR. Chance SHRA.
Saturday Night: VFR. Slight Chance SHRA.
Sunday: VFR. Chance SHRA.
&&
.HYDROLOGY...
As of 310 PM EDT Tuesday...Numerous showers and a few
thunderstorms will affect the region this evening. The potential
still exists for a swath of heavier rainfall to develop across
portions of central NY state east-northeast into the southern
Adirondacks and central/southern VT. A semi-stationary
convergence zone in this area will likely serve as a focus for
the activity, which may tend to take on training
characteristics. PWATS aren`t overly excessive (1-1.25 inches),
but enough confidence given most recent CAM QPF output to
support locally heavy rainfall along and south of a KSLK-KBTV-
KISL line where scattered totals of 1-2 inches may occur with
isolated higher totals. This is in close agreement with latest
WPC Day 1 Excessive Rainfall Outlook. While a larger-scale flash
flood threat is not expected, 3 hour FFG in this area is
running around 2 inches, a bit on the low side. Conditions will
be monitored closely as the afternoon/evening progresses. Should
training characteristics develop, quick rises on fast- response
streams will certainly be possible.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...JMG
NEAR TERM...JMG/Lahiff
SHORT TERM...SLW
LONG TERM...SLW
AVIATION...KGM
HYDROLOGY...JMG
Area Forecast Discussion
National Weather Service Columbia SC
816 PM EDT Tue May 30 2017
.SYNOPSIS...
A diffuse front will remain stalled in the region during the
rest of the week. Expect mainly diurnal scattered thunderstorms.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Convection this evening has focused in Georgia. Latest radar
indicating weak returns over the CSRA region. Other showers back
to the west associated with weak short waves. Air mass across
the region will be weakly unstable overnight. Forcing appears
weak. Latest high resolution models including HRRR suggest
showers in eastern Alabama may move into the CSRA or Piedmont
around daybreak. Will keep a slight chance pop overnight
increasing slightly around daybreak west. Warm temperatures
similar to last night with considerable clouds.
&&
.SHORT TERM /WEDNESDAY NIGHT/...
The weak front will remain across the area through Wednesday
night. Upper air pattern will still show an east coast trough,
with weak high pressure over the area. Models indicate there
will still be the possibility of isolated or scattered afternoon
showers/storms. 20 to 30 percent pops seem reasonable.
Generally went with a model blend of guidance which gives
temperatures in the mid to upper 80s through the afternoon, and
lows in the middle 60s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Upper trough remains over the eastern US into Friday before
flattening out ahead of another approaching system. At the
surface, high pressure will be off in the Western Atlantic
through the end of the week, helping to circulate southerly
winds and moisture into the region. A cold front is poised to
approach the area over the weekend. Can not rule out a slight
chance of an afternoon shower/storm on Thursday. Increasing rain
chances into the weekend ahead of the next system. Chance pops
seem reasonable for now. Temperatures close to normal.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions expected outside of possible patchy early morning fog
and afternoon and evening convection.
Most of the shower and thunderstorm activity has remained south
and west of the terminals this evening. A slight chance of
showers will continue overnight. Cannot rule out patchy MVFR
fog in the usual fog prone locations towards sunrise Wednesday
morning. However, mid-level clouds over the region will be a
limiting factor, so confidence remains too low to include. A
frontal boundary in the area on Tuesday will bring another
chance for showers and thunderstorms mainly during the afternoon
and evening. Confidence in coverage and timing is too low to
warrant mention in current TAF issuance. Winds remain generally
out of the west through the period.
EXTENDED AVIATION OUTLOOK...A cold front will stall over the
region through much of the week. The front will help support
scattered thunderstorms and possible restrictions each day.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service State College PA
1004 PM EDT Tue May 30 2017
.SYNOPSIS...
An upper level trough will remain centered over eastern Canada
through the week. With the exception of Thursday, several
shortwaves rotating through the trough will bring periods of
showers and thunderstorms.
&&
.NEAR TERM /UNTIL 9 AM WEDNESDAY MORNING/...
Previously noted short wave touching off isold shra, but
coverage is expanding over the NW cos. 30-40 POPs look fine. No
risk of thunder there. These should slide steadily NE and may
actually exit stage right before sunrise. BFD dewpoint rising
and stratus has expanded to cover most of the area east of the
Allegheny front. Small holes here and there will only serve to
allow fog to form as everyone got wet today and dewpoints are
generally just a few degs away now.
Prev...
Strat-us lurking over Mt Nittany and headed at-us. GOES-R fog
difference channel portrays a widespread/expansive and expanding
area of stratus over the eastern half of the area. Those that
did not lose the stratus will not see clearing and those that
did - like State College - soon will have it back. Thanks, east
wind. The dewpoints did very briefly touch the 40s in AOO, but
it has already popped back into the 60s. Expect the stratus to
hang on and fog to form - esp in places that got some decent
rain today. We have seen no lingering flooding issues and have
allowed all the flood advisories to expire. But, there were a
few spots which received >3" of rain.
HRRR and RAP do increase the POPs (make some QPF) through the
evening hours NW of UNV and in and around BFD and FIG. This
seems strange with little instability and dewpoints in the 40s.
There must be a subtle short wave in there over OH, but I can`t
pick it up on the IR. The only hint is one patch of rain headed
quickly for HLG and PIT. This seems on track with the forecast
timing of the showers generated by the mdls, so I will hold a
small chc in the NW for a few hours around midnight.
Have mentioned widespread fog, but the areas which have stratus
may not get terribly foggy due to the clouds. On the other hand,
it is good to mention as the ridge tops will probably be
shrouded in fog as Tussey Mtn is right now. Have kept mins up in
the 50s everywhere except the far NW (for now). Even there, the
clouds may keep the temps up in the 50s.
