379 
FXUS64 KMOB 051017
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
517 AM CDT Sat Sep 5 2020

.NEAR TERM UPDATE /Now Through Sunday/...Early morning surface analysis 
indicates a weak cold front pushing into central portions of MS and 
AL, and is approaching our interior southeast MS and southwest AL 
counties as of 4 AM CDT. Scattered mid and high level clouds are 
spreading overhead across the area and surface observations show 
little in the way of fog development early this morning, though 
there is still opportunity for a few sites to briefly drop to 2-4 
statute mile visibility reductions, especially over southern parts 
of the area ahead of the approaching boundary.

The weak front is forecast to slowly sink southward across the 
region through this afternoon as surface high pressure builds across 
the Mid-Mississippi and Tennessee Valley regions and into northern 
MS/AL. Probably the most notable sensible weather element associated 
with this boundary will be a much drier airmass that will be 
advecting into interior southeast MS and southwest and 
south central AL by this afternoon where dewpoints are forecast to 
fall into the upper 50s to mid 60s. Dewpoints will be slower to mix 
out closer to the coast and may hold around 70 to the mid 70s into 
this afternoon. Upper level ridging will continue to extend across 
the north central Gulf Coast region today and hot temperatures are 
expected over the forecast area today with this feature overhead 
despite the weak boundary slipping across our area. Short range 
model guidance also shows low level thermal ridging becoming 
enhanced over southern portions of the CWA ahead of the approaching 
front, with 925 mb temperatures between 25-26.5 C, which may be a 
degree or two C higher than yesterday. We trended high temperatures 
today close to and maybe a degree or two higher than the blended 
guidance this afternoon, particularly over the southern zones. Highs 
are forecast to range between 94-97 over the southern half of the 
region, and a little cooler between 90-94 over interior southeast MS 
and southwest AL. The challenge for the forecast today was the 
dewpoints, particularly how much they may mix closer to the coast. 
Some of the guidance indicated dewpoints mixing into the upper 60s 
over our southern zones again by this afternoon, but could still 
hold in the lower to mid 70s near the immediate coast as a weak 
seabreeze develops. The dewpoint forecast was trended maybe just a 
bit lower than the NBM guidance this afternoon, which yielded 
maximum heat indices between 105-108 over much of the southern CWA. 
Thinking was this was close enough to advisory criteria to go ahead 
and issue a Heat Advisory for the southern zones this afternoon, 
especially considering the amount of outdoor activities that may be 
occurring with the Labor Day Weekend. 

Moisture convergence along the weak surface front/seabreeze may 
initiate isolated convection near the coast, but coverage should be 
few and far between. Capped POPs just below 15% but kept isolated 
mention with 10% coverage mentioned in the forecast.

Cooler temps return tonight - lows should range in the mid 60s to 
around 70 degrees inland and in the lower to mid 70s near the 
immediate coast. A similar pattern returns Sunday with isolated to 
locally scattered storms possible mainly along and east of the I-65 
corridor. Another hot day is expected with highs in the lower to mid 
90s but a drier surface airmass (dewpoints in the 60s) should result 
in lower max heat indices.  A low risk of rip currents continues 
through the weekend. /21 

&&

.SHORT TERM /Sunday night Through Tuesday night/...A westward 
drifting upper system over the western Caribbean combines with an 
upper trough over the eastern Conus to bring a mean upper trough 
along the east coast Sunday night into Monday. More upper level 
shortwave energy moving around the eastern edge of an upper ridge 
stretching east over the southern half of the Conus combines to form 
another upper trough over the Southern Plains, leaving upper high 
pressure stretching northeast from the western Gulf of Mexico to the 
Tennessee River Valley. A low level ridge that has built southwest 
over the Appalachians organizes a bit more, bring a more northeast to 
easterly low level flow to the northeastern Gulf coast and nearby 
portions of the Southeast, shifting a stalled surface boundary along 
the northcentral/northeastern Gulf coast farther south over open 
Gulf waters in the process. With a more northeasterly component to 
the low level flow advertised by today's guidance, moisture return 
off the Gulf is slowed significantly from yesterday's 00z guidance. 
One item that is consistent from yesterday's guidance is the GFS 
advertising a weaker northerly push in the Near Term, leaving a bit 
high available moisture, mainly south of I-65 Monday. By sunrise 
Wednesday, a strong upper low digging southeast over the western 
Conus/ US Rockies shifts the upper ridge over the Southeast 
eastward, leaving an upper ridge stretching west over the eastern 
Conus, with a weak upper trough centered over Florida.