&&
.SHORT TERM /9 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Next in series of shortwaves is progged to swing through the
region Wednesday, accompanied by scattered showers/storms
occurring mainly during the afternoon. The eastern half or more
of the CWA will start out with a serious handicap on temps - the
low stratus and fog. NAM from 18z Tues does keep much of the
area dry - only making convection over the NW half. Only a few
shra survive into the SE. Will only nudge POPs down in the SE
and up a few notches in the NW based on current trends.
Despite lack of much CAPE, strong mid level flow and associated
0-6km shear could support organized convection with the threat
of damaging wind gusts in a few locations. SPC still have a good
portion of the area in MRGL risk - and mainly in the east where
the best moisture is. This is at risk if the clouds hang on too
long. Well mixed soundings and mean 850mb temps of 8-12C should
translate to max temps from the mid 60s over the highest
terrain of the Alleghenies, to the upper 70s across the Lower
Susq Valley.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
There is fairly strong model consensus for a mostly sunny/dry
Thursday, as surface ridge and associated low PWAT air mass
builds across the region. In the longer range, the persistent
upper level trough over southeast Canada and the northeast conus
will dominant our wx pattern Fri-Mon, producing frequent
opportunities for showers and temperatures around to slightly
below normal. The best chance for precipitation will be Friday
night and Sunday night. Sunday looks like higher QPF amounts but
the models have a divergent solution on whether it is a closed
low or upper wave. Expect a wet period of weather through the
weekend into next week.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Convection has moved east of all but far southeast/lower
Susquehanna Valley airfields /KMDT/KCXY/KLNS...with VFR conds
generally in the wake. Few showers moving into the Lower Susq
should help stir up the lowered cigs/vsbys in place all day, but
probably only temporarily.
Models seem to be in agreement with patchy fog/low stratus
redeveloping tonight especially over the eastern 1/2 of the
airspace with restrictions possible into Wednesday morning.
Another round of showers and tstorms looks likely Wednesday
afternoon and evening as a cold front pushes east through PA
with temporary reductions to MVFR/IFR conds at times.
.OUTLOOK...
Thu...AM fog/low cigs psbl wrn 1/2. VFR remainder of day.
Fri-Sun...Periods of sub-VFR likely with showers and
thunderstorms.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Dangelo/Lambert
NEAR TERM...Dangelo
SHORT TERM...Dangelo/Fitzgerald/Lambert
LONG TERM...Fitzgerald/Ceru
AVIATION...Lambert/Gartner
Area Forecast Discussion
National Weather Service Cheyenne WY
432 PM MDT Tue May 30 2017
.SHORT TERM...(This evening through Thursday night)
Issued at 200 PM MDT Tue May 30 2017
Currently...Water vapor imagery showing upper ridge just moving
into western Wyoming this afternoon. Upper low that was over the
Great Lakes area yesterday, slowly moving north northeast . Still
have northwest flow over the CWFA. Much drier today with PWATs
analyzed on area soundings around .38 inches or less. Getting some
CU buildups over the north Laramie Range. Most other areas are
experiencing pretty flat CU under these dry/stable conditions.
Later this afternoon and evening...latest HRRR guidance showing a
pretty late start for convective development today. Convection not
starting til maybe 23Z at the earliest. Get cells developing over
the Laramie Range and then drifting south southeast. It does show
some weak thunderstorms over Cheyenne around the 01-02Z timeframe.
Do think with loss of surface heating and instability that a lot
of this convection will either not materialize or die off quickly.
So did keep the Cheyenne area dry. Did add some low PoPs into the
south Laramie Range for the 00-02Z timeframe.
Upper ridge axis overhead for Wednesday with 700mb temperatures
climbing to +8C. Low level winds continue to be forecast to shift
to a southeast direction for Wednesday. Do have a very weak
shortwave moving through the ridge that could kick off some
afternoon convection, particularly over the Laramie Range and
areas east. ECMWF and SREF guidance does show some qpf across much
of the CWFA tomorrow. Cant rule it out, so have slight chance PoPs
going for areas east of the Laramie Range for Wednesday afternoon.
Nothing severe expected with surface based CAPE around 500-600 J/KG.
Weak upper level steering flow should allow for slow moving storms
if they do develop at all, so hazards look to be gusty winds and
possibly localized heavy rainfall.
Upper ridge axis moves east Wednesday night into Thursday morning
with a stronger low pressure system tracking into western Montana
and western Wyoming Thursday night. Could see increased coverage
of convection mainly out west, closer to the shortwave Thursday
afternoon.
.LONG TERM...(Friday through Tuesday)
Issued at 200 PM MDT Tue May 30 2017
Friday...Westerly flow aloft prevails and with just enough low and
mid level moisture present, expect to see isolated afternoon showers
and thunderstorms form mainly along and east of Interstate 25.
Saturday...As the flow aloft turns northwest, somewhat drier and
cooler airmass moves in, producing a more stable airmass and little,
if any, chance of showers and thunderstorms.
Sunday...Ridging aloft develops with low level southeast winds
helping to advect low level moisture northwestward to the foothills
of the mountains. This will aid in producing isolated afternoon and
evening thunderstorms, mainly along and east of Interstate 25.
Monday...Southwest flow aloft strengthens ahead of the Idaho upper
low. With diffluence aloft combined with moist upslope in the low
levels, expect isolated to scattered afternoon and evening showers
and thunderstorms to erupt along and east of Interstate 25, then
propagate northeastward across western Nebraska in the evening.
Tuesday...Similar pattern to Monday with southwest flow aloft.
Perhaps a few degrees cooler due to expansive cloud cover and
scattered nature of showers and thunderstorms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 430 PM MDT Tue May 30 2017
VFR. Isolated showers near Laramie and Cheyenne through 02Z.
Wind gusts to 20 knots through 02Z. Wind gusts 20 to 27 knots
after 15Z Wednesday.
&&
.FIRE WEATHER...
Issued at 200 PM MDT Tue May 30 2017
Fire weather concerns minimal at this time with greenup and recent
rain/snow fall. Afternoon humidities could get near critical
Wednesday as temperatures warm into the 70s and low 80s. Carbon
County looks to be the area where lowest humidities will occur
tomorrow. Fortunately, winds are expected to be light and fuels
are green, so no fire weather concerns expected. Next chance for
widespread wetting rains will be this weekend as another Pacific
low pressure system moves through the area.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Dodge City KS
600 PM CDT Tue May 30 2017
...updated aviation...
.SHORT TERM...(This evening through Wednesday)
Issued at 328 PM CDT Tue May 30 2017
Convective chances exist very late this afternoon beginning in the
extreme southwest counties, and spreading slowly eastward through he
evening. Moderate instability/CAPE will be present with around 30
knots of bulk shear across western Kansas; an environment which the
HRRR drives current ongoing convection across the Sangre de Cristos
into by this evening. Given the limited instability and shear,
widespread high impact severe weather is not expected; LHP parameter
is only indicating around 4 to 5, on the low end of the 1.5 inch
hail spectrum, and storm may be too closely clustered as well.
Probably more commonly small hail and gusty winds with this event.
However the set up by Wednesday may be better suited for severe
weather reports (higher CAPE) especially if convection develops
earlier in the day across a stationary frontal boundary draped
from northwest though central Kansas.
A mild overnight with temperatures only falling to the upper 50s,
and the models are averaging about 5 degrees warmer than MOS. This
will be a jump start to warmer highs as well on Wednesday, as highs
climb into the mid and possibly upper 80s south.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 328 PM CDT Tue May 30 2017
No significant chances to the extended period. Continuing with
near climatological weather, with highs in the 80s. Better
opportunity for more organized convection will be next week as a
western Plains ridge breaks down and low pressure develops across
the northern rockies and Central Plains (ECMWF/GFS).
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 600 PM CDT Tue May 30 2017
VFR is expected through TAF pd. Recent mosaic radar trends shows only
isolated tsra across NW Kansas. Activity is fairly weak and is not
moving very fast. Chance of impacting the terminals is on the low side.
Winds will be light/variable tonight to a light southerly wind increasing
10-15 kt tomorrow.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 57 85 61 85 / 20 40 30 10
GCK 55 86 59 85 / 20 40 30 10
EHA 55 85 58 83 / 20 30 20 10
LBL 57 86 60 84 / 20 30 30 20
HYS 55 83 61 86 / 20 40 30 10
P28 60 87 63 86 / 20 30 20 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Sugden
Please see the 00Z aviation forecast discussion below.
AVIATION...
Showers and thunderstorms continue across portions of south central
Texas this evening. Radar trends show activity along the I-35
corridor near KSAT and KSSF is decreasing and we will opt to keep -RA
in the forecast until 01Z. For the remainder of the evening we should
see plenty of mid and high level clouds and this should help keep
cigs just above MVFR. The boundary layer continues to cool early
Wednesday morning and this along with wet ground should allow some
MVFR cigs to develop. MVFR cigs continue through the morning, then
lift/scatter back into VFR in the afternoon. With daytime heating, we
should see showers around and will carry VCSH after 18Z.
Out west at DRT, we have gone with prevailing -RA this evening given
plenty of convection over the higher terrain of Mexico. However, we
will keep vsbys and cigs VFR. After 08Z, we should start to see a
gradual increase in convection and have gone with prevailing -SHRA
with cigs just above MVFR. Around 10Z, we should start to see an
increase in thunderstorms and have gone with a TEMPO group between
10-14Z. Uncertainty in the forecast after 16Z is high and while we
could see additional thunderstorms, we have only gone with VCSH for
now.
PREV DISCUSSION... /ISSUED 308 PM CDT Tue May 30 2017/
SHORT TERM (Tonight through Wednesday Night)...
Ongoing convection will continue to drift east-southeast as semi-
persistent MCVs and outflows provide the lift for new convection to
develop. There will be an overall reduction in coverage and intensity
as diurnal heating ends, and most current activity should die out
completely by 03Z. Rainfall will be spotty, but some locations in the
Hill Country and San Antonio Metro could receive 1-3 inches of rain.
A mid and upper-level low will continue to progress across the Desert
Southwest over the next 24 hours. The first shortwave trough rotating
around the low is expected to reach the lower Rio Grande by 12Z
Wednesday. Mesoscale models, particularly the Texas Tech WRF, HRRR,
and experimental HRRR all develop a line of convection or weak MCS
over the Sierra Madre, then propagate it eastward ahead of the
shortwave trough. This could reach the Rio Grande Plains as early as
09Z, but is more likely closer to 11Z. The low level jet will help
maintain this activity through about 15Z...when the climatological
diurnal convective lull occurs as the low level jet wanes and before
daytime heating ramps up. Additional scattered storms are likely
during Wednesday afternoon.
LONG TERM (Thursday through Tuesday)...
The upper low will continue to progress eastward on Thursday, so
another day with fairly high PoPs and the potential for localized
heavy rain, but not enough coverage nor amounts to require a flash
flood watch.