For Sunday night through Monday night, a generally dry forecast is 
expected. A few afternoon thunderstorms near the coast are possible 
Monday as a seabreeze moves inland from the coast, but northward 
extent will be limited. As stated above, most guidance is 
advertising dryer conditions Monday due to the limited moisture 
availability. Have also leaned on the warmer end of guidance with 
respect to Monday's high temperatures, with a drier airmass and 
upper level subsidence the cause. High temperatures in the low to 
mid 90s inland, around 90 along the coast are expected. The drier 
airmass will also allow for better overnight radiational cooling, 
especially over areas northwest of I-65. Low temperatures Sunday 
night are expected to range from the mod 60s northwest of I-65 to 
upper 60s to around 70 southeast and low 70s along the coast. Monday 
night, low temperatures ranging from the upper 60s to around 70 
northwest of I-65 are expected, low to mid 70s south. 

Tuesday into Tuesday night, with the upper ridged building west over 
the eastern Conus, the low level ridge over the eastern Conus shifts 
south a bit, bringing a more east to southeast flow to the Southeast 
and an increase in Gulf moisture. Rain chances will see an uptick 
Tuesday, though best rain chances remain southeast of I-65. Tueday's 
high temperatures will see a bit of a downward trend with increased 
mid and upper level cloud cover expected from the increase in 
daytime cloud cover and moisture levels. High temperatures ranging 
from the upper 80s to around 90 expected. Low temperatures Tuesday 
night will see an uptick with the increased moisture levels, with 
readings from around 70 to low 70s inland, mid to upper 70s along 
the coast. 
/16 

&&

.EXTENDED TERM /Wednesday Through Friday/...Global models continue to 
come into much better agreement through the extended period. This 
leads to increasing confidence during the period. The ECMWF has come 
around the GFS solution of being more progressive with the upper 
trough over the plains which will eject northeast into the 
midwestern states late in the week. An associated cold front will 
move into southeast late in the week, potentially bringing some 
slightly cooler and drier air to the area for next weekend. Although 
they do still differ in the speed of the upper trough, due to how 
fast the upper ridging over the southeastern states breaks down. 
Either way, good chance POPs, mainly afternoon and evening in daily 
diurnal pattern, will continue trough the extended term period. High 
temperatures will be in the upper 80s to lower 90s. Low temperatures 
will continue to range from the upper 60s to lower 70s inland to the 
mid 70s near the immediate coast. /13

&&

.MARINE...No impacts expected throughout the week outside of an 
increasing chance of showers and thunderstorms Sunday through 
Tuesday. /21

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      96  69  93  69  92  71  89  72 /  10   0  10   0  20   0  30  10 
Pensacola   96  73  93  72  90  74  89  74 /  10   0  20  10  20  10  20  20 
Destin      94  76  91  75  89  76  88  75 /  10  10  30  10  20  10  20  20 
Evergreen   94  68  93  68  92  70  88  71 /  10   0  20  10  10   0  40  10 
Waynesboro  92  66  91  64  92  68  89  69 /  10   0  10   0  10   0  30  10 
Camden      92  66  92  67  92  69  88  70 /   0   0  10   0  10   0  30  10 
Crestview   97  69  93  69  93  71  90  71 /  10   0  30  10  20   0  40  10 

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory from noon today to 6 PM CDT this evening for 
     ALZ261>266.

FL...Heat Advisory from noon today to 6 PM CDT this evening for 
     FLZ201>206.

MS...Heat Advisory from noon today to 6 PM CDT this evening for 
     MSZ078-079.

GM...None.
&&

$$

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