The general flow across North America will be relatively zonal
starting on Friday, but will low amplitude ripples, and a bit
further south than climatologically normal for this coming weekend
and into early next week. Given the generally unchanged moist and
slightly unstable airmass in place, this implies scattered showers
and thunderstorms, but relatively low 20-30 PoPs, each day. Rainfall
will be spotty and generally light, but a few spots could receive a
few inches of rain from any given storm.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 70 88 69 85 71 / 20 30 40 70 20
Austin Bergstrom Intl Airport 68 88 69 84 70 / 20 30 40 70 20
New Braunfels Muni Airport 68 86 69 84 70 / 20 30 50 60 20
Burnet Muni Airport 67 84 67 82 68 / 20 40 40 60 20
Del Rio Intl Airport 70 84 69 86 72 / 50 50 60 30 20
Georgetown Muni Airport 67 86 68 84 69 / 20 30 40 60 20
Hondo Muni Airport 69 87 69 86 70 / 40 40 50 50 20
San Marcos Muni Airport 68 87 68 85 70 / 20 30 50 60 20
La Grange - Fayette Regional 69 88 70 86 71 / 20 40 40 70 20
San Antonio Intl Airport 70 87 70 86 71 / 30 30 50 60 20
Stinson Muni Airport 70 87 70 85 71 / 30 30 50 60 20
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...24
Synoptic/Grids...Williams
Public Service/Data Collection...YB
Area Forecast Discussion
National Weather Service Hastings NE
649 PM CDT Tue May 30 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 232 PM CDT Tue May 30 2017
Primary concern for this time frame include small chances for
tstms later this afternoon and then again during the daytime on
Wednesday. Looking at the big picture, upper air analysis along
with water vapor imagery showing closed low over northern Ontario
with troughing over the eastern third/half of the CONUS. A high
amplitude ridge prevails over the Rockies with the next upstream
low approaching the Pacific NW coast. This puts the central Plains
in northwest flow with occasional weak shortwaves rotating
through the area. At the surface, weak pressure pattern in place
with surface low centered near the upper low over Ontario, with
high pressure building into the region from the northwest. Surface
dewpoints vary over the CWA, ranging from the mid 30s in the
northwest part of the CWA, to the mid 50s in north central KS.
First question is what are the chances for tstms in our south later
this afternoon? As of 18Z no cumulus development in or close to
the CWA. Checking the latest MSAS plots, perhaps some weak
convergence going on near the southern CWA but nothing impressive.
Models do prog ML CAPE values greater than 500 J/kg in that area.
Earlier runs of some of the CAM models this morning had little in
the way of convection this afternoon, but last few runs of the
HRRR now popping isolated tstms in the KS part of our CWA. Earlier
forecast had a slight chance of tstms in this area, and while I
don`t plan to up the POPs, probably can`t remove them completely
at this point.
Precip chances then diminish over night as we lose daytime heating.
Will need to introduce POPs again Wed morning starting in the
west and then expanding east during the morning hours. Don`t see
alot of forcing especially aloft, but the models do forecast a
weak low level jet riding over the subtle surface boundary.
Time/height section over the middle of the CWA does show decent
omega and RH values in the 700-400 mb level from 12-18Z. Believe
convection will be spotty across the CWA during the day, so at
this point 20 percent coverage should cover it. Instability
marginal during the morning hours but becomes more robust during
the afternoon with progged CAPE values in excess of 2000 J/kg in
the KS part of our CWA. 0-6 km shear could be near 40 kt which is
enough to support strong or severe storms. Latest SPC Day 2
outlook has the southwest half of our CWA in a marginal risk,
which seems reasonable at this time. Biggest question here is
whether the severe threat is centered over our southern CWA or a
little south of there.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 232 PM CDT Tue May 30 2017
Any tstms that develop Wed afternoon should linger into the night
before moving off to the east. Thu should be quiet as the upper
ridge noted above slides over us. By mid day Friday the ridge axis
should be just to our east, with a broad trough moving over the
western half of the country. It appears there will be a surface
cold front moving through our area sometime Friday afternoon,
bringing us our next chance for rain. Models diverge heading into
the weekend with the GFS showing more of a progressive flow while
the EC builds another ridge into the northern Rockies. However, it
also allows a few disturbances to slide under the ridge so either
way, continued chances for at least isolated/scattered convection
continue into the weekend and the early part of next week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 646 PM CDT Tue May 30 2017
VFR conditions are expected. The slight gustiness to the wind will
wane after a few hours this evening.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Ewald
LONG TERM...Ewald
AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Lincoln IL
907 PM CDT Tue May 30 2017
.UPDATE...
Issued at 900 PM CDT Tue May 30 2017
Weak surface trof/cool front continues to edge slowly southeast
with isolated showers and thunderstorms located just ahead of the
boundary. We expect a slow decrease in activity as we head through
the late evening and into the early morning hours with the
southeast the last to see the activity move out. A few of the
heavier showers produced some strong winds in a few locations
with gusts around 50 mph reported in Lane and estimated winds of
45 to 50 mph here in Lincoln early this evening. High pressure is
expected to build into our area on Wednesday bringing a quiet
weather scene to the area with pleasant afternoon temperatures
ranging from the lower 70s far north to the upper 70s along the
Interstate 70 corridor.
Have already updated the zones to reflect the current thinking
with some minor adjustments to the precip wording through the rest
of the evening along with some tweaks to the temperatures.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 305 PM CDT Tue May 30 2017
A weak cold front and shortwave will trigger scattered showers and
thunderstorms this evening. The front appears to have reached a
line from Springfield to Champaign already, but the gradients in
dewpoints and winds are not all that noticeable with this
weakening front. The showers and storms will be primarily
triggered by the shortwave and cold pool aloft that are rotating
around the upper low in the western Great Lakes. Cloud-to-cloud
lightning flashes have already developed along I-80 just to the
north of our counties, so some cloud-to-ground strikes may not be
far off as the showers/storms advance southward farther into our
forecast area. Have increased the coverage of PoPs/Storms the rest
of the afternoon into the evening, which seems reasonable based
on the latest updates of the HRRR and RAP models. There are some
indications that a few showers/storms may linger south of I-72/74
to Danville after midnight, so have continued isolated chances
mainly east of I-57 a couple hours after midnight.
Clearing should progress across central IL late tonight, with lows
bottoming out in the low 50s toward Galesburg and in the upper 50s
toward Lawrenceville.
Advancing high pressure on Wednesday should provide a dry day.
The colder air aloft will allow for some diurnal cumulus to
develop during the afternoon, but high temps should still have
enough boost from the late May sun to reach the low 70s north of
I-74 and upper 70s south of I-70.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 305 PM CDT Tue May 30 2017
A warm front advancing north toward Illinois Wed night will
produce some increasing clouds late in the night. At some point on
Thursday, the models are indicating an MCS will develop in the
central Plains and advance eastward toward Illinois. SPC has a
Marginal Risk for severe in western Illinois to account for the
possibility of that system still producing severe weather this
far east. MUCAPEs are projected to reach 1400 J/kg in our western
counties, with bulk shear of 30 to 35 kts. Surface moisture will
be lacking, so we kept PoPs in the chance and slight chance category
on Thursday for now. A secondary storm complex is expected to
advance across our northern counties after midnight Thursday
night, so PoPs were ramped up to high chance along and north of
I-74.
Storm chances on Friday and Friday evening look to be on the low
side, as the warm front advances north of our counties and we
experience a lack of noticeable triggers.
The Canadian and GFS show an enhanced area of lift developing
after midnight Friday night east of Peoria to Mattoon, mainly due
to an apparent southward drift of the warm front toward I-74.
High chance PoPs /40-50%/ were included in that area as a result.
The surface low is expected to eventually push across northern IL
Saturday night, dragging a cold front across the rest of Illinois
in the process. High chances of showers and storms will be in the
forecast from midnight Friday night through Saturday evening,
fueled by MUCAPEs in the 1500-1800 J/Kg range. Bulk shear looks to
be weak during that time at 20-30kts.
Spotty showers and storms will linger on Sunday into Sunday
evening behind the surface low as the upper trough axis and cold
pool slowly progress across Illinois.
There is relative agreement in the ECMWF/GFS/Canadian that high
pressure will settle into Illinois for Monday and Tuesday,
increasing the chances of dry weather during that time. However,
temps look to be at or below normal under the influence of a
cooler Canadian air mass.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 540 PM CDT Tue May 30 2017
A weak cold front will push across the forecast area this evening
bringing widely scattered showers and possibly a thunderstorm to
central and east central Illinois. We may have to add a tempo
group in PIA as the area of showers is closest to that site, while
further east and south, coverage at this time looks too limited
to carry anything but VCTS for a few hours into this evening.
Otherwise, VFR conditions are expected through this forecast
period as the weak upper level wave and surface boundary shifts
away from our area later tonight with high pressure drifting in
for Wednesday.
Surface winds ahead of the front will be southwest to west at
12 to 17 kts early this evening with a few gusts around 25 kts,
especially in and close to the area of showers. We look for
winds to quickly diminish at or just after sunset this evening
with a light westerly flow prevailing overnight. Northwest winds
are expected on Wednesday at 10 to 15 kts.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...Smith
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
915 PM CDT Tue May 30 2017
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
The afternoon showers and storms have dissipated with the loss of
diurnal heating and the CWA is clear of rain at the moment. The
hi-res models still show some warm advection showers moving up
from south MS and LA overnight and can see some of these already
on radar in south LA. Still expect a bit of fog to form in the
northern third of the CWA after midnight tonight too. Did not
really make any changes to the forecast. Everything looks pretty
good so far. /10/
Prior discussion below:
This afternoon/tonight through Wednesday:
Rain and storms have been ongoing this afternoon across portions
along and north of the Highway 82 corridor with some increasing
chances slowly as you go towards the I-20 corridor, due to some
efficient warming and diurnal heating. Left in some chances of PoPs
in the I-20 corridor due to some heating and some of these storms
and outflow boundaries helping induce convection near I-20 over the
next several hours. HRRR shows this as well over the next few hours
so won`t adjust PoPs downward due to this. In this area temperatures
have warmed nicely into the lower 80s.
The airmass will stay stagnant overnight as the chances of rain wind
down over the central and northern half of the area after 00Z. With
temperatures falling into the low-mid 60s, especially across the
northern half of the area, some patchy to patchy dense fog are
possible across the Highway 82 corridor. This is similar to last
night into this morning, where we got some decent fog in the Delta.
The best chance for patchy dense fog will remain across the Delta.
Due to this, added a limited in the HWO/graphics late tonight
through mid-morning Wednesday.
Expect moisture transport from weak perturbations/shortwaves to move
in tonight into south Mississippi, with some PWs approaching the 1.5
to 1.75 inch range, which will help advect back in some showers and
storms across south Mississippi. Expect the best chances to come
after 07-08Z, with increasing chances towards the I-20 corridor by
daybreak and central and northeast Mississippi towards mid morning.
These increasing rain chances will continue Wednesday as the
boundary lingers around to just north of our area. With a continued
feed of moisture transport/convergence, expect scattered showers and
storms again tomorrow. With a widespread nature of convection and
weak lapse rates/weak flow, expect most storms to remain below
strong to severe limits. Due to weak flow, some locally heavy
rainfall can`t be ruled out. But these will be scattered enough to
preclude mentioning in the HWO. A warm and cloudy day is expected
Wednesday in the low 80s in southeast Mississippi where more
convection will cause more widespread cloud cover and all. In areas
closer to the front, we should warm into the mid 80s, unless some
lower clouds/fog hamper heating early in the morning. /DC/
Wednesday night through next Monday:
All the models and their ensembles show a generally wet week is
in store for the ArkLaMiss as a series of southern stream
shortwave troughs dip southward and interact with a persist
moisture convergence axis across the Gulf Coast states.
Precipitable water values will rise to around 2 inches during the
period, especially later in the week when deeper tropical moisture
associated with a tropical disturbance near Central America is
transported northward through the western Gulf of Mexico.
We will get into a mostly diurnal pattern of convection through
the rest of the work week, but with greater moisture returning
ahead of a more significant shortwave trough this weekend we may
see an increase in convective precipitation and at least locally
heavy rainfall. We will monitor for the heavy rainfall potential
as we get closer in time, but will leave any mention of this out
of the graphics/HWO for now. Highs will generally be in the lower
to middle 80s with lows in the middle 60s to the lower 70s. /17/EC/
&&
.AVIATION...
00Z TAF discussion:
VFR conditions are occurring this afternoon as most of the ongoing
showers and storms are not affecting TAF sites. Some rain is
affecting HBG but not enough to limit flight categories. Some fog
will be possible for Highway 82 corridor TAF sites later tonight.
Another round of rain and storms possible tomorrow, potentially
moving in early in the south. /28/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 65 84 68 83 / 14 47 17 55
Meridian 64 83 67 83 / 12 43 15 54
Vicksburg 65 83 68 83 / 12 47 19 60
Hattiesburg 67 82 69 83 / 39 67 18 56
Natchez 66 82 69 82 / 19 56 22 60
Greenville 66 85 68 83 / 10 16 6 52
Greenwood 65 86 67 83 / 12 25 10 52
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
Area Forecast Discussion
National Weather Service Louisville KY
958 PM EDT Tue May 30 2017
.Forecast Update...
Issued at 945 PM EDT Tue May 30 2017
Skies are clear at this time over south-central IN and partly cloudy
over south-central KY. Isolated diurnal thunderstorms over south-
central KY have dissipated. The question is whether new showers or
storms will form overnight as suggested by previous model guidance.
Scattered thunderstorms have developed over west-central MO as
suggested by models but these are sagging mainly SE. Additional
elevated isolated showers and storms over central IL are forecast by
the latest HRRR to move east and stay mainly north of our area
overnight. The 12z and 18z GFS and NAM suggested isolated to
scattered showers and a few storms would develop overnight in our
forecast area. The latest HRRR is less enthused about precip in our
area, which is supported by the latest observations. But the HRRR
does hint that isolated light showers could still occur well after
midnight as a weak shortwave rotates eastward to the south of the
upper low over the northern Great Lakes. Thus, will leave mention of
a few showers overnight, but have trimmed back probabilities. Winds
will become light from the S to SW. Current forecasted lows mostly
in the upper 50s to lower 60s still looks reasonable. Any isolated
showers early Wednesday morning will move quickly eastward out of
our area.
&&
.Short Term (Now through Wednesday Night)...
Issued at 255 PM EDT Tue May 30 2017
Surface analysis shows a weak surface boundary extending from
Indiana to Arkansas. This boundary is moving into an unstable
atmosphere (LI around -5 and CAPE 1000-1500) and is sparking widely
scattered showers and a few thunderstorms in the heat of the day.
This activity should diminish this evening as the sun sets.
An upper level disturbance over Minnesota this afternoon will drop
southward into the base of an upper trof and help to spark shower
redevelopment tonight, especially after midnight. Low temperatures
tonight should be around 60.
Wednesday the upper trof will gradually push off to the east with
scattered shower activity tapering off from west to east.
Atmospheric cross-sections suggest that the moisture associated with
the showers will decrease quickly behind the precipitation and we`ll
probably see a fair amount of partial sunshine by afternoon. So,
despite morning rain and clouds will still go for afternoon highs
near 80.
A compact dome of high pressure over Saskatchewan today will enter
the Ohio/Tennessee Valleys Wednesday night and provide quiet weather
with lows in the middle and upper 50s.
.Long Term (Thursday through Tuesday)...
Issued at 308 PM EDT Tue May 30 2017
An upper ridge over the Plains early in the long term will try to
move east but instead will get squashed by an upper low sinking
southeast out of Canada and across the Great Lakes over the weekend
and into early next week.
A slug of deeper moisture is expected to advect in from the mid-
Missouri Valley to the Ohio Valley Thursday afternoon and night. A
very subtle wave crossing southern Illinois may spark some
thunderstorms in the afternoon and evening. High pressure will still
be in the vicinity at the surface and the operational GFS is likely
overdone with its QPF with this feature, though, so will lean toward
the drier ECMWF/GEM and keep PoPs low.
That surface high will continue to push to the ESE and eventually
absorb into high pressure over the Atlantic. This will put southern
Indiana and central Kentucky on the back side of the large swath of
high pressure and in an area of southerly 1000-700mb flow bringing
Gulf moisture northward...especially Friday through Sunday morning.
To trigger convection, a complex storm system will proceed from the
upper Plains through the Great Lakes and OV on its way to the
Northeast. Soundings, especially in southern Kentucky Saturday
evening through Sunday morning, become very wet. This is reflected
by precipitable water amounts approaching 1.8 inches. Deep flow
looks to be on the weak side. So, heavy rainers will be a
possibility. WPC has indicated a swath of high QPF along the KY/TN
border, but it should be noted that there are still large
differences among the models.
High pressure nosing in from Canada should then dry us out for the
beginning of the new work week.
&&
.Aviation (00z TAF Update)...
Issued at 740 PM EDT Tue May 30 2017
Skies are mostly clear over southern IN and partly cloudy over
southern KY at this time, with diurnal isolated convection downstate
dying off. Area will be precip free next few hours. Then a weak
disturbance to our west could again initiate isolated to scattered
showers (perhaps a thunderstorm) later tonight as it tracks across
KY. Have included VCSH in all 3 TAFs after 06z for a few hours.
However, prevailing conditions should remain VFR, unless a quick
downpour briefly lowers vsbys over the terminal. Prevailing winds
overnight will become light from the south.
On Wednesday, any sct showers overnight will exit east in the
morning with surface winds becoming SW and then W around 10-12 kts
in the afternoon with VFR conditions.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update.........TWF
Short Term.....13
Long Term......13
Aviation.......TWF
Area Forecast Discussion
National Weather Service Mount Holly NJ
1204 AM EDT Wed May 31 2017
.SYNOPSIS...
A stationary front will remain to the south of the region
through Wednesday. A surface trough will weaken as it approaches
the area tonight. A cold front will move through the Northeast
Wednesday and Wednesday night. High pressure briefly builds into
the East to close the week. A cold front will sag southward
from southern Canada this weekend. A surface low will move into
the Northeast early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Widespread fog and drizzle across the region through the
overnight. Some spots have dropped to under a mile, and it is
possible for patchy dense fog, but will hold off on a Dense Fog
Advisory.
Area of showers and thunderstorms south and east of Washington
D.C. and tracking to the east. Could have some of those showers
and storms entering southern portions of northeast Maryland and
southern portions of Delaware through the early morning hours.
Latest HRRR has it passing through there from 05-08Z. Very
little, if any SBCAPE, but MUCAPE ranges from 750-1000 J/kg, so
there should be enough elevated instability to keep storms
alive.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
It appears the the low level moisture will finally begin to
decrease over the area, allowing at least some sunshine across
the forecast area Wednesday. An approaching front will cause
winds to become S or SWrly during the morning. This will help
mix out some of the trapped clouds over the area. Temperatures
will respond by climbing into the low/mid 70s across the north
and close to 80 over Delmarva and metro Philadelphia. We will
continue to carry the chc for showers and tstms for the
afternoon. The favored areas will be N/W, however.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Main concern in the long term is the potential for a prolonged
period of occasional chances for showers and storms Friday
through early next week.
Model discussion: The operational model suite continues to
struggle with the evolution of a high-amplitude ridge in
central Canada through the period, with omega blocking in Canada
and the presence of weak high-over-low blocking in the central
U.S., at least through the weekend. Though the details of the
planetary- scale features have improved somewhat compared to
this time yesterday, the smaller-scale perturbations within both
the large-scale trough in eastern Canada and the low-amplitude
flow over the conterminous United States continue to be large
sources of model variability from run to run (and from model to
model). Thus, the forecast remains very low confidence Friday
onward, with potential for considerable changes to portions of
the forecast as the setup/event(s) approach(es).
Many of the model discrepancies in yesterday`s discussion remain
to some degree, including the westward bias of the CMC with
regard to the placement of the first upper-level low in eastern
Canada that will eject eastward early this weekend. The GFS
becomes a somewhat deep/slow outlier as the trough pivots
eastward into New England on Saturday, though closer to
consensus than yesterday. Considerable spatial variability
remains with the reloading vort max late this weekend, with
subtle but important differences in timing/phasing with the
southern-stream vort max progressing eastward through the
central U.S. Nevertheless, the operational models are beginning
to stabilize on their solutions, with the 12Z ECMWF showing a
strong surface low progressing into the Great Lakes region and
stalling late this weekend into early next week before pivoting
southeastward through the Northeast. The 12Z CMC has, for
several days, suggested a more zonal track of the low through
the Midwest/Ohio Valley into adjacent New York and the northern
Mid-Atlantic during this same period. The GFS remains the most
variable of the three, but has consistently produced a more
southern track of the surface low (which is internally
consistent with its somewhat deeper upper-level trough).
Finally, the 12Z CMC continues to show a southern-stream low
developing in the Gulf of Mexico moving northeastward through
the Mid-Atlantic (or vicinity) early next week, though
substantial variation exists on track and timing.
Unfortunately, larger discrepancies remain with smaller-scale
lift and associated precipitation, which will largely depend on
the aforementioned vorticity maxima and their interactions
through this period. Forecast skill with these details is simply
too low at this time range to provide specifics. The forecast
details below provide information on the details that appear to
be emerging from the model chaos, but as these trends are just
developing and subject to large errors owing to the low-
predictability pattern, there remains a long way to go in
sifting through the "close-to-reality" versus the computational
garbage.
Forecast basis was a 30/25/25/20 blend of the ECMWF, NAM, GFS,
and CMC (respectively) through Friday followed by a 30/25/25/20
blend of the ECMWF, GFS, CMC, and WPC guidance thereafter.
Modifications were made to include statistical guidance for
temperatures (and to lesser degrees, PoPs and QPF) to increase
collaborative agreement with surrounding offices.
Forecast details:
Wednesday night: Remnant convection from a cold front moving
through the area is expected to continue but weaken rapidly with
loss of daytime heating. Primary chances appear to be in the
southern CWA, though slight chances remain farther north based
on more aggressive look to longer-range higher-resolution
guidance to this point (e.g., the RGEM). Kept lows close to a
MAV/MET consensus here, with improving skies overnight.
Thursday and Thursday night: Nice day. With transient shortwave
ridging upstream of the departing vort max and attendant
surface ridge moving through the Eastern Seaboard, a seasonal
day with mostly sunny skies is expected. There could be some
wind gusts 20 to 25 mph or so, as deep mixing is expected
upstream of the cold front with 850-mb flow around 30 kts.
Temperatures on Thursday night may be a little cooler than
Wednesday night with calmer winds and clearer skies.
Friday through Saturday: A vort max from central Canada digs
southeastward to the U.S./Canada border near/east of the Great
Lakes during the period. A strong, cyclonically-curved 250-mb
jet streak intensifies as it rounds the base of the longwave
trough. An attendant baroclinic zone will develop from the Ohio
Valley eastward to the Atlantic coast, with only slow movement
of this front/temperature gradient southward given upper-level
flow nearly parallel to the surface boundary. Strength of the
vorticity maximum and substantial warm advection downstream will
provide sustained large-scale lift in much of the eastern U.S.
during this period. However, with antecedent drying from the
cold front moving through during the short-term period, there
is some question regarding the degree of
moistening/destabilization for precipitation coverage during
this period, with the GFS notably dry (mostly from poor timing
of the deepest lift -- i.e., this occurs Friday night, when
instability will be naturally more limited) and the CMC too far
south with the moisture pooling (which may be suspect, since it
is on the fast side of the guidance envelope with frontal
passage). PoPs were capped at chance during this period given
these discrepancies.
Saturday night: More disagreement, as the GFS moves another vort
max through the region, with considerable precipitation breaking
out across the baroclinic zone (now positioned generally south
of the CWA). The ECMWF suggests this to some degree as well, but
pushes the front much farther to the south. The CMC does not
show much hint of this at all, and places the front well to the
south. The CMC looks unreasonable here, as the upper-level flow
does not really justify such a southward push. Thus, think
slight chance to chance PoPs are a reasonable forecast for now,
though this may end up being a dry period. Chances are primarily
for showers during this period given the reduced instability on
the north side of the boundary.
Sunday and Monday: A strong surface low approaches the region
from the west. GFS/ECMWF solutions look wet, but there is
disagreement on the nature of the precipitation. The farther
south GFS low track would suggest a heavy rain event (with
little thunder), but the ECMWF and drier CMC suggest a somewhat
more convective look to the precipitation, particularly in the
southern CWA. Hard to say at this time frame, as competing
factors are in play here (including models` general inability to
simulate cold air damming versus models` general tendency to
push cold fronts too fast in patterns like this). For now,
generally chance PoPs in this time frame with slight chance of
thunder. Potential for heavy rain in this period, but details
too unclear to include mention at this time. Pattern recognition
suggests this a time window worth watching closely.
Tuesday: Longwave trough persists in eastern U.S./Canada. Cool
and showery look to the simulations on the upstream side of the
low. Kept slight chance PoPs during this time.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Widespread IFR/LIFR CIGs/VSBYs during the overnight with LGT/VRB
to calm winds.
Conditions improve throughout Wednesday morning, becoming VFR
by Wednesday afternoon.
Scattered SHRA/TSRA in the afternoon.
OUTLOOK...
Wednesday night: Scattered showers/storms in the evening, then
clearing skies with west/northwest winds at or below 10 kts.
Confidence average.
Thursday and Thursday night: VFR. Winds west or northwest 5 to
15 kts with gusts to 20 kts or so during the day and below 10
kts at night. Confidence well above average.
Friday through Saturday night: Gradually deteriorating
conditions, with locally MVFR/IFR conditions in proximity to showers
and storms Friday night and Saturday. Southwest winds 5 to 15
kts. Winds may become north/northeast on Saturday or Saturday
night, with longer-term MVFR/IFR conditions possible
thereafter. Confidence well below average.
Sunday: Potential for MVFR/IFR with chances of showers/storms.
Winds generally east or southeast 5 to 15 kts. Confidence below
average.
&&
.MARINE...
Offshore buoy data continues to be missing.
Sub-SCA conditions on the waters with LGT/VRB winds and 3-4 ft
seas on the ocean. Fog/drizzle will reduce VSBY to 1-3 NM. There
is the potential for VSBY less than 1 NM, and if VSBY continues
to deteriorate, will issue a Marine Dense Fog Advy.
OUTLOOK...
Wednesday night through Thursday night: Sub-advisory conditions
expected. Chance of showers/storms Wednesday evening.
Friday and Friday night: Marginal advisory conditions possible
with gusts around 25 kts and seas building to around 4 to 5
feet. Low confidence at this time.
Saturday through Sunday: Sub-advisory conditions expected.
Chances of showers and storms through much of the period.
RIP CURRENTS...
The potential for the development of dangerous rip currents is
moderate today, with a low risk currently anticipated for
Wednesday.
&&
.TIDES/COASTAL FLOODING...
As astronomical tides continue to fall, the threat for coastal
flooding will be reduced, even through the onshore flow
continues. Therefore, no coastal flood advisory was issued.
&&
.CLIMATE...
ACY now 7.5" for the month ranked #2 behind the 8.8 in 1948. POR 1874
PHL now 6.33 for the month ranked #11. record 9.46 -1894. POR
1872. #10 is last years 6.65
Since the 20th of May including today its rained a trace or more
PHL 9 of 11 days
ILG 9 of 11 days including current 9 consecutive
ABE 10 of 11 days including current 7 consecutive
TTN 10 of 11 days including current 7 consecutive.
ACY 9 of 11 days including current 9 consecutive
MPO 9 of 11 days including current 6 consecutive
RDG 9 of 11 days
GED 9 of 11 days
The month will generally average below normal to varying values
of generally 1 degree or less, except MPO around 2.5 degrees.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.
&&
$$
Synopsis...CMS
Near Term...MPS
Short Term...O`Hara
Long Term...CMS
Aviation...CMS/Kruzdlo/MPS/O`Hara
Marine...CMS/Kruzdlo/MPS/O`Hara
Tides/Coastal Flooding...
Climate